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Spatial and Temporal Trends in Sediment Contamination in Lake Ontario
J. Great Lakes Res. 29(2):317–331 Internat. Assoc. Great Lakes Res., 2003
Spatial and Temporal Trends in Sediment Contamination in Lake Ontario Christopher H. Marvin1*, Murray N. Charlton1, Gary A. Stern2, Eric Braekevelt2, Eric J. Reiner3, and Scott Painter1 1Environment
Canada 867 Lakeshore Road, PO Box 5050 Burlington, Ontario L7R 4A6 2Freshwater
Institute, Department of Fisheries and Oceans 501 University Crescent Winnipeg, Manitoba R3T 2N6
3Ontario
Ministry of the Environment 125 Resources Road Toronto, Ontario M9P 3V6
ABSTRACT. A Lake Ontario sediment survey was conducted in 1998 to characterize spatial and temporal trends in contamination, and for comparison with data from previous surveys in order to assess any changes in environmental quality since the advent of measures to reduce contaminant sources. This survey was also designed to assist in tracing possible sources and vectors of contamination, and to identify areas where contamination exceeded Canadian sediment quality guidelines for the protection of aquatic biota. In addition, levels of a suite of eight metals were compared to pre-colonial concentrations, and surficial sediment enrichment factors were calculated. The highest levels of contaminants were observed at stations within the three major depositional basins; the spatial distributions across the individual basins were similar. Lake-wide averages for polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/PCDFs) were 100 ng/g and 111 pg/g TEQs, respectively. Concentrations of mercury and lead were observed to have decreased from 0.79 µg/g and 125 µg/g, respectively, in 1968 to 0.59 µg/g and 69 µg/g, respectively, in 1998. Exceedances of the Canadian Sediment Quality Probable Effect Level (PEL) guidelines were most numerous for arsenic (67%), PCDDs/PCDFs (58%), mercury (62%) and lead (38%). Concentrations of PCBs at all sampling stations were below the Canadian PEL of 277 ng/g. INDEX WORDS: Lake Ontario, polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins, mercury, lead, metals, sediment.
INTRODUCTION The presence of persistent pollutants can adversely impact Great Lakes wildlife, biodiversity, and aquatic ecosystems. Environment Canada, together with collaborating agencies, conducts Great Lakes sediment surveys to measure the occurrence and spatial distribution of environmental contaminants in order to further understanding of the role human activities play in releasing toxic substances *Corresponding
to the environment, and to provide information for devising effective strategies to mitigate potentially deleterious health effects. Earlier Environment Canada surveys in Lake Ontario were conducted to characterize the spatial extent of surficial sediment contamination by a variety of contaminants including metals (Kemp and Thomas 1976), polychlorinated biphenyls (PCBs) and organochlorine pesticides (Frank et al. 1979), mercury (Thomas 1972), and mirex (Van Hove Holdrinet et al. 1978). In addition, the cultural impact of human activities over time was assessed using sediment cores (Kemp
author. E-mail: [email protected]
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and Thomas 1976, Mudroch 1993, Frank et al. 1979); levels of metals including total mercury and lead were compared to pre-colonial concentrations. In 1998, Environment Canada revisited 66 of the original 229 sites from the 1968 survey by Frank et al. (1979) in order to undertake a comprehensive suite of analyses for assessment of contemporary sediment contamination relative to sediment quality guidelines, and to assess any changes in sediment contaminant concentrations from earlier surveys conducted in 1968 and 1976. Spatial and temporal distributions of selected contaminants in Lake Ontario sediments collected during the 1998 survey have already been reported as part of a study comparing surficial sediment contamination in Lakes Erie and Ontario (Marvin et al. 2002). This paper presents a more detailed overview of the spatial and temporal characterization of sediment contamination in Lake Ontario using results from 1998 and data from historical surveys, particularly the 1968 survey. Data for metals, (including total mercury and lead), nutrients, polychlorinated biphenyls (PCBs), and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/PCDFs) are presented. The results are also presented within the context of the Canadian Sediment Quality Guidelines (CCME 1999). These guidelines are routinely applied as screening tools in the assessment of potential risk and determination of the relative priority of sedi-
ment quality concerns. In addition, the ratios of surficial sediment concentrations to background concentrations were determined for eight metals, and the average values expressed as “enrichment ratios.” These enrichment ratios were used to assess the general influence of anthropogenic activities on sediment quality in Lake Ontario. METHODS Sample Collection Surficial sediment samples were collected aboard the Canadian Coast Guard Ship Limnos in 1998 from sixty-six stations (Fig. 1) using a mini box core sampling procedure. The top 3 cm of the sediment were sub-sampled from the mini-box core for the analyses of organic contaminants, metals, grain size, and nutrients. Samples for organic contaminant analyses were collected in solvent-washed glass jars. Samples for other characterizations were collected in either high-density polypropylene or Teflon jars. All samples were frozen for transport to the laboratory. At an index station in the Mississauga basin (station 1034), mini box core and benthos gravity core samples were obtained for surficial sediment sampling, and sampling with sediment depth. Cores were immediately extruded and sectioned on board the vessel. Butyrate core tubes (6.7 cm diameter)
FIG. 1. Map of Lake Ontario showing sampling stations for the 1998 sediment survey. Also shown are the major non-depositional (near shore) and depositional basin areas of Lake Ontario.
Spatial and Temporal Trends in Sediment Contamination in Lake Ontario were used in conjunction with the corers. Mini box cores for the study of temporal accumulation of contaminants were sub-sampled in 1 cm increments from 0 to 15 cm, in 2 cm increments from 16 to 30 cm, and in 5 cm increments to a depth of 40 cm. Benthos gravity cores were sub-sampled in 1 cm intervals from 0–1 cm, 9–10 cm, 14–15 cm, 19–20 cm, 29–30 cm, and every 10 cm thereafter (i.e., 39–40 cm, 49–50 cm) to the bottom of the core. Core profiles for mercury, lead, nitrogen, and phosphorus presented in this paper represent the combination of mini-box core data to a depth of 40 cm, and benthos core data at depths greater than 40 cm. A detailed description of the coring methods, including sampling protocols and equipment, can be found in Mudroch and MacKnight (1991). Analyses Extraction of freeze-dried sediments (10-15 g) was performed using an Accelerated Solvent Extractor (ASE) (Dionex). Dichloromethane (DCM) was used as the extraction solvent. Solvent extracts were evaporated, exchanged into hexane, and separated into three fractions of increasing polarity on Florisil (8 g; 1.2% v/w water deactivated). The first fraction was eluted with hexane and contained PCBs, along with p,p′-DDE, trans-nonachlor, mirex and a small portion of the toxaphene congeners. The eluate was treated with activated copper powder to remove elemental sulfur followed by addition of aldrin for volume correction. Solvent extracts were analyzed by high-resolution gas chromatography (HRGC) using a Varian 3600 GC (Varian Instruments, Palo Alto, CA) with a 60 m × 0.25 mm i.d. DB-5 column (stationary phase thickness 0.25 µm, J&W Scientific) equipped with a 63Ni electron capture detector (ECD). Hydrogen was used as the carrier gas (initial flow 1 mL/min) with nitrogen as a make-up gas (40 mL/min). A total of 103 PCB congeners (including co-eluting congeners) were quantified using external standard mixtures (Ultra Scientific, North Kingstown, RI) that were run after every six samples. A few congeners, for which standards were not available, were quantified with response factors (RFs) estimated from other congeners of the same chlorine number and similar retention time. Total PCB (ΣPCB) values were calculated as the sum of all congeners. Recovery standards PCB 30 and octachloronaphthalene (OCN) were added to all sediment samples prior to extraction. Recoveries of the surrogates were uniformly greater than 90% and no corrections were made for
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recoveries. Procedural blanks were run with every 10 sediment samples. Procedural blanks and surrogate recoveries were also evaluated against criteria established by the National Laboratory for Environmental Testing (Environment Canada) resulting from replicate analyses of SRMs over a two-year period. Field replicates were typically within 30%. Analyses of sediment for PCDDs/PCDFs were carried out using Ontario Ministry of the Environment (OME) standard methods (OME 2000). Prior to extraction, samples were spiked with 13 C-labelled surrogate standards. Toluene sediment extracts were subjected to a sequential cleanup that included a modified silica column, alumina column, and an Amoco PX21 carbon-activated silica column procedure (OME 2000). Analysis by high-resolution gas chromatography—high-resolution mass spectrometry was carried out in selected ion monitoring (SIM) mode using a VG Autospec high-resolution mass spectrometer equipped with a Hewlett-Packard 6890 gas chromatograph (Agilent Technologies Inc., Mississauga, ON). Chromatographic separation was carried out using a 0.25 mm i.d. 60 m DB-5 column with a 0.25 µm stationary phase thickness. Procedural blanks and precision and recovery samples were processed with each sample batch and all data for individual samples were checked against surrogate recoveries. Toxic equivalents (TEQs) were calculated using the International Toxicity Equivalency Factor (ITEF) method (Van den Berg et al. 1998); congeners present at levels lower than the method detection limits were given zero values for TEQ calculations. Trace metals and mercury analyses were performed by Seprotech Laboratories (Ottawa, ON). Trace metal concentrations were determined by a hot aqua-regia extraction with measurement by ICP-AES as described in McLaren (1981). Total mercury was determined by digestion with hot nitric acid and hydrochloric acid followed by cold vapour atomic absorption spectrometer (USEPA 1981). Nitrogen was measured using a PerkinElmer 2400 CHN elemental analyzer as N 2 after oxidation of sediment (NLET 1997). Total phosphorus (organic + inorganic) was determined by conversion to orthophosphate followed by extraction in 0.1 N HCl and subsequent conversion to molybdophosphoric acid. Reduction with ascorbic acid resulted in formation of a molybophosphoric acid complex that was subsequently measured photometrically at 660 nm (NLET 1997).
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Marvin et al. RESULTS AND DISCUSSION
Sediment Distribution The convention for sediment characterization described by Thomas et al. (1972) was used to describe trends in sediment contamination related to sediment distribution and transport processes for Lake Ontario. Sediments collected during the 1998 survey were classified as non-depositional, consisting of bedrock, glacial tills, and glacio-lacustrine clays, or depositional, which were comprised of fine-grained post-glacial material including silts and clays that accumulate in deep water areas. Lake Ontario was classified according to three major depositional areas; the Niagara basin was separated from the Mississauga basin by the Whitby—Olcott sill, and the Scotch Bonnet sill separated the Mississauga basin from the Rochester basin (Fig. 1). The Kingston basin is located at the outflow of Lake Ontario at the head of the St. Lawrence River; however, this area receives reduced loadings of sediment from the main open lake area due to the presence of a major topographical barrier, the Duck-Galloo sill. Spatial and Temporal Distributions of Metals and Nutrients The metals data for surficial sediments from the each of the individual major lake basins (Tables 1 and 2) of Lake Ontario were assessed for spatial patterns to assist in identification of source areas, to identify areas of non-compliance with Canadian Sediment Quality Guidelines (Table 3), and, in conjunction with the core data, to assess surficial sediment enrichment compared to historical norms. Benthos and mini box-core samples from an individual site in the Mississauga basin (station 1034) were assumed to be generally representative of temporal gradients on a lake-wide basis, due to the homogeneity of fine-grained sediments across the three major lake basins (Mudroch 1993). There were no statistically significant trends among contaminant distributions across the three major lake basins (t-test, p < 0.05 and ANOVA). The benthos core profiles of most metals at station 1034 generally exhibited a gradient of increasing concentrations from the surface to concentration maximums at depths of approximately 5 cm to 10 cm, gradients of decreasing concentrations from depths of the observed maximum values down to approximately 40 cm, and then relatively constant concentrations from approximately 40 cm to the bottom of the
core. This general trend in sediment accumulation by metals is shown in core profiles from station 1034 (Mississauga basin) for mercury and lead (Fig. 2). The lead profile was presumably primarily influenced by anthropogenic activities, the most important of which was the use and subsequent phasing-out of leaded gasoline. The sedimentation rate determined for the cores sampled at station 1034 was based on 210Pb dating of a box core sampled during the same survey in 1998 (Turner and Yang 2000). Uncompacted core mid-depths of 8.89 cm and 14.2 cm were estimated to represent mean dates of 1974 and 1959, respectively. Based on these data, peak accumulation of most metals in Lake Ontario sediments was estimated to have occurred in the early- to mid-1970s. Mudroch (1993) also estimated maximum lead contamination in Lake Ontario sediments occurred in the early 1970s. The core profile for mercury was similar to those of Lake Ontario cores analyzed and dated by Pirrone et al. (1998), in that the highest levels were detected in sections corresponding to the Second World War. Our mercury core profile indicates that mercury contamination began to trend toward decreasing values after 1980, while data from Pirrone et al. show that mercury accumulation rates began to decrease significantly in the late 1960s. In contrast to the core profile observed for metals, total phosphorus and nitrogen showed a general trend toward increasing concentrations from a depth roughly representing the turn of the 20th century to the surface of the core (Fig. 2). The individual basin background metal concentrations were determined from the average of the concentrations in sections at depths greater than 40 cm in a single benthos core from station 1034 (Table 3); the percentages of stations exceeding basin-specific background concentrations for each chemical were also summarized. Mudroch et al. (1988) reported background concentrations ranging from 18 µg/g to 32 µg/g for lead and 0.03 µg/g to 0.09 µg/g for mercury. The background levels of metals shown in Table 3 are thought to be generally representative of sediment concentrations prior to the onset of significant anthropogenic activities. However, Pirrone et al. (1998) estimated that atmospheric emissions of mercury in North America peaked in the late 1870s as a result of processing gold and silver. Therefore, “background” concentrations for mercury may not entirely predate industrial activities. There were no discernable differences in the extent of exceedances of background metal concentrations among the three indi-
Spatial and Temporal Trends in Sediment Contamination in Lake Ontario
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TABLE 1. Total trace metal, nitrogen, phosphorus, iron, manganese, and aluminum data from surficial (0–3 cm) sediment samples in the Niagara and Mississauga basins of Lake Ontario in 1998. Latitude Longitude (°N) (°W) Site Niagara Basin
As Cd Cr µg/g µg/g µg/g
43-12-59 43-21-40 43-21-39 43-21-41 43-21-39 43-21-41 43-26-01 43-30-18 43-30-20 43-39-00 43-39-01 43-17-19 43-16-49
Cu µg/g
Pb µg/g
79-17-56 79-42-01 79-30-00 79-17-59 79-05-58 78-54-00 79-24-00 79-18-01 79-05-58 79-06-00 78-54-01 79-50-30 79-52-20
1001 1002 1003 1004 1005 1006 1007 1020 1021 1035 1036 1073 1074
4.6 14.7 19.2 33.3 26.7 16.9 34.5 36.7 24.6 17.0 22.2 28.5 19.7
1.1 29.4 31.0 24.1 1.7 45.3 41.9 56.1 3.6 58.3 83.7 103.7 3.4 59.5 88.3 107.0 3.0 52.4 71.1 82.5 1.6 46.7 49.8 55.6 4.1 63.1 102.7 123.2 3.6 60.4 98.1 129.7 1.2 37.4 56.5 47.6 1.8 10.1 17.7 12.1 ND 24.1 35.0 47.2 ND 109.8 106.6 196.6 1.4 69.8 79.0 112.0
Mississauga Basin 43-26-04 78-41-57 43-26-01 78-29-59 43-25-57 78-17-52 43-26-00 78-05-55 43-25-58 77-53-59 43-21-39 77-41-52 43-30-20 78-41-56 43-30-20 78-29-59 43-30-18 78-17-59 43-30-20 78-06-00 43-30-19 77-53-59 43-30-20 77-42-00 43-34-39 78-11-58 43-38-58 78-42-01 43-39-00 78-29-59 43-39-00 78-17-59 43-39-00 78-05-59 43-38-57 77-54-01 43-39-00 77-42-01 43-47-39 78-41-58 43-47-38 78-29-56 43-47-38 78-18-02 43-47-41 78-06-01 43-47-38 77-54-01 43-47-40 77-42-02 43-38-56 78-13-26
1008 1009 1010 1011 1012 1013 1023 1024 1025 1026 1027 1028 1034 1037 1038 1039 1040 1041 1042 1052 1053 1054 1055 1056 1057 1082
6.6 7.0 16.2 32.9 44.0 7.0 28.8 17.9 19.8 6.9 13.4 17.2 40.2 21.0 28.2 10.8 22.4 24.0 28.0 14.0 ND 14.0 ND 29.3 4.6 11.9
0.7 1.8 1.8 2.3 1.2 0.7 3.8 3.9 4.1 3.6 2.6 0.5 3.4 5.8 3.7 2.9 4.4 3.9 3.9 ND ND 0.9 ND ND ND 0.8
Ni µg/g
Zn µg/g
29.1 128.3 27.0 169.8 70.5 322.4 89.4 365.3 64.5 267.6 46.1 210.6 98.8 401.2 95.3 410.2 50.0 179.3 19.1 31.0 34.5 131.4 43.2 1,342.7 37.9 877.2
11.6 14.4 5.2 14.9 46.2 51.0 60.8 48.7 51.0 54.9 61.9 54.5 48.2 53.6 63.3 57.1 51.4 61.6 69.1 65.7 19.5 18.5 20.4 22.2 61.0 104.6 136.2 95.8 52.5 90.4 111.3 76.3 58.2 89.9 116.3 80.7 51.3 81.5 92.5 72.4 51.6 80.0 97.4 69.9 18.0 28.3 27.3 28.2 63.7 93.2 144.9 80.4 51.8 108.6 118.3 85.8 53.0 98.8 120.0 85.1 53.8 97.8 115.3 78.3 60.3 98.9 131.5 84.9 53.2 98.7 120.7 99.4 62.9 100.9 118.7 100.2 4.2 8.0 36.0 45.9 5.1 7.3 28.6 28.7 17.9 17.3 54.9 56.4 5.2 3.7 6.5 7.5 14.6 15.1 14.4 16.0 8.3 7.7 11.7 19.6 35.7 39.7 48.9 32.8
41.0 217.3 235.5 238.4 267.0 92.3 455.4 368.5 394.6 326.2 321.4 97.8 436.9 371.8 397.4 384.1 435.1 402.9 413.0 50.7 27.6 74.1 11.2 50.0 21.6 223.7
Hg µg/g
N µg/g
P µg/g
Fe %
Mn µg/g
Al %
0.65 0.15 0.29 0.72 0.47 0.34 0.56 1.20 0.73 0.67 0.48 0.51 0.45
1,540 1,760 4,130 5,140 4,460 2,710 6,400 3,990 2,600 260 1,360 5,740 3,380
695 788 1,070 1,280 1,120 808 1,620 1,580 1,610 861 908 2,100 1,360
2.0 1.9 2.7 3.1 3.5 2.6 3.3 2.9 4.2 1.4 1.5 4.4 3.6
763 445 3,771 7,712 5,012 1,033 9,995 7,182 2,089 1,181 1,651 2,268 1,638
0.8 0.7 1.2 1.4 1.7 1.0 1.5 1.3 1.4 0.5 0.6 1.6 1.6
0.06 0.65 0.60 0.73 0.84 0.12 1.38 1.33 1.30 0.90 1.01 0.07 1.0 0.43 0.58 1.13 0.11 0.78 0.96 0.08 0.05 0.08 0.79 0.21 0.02 0.361
488 2,780 3,000 3,230 3,700 936 4,410 4,560 4,300 4,280 5,060 1,220 6,180 5,750 6,010 4,030 5,230 5,620 6,950 497 242 567 198 757 352 4,410
504 837 854 885 112 574 981 1,490 1,100 1,230 1,160 681 1,180 1,200 1,220 957 1,130 1,130 1,330 283 565 699 506 711 619 1,040
1.4 600 0.5 2.4 1,426 1.0 2.9 1,301 1.2 2.8 3,295 1.1 3.0 4,258 1.2 1.6 741 0.6 2.9 4,965 1.4 2.7 3,302 1.3 2.8 4,811 1.3 2.6 4,821 1.3 2.6 3,310 1.3 1.5 843 0.6 2.7 6,545 1.2 3.0 6,174 1.6 2.7 5,446 1.3 3.2 2,384 1.6 2.9 2,632 1.3 3.1 12,503 1.4 3.4 6,060 1.5 0.4 2,282 0.1 0.7 2,295 0.2 1.8 3,779 0.9 0.8 475 0.2 0.9 224 0.3 1.1 1,534 0.3 2.6 850 1.5
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TABLE 2. Total trace metal, nitrogen, phosphorus, iron manganese, and aluminum data from surficial. (0–3 cm) sediment samples in the Rochester and Kingston basins of Lake Ontario in 1998. Latitude Longitude (°N) (°W) Niagara Basin 43-21-43 77-30-02 43-21-36 77-17-58 43-21-40 77-05-58 43-21-41 76-54-00 43-25-58 76-47-59 43-30-21 77-30-06 43-30-16 77-17-57 43-30-21 77-05-58 43-30-21 76-53-59 43-30-19 76-42-00 43-39-01 77-29-56 43-39-01 77-18-00 43-38-58 77-06-00 43-39-01 76-54-00 43-39-00 76-41-59 43-38-58 76-35-59 43-39-00 76-30-00 43-39-00 76-18-00 43-47-38 77-30-00 43-47-40 76-53-58 43-47-37 76-41-58 43-47-41 76-30-01 44-34-41 76-30-00
Site
As Cd Cr µg/g µg/g µg/g
Cu µg/g
Pb µg/g
Ni µg/g
Zn µg/g
Hg µg/g
N µg/g
P µg/g
Fe %
Mn µg/g
Al %
1014 1015 1016 1017 1018 1029 1030 1031 1032 1033 1043 1044 1045 1046 1047 1048 1049 1050 1058 1060 1061 1062 1069
30.6 47.2 33.0 12.8 40.5 26.5 29.1 34.9 33.2 31.0 22.4 17.0 26.3 13.9 13.6 32.0 27.0 28.3 ND 24.3 29.9 32.4 25.8
1.1 0.7 1.8 0.9 1.1 3.3 3.4 2.8 3.4 2.4 2.9 3.3 2.6 3.1 2.4 1.3 ND ND ND 0.9 0.6 ND ND
52.6 46.0 45.4 26.4 47.7 48.9 59.5 59.8 48.9 51.3 60.7 56.2 53.1 55.5 51.1 46.5 45.8 15.2 7.7 44.4 37.4 28.9 36.8
61.2 58.2 56.3 25.7 57.4 87.2 87.2 82.3 84.4 72.6 92.6 85.2 76.5 72.1 68.1 60.6 46.2 9.1 4.5 62.0 51.7 35.2 49.3
67.2 59.2 59.0 29.4 66.8 96.3 113.6 119.1 101.9 93.3 110.1 97.8 84.9 89.3 79.5 62.5 54.9 15.4 8.1 54.0 44.8 30.6 44.1
64.6 53.9 55.1 30.7 61.1 87.7 77.8 75.8 80.7 68.6 86.1 85.5 76.9 71.9 64.3 57.0 49.4 12.0 13.7 51.1 44.8 31.7 42.5
263.5 229.8 232.0 124.4 240.7 347.3 393.8 371.2 335.9 310.3 363.3 337.7 310.9 313.5 283.7 239.9 199.2 59.8 19.5 213.4 184.2 136.5 176.1
0.77 0.65 0.68 0.28 0.68 0.90 1.11 1.15 0.86 0.79 0.66 0.87 0.70 0.72 0.78 0.58 0.79 0.28 0.02 0.51 0.48 0.37 0.65
6,510 4,010 3,700 1,750 3,510 5,894 4,965 5,030 6,060 4,630 6,380 6,390 4,840 4,300 4,600 4,690 3,950 568 222 5,090 4,840 4,000 3,860
1,100 1,050 1,110 745 926 948 1,050 1,200 1,310 834 1,210 1,290 1,100 838 870 1,470 1,200 617 528 997 1,140 818 936
2.9 2,094 3.0 3,600 2.9 3,145 1.8 708 2.8 2,353 2.9 7,042 2.7 4,041 2.7 2,681 3.2 12,268 2.8 4,080 3.0 3,531 3.3 5,133 3.3 4,353 3.0 2,310 3.0 2,517 3.0 4,482 2.4 2,476 0.9 305 1.0 687 2.9 2,096 2.8 2,308 2.0 687 2.9 1,848
1.2 1.2 1.2 0.7 1.1 1.2 1.2 1.2 1.6 1.2 1.5 1.4 1.4 1.3 1.3 1.5 0.9 0.3 0.2 1.6 1.4 1.0 1.4
Kingston Basin 43-58-31 76-52-58 43-56-19 76-42-00 43-56-21 76-30-00 44-00-42 76-42-03 44-00-35 76-30-07 43-52-00 76-17-59 43-56-04 76-18-08 43-55-59 76-12-00
1064 1065 1066 1067 1068 1070 1071 1072
22.4 19.2 20.3 9.8 15.5 11.8 46.7 NA
1.4 ND 0.8 ND ND 1.0 ND NA
62.4 27.6 41.3 13.5 30.3 38.1 19.0 NA
72.1 103.9 38.2 32.6 55.1 57.3 9.0 20.5 34.2 39.7 45.8 51.4 9.4 15.3 NA NA
65.8 25.4 45.4 18.8 29.6 35.7 16.8 NA
281.4 120.9 193.0 51.5 134.8 220.1 67.8 NA
1.00 0.27 0.47 0.18 0.38 0.87 0.30 0.31
7,720 1,530 4,820 1,190 4,660 1,410 745 604 2,980 635 4,980 900 609 581 NA NA
2.8 1.7 2.4 0.8 2.0 2.4 4.0 NA
1.7 1.0 1.4 0.3 1.0 1.5 0.5 NA
vidual major lake basins, indicating that anthropogenic impacts generally occurred on a lake-wide basis. More than 60% of the stations in Lake Ontario exhibited elevated surficial sediment concentrations for total mercury, zinc, lead, copper, chromium, and nickel, relative to the background concentrations (Table 3). Total mercury had the highest percentage of stations (97%) that exceeded background concentrations. Average background concentrations were used to express surficial sediment concentrations as a ratio above the background concentration as a means of estimating enrichment due to anthropogenic activities. The surficial concentrations of chromium, copper, lead,
1,915 657 1,164 548 547 470 1,920 NA
nickel, and zinc were compared to their respective background concentrations, and an enrichment ratio for each metal was calculated. The distribution of the average enrichment ratios for the five metals at each station is shown in Figure 3. The spatial pattern in anthropogenic enrichment was presumably an indication of the influence of both historical and present day human activities. However, the spatial distributions were also influenced by substrate type. The highest enrichment factors were associated with depositional areas in the major basins characterized by depositional sediment distributions as described by Thomas et al. (1972). Fine-grain silts and clays that adsorb contaminants more effectively
Spatial and Temporal Trends in Sediment Contamination in Lake Ontario
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TABLE 3. Lake Ontario background sediment contaminant concentrations, surficial basin-specific 75th percentiles, Canadian Sediment Quality Guidelines, and percentages of sites exceeding guideline values. Guideline values for nitrogen and phosphorus represent the Ontario Provincial lowest effect level (LEL) and severe effect level (SEL).
Arsenic (µg/g) Cadmium (µg/g) Chromium (µg/g) Copper (µg/g) Iron (%) Lead (µg/g) Manganese (µg/g) Mercury (µg/g) Nickel (µg/g) Nitrogen (µg/g) Phosphorus (µg/g) Zinc (µg/g) Aluminum (%) PCBs (ng/g) Dioxin (pg/g TEQs)
Background Concentrations <5 <1 27 50 3.5 15 730 0.04 43 2,560 740 103 1.88
Surficial vs. Background % Exceeding NA NA 77 62 6 91 83 97 67 74 77 80 0
Surficial 75th Percentile 30 3.3 54 86 2.98 110 4,300 0.79 77 5,100 1,200 360 1.4 140 180
Sediment Quality Guidelines % of sites Exceeding Ontario Ontario TEL PEL TEL PEL 5.9 17 93 67 0.596 3.53 75 17 37.3 90 69 1 35.7 196.6 72 0 35.0 0.174 550 600 123.1 34.1 0.85
91.3 0.486 4,800 2,000 314.8 277 21.5
76
38
87
62
78
35 0 58
FIG. 2. Profiles of total mercury (µg/g dry wt.), lead (µg/g dry wt.), nitrogen and phosphorus (µg/g dry wt.), and total DDT (ng/g dry wt.) levels in core samples from station 1034 in the Mississauga basin of Lake Ontario.
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FIG. 3. Maps of Lake Ontario showing surficial sediment enrichment by metals, total mercury concentrations (µg/g dry wt.) in 1998, total mercury concentrations (µg/g dry wt.) in samples collected in 1968, total lead concentrations (µg/g dry wt.) in 1998, total lead concentrations (µg/g dry wt.) in 1968, and total phosphorus concentrations (µg/g dry wt.) in 1998. Sediment enrichment ratio is the mean ratio of surficial to background concentrations for the 8 metals exceeding background concentrations. than sediments characterized by coarser sands that dominate sediments in the depositional basins. The spatial pattern evident in the surficial sediment enrichment map (Fig. 3) was reflective of the distribution of most individual contaminants. The highest total mercury concentrations were detected in the major lake basins (Fig. 3). Concurrent with the highest levels of mercury contamination, the depositional basins also exhibited the greatest numbers of exceedances of the Canadian Sediment Quality probable effects level (PEL, CCME 1999) guidelines (Table 3). Applicable guideline values are represented as breakpoints in the maps showing
the spatial distributions of individual contaminants. These recently adopted sediment quality guidelines can be applied as screening tools in the assessment of potential risk, and determination of the relative priority of sediment quality concerns. Two benchmarks have been established; the threshold effect level (TEL) represents a concentration below which adverse biological effects are expected to occur rarely, and; the probable effect level (PEL) that defines the concentration above which adverse effects are expected to occur frequently (CCME 1999). These guidelines were selected over other Canadian and U.S. guidelines because of their applicability to
Spatial and Temporal Trends in Sediment Contamination in Lake Ontario a broad suite of analytes, and because they are considered to represent a conservative approach to evaluating sediment quality (Rheaume et al. 2000). Comparisons of different sediment quality guidelines and their application can be found in Rheaume et al. (2000), Smith et al. (1996), and MacDonald et al. (2000). In cases where Canadian Federal guidelines were not available, such as in the case of nitrogen and phosphorus, applicable Ontario Provincial guidelines were used. MacDonald et al. (2000) provide an overview of the advantages and limitations of using sediment quality guidelines in the assessment of sediment quality. The mean 75th percentile surficial sediment concentration of mercury (0.79 µg/g) for the three lake basins was roughly 20 times the background concentration (0.04 µg/g, Table 3), and over 60% of the stations exceeded the Canadian PEL (0.486 µg/g, Table 3). The 1968 surficial sediment total mercury concentrations as reported by Thomas et al. (1972) are shown in Figure 3. Consistent with the temporal trends apparent in the core profile (Fig. 2), sediment concentrations were found to have decreased over the past thirty years throughout the entire lake. In 1968, the basin mean 75th percentile for mercury was 1.13 µg/g, compared to a value of 0.79 µg/g in 1998. The lake-wide average surficial sediment mercury concentration in 1968 was 0.79 µg/g, compared to a value of 0.59 µg/g in 1998. The average mercury concentration calculated for 1968 was based on data for the same 66 sites that were resampled in the1998 survey. The spatial pattern for surficial sediment total lead concentrations in Lake Ontario in 1998 is shown in Figure 3. Of the stations sampled in 1998, 38% exceeded the Canadian PEL guideline value (Table 3). The basin mean 75 th percentile was roughly 7-times the background concentration (Table 3). The 1968 pattern for total lead in surficial sediments in Lake Ontario as reported by Kemp and Thomas (1976) is shown in Figure 3; lake-wide concentrations have decreased over time, which was consistent with the observed trend in the core profile (Fig. 2). The lake-wide average surficial sediment lead concentration in 1968 was 125 µg/g (based on the 66 sites re-sampled in 1998), compared to a value of 69 µg/g in 1998. In 1968, the basin mean 75th percentile for lead was 182 µg/g, compared to a value of 104 µg/g in 1998. Control measures restricting the use of leaded gasoline have undoubtedly contributed to the observed decreases. Spatial distributions of other metals exhibited spatial patterns similar to lead and mercury, including
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arsenic (PEL exceeded at 67% of the stations), zinc (PEL exceeded at 35% of the stations), and cadmium (PEL exceeded at 17% of the stations). Total nitrogen (data not shown) and total phosphorus (Fig. 3) concentrations, compared to Ontario Provincial Sediment Quality Guideline lowest effect level (LEL) and severe effect level (SEL, Persaud et al. 1993), depicted more widespread spatial contamination compared to metals that included areas of the Kingston Basin that typically did not exhibit levels of organic contaminants and metals as high as the three other lake basins. However, none of the stations exceeded the Ontario provincial SEL. Polychlorinated Dibenzo-p-dioxins and Dibenzofurans Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/PCDFs) were analyzed in a subset of roughly half of the survey stations (Fig. 4); concentrations were expressed as toxic equivalents (TEQs) calculated using the International Toxicity Equivalency Factor (ITEF) method (Van den Berg et al. 1998). Data for a smaller subset of PCDDs/PCDFs in Lake Ontario were previously reported (Marvin et al. 2002). The spatial pattern observed was similar to the patterns for metals and the basin mean 75th percentile values of PCDDs/PCDFs, expressed as TEQs (pg/g), are shown in Table 3. These contaminants were particularly prevalent in the depositional basin sediments as evidenced by a 75 th percentile PCDD/PCDF TEQ value of 183 pg/g, which significantly exceeded the Canadian PEL guideline value of 21.5 pg/g TEQs by a factor of roughly nine-fold. The lake-wide average PCDD/PCDF value of 111 pg/g TEQs exceeded the PEL by roughly five-fold; in total, over half of the stations in Lake Ontario exceeded the PEL. Sediments from the three major depositional basins were enriched in the higher-chlorinated PCDF homologs and 2,3,7,8tetrachlorodibenzodioxin and 1,2,3,4,7,8-hexachlorodibenzofuran congeners, which implicated the Niagara River as a potential source (Marvin et al. 2002, Woodfield and Estabrooks 1999). Consumption advisories for PCDDs/PCDFs have been implemented for some fish species in Canadian waters of Lake Ontario (Ontario Ministry of the Environment 2001). Temporal trends in accumulation of PCDDs/ PCDFs in Lake Ontario sediment were previously studied using dated slices from a core sampled from the Mississauga basin (Marvin et al. 2002). Levels
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FIG. 4. Lake Ontario surficial sediment polychlorinated dibenzo-p-dioxin and dibenzofuran concentrations (pg/g dry wt. TEQ) in 1998, total polychlorinated biphenyl concentrations (ng/g dry wt.) in 1998, and total DDT (ng/g dry wt.) in 1998. of PCDDs/PCDFs increased rapidly in the early part of the 20th century, remained at a concentration of approximately 300 pg/g TEQs during the period of roughly 1950 to 1970, and then decreased to approximately 100 pg/g TEQs between 1970 and 1980. Levels of PCDD/PCDF contamination appear to have leveled off in the period of 1980 to 1998; these observations were consistent with previous findings (Pearson et al. 1997, Pearson et al. 1998). Polychlorinated Biphenyls and Organochlorine Pesticides The pattern of polychlorinated biphenyl (PCB) and organochlorine contamination in Lake Ontario surficial sediments was similar to metals. The lakewide average total PCB concentration in Lake On-
tario in 1998 was 100 ng/g (Fig. 4), while the mean basin 75th percentile was 141 ng/g (Table 3). None of the stations surveyed in Lake Ontario in 1998 exceeded the Canadian PEL for total PCBs (277 ng/g). In comparison, total PCB concentrations for the three major lake basins in 1981 ranged from 510 ng/g to 630 ng/g; the Kingston basin mean total was 200 ng/g (Oliver et al. 1989). The DDT compounds were quite prevalent in sediments in the major depositional basins; total DDT (sum of the six individual o,p′- and p,p′-DDD, DDE and DDT compounds) exhibited a lake-wide average value of 32.0 ng/g (Fig. 4). The p,p′-isomers were detected at higher concentrations than the o,p′-isomers, with the parent p,p′ DDT compound (3.77 ng/g lakewide average) generally detected at lower concentrations than the anaerobic metabolite p,p’-DDD
Spatial and Temporal Trends in Sediment Contamination in Lake Ontario (9.27 ng/g lake-wide average) and the aerobic metabolite p,p′-DDE (14.7 ng/g). Mirex was also frequently detected; the lake-wide average of 6.6 ng/g represented a roughly 80% reduction from the corresponding average (35 ng/g) determined for samples collected in 1981 (Oliver et al. 1989). Dieldrin was frequently detected, but the lake-wide average of 1.34 ng/g was relatively low. The lakewide average concentration of hexachlorobenzene (HCB) in 1998 was 22.9 ng/g, compared to concentrations for the three major lake basins in 1981 that ranged from 100 ng/g to 130 ng/g (Oliver et al. 1989). Accumulation of organochlorine compounds was also studied through analyses of dated slices from box cores from station 1034 in the Mississauga basin; however, assigned dates based on different 210Pb dating models were inconsistent with known
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production and usage patterns. These discrepancies may have resulted from sediment mixing, contaminant diffusion, or loss of integrity of the core during sampling or sectioning. Reports by Oliver et al. (1989), Wong et al. (1995) and Eisenreich et al. (1989) generally showed maximum accumulation of DDT in Lake Ontario sediments occurred in the late 1950s, while accumulation of PCBs and mirex was greatest in the mid-1960s. The overall shape of our core profiles of organic contaminants including DDT (Fig. 2) and PCBs (Fig. 5) are similar to those of the other studies, and allow an assessment of temporal trends in contaminant accumulation and estimates of reductions from peak levels. Surficial concentrations for mirex and PCBs were roughly 40% lower than maximum concentrations at depth in the core, while total DDT was 60% lower. The relative contributions of the individual homologs to
FIG. 5. Profiles of selected polychlorinated biphenyl homologs and total PCBs in a box core sample from station 1034 in the Mississauga basin of Lake Ontario.
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the composition of total PCBs varied with depth (Fig. 5). Below the depth of maximum accumulation of PCBs (5 cm), relative contributions of the lower chlorinated (tri-penta) congeners generally decreased while relative contributions of the higher chlorinated (hepta-nona) increased. These data are in agreement with those of Oliver et al. (1989) and Wong et al. (1995). The core profile for the DDT compounds (Fig. 2) was similar to that of a core collected from the Niagara Basin by Oliver et al. (1989) in 1982. As with the surficial sediment samples, the p,p′-DDD and p,p′-DDE metabolites were predominant. We are currently collecting additional core samples in order to attempt to achieve profiles that exhibit greater consistency with known production and usage, and for further study of accumulation rates and inventories. Influences on Spatial and Temporal Distributions of Contaminants The predominant circulation patterns in Lake Ontario resemble a counterclockwise gyre (Pickett and Bermick 1977) that contributes to the consistency in distributions of contaminants across the major lake basins. For example, Thomas (1972) reported that the mercury distribution in Lake Ontario was related to this surface water circulation pattern, and that mercury was ultimately deposited at downstream locations. In general, the highest contaminant concentrations for the 1998 sediment survey were detected in the depositional areas. Greater than 50% of the stations surveyed in Lake Ontario exceeded the Canadian PEL for mercury and PCDDs/PCDFs. The maps showing the distributions of the individual contaminant classes were generally similar to those determined by Oliver et al. (1989), in that contamination was distributed roughly uniformly across the three major depositional basins, while the Kingston basin exhibited correspondingly lower levels. The results of Oliver et al. (1989) were spurious compared to previous studies (Van Hove Holdrinet et al. 1978, Frank et al. 1979), in that the magnitude of contamination by a number of compounds including PCBs, DDT, and mirex, were higher, compared to the earlier studies. These differences were attributed to differences in sampling protocols and analytical methods. Frank et al. (1979) employed a shipek sampling protocol, which may have resulted in loss of some surficial sediment, and used packed-column GC to measure organic contaminants. Our 1998 study employed sampling (mini-box core) and analytical (capillary
column GC) methods similar to those of Oliver et al. (1989). Any differences in sampling and analytical protocols should be considered in comparing the 1998 data, and historical data. However, in considering the banning of DDT and PCBs, the phasing out of leaded gasoline, and the subsequent well documented decreases in loadings, the comparisons with data from Oliver et al. (1989) and Frank et al. (1979) appear reasonable. There are numerous reports in the literature (Kuntz and Warry 1983, Warry and Chan 1981, Jaffe and Hites 1986, Whittle and Fitzsimons 1983, Durham and Oliver 1983, Van Hove Holdrinet et al. 1978) that provide compelling evidence for the Niagara River as a primary source of many contaminants in Lake Ontario, including mercury and PCBs. In contrast to other Laurentian Great Lakes such as Lake Superior, Lake Ontario is more significantly impacted by local contaminant sources, compared to atmospheric deposition. Thompson et al. (1993) estimated that the Niagara River contributes two-thirds of the total loadings of contaminants, including PCBs and lead, to Lake Ontario. Diamond et al. (1993) reported that control of landbased sources is needed to reduce mercury contamination in Lake Ontario, in contrast to Lake Superior where atmospheric sources predominate. Pearson et al. (1998) estimated that 65–95% of PCDD accumulation and greater than 95% of PCDF accumulation in Lake Ontario was due to the influence of non-atmospheric sources, including the Niagara River. The Niagara River watershed in western New York is replete with numerous hazardous waste facilties (Jaffe and Hites 1986, Howdeshell and Hites 1996), some of which contain significant inventories of PCDDs/PCDFs. The influence of the Hyde Park dump, which is linked to the Niagara River via Bloody Run Creek, has been the focus of several studies (Jaffe and Hites 1986, Howdeshell and Hites 1996). This facility was closed in 1975, but sediment sampling conducted in 1993 determined that contaminants exclusively associated with this site continued to migrate from the dump, and were ultimately deposited in open lake sediments of Lake Ontario (Howdeshell and Hites 1996). More recent data from sediment and biomonitoring studies conducted during the period 1995–1997 in the Niagara River, at sites including Bloody Run Creek (Hyde Park) and Pettit Flume (Tonawanda Island), showed high levels of PCDD/PCDF contamination (Richman 1999, Woodfield and Estabrooks 1999). These studies indicated that hazardous waste sites continue to be
Spatial and Temporal Trends in Sediment Contamination in Lake Ontario sources of significant quantities of PCDDs/PCDFs to the Niagara River. However, while contamination of Lake Ontario from the Niagara River watershed reportedly continued to occur into the 1980s, the severity of pollution was reduced from the highest levels of the 1960s (Durham and Oliver 1983). Wong et al. (1995) estimated that accumulation rates of some contaminants measured during the mid-1990s were 15–30% of earlier peak accumulation rates, but had remained relatively constant since the mid-1980s. CONCLUSIONS The observed spatial trends in sediment contamination in Lake Ontario were similar for a number of compound classes including total PCBs, total DDT, polychlorinated dibenzo-p-dioxins and dibenzofurans, organochlorine pesticides, and a host of metals, including total mercury and lead. The highest levels of contamination were associated with finegrained sediments confined to the three major lake basins, while stations characteristic of inshore environments exhibited relatively lower contaminant levels. Presumably, these trends were influenced by industrial activities in the watersheds and along major tributaries, including the Niagara River; contaminated sediment originating within the tributary watersheds is ultimately deposited in the depositional basin areas of Lake Ontario. Other major influences in the observed trends may have included open-lake disposal of dredged material, atmospheric deposition and remediation of contaminated areas. In general, levels of contaminants in Lake Ontario surficial sediments decreased over the period 1968 to 1998. This trend was also evidenced by individual contaminant profiles in core samples from one of the three major lake basins (station 1034, Mississauga basin, Fig. 1). Lake-wide surficial sediment concentrations of mercury decreased from 0.79 µg/g in 1968 to to 0.59 µg/g in 1998, while lead concentrations decreased from 125 µg/g to 69 µg/g over the same time period. Similarly, core profiles showed a 40% and 60% decline from peak concentrations for total PCBs and total DDT, respectively. Surficial sediment concentrations in Lake Ontario in 1998 also indicated improvement in environmental quality compared to studies conducted in the 1960s and 1980s. However, assessment of current spatial trends in contamination, and temporal trends in PCDDs/PCDFs using a dated core, indicated that the major depositional basins
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are still being subjected to active loadings of contaminants. Concentrations of PCDDs/PCDFs in Lake Ontario sediments in 1998 remained well above ambient environmental background levels. The Niagara River watershed, with its many hazardous waste facilities, appears to remain a primary contributor. Despite the substantial improvement in Lake Ontario sediment quality over the period 1968 to 1998, sediments in many areas of Lake Ontario still exceeded the Canadian Sediment Quality Guidelines probable effect level (PEL) guidelines. These guideline exceedences were prevalent in all three major lake basins. Exceedences of the Canadian Sediment Quality PELs were most numerous for arsenic (67%), mercury (62%), and PCDDs/PCDFs (58%). None of the stations surveyed exceeded the Canadian PEL for total PCBs. Some pollutants identified as exceeding the guideline values, such as mercury and PCDDs/PCDFs, are responsible for the fish consumption advisories in Lake Ontario. ACKNOWLEDGMENTS The authors thank the Captain and Crew of the Canadian Coast Guard Ship Limnos, staff of the National Water Research Institute Technical Operations, Environment Canada, and staff of the Dioxins and Toxic Organics Section, Laboratory Services Branch, Ontario Ministry of the Environment. REFERENCES Canadian Council of Ministers of the Environment (CCME). 1999. Canadian Environmental Quality Guidelines. Winnipeg, Manitoba. Diamond, M.L., Mackay, D., and Sang, S. 1993. A mass balance analysis of mercury in Lakes Ontario and Superior. In 36th Conf. Internat. Assoc. Great Lakes Res., Program and Abstracts, pp. 133. Internat. Assoc. Great Lakes Res. Durham, R.W., and Oliver, B.G. 1983. History of Lake Ontario contamination from the Niagara River by sediment radiodating and chlorinated hydrocarbon analysis. J. Great Lakes Res. 9:160–168. Eisenreich, S.J., Cope, P.D., Robbins, J.A., and Bourbonniere, R. 1989. Accumulation and diagenesis of chlorinated hydrocarbons in lacustrine sediments. Environ. Sci. Technol. 23:1116–1126. Frank, R., Thomas, R.L., Holdrinet, M., Kemp, A.L.W., and Braun, H.E. 1979. Organochlorine insecticides and PCB in surficial sediments (1968) and sediment cores (1976) from Lake Ontario. J. Great Lakes Res. 5:18–27. Howdeshell, M.J., and Hites, R.A. 1996. Is the Hyde
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Park Dump, near the Niagara River, still affecting the sediment of Lake Ontario? Environ. Sci. Technol. 30:969–974. Jaffe, R., and Hites, R.A. 1986. Fate of hazardous waste derived organic compounds in Lake Ontario. Environ. Sci. Technol. 20:267–274. Kemp, A.L.W., and Thomas, R.L. 1976. Impact of man’s activities on the chemical composition in the sediments of Lakes Ontario, Erie, and Huron. Water, Air, and Soil Pollution 5:469–490. Kuntz, K.W., and Warry, N.D. 1983. Chlorinated organic contaminants in water and suspended sediments of the lower Niagara River. J. Great Lakes Res. 9:241–248. MacDonald, D.D., Ingersoll, C.G., and Berger, T.A. 2000. Development and evaluation of consensus-based sediment quality guidelines for freshwater ecosystems. Arch. Environ. Contam. Toxicol. 39:20–31 Marvin, C.H., Charlton, M.N., Reiner, E.J., Kolic, T., MacPherson, K., Stern, G.A., Braekevelt, E., Estenik, J.F., Thiessen, P.A., and Painter, S. 2002. Surficial sediment contamination in Lakes Erie and Ontario: A comparative analysis. J. Great Lakes Res. 28:437–450. McLaren, J.W. 1981. Simultaneous Determination of Major, Minor, and Trace Elements in Marine Sediments by Inductively Coupled Plasma Atomic Emission Spectrometry. Analytical Chemistry Section, Chemistry Division, National Research Council of Canada, Ottawa, Ontario, Canada. Mudroch, A. 1993. Lake Ontario sediments in monitoring pollution. Environmental Monitoring and Assessment 28:117–129. ———, and MacKnight, S.D. 1991. Handbook of Techniques for Aquatic Sediments Sampling. Boca Raton, Florida: CRC Press. ———, Serazin, L., and Lomas, T. 1988. Summary of surface and background concentrations of selected elements in Great Lakes sediments. J. Great Lakes Res. 14:241–251. National Laboratory for Environmental Testing (NLET). 1997. Manual of Analytical Methods, Volume 1. Burlington, Ontario: Environment Canada. Oliver, B.G., Charlton, M.N., and Durham, R.W. 1989. Distribution, redistribution, and geochronology of polychlorinated biphenyl congeners and other chlorinated hydrocarbons in Lake Ontario sediments. Environ. Sci. Technol. 23:200–208. Ontario Ministry of the Environment (OME). 2000. The determination of polychlorinated dibenzo-p-dioxins, polychlorinated furans and dioxin-like PCBs in environmental matrices by GC-MS. Environment Ontario Laboratory Services Branch Method DFPCB-E3418. Toronto, ON, Canada. ———. 2001. Guide to eating Ontario sport fish. 21st Edition. Queen’s Printer for Ontario, Toronto, ON, CA. Pearson, R.F., Swackhamer, D.L., Eisenreich, S.J., and
Long, D.T. 1997. Concentrations, accumulations, and inventories of polychlorinated dibenzo-p-dioxins and dibenzofurans in sediments of the Great Lakes. Environ. Sci. Technol. 31:2903–2909. ———, Swackhamer, D.L., Eisenreich, S.J., and Long, D.T. 1998. Atmospheric inputs of polychlorinated dibenzo-p-dioxins and dibenzofurans to the Great Lakes: Compositional comparison of PCDD and PCDF in sediments. J. Great. Lakes Res. 24:65–82. Persaud, D., Jaagumagi, R., and Hayton, A. 1993. Guidelines for the protection and management of aquatic sediment quality in Ontario. Ontario Ministry of Environment. Toronto. Pickett, R.L., and Bermick, S. 1977. Observed resultant circulation in Lake Ontario. Limnol. Oceanogr. 22:1071–1076. Pirrone, N., Allegrini, I., Keeler, G.J., Nriagu, J.O., Rossmann, R., and Robbins, J.A. 1998. Historical atmospheric mercury emissions and depositions in North America compared to mercury accumulations in sedimentary records. Atmospheric Environment 32:929–940. Rheaume, S.J., Button, D.T., Myers, D.N., and Hubbell, D.L. 2000. Areal distribution and concentrations of contaminants of concern surficial streambed and lakebed sediments, Lake Erie-Lake St. Clair drainages, 1990–97. Water Resources Investigations Report 00-4200. United States Department of the Interior, United States Geological Survey. Richman, L.A. 1999. Niagara River mussel biomonitoring program, 1997. Water Monitoring Section, Environmental Monitoring and Reporting Branch, Ontario Ministry of the Environment, Toronto, Ontario. Smith, S.L., MacDonald, D.D., Keenleyside, K.A., Ingersoll, C.G., and Field, L.J. 1996. A preliminary evaluation of sediment quality assessment values for freshwater ecosystems. J. Great Lakes Res. 22:624–638 Thomas, R.L. 1972. The distribution of mercury in the sediments of Lake Ontario. Can. J. Earth Sci. 9:636–651. ———, Kemp, A.L.W., and Lewis, C.F.M. 1972. Distribution, composition and characteristics of the surficial sediments of Lake Ontario. J. Sedimentary Petrology 42(1):66–84. Thompson, S., Sang, S., and Mackay, D. 1993. Impacts of reduced loadings of six persistent toxics on Lake Ontario concentrations. In 36th Conf. Internat. Assoc. Great Lakes Res., Program and Abstracts, pp. 134. Internat. Assoc. Great Lakes Res. Turner, L.J., and Yang, F. 2000. 210Pb dating of lacustrine sediments from Lake Ontario (station 1034, core 223). National Water Research Institute, Burlington, ON. NWRI report 2000-1. United States Environmental Protection Agency (USEPA). 1981. Procedures for Handling and Chemical Analysis of Sediment and Water Samples. Environmental Laboratory, US. Army Engineer Water-
Spatial and Temporal Trends in Sediment Contamination in Lake Ontario ways Experiment Station, Vicksburg, Mississippi, pp. 3–118. Van den Berg, M., Birnbaum, L., Bosveld, B.T.C., Brunstrom, B., Cook, P., Feeley, M., Giesy, J.P., Hanberg, A., Hasegawa, R., Kennedy, S.W., Kubiak, T., Larsen, J.C., Rolaf van Leeuwen, F.X., Liem, A.K.D., Nolt, C., Peterson, R.E., Poellinger, L., Safe, S., Schrenk, D., Tillitt, D., Tysklind, M., Younes, M., Waern, F., and Zacharewski, T. 1998. Toxic equivalency factors (TEFs) for PCBs, PCDDs, PCDFs for humans and wildlife. Environ. Health Perspect. 106:775–792. Van Hove Holdrinet, M., Frank, R., Thomas, R.L., and Hetling, L.J. 1978. Mirex in the sediments of Lake Ontario. J. Great Lakes Res. 4:69–74. Warry, N.D., and Chan, C.H. 1981. Organic contaminants in the suspended sediments of the Niagara River. J. Great Lakes Res. 7:394–403.
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Whittle, D.M., and Fitzsimons, J.D. 1983. The influence of the Niagara River on contaminant burdens of Lake Ontario biota. J. Great Lakes Res. 9:295–302. Wong, C.S., Sanders, G., Engstrom, D.R., Long, D.T., Swackhamer, D.L., and Eisenreich, S.J. 1995. Accumulation, inventory, diagenesis of chlorinated hydrocarbons in Lake Ontario sediments. Environ. Sci. Technol. 29:2661–2672. Woodfield, K., and Estabrooks, F. 1999. Dioxin/furan in Lake Ontario tributaries 1995–1997. Bureau of Watershed Assessment and Research, Division of Water, New York State Department of Environmental Conservation, Albany, New York. Submitted: 16 September 2002 Accepted: 27 February 2003 Editorial handling: Ronald Rossmann
Spatial and Temporal Trends in Sediment Contamination in Lake Ontario Christopher H. Marvin1*, Murray N. Charlton1, Gary A. Stern2, Eric Braekevelt2, Eric J. Reiner3, and Scott Painter1 1Environment
Canada 867 Lakeshore Road, PO Box 5050 Burlington, Ontario L7R 4A6 2Freshwater
Institute, Department of Fisheries and Oceans 501 University Crescent Winnipeg, Manitoba R3T 2N6
3Ontario
Ministry of the Environment 125 Resources Road Toronto, Ontario M9P 3V6
ABSTRACT. A Lake Ontario sediment survey was conducted in 1998 to characterize spatial and temporal trends in contamination, and for comparison with data from previous surveys in order to assess any changes in environmental quality since the advent of measures to reduce contaminant sources. This survey was also designed to assist in tracing possible sources and vectors of contamination, and to identify areas where contamination exceeded Canadian sediment quality guidelines for the protection of aquatic biota. In addition, levels of a suite of eight metals were compared to pre-colonial concentrations, and surficial sediment enrichment factors were calculated. The highest levels of contaminants were observed at stations within the three major depositional basins; the spatial distributions across the individual basins were similar. Lake-wide averages for polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/PCDFs) were 100 ng/g and 111 pg/g TEQs, respectively. Concentrations of mercury and lead were observed to have decreased from 0.79 µg/g and 125 µg/g, respectively, in 1968 to 0.59 µg/g and 69 µg/g, respectively, in 1998. Exceedances of the Canadian Sediment Quality Probable Effect Level (PEL) guidelines were most numerous for arsenic (67%), PCDDs/PCDFs (58%), mercury (62%) and lead (38%). Concentrations of PCBs at all sampling stations were below the Canadian PEL of 277 ng/g. INDEX WORDS: Lake Ontario, polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins, mercury, lead, metals, sediment.
INTRODUCTION The presence of persistent pollutants can adversely impact Great Lakes wildlife, biodiversity, and aquatic ecosystems. Environment Canada, together with collaborating agencies, conducts Great Lakes sediment surveys to measure the occurrence and spatial distribution of environmental contaminants in order to further understanding of the role human activities play in releasing toxic substances *Corresponding
to the environment, and to provide information for devising effective strategies to mitigate potentially deleterious health effects. Earlier Environment Canada surveys in Lake Ontario were conducted to characterize the spatial extent of surficial sediment contamination by a variety of contaminants including metals (Kemp and Thomas 1976), polychlorinated biphenyls (PCBs) and organochlorine pesticides (Frank et al. 1979), mercury (Thomas 1972), and mirex (Van Hove Holdrinet et al. 1978). In addition, the cultural impact of human activities over time was assessed using sediment cores (Kemp
author. E-mail: [email protected]
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and Thomas 1976, Mudroch 1993, Frank et al. 1979); levels of metals including total mercury and lead were compared to pre-colonial concentrations. In 1998, Environment Canada revisited 66 of the original 229 sites from the 1968 survey by Frank et al. (1979) in order to undertake a comprehensive suite of analyses for assessment of contemporary sediment contamination relative to sediment quality guidelines, and to assess any changes in sediment contaminant concentrations from earlier surveys conducted in 1968 and 1976. Spatial and temporal distributions of selected contaminants in Lake Ontario sediments collected during the 1998 survey have already been reported as part of a study comparing surficial sediment contamination in Lakes Erie and Ontario (Marvin et al. 2002). This paper presents a more detailed overview of the spatial and temporal characterization of sediment contamination in Lake Ontario using results from 1998 and data from historical surveys, particularly the 1968 survey. Data for metals, (including total mercury and lead), nutrients, polychlorinated biphenyls (PCBs), and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/PCDFs) are presented. The results are also presented within the context of the Canadian Sediment Quality Guidelines (CCME 1999). These guidelines are routinely applied as screening tools in the assessment of potential risk and determination of the relative priority of sedi-
ment quality concerns. In addition, the ratios of surficial sediment concentrations to background concentrations were determined for eight metals, and the average values expressed as “enrichment ratios.” These enrichment ratios were used to assess the general influence of anthropogenic activities on sediment quality in Lake Ontario. METHODS Sample Collection Surficial sediment samples were collected aboard the Canadian Coast Guard Ship Limnos in 1998 from sixty-six stations (Fig. 1) using a mini box core sampling procedure. The top 3 cm of the sediment were sub-sampled from the mini-box core for the analyses of organic contaminants, metals, grain size, and nutrients. Samples for organic contaminant analyses were collected in solvent-washed glass jars. Samples for other characterizations were collected in either high-density polypropylene or Teflon jars. All samples were frozen for transport to the laboratory. At an index station in the Mississauga basin (station 1034), mini box core and benthos gravity core samples were obtained for surficial sediment sampling, and sampling with sediment depth. Cores were immediately extruded and sectioned on board the vessel. Butyrate core tubes (6.7 cm diameter)
FIG. 1. Map of Lake Ontario showing sampling stations for the 1998 sediment survey. Also shown are the major non-depositional (near shore) and depositional basin areas of Lake Ontario.
Spatial and Temporal Trends in Sediment Contamination in Lake Ontario were used in conjunction with the corers. Mini box cores for the study of temporal accumulation of contaminants were sub-sampled in 1 cm increments from 0 to 15 cm, in 2 cm increments from 16 to 30 cm, and in 5 cm increments to a depth of 40 cm. Benthos gravity cores were sub-sampled in 1 cm intervals from 0–1 cm, 9–10 cm, 14–15 cm, 19–20 cm, 29–30 cm, and every 10 cm thereafter (i.e., 39–40 cm, 49–50 cm) to the bottom of the core. Core profiles for mercury, lead, nitrogen, and phosphorus presented in this paper represent the combination of mini-box core data to a depth of 40 cm, and benthos core data at depths greater than 40 cm. A detailed description of the coring methods, including sampling protocols and equipment, can be found in Mudroch and MacKnight (1991). Analyses Extraction of freeze-dried sediments (10-15 g) was performed using an Accelerated Solvent Extractor (ASE) (Dionex). Dichloromethane (DCM) was used as the extraction solvent. Solvent extracts were evaporated, exchanged into hexane, and separated into three fractions of increasing polarity on Florisil (8 g; 1.2% v/w water deactivated). The first fraction was eluted with hexane and contained PCBs, along with p,p′-DDE, trans-nonachlor, mirex and a small portion of the toxaphene congeners. The eluate was treated with activated copper powder to remove elemental sulfur followed by addition of aldrin for volume correction. Solvent extracts were analyzed by high-resolution gas chromatography (HRGC) using a Varian 3600 GC (Varian Instruments, Palo Alto, CA) with a 60 m × 0.25 mm i.d. DB-5 column (stationary phase thickness 0.25 µm, J&W Scientific) equipped with a 63Ni electron capture detector (ECD). Hydrogen was used as the carrier gas (initial flow 1 mL/min) with nitrogen as a make-up gas (40 mL/min). A total of 103 PCB congeners (including co-eluting congeners) were quantified using external standard mixtures (Ultra Scientific, North Kingstown, RI) that were run after every six samples. A few congeners, for which standards were not available, were quantified with response factors (RFs) estimated from other congeners of the same chlorine number and similar retention time. Total PCB (ΣPCB) values were calculated as the sum of all congeners. Recovery standards PCB 30 and octachloronaphthalene (OCN) were added to all sediment samples prior to extraction. Recoveries of the surrogates were uniformly greater than 90% and no corrections were made for
319
recoveries. Procedural blanks were run with every 10 sediment samples. Procedural blanks and surrogate recoveries were also evaluated against criteria established by the National Laboratory for Environmental Testing (Environment Canada) resulting from replicate analyses of SRMs over a two-year period. Field replicates were typically within 30%. Analyses of sediment for PCDDs/PCDFs were carried out using Ontario Ministry of the Environment (OME) standard methods (OME 2000). Prior to extraction, samples were spiked with 13 C-labelled surrogate standards. Toluene sediment extracts were subjected to a sequential cleanup that included a modified silica column, alumina column, and an Amoco PX21 carbon-activated silica column procedure (OME 2000). Analysis by high-resolution gas chromatography—high-resolution mass spectrometry was carried out in selected ion monitoring (SIM) mode using a VG Autospec high-resolution mass spectrometer equipped with a Hewlett-Packard 6890 gas chromatograph (Agilent Technologies Inc., Mississauga, ON). Chromatographic separation was carried out using a 0.25 mm i.d. 60 m DB-5 column with a 0.25 µm stationary phase thickness. Procedural blanks and precision and recovery samples were processed with each sample batch and all data for individual samples were checked against surrogate recoveries. Toxic equivalents (TEQs) were calculated using the International Toxicity Equivalency Factor (ITEF) method (Van den Berg et al. 1998); congeners present at levels lower than the method detection limits were given zero values for TEQ calculations. Trace metals and mercury analyses were performed by Seprotech Laboratories (Ottawa, ON). Trace metal concentrations were determined by a hot aqua-regia extraction with measurement by ICP-AES as described in McLaren (1981). Total mercury was determined by digestion with hot nitric acid and hydrochloric acid followed by cold vapour atomic absorption spectrometer (USEPA 1981). Nitrogen was measured using a PerkinElmer 2400 CHN elemental analyzer as N 2 after oxidation of sediment (NLET 1997). Total phosphorus (organic + inorganic) was determined by conversion to orthophosphate followed by extraction in 0.1 N HCl and subsequent conversion to molybdophosphoric acid. Reduction with ascorbic acid resulted in formation of a molybophosphoric acid complex that was subsequently measured photometrically at 660 nm (NLET 1997).
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Marvin et al. RESULTS AND DISCUSSION
Sediment Distribution The convention for sediment characterization described by Thomas et al. (1972) was used to describe trends in sediment contamination related to sediment distribution and transport processes for Lake Ontario. Sediments collected during the 1998 survey were classified as non-depositional, consisting of bedrock, glacial tills, and glacio-lacustrine clays, or depositional, which were comprised of fine-grained post-glacial material including silts and clays that accumulate in deep water areas. Lake Ontario was classified according to three major depositional areas; the Niagara basin was separated from the Mississauga basin by the Whitby—Olcott sill, and the Scotch Bonnet sill separated the Mississauga basin from the Rochester basin (Fig. 1). The Kingston basin is located at the outflow of Lake Ontario at the head of the St. Lawrence River; however, this area receives reduced loadings of sediment from the main open lake area due to the presence of a major topographical barrier, the Duck-Galloo sill. Spatial and Temporal Distributions of Metals and Nutrients The metals data for surficial sediments from the each of the individual major lake basins (Tables 1 and 2) of Lake Ontario were assessed for spatial patterns to assist in identification of source areas, to identify areas of non-compliance with Canadian Sediment Quality Guidelines (Table 3), and, in conjunction with the core data, to assess surficial sediment enrichment compared to historical norms. Benthos and mini box-core samples from an individual site in the Mississauga basin (station 1034) were assumed to be generally representative of temporal gradients on a lake-wide basis, due to the homogeneity of fine-grained sediments across the three major lake basins (Mudroch 1993). There were no statistically significant trends among contaminant distributions across the three major lake basins (t-test, p < 0.05 and ANOVA). The benthos core profiles of most metals at station 1034 generally exhibited a gradient of increasing concentrations from the surface to concentration maximums at depths of approximately 5 cm to 10 cm, gradients of decreasing concentrations from depths of the observed maximum values down to approximately 40 cm, and then relatively constant concentrations from approximately 40 cm to the bottom of the
core. This general trend in sediment accumulation by metals is shown in core profiles from station 1034 (Mississauga basin) for mercury and lead (Fig. 2). The lead profile was presumably primarily influenced by anthropogenic activities, the most important of which was the use and subsequent phasing-out of leaded gasoline. The sedimentation rate determined for the cores sampled at station 1034 was based on 210Pb dating of a box core sampled during the same survey in 1998 (Turner and Yang 2000). Uncompacted core mid-depths of 8.89 cm and 14.2 cm were estimated to represent mean dates of 1974 and 1959, respectively. Based on these data, peak accumulation of most metals in Lake Ontario sediments was estimated to have occurred in the early- to mid-1970s. Mudroch (1993) also estimated maximum lead contamination in Lake Ontario sediments occurred in the early 1970s. The core profile for mercury was similar to those of Lake Ontario cores analyzed and dated by Pirrone et al. (1998), in that the highest levels were detected in sections corresponding to the Second World War. Our mercury core profile indicates that mercury contamination began to trend toward decreasing values after 1980, while data from Pirrone et al. show that mercury accumulation rates began to decrease significantly in the late 1960s. In contrast to the core profile observed for metals, total phosphorus and nitrogen showed a general trend toward increasing concentrations from a depth roughly representing the turn of the 20th century to the surface of the core (Fig. 2). The individual basin background metal concentrations were determined from the average of the concentrations in sections at depths greater than 40 cm in a single benthos core from station 1034 (Table 3); the percentages of stations exceeding basin-specific background concentrations for each chemical were also summarized. Mudroch et al. (1988) reported background concentrations ranging from 18 µg/g to 32 µg/g for lead and 0.03 µg/g to 0.09 µg/g for mercury. The background levels of metals shown in Table 3 are thought to be generally representative of sediment concentrations prior to the onset of significant anthropogenic activities. However, Pirrone et al. (1998) estimated that atmospheric emissions of mercury in North America peaked in the late 1870s as a result of processing gold and silver. Therefore, “background” concentrations for mercury may not entirely predate industrial activities. There were no discernable differences in the extent of exceedances of background metal concentrations among the three indi-
Spatial and Temporal Trends in Sediment Contamination in Lake Ontario
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TABLE 1. Total trace metal, nitrogen, phosphorus, iron, manganese, and aluminum data from surficial (0–3 cm) sediment samples in the Niagara and Mississauga basins of Lake Ontario in 1998. Latitude Longitude (°N) (°W) Site Niagara Basin
As Cd Cr µg/g µg/g µg/g
43-12-59 43-21-40 43-21-39 43-21-41 43-21-39 43-21-41 43-26-01 43-30-18 43-30-20 43-39-00 43-39-01 43-17-19 43-16-49
Cu µg/g
Pb µg/g
79-17-56 79-42-01 79-30-00 79-17-59 79-05-58 78-54-00 79-24-00 79-18-01 79-05-58 79-06-00 78-54-01 79-50-30 79-52-20
1001 1002 1003 1004 1005 1006 1007 1020 1021 1035 1036 1073 1074
4.6 14.7 19.2 33.3 26.7 16.9 34.5 36.7 24.6 17.0 22.2 28.5 19.7
1.1 29.4 31.0 24.1 1.7 45.3 41.9 56.1 3.6 58.3 83.7 103.7 3.4 59.5 88.3 107.0 3.0 52.4 71.1 82.5 1.6 46.7 49.8 55.6 4.1 63.1 102.7 123.2 3.6 60.4 98.1 129.7 1.2 37.4 56.5 47.6 1.8 10.1 17.7 12.1 ND 24.1 35.0 47.2 ND 109.8 106.6 196.6 1.4 69.8 79.0 112.0
Mississauga Basin 43-26-04 78-41-57 43-26-01 78-29-59 43-25-57 78-17-52 43-26-00 78-05-55 43-25-58 77-53-59 43-21-39 77-41-52 43-30-20 78-41-56 43-30-20 78-29-59 43-30-18 78-17-59 43-30-20 78-06-00 43-30-19 77-53-59 43-30-20 77-42-00 43-34-39 78-11-58 43-38-58 78-42-01 43-39-00 78-29-59 43-39-00 78-17-59 43-39-00 78-05-59 43-38-57 77-54-01 43-39-00 77-42-01 43-47-39 78-41-58 43-47-38 78-29-56 43-47-38 78-18-02 43-47-41 78-06-01 43-47-38 77-54-01 43-47-40 77-42-02 43-38-56 78-13-26
1008 1009 1010 1011 1012 1013 1023 1024 1025 1026 1027 1028 1034 1037 1038 1039 1040 1041 1042 1052 1053 1054 1055 1056 1057 1082
6.6 7.0 16.2 32.9 44.0 7.0 28.8 17.9 19.8 6.9 13.4 17.2 40.2 21.0 28.2 10.8 22.4 24.0 28.0 14.0 ND 14.0 ND 29.3 4.6 11.9
0.7 1.8 1.8 2.3 1.2 0.7 3.8 3.9 4.1 3.6 2.6 0.5 3.4 5.8 3.7 2.9 4.4 3.9 3.9 ND ND 0.9 ND ND ND 0.8
Ni µg/g
Zn µg/g
29.1 128.3 27.0 169.8 70.5 322.4 89.4 365.3 64.5 267.6 46.1 210.6 98.8 401.2 95.3 410.2 50.0 179.3 19.1 31.0 34.5 131.4 43.2 1,342.7 37.9 877.2
11.6 14.4 5.2 14.9 46.2 51.0 60.8 48.7 51.0 54.9 61.9 54.5 48.2 53.6 63.3 57.1 51.4 61.6 69.1 65.7 19.5 18.5 20.4 22.2 61.0 104.6 136.2 95.8 52.5 90.4 111.3 76.3 58.2 89.9 116.3 80.7 51.3 81.5 92.5 72.4 51.6 80.0 97.4 69.9 18.0 28.3 27.3 28.2 63.7 93.2 144.9 80.4 51.8 108.6 118.3 85.8 53.0 98.8 120.0 85.1 53.8 97.8 115.3 78.3 60.3 98.9 131.5 84.9 53.2 98.7 120.7 99.4 62.9 100.9 118.7 100.2 4.2 8.0 36.0 45.9 5.1 7.3 28.6 28.7 17.9 17.3 54.9 56.4 5.2 3.7 6.5 7.5 14.6 15.1 14.4 16.0 8.3 7.7 11.7 19.6 35.7 39.7 48.9 32.8
41.0 217.3 235.5 238.4 267.0 92.3 455.4 368.5 394.6 326.2 321.4 97.8 436.9 371.8 397.4 384.1 435.1 402.9 413.0 50.7 27.6 74.1 11.2 50.0 21.6 223.7
Hg µg/g
N µg/g
P µg/g
Fe %
Mn µg/g
Al %
0.65 0.15 0.29 0.72 0.47 0.34 0.56 1.20 0.73 0.67 0.48 0.51 0.45
1,540 1,760 4,130 5,140 4,460 2,710 6,400 3,990 2,600 260 1,360 5,740 3,380
695 788 1,070 1,280 1,120 808 1,620 1,580 1,610 861 908 2,100 1,360
2.0 1.9 2.7 3.1 3.5 2.6 3.3 2.9 4.2 1.4 1.5 4.4 3.6
763 445 3,771 7,712 5,012 1,033 9,995 7,182 2,089 1,181 1,651 2,268 1,638
0.8 0.7 1.2 1.4 1.7 1.0 1.5 1.3 1.4 0.5 0.6 1.6 1.6
0.06 0.65 0.60 0.73 0.84 0.12 1.38 1.33 1.30 0.90 1.01 0.07 1.0 0.43 0.58 1.13 0.11 0.78 0.96 0.08 0.05 0.08 0.79 0.21 0.02 0.361
488 2,780 3,000 3,230 3,700 936 4,410 4,560 4,300 4,280 5,060 1,220 6,180 5,750 6,010 4,030 5,230 5,620 6,950 497 242 567 198 757 352 4,410
504 837 854 885 112 574 981 1,490 1,100 1,230 1,160 681 1,180 1,200 1,220 957 1,130 1,130 1,330 283 565 699 506 711 619 1,040
1.4 600 0.5 2.4 1,426 1.0 2.9 1,301 1.2 2.8 3,295 1.1 3.0 4,258 1.2 1.6 741 0.6 2.9 4,965 1.4 2.7 3,302 1.3 2.8 4,811 1.3 2.6 4,821 1.3 2.6 3,310 1.3 1.5 843 0.6 2.7 6,545 1.2 3.0 6,174 1.6 2.7 5,446 1.3 3.2 2,384 1.6 2.9 2,632 1.3 3.1 12,503 1.4 3.4 6,060 1.5 0.4 2,282 0.1 0.7 2,295 0.2 1.8 3,779 0.9 0.8 475 0.2 0.9 224 0.3 1.1 1,534 0.3 2.6 850 1.5
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TABLE 2. Total trace metal, nitrogen, phosphorus, iron manganese, and aluminum data from surficial. (0–3 cm) sediment samples in the Rochester and Kingston basins of Lake Ontario in 1998. Latitude Longitude (°N) (°W) Niagara Basin 43-21-43 77-30-02 43-21-36 77-17-58 43-21-40 77-05-58 43-21-41 76-54-00 43-25-58 76-47-59 43-30-21 77-30-06 43-30-16 77-17-57 43-30-21 77-05-58 43-30-21 76-53-59 43-30-19 76-42-00 43-39-01 77-29-56 43-39-01 77-18-00 43-38-58 77-06-00 43-39-01 76-54-00 43-39-00 76-41-59 43-38-58 76-35-59 43-39-00 76-30-00 43-39-00 76-18-00 43-47-38 77-30-00 43-47-40 76-53-58 43-47-37 76-41-58 43-47-41 76-30-01 44-34-41 76-30-00
Site
As Cd Cr µg/g µg/g µg/g
Cu µg/g
Pb µg/g
Ni µg/g
Zn µg/g
Hg µg/g
N µg/g
P µg/g
Fe %
Mn µg/g
Al %
1014 1015 1016 1017 1018 1029 1030 1031 1032 1033 1043 1044 1045 1046 1047 1048 1049 1050 1058 1060 1061 1062 1069
30.6 47.2 33.0 12.8 40.5 26.5 29.1 34.9 33.2 31.0 22.4 17.0 26.3 13.9 13.6 32.0 27.0 28.3 ND 24.3 29.9 32.4 25.8
1.1 0.7 1.8 0.9 1.1 3.3 3.4 2.8 3.4 2.4 2.9 3.3 2.6 3.1 2.4 1.3 ND ND ND 0.9 0.6 ND ND
52.6 46.0 45.4 26.4 47.7 48.9 59.5 59.8 48.9 51.3 60.7 56.2 53.1 55.5 51.1 46.5 45.8 15.2 7.7 44.4 37.4 28.9 36.8
61.2 58.2 56.3 25.7 57.4 87.2 87.2 82.3 84.4 72.6 92.6 85.2 76.5 72.1 68.1 60.6 46.2 9.1 4.5 62.0 51.7 35.2 49.3
67.2 59.2 59.0 29.4 66.8 96.3 113.6 119.1 101.9 93.3 110.1 97.8 84.9 89.3 79.5 62.5 54.9 15.4 8.1 54.0 44.8 30.6 44.1
64.6 53.9 55.1 30.7 61.1 87.7 77.8 75.8 80.7 68.6 86.1 85.5 76.9 71.9 64.3 57.0 49.4 12.0 13.7 51.1 44.8 31.7 42.5
263.5 229.8 232.0 124.4 240.7 347.3 393.8 371.2 335.9 310.3 363.3 337.7 310.9 313.5 283.7 239.9 199.2 59.8 19.5 213.4 184.2 136.5 176.1
0.77 0.65 0.68 0.28 0.68 0.90 1.11 1.15 0.86 0.79 0.66 0.87 0.70 0.72 0.78 0.58 0.79 0.28 0.02 0.51 0.48 0.37 0.65
6,510 4,010 3,700 1,750 3,510 5,894 4,965 5,030 6,060 4,630 6,380 6,390 4,840 4,300 4,600 4,690 3,950 568 222 5,090 4,840 4,000 3,860
1,100 1,050 1,110 745 926 948 1,050 1,200 1,310 834 1,210 1,290 1,100 838 870 1,470 1,200 617 528 997 1,140 818 936
2.9 2,094 3.0 3,600 2.9 3,145 1.8 708 2.8 2,353 2.9 7,042 2.7 4,041 2.7 2,681 3.2 12,268 2.8 4,080 3.0 3,531 3.3 5,133 3.3 4,353 3.0 2,310 3.0 2,517 3.0 4,482 2.4 2,476 0.9 305 1.0 687 2.9 2,096 2.8 2,308 2.0 687 2.9 1,848
1.2 1.2 1.2 0.7 1.1 1.2 1.2 1.2 1.6 1.2 1.5 1.4 1.4 1.3 1.3 1.5 0.9 0.3 0.2 1.6 1.4 1.0 1.4
Kingston Basin 43-58-31 76-52-58 43-56-19 76-42-00 43-56-21 76-30-00 44-00-42 76-42-03 44-00-35 76-30-07 43-52-00 76-17-59 43-56-04 76-18-08 43-55-59 76-12-00
1064 1065 1066 1067 1068 1070 1071 1072
22.4 19.2 20.3 9.8 15.5 11.8 46.7 NA
1.4 ND 0.8 ND ND 1.0 ND NA
62.4 27.6 41.3 13.5 30.3 38.1 19.0 NA
72.1 103.9 38.2 32.6 55.1 57.3 9.0 20.5 34.2 39.7 45.8 51.4 9.4 15.3 NA NA
65.8 25.4 45.4 18.8 29.6 35.7 16.8 NA
281.4 120.9 193.0 51.5 134.8 220.1 67.8 NA
1.00 0.27 0.47 0.18 0.38 0.87 0.30 0.31
7,720 1,530 4,820 1,190 4,660 1,410 745 604 2,980 635 4,980 900 609 581 NA NA
2.8 1.7 2.4 0.8 2.0 2.4 4.0 NA
1.7 1.0 1.4 0.3 1.0 1.5 0.5 NA
vidual major lake basins, indicating that anthropogenic impacts generally occurred on a lake-wide basis. More than 60% of the stations in Lake Ontario exhibited elevated surficial sediment concentrations for total mercury, zinc, lead, copper, chromium, and nickel, relative to the background concentrations (Table 3). Total mercury had the highest percentage of stations (97%) that exceeded background concentrations. Average background concentrations were used to express surficial sediment concentrations as a ratio above the background concentration as a means of estimating enrichment due to anthropogenic activities. The surficial concentrations of chromium, copper, lead,
1,915 657 1,164 548 547 470 1,920 NA
nickel, and zinc were compared to their respective background concentrations, and an enrichment ratio for each metal was calculated. The distribution of the average enrichment ratios for the five metals at each station is shown in Figure 3. The spatial pattern in anthropogenic enrichment was presumably an indication of the influence of both historical and present day human activities. However, the spatial distributions were also influenced by substrate type. The highest enrichment factors were associated with depositional areas in the major basins characterized by depositional sediment distributions as described by Thomas et al. (1972). Fine-grain silts and clays that adsorb contaminants more effectively
Spatial and Temporal Trends in Sediment Contamination in Lake Ontario
323
TABLE 3. Lake Ontario background sediment contaminant concentrations, surficial basin-specific 75th percentiles, Canadian Sediment Quality Guidelines, and percentages of sites exceeding guideline values. Guideline values for nitrogen and phosphorus represent the Ontario Provincial lowest effect level (LEL) and severe effect level (SEL).
Arsenic (µg/g) Cadmium (µg/g) Chromium (µg/g) Copper (µg/g) Iron (%) Lead (µg/g) Manganese (µg/g) Mercury (µg/g) Nickel (µg/g) Nitrogen (µg/g) Phosphorus (µg/g) Zinc (µg/g) Aluminum (%) PCBs (ng/g) Dioxin (pg/g TEQs)
Background Concentrations <5 <1 27 50 3.5 15 730 0.04 43 2,560 740 103 1.88
Surficial vs. Background % Exceeding NA NA 77 62 6 91 83 97 67 74 77 80 0
Surficial 75th Percentile 30 3.3 54 86 2.98 110 4,300 0.79 77 5,100 1,200 360 1.4 140 180
Sediment Quality Guidelines % of sites Exceeding Ontario Ontario TEL PEL TEL PEL 5.9 17 93 67 0.596 3.53 75 17 37.3 90 69 1 35.7 196.6 72 0 35.0 0.174 550 600 123.1 34.1 0.85
91.3 0.486 4,800 2,000 314.8 277 21.5
76
38
87
62
78
35 0 58
FIG. 2. Profiles of total mercury (µg/g dry wt.), lead (µg/g dry wt.), nitrogen and phosphorus (µg/g dry wt.), and total DDT (ng/g dry wt.) levels in core samples from station 1034 in the Mississauga basin of Lake Ontario.
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FIG. 3. Maps of Lake Ontario showing surficial sediment enrichment by metals, total mercury concentrations (µg/g dry wt.) in 1998, total mercury concentrations (µg/g dry wt.) in samples collected in 1968, total lead concentrations (µg/g dry wt.) in 1998, total lead concentrations (µg/g dry wt.) in 1968, and total phosphorus concentrations (µg/g dry wt.) in 1998. Sediment enrichment ratio is the mean ratio of surficial to background concentrations for the 8 metals exceeding background concentrations. than sediments characterized by coarser sands that dominate sediments in the depositional basins. The spatial pattern evident in the surficial sediment enrichment map (Fig. 3) was reflective of the distribution of most individual contaminants. The highest total mercury concentrations were detected in the major lake basins (Fig. 3). Concurrent with the highest levels of mercury contamination, the depositional basins also exhibited the greatest numbers of exceedances of the Canadian Sediment Quality probable effects level (PEL, CCME 1999) guidelines (Table 3). Applicable guideline values are represented as breakpoints in the maps showing
the spatial distributions of individual contaminants. These recently adopted sediment quality guidelines can be applied as screening tools in the assessment of potential risk, and determination of the relative priority of sediment quality concerns. Two benchmarks have been established; the threshold effect level (TEL) represents a concentration below which adverse biological effects are expected to occur rarely, and; the probable effect level (PEL) that defines the concentration above which adverse effects are expected to occur frequently (CCME 1999). These guidelines were selected over other Canadian and U.S. guidelines because of their applicability to
Spatial and Temporal Trends in Sediment Contamination in Lake Ontario a broad suite of analytes, and because they are considered to represent a conservative approach to evaluating sediment quality (Rheaume et al. 2000). Comparisons of different sediment quality guidelines and their application can be found in Rheaume et al. (2000), Smith et al. (1996), and MacDonald et al. (2000). In cases where Canadian Federal guidelines were not available, such as in the case of nitrogen and phosphorus, applicable Ontario Provincial guidelines were used. MacDonald et al. (2000) provide an overview of the advantages and limitations of using sediment quality guidelines in the assessment of sediment quality. The mean 75th percentile surficial sediment concentration of mercury (0.79 µg/g) for the three lake basins was roughly 20 times the background concentration (0.04 µg/g, Table 3), and over 60% of the stations exceeded the Canadian PEL (0.486 µg/g, Table 3). The 1968 surficial sediment total mercury concentrations as reported by Thomas et al. (1972) are shown in Figure 3. Consistent with the temporal trends apparent in the core profile (Fig. 2), sediment concentrations were found to have decreased over the past thirty years throughout the entire lake. In 1968, the basin mean 75th percentile for mercury was 1.13 µg/g, compared to a value of 0.79 µg/g in 1998. The lake-wide average surficial sediment mercury concentration in 1968 was 0.79 µg/g, compared to a value of 0.59 µg/g in 1998. The average mercury concentration calculated for 1968 was based on data for the same 66 sites that were resampled in the1998 survey. The spatial pattern for surficial sediment total lead concentrations in Lake Ontario in 1998 is shown in Figure 3. Of the stations sampled in 1998, 38% exceeded the Canadian PEL guideline value (Table 3). The basin mean 75 th percentile was roughly 7-times the background concentration (Table 3). The 1968 pattern for total lead in surficial sediments in Lake Ontario as reported by Kemp and Thomas (1976) is shown in Figure 3; lake-wide concentrations have decreased over time, which was consistent with the observed trend in the core profile (Fig. 2). The lake-wide average surficial sediment lead concentration in 1968 was 125 µg/g (based on the 66 sites re-sampled in 1998), compared to a value of 69 µg/g in 1998. In 1968, the basin mean 75th percentile for lead was 182 µg/g, compared to a value of 104 µg/g in 1998. Control measures restricting the use of leaded gasoline have undoubtedly contributed to the observed decreases. Spatial distributions of other metals exhibited spatial patterns similar to lead and mercury, including
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arsenic (PEL exceeded at 67% of the stations), zinc (PEL exceeded at 35% of the stations), and cadmium (PEL exceeded at 17% of the stations). Total nitrogen (data not shown) and total phosphorus (Fig. 3) concentrations, compared to Ontario Provincial Sediment Quality Guideline lowest effect level (LEL) and severe effect level (SEL, Persaud et al. 1993), depicted more widespread spatial contamination compared to metals that included areas of the Kingston Basin that typically did not exhibit levels of organic contaminants and metals as high as the three other lake basins. However, none of the stations exceeded the Ontario provincial SEL. Polychlorinated Dibenzo-p-dioxins and Dibenzofurans Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/PCDFs) were analyzed in a subset of roughly half of the survey stations (Fig. 4); concentrations were expressed as toxic equivalents (TEQs) calculated using the International Toxicity Equivalency Factor (ITEF) method (Van den Berg et al. 1998). Data for a smaller subset of PCDDs/PCDFs in Lake Ontario were previously reported (Marvin et al. 2002). The spatial pattern observed was similar to the patterns for metals and the basin mean 75th percentile values of PCDDs/PCDFs, expressed as TEQs (pg/g), are shown in Table 3. These contaminants were particularly prevalent in the depositional basin sediments as evidenced by a 75 th percentile PCDD/PCDF TEQ value of 183 pg/g, which significantly exceeded the Canadian PEL guideline value of 21.5 pg/g TEQs by a factor of roughly nine-fold. The lake-wide average PCDD/PCDF value of 111 pg/g TEQs exceeded the PEL by roughly five-fold; in total, over half of the stations in Lake Ontario exceeded the PEL. Sediments from the three major depositional basins were enriched in the higher-chlorinated PCDF homologs and 2,3,7,8tetrachlorodibenzodioxin and 1,2,3,4,7,8-hexachlorodibenzofuran congeners, which implicated the Niagara River as a potential source (Marvin et al. 2002, Woodfield and Estabrooks 1999). Consumption advisories for PCDDs/PCDFs have been implemented for some fish species in Canadian waters of Lake Ontario (Ontario Ministry of the Environment 2001). Temporal trends in accumulation of PCDDs/ PCDFs in Lake Ontario sediment were previously studied using dated slices from a core sampled from the Mississauga basin (Marvin et al. 2002). Levels
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FIG. 4. Lake Ontario surficial sediment polychlorinated dibenzo-p-dioxin and dibenzofuran concentrations (pg/g dry wt. TEQ) in 1998, total polychlorinated biphenyl concentrations (ng/g dry wt.) in 1998, and total DDT (ng/g dry wt.) in 1998. of PCDDs/PCDFs increased rapidly in the early part of the 20th century, remained at a concentration of approximately 300 pg/g TEQs during the period of roughly 1950 to 1970, and then decreased to approximately 100 pg/g TEQs between 1970 and 1980. Levels of PCDD/PCDF contamination appear to have leveled off in the period of 1980 to 1998; these observations were consistent with previous findings (Pearson et al. 1997, Pearson et al. 1998). Polychlorinated Biphenyls and Organochlorine Pesticides The pattern of polychlorinated biphenyl (PCB) and organochlorine contamination in Lake Ontario surficial sediments was similar to metals. The lakewide average total PCB concentration in Lake On-
tario in 1998 was 100 ng/g (Fig. 4), while the mean basin 75th percentile was 141 ng/g (Table 3). None of the stations surveyed in Lake Ontario in 1998 exceeded the Canadian PEL for total PCBs (277 ng/g). In comparison, total PCB concentrations for the three major lake basins in 1981 ranged from 510 ng/g to 630 ng/g; the Kingston basin mean total was 200 ng/g (Oliver et al. 1989). The DDT compounds were quite prevalent in sediments in the major depositional basins; total DDT (sum of the six individual o,p′- and p,p′-DDD, DDE and DDT compounds) exhibited a lake-wide average value of 32.0 ng/g (Fig. 4). The p,p′-isomers were detected at higher concentrations than the o,p′-isomers, with the parent p,p′ DDT compound (3.77 ng/g lakewide average) generally detected at lower concentrations than the anaerobic metabolite p,p’-DDD
Spatial and Temporal Trends in Sediment Contamination in Lake Ontario (9.27 ng/g lake-wide average) and the aerobic metabolite p,p′-DDE (14.7 ng/g). Mirex was also frequently detected; the lake-wide average of 6.6 ng/g represented a roughly 80% reduction from the corresponding average (35 ng/g) determined for samples collected in 1981 (Oliver et al. 1989). Dieldrin was frequently detected, but the lake-wide average of 1.34 ng/g was relatively low. The lakewide average concentration of hexachlorobenzene (HCB) in 1998 was 22.9 ng/g, compared to concentrations for the three major lake basins in 1981 that ranged from 100 ng/g to 130 ng/g (Oliver et al. 1989). Accumulation of organochlorine compounds was also studied through analyses of dated slices from box cores from station 1034 in the Mississauga basin; however, assigned dates based on different 210Pb dating models were inconsistent with known
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production and usage patterns. These discrepancies may have resulted from sediment mixing, contaminant diffusion, or loss of integrity of the core during sampling or sectioning. Reports by Oliver et al. (1989), Wong et al. (1995) and Eisenreich et al. (1989) generally showed maximum accumulation of DDT in Lake Ontario sediments occurred in the late 1950s, while accumulation of PCBs and mirex was greatest in the mid-1960s. The overall shape of our core profiles of organic contaminants including DDT (Fig. 2) and PCBs (Fig. 5) are similar to those of the other studies, and allow an assessment of temporal trends in contaminant accumulation and estimates of reductions from peak levels. Surficial concentrations for mirex and PCBs were roughly 40% lower than maximum concentrations at depth in the core, while total DDT was 60% lower. The relative contributions of the individual homologs to
FIG. 5. Profiles of selected polychlorinated biphenyl homologs and total PCBs in a box core sample from station 1034 in the Mississauga basin of Lake Ontario.
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the composition of total PCBs varied with depth (Fig. 5). Below the depth of maximum accumulation of PCBs (5 cm), relative contributions of the lower chlorinated (tri-penta) congeners generally decreased while relative contributions of the higher chlorinated (hepta-nona) increased. These data are in agreement with those of Oliver et al. (1989) and Wong et al. (1995). The core profile for the DDT compounds (Fig. 2) was similar to that of a core collected from the Niagara Basin by Oliver et al. (1989) in 1982. As with the surficial sediment samples, the p,p′-DDD and p,p′-DDE metabolites were predominant. We are currently collecting additional core samples in order to attempt to achieve profiles that exhibit greater consistency with known production and usage, and for further study of accumulation rates and inventories. Influences on Spatial and Temporal Distributions of Contaminants The predominant circulation patterns in Lake Ontario resemble a counterclockwise gyre (Pickett and Bermick 1977) that contributes to the consistency in distributions of contaminants across the major lake basins. For example, Thomas (1972) reported that the mercury distribution in Lake Ontario was related to this surface water circulation pattern, and that mercury was ultimately deposited at downstream locations. In general, the highest contaminant concentrations for the 1998 sediment survey were detected in the depositional areas. Greater than 50% of the stations surveyed in Lake Ontario exceeded the Canadian PEL for mercury and PCDDs/PCDFs. The maps showing the distributions of the individual contaminant classes were generally similar to those determined by Oliver et al. (1989), in that contamination was distributed roughly uniformly across the three major depositional basins, while the Kingston basin exhibited correspondingly lower levels. The results of Oliver et al. (1989) were spurious compared to previous studies (Van Hove Holdrinet et al. 1978, Frank et al. 1979), in that the magnitude of contamination by a number of compounds including PCBs, DDT, and mirex, were higher, compared to the earlier studies. These differences were attributed to differences in sampling protocols and analytical methods. Frank et al. (1979) employed a shipek sampling protocol, which may have resulted in loss of some surficial sediment, and used packed-column GC to measure organic contaminants. Our 1998 study employed sampling (mini-box core) and analytical (capillary
column GC) methods similar to those of Oliver et al. (1989). Any differences in sampling and analytical protocols should be considered in comparing the 1998 data, and historical data. However, in considering the banning of DDT and PCBs, the phasing out of leaded gasoline, and the subsequent well documented decreases in loadings, the comparisons with data from Oliver et al. (1989) and Frank et al. (1979) appear reasonable. There are numerous reports in the literature (Kuntz and Warry 1983, Warry and Chan 1981, Jaffe and Hites 1986, Whittle and Fitzsimons 1983, Durham and Oliver 1983, Van Hove Holdrinet et al. 1978) that provide compelling evidence for the Niagara River as a primary source of many contaminants in Lake Ontario, including mercury and PCBs. In contrast to other Laurentian Great Lakes such as Lake Superior, Lake Ontario is more significantly impacted by local contaminant sources, compared to atmospheric deposition. Thompson et al. (1993) estimated that the Niagara River contributes two-thirds of the total loadings of contaminants, including PCBs and lead, to Lake Ontario. Diamond et al. (1993) reported that control of landbased sources is needed to reduce mercury contamination in Lake Ontario, in contrast to Lake Superior where atmospheric sources predominate. Pearson et al. (1998) estimated that 65–95% of PCDD accumulation and greater than 95% of PCDF accumulation in Lake Ontario was due to the influence of non-atmospheric sources, including the Niagara River. The Niagara River watershed in western New York is replete with numerous hazardous waste facilties (Jaffe and Hites 1986, Howdeshell and Hites 1996), some of which contain significant inventories of PCDDs/PCDFs. The influence of the Hyde Park dump, which is linked to the Niagara River via Bloody Run Creek, has been the focus of several studies (Jaffe and Hites 1986, Howdeshell and Hites 1996). This facility was closed in 1975, but sediment sampling conducted in 1993 determined that contaminants exclusively associated with this site continued to migrate from the dump, and were ultimately deposited in open lake sediments of Lake Ontario (Howdeshell and Hites 1996). More recent data from sediment and biomonitoring studies conducted during the period 1995–1997 in the Niagara River, at sites including Bloody Run Creek (Hyde Park) and Pettit Flume (Tonawanda Island), showed high levels of PCDD/PCDF contamination (Richman 1999, Woodfield and Estabrooks 1999). These studies indicated that hazardous waste sites continue to be
Spatial and Temporal Trends in Sediment Contamination in Lake Ontario sources of significant quantities of PCDDs/PCDFs to the Niagara River. However, while contamination of Lake Ontario from the Niagara River watershed reportedly continued to occur into the 1980s, the severity of pollution was reduced from the highest levels of the 1960s (Durham and Oliver 1983). Wong et al. (1995) estimated that accumulation rates of some contaminants measured during the mid-1990s were 15–30% of earlier peak accumulation rates, but had remained relatively constant since the mid-1980s. CONCLUSIONS The observed spatial trends in sediment contamination in Lake Ontario were similar for a number of compound classes including total PCBs, total DDT, polychlorinated dibenzo-p-dioxins and dibenzofurans, organochlorine pesticides, and a host of metals, including total mercury and lead. The highest levels of contamination were associated with finegrained sediments confined to the three major lake basins, while stations characteristic of inshore environments exhibited relatively lower contaminant levels. Presumably, these trends were influenced by industrial activities in the watersheds and along major tributaries, including the Niagara River; contaminated sediment originating within the tributary watersheds is ultimately deposited in the depositional basin areas of Lake Ontario. Other major influences in the observed trends may have included open-lake disposal of dredged material, atmospheric deposition and remediation of contaminated areas. In general, levels of contaminants in Lake Ontario surficial sediments decreased over the period 1968 to 1998. This trend was also evidenced by individual contaminant profiles in core samples from one of the three major lake basins (station 1034, Mississauga basin, Fig. 1). Lake-wide surficial sediment concentrations of mercury decreased from 0.79 µg/g in 1968 to to 0.59 µg/g in 1998, while lead concentrations decreased from 125 µg/g to 69 µg/g over the same time period. Similarly, core profiles showed a 40% and 60% decline from peak concentrations for total PCBs and total DDT, respectively. Surficial sediment concentrations in Lake Ontario in 1998 also indicated improvement in environmental quality compared to studies conducted in the 1960s and 1980s. However, assessment of current spatial trends in contamination, and temporal trends in PCDDs/PCDFs using a dated core, indicated that the major depositional basins
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are still being subjected to active loadings of contaminants. Concentrations of PCDDs/PCDFs in Lake Ontario sediments in 1998 remained well above ambient environmental background levels. The Niagara River watershed, with its many hazardous waste facilities, appears to remain a primary contributor. Despite the substantial improvement in Lake Ontario sediment quality over the period 1968 to 1998, sediments in many areas of Lake Ontario still exceeded the Canadian Sediment Quality Guidelines probable effect level (PEL) guidelines. These guideline exceedences were prevalent in all three major lake basins. Exceedences of the Canadian Sediment Quality PELs were most numerous for arsenic (67%), mercury (62%), and PCDDs/PCDFs (58%). None of the stations surveyed exceeded the Canadian PEL for total PCBs. Some pollutants identified as exceeding the guideline values, such as mercury and PCDDs/PCDFs, are responsible for the fish consumption advisories in Lake Ontario. ACKNOWLEDGMENTS The authors thank the Captain and Crew of the Canadian Coast Guard Ship Limnos, staff of the National Water Research Institute Technical Operations, Environment Canada, and staff of the Dioxins and Toxic Organics Section, Laboratory Services Branch, Ontario Ministry of the Environment. REFERENCES Canadian Council of Ministers of the Environment (CCME). 1999. Canadian Environmental Quality Guidelines. Winnipeg, Manitoba. Diamond, M.L., Mackay, D., and Sang, S. 1993. A mass balance analysis of mercury in Lakes Ontario and Superior. In 36th Conf. Internat. Assoc. Great Lakes Res., Program and Abstracts, pp. 133. Internat. Assoc. Great Lakes Res. Durham, R.W., and Oliver, B.G. 1983. History of Lake Ontario contamination from the Niagara River by sediment radiodating and chlorinated hydrocarbon analysis. J. Great Lakes Res. 9:160–168. Eisenreich, S.J., Cope, P.D., Robbins, J.A., and Bourbonniere, R. 1989. Accumulation and diagenesis of chlorinated hydrocarbons in lacustrine sediments. Environ. Sci. Technol. 23:1116–1126. Frank, R., Thomas, R.L., Holdrinet, M., Kemp, A.L.W., and Braun, H.E. 1979. Organochlorine insecticides and PCB in surficial sediments (1968) and sediment cores (1976) from Lake Ontario. J. Great Lakes Res. 5:18–27. Howdeshell, M.J., and Hites, R.A. 1996. Is the Hyde
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Park Dump, near the Niagara River, still affecting the sediment of Lake Ontario? Environ. Sci. Technol. 30:969–974. Jaffe, R., and Hites, R.A. 1986. Fate of hazardous waste derived organic compounds in Lake Ontario. Environ. Sci. Technol. 20:267–274. Kemp, A.L.W., and Thomas, R.L. 1976. Impact of man’s activities on the chemical composition in the sediments of Lakes Ontario, Erie, and Huron. Water, Air, and Soil Pollution 5:469–490. Kuntz, K.W., and Warry, N.D. 1983. Chlorinated organic contaminants in water and suspended sediments of the lower Niagara River. J. Great Lakes Res. 9:241–248. MacDonald, D.D., Ingersoll, C.G., and Berger, T.A. 2000. Development and evaluation of consensus-based sediment quality guidelines for freshwater ecosystems. Arch. Environ. Contam. Toxicol. 39:20–31 Marvin, C.H., Charlton, M.N., Reiner, E.J., Kolic, T., MacPherson, K., Stern, G.A., Braekevelt, E., Estenik, J.F., Thiessen, P.A., and Painter, S. 2002. Surficial sediment contamination in Lakes Erie and Ontario: A comparative analysis. J. Great Lakes Res. 28:437–450. McLaren, J.W. 1981. Simultaneous Determination of Major, Minor, and Trace Elements in Marine Sediments by Inductively Coupled Plasma Atomic Emission Spectrometry. Analytical Chemistry Section, Chemistry Division, National Research Council of Canada, Ottawa, Ontario, Canada. Mudroch, A. 1993. Lake Ontario sediments in monitoring pollution. Environmental Monitoring and Assessment 28:117–129. ———, and MacKnight, S.D. 1991. Handbook of Techniques for Aquatic Sediments Sampling. Boca Raton, Florida: CRC Press. ———, Serazin, L., and Lomas, T. 1988. Summary of surface and background concentrations of selected elements in Great Lakes sediments. J. Great Lakes Res. 14:241–251. National Laboratory for Environmental Testing (NLET). 1997. Manual of Analytical Methods, Volume 1. Burlington, Ontario: Environment Canada. Oliver, B.G., Charlton, M.N., and Durham, R.W. 1989. Distribution, redistribution, and geochronology of polychlorinated biphenyl congeners and other chlorinated hydrocarbons in Lake Ontario sediments. Environ. Sci. Technol. 23:200–208. Ontario Ministry of the Environment (OME). 2000. The determination of polychlorinated dibenzo-p-dioxins, polychlorinated furans and dioxin-like PCBs in environmental matrices by GC-MS. Environment Ontario Laboratory Services Branch Method DFPCB-E3418. Toronto, ON, Canada. ———. 2001. Guide to eating Ontario sport fish. 21st Edition. Queen’s Printer for Ontario, Toronto, ON, CA. Pearson, R.F., Swackhamer, D.L., Eisenreich, S.J., and
Long, D.T. 1997. Concentrations, accumulations, and inventories of polychlorinated dibenzo-p-dioxins and dibenzofurans in sediments of the Great Lakes. Environ. Sci. Technol. 31:2903–2909. ———, Swackhamer, D.L., Eisenreich, S.J., and Long, D.T. 1998. Atmospheric inputs of polychlorinated dibenzo-p-dioxins and dibenzofurans to the Great Lakes: Compositional comparison of PCDD and PCDF in sediments. J. Great. Lakes Res. 24:65–82. Persaud, D., Jaagumagi, R., and Hayton, A. 1993. Guidelines for the protection and management of aquatic sediment quality in Ontario. Ontario Ministry of Environment. Toronto. Pickett, R.L., and Bermick, S. 1977. Observed resultant circulation in Lake Ontario. Limnol. Oceanogr. 22:1071–1076. Pirrone, N., Allegrini, I., Keeler, G.J., Nriagu, J.O., Rossmann, R., and Robbins, J.A. 1998. Historical atmospheric mercury emissions and depositions in North America compared to mercury accumulations in sedimentary records. Atmospheric Environment 32:929–940. Rheaume, S.J., Button, D.T., Myers, D.N., and Hubbell, D.L. 2000. Areal distribution and concentrations of contaminants of concern surficial streambed and lakebed sediments, Lake Erie-Lake St. Clair drainages, 1990–97. Water Resources Investigations Report 00-4200. United States Department of the Interior, United States Geological Survey. Richman, L.A. 1999. Niagara River mussel biomonitoring program, 1997. Water Monitoring Section, Environmental Monitoring and Reporting Branch, Ontario Ministry of the Environment, Toronto, Ontario. Smith, S.L., MacDonald, D.D., Keenleyside, K.A., Ingersoll, C.G., and Field, L.J. 1996. A preliminary evaluation of sediment quality assessment values for freshwater ecosystems. J. Great Lakes Res. 22:624–638 Thomas, R.L. 1972. The distribution of mercury in the sediments of Lake Ontario. Can. J. Earth Sci. 9:636–651. ———, Kemp, A.L.W., and Lewis, C.F.M. 1972. Distribution, composition and characteristics of the surficial sediments of Lake Ontario. J. Sedimentary Petrology 42(1):66–84. Thompson, S., Sang, S., and Mackay, D. 1993. Impacts of reduced loadings of six persistent toxics on Lake Ontario concentrations. In 36th Conf. Internat. Assoc. Great Lakes Res., Program and Abstracts, pp. 134. Internat. Assoc. Great Lakes Res. Turner, L.J., and Yang, F. 2000. 210Pb dating of lacustrine sediments from Lake Ontario (station 1034, core 223). National Water Research Institute, Burlington, ON. NWRI report 2000-1. United States Environmental Protection Agency (USEPA). 1981. Procedures for Handling and Chemical Analysis of Sediment and Water Samples. Environmental Laboratory, US. Army Engineer Water-
Spatial and Temporal Trends in Sediment Contamination in Lake Ontario ways Experiment Station, Vicksburg, Mississippi, pp. 3–118. Van den Berg, M., Birnbaum, L., Bosveld, B.T.C., Brunstrom, B., Cook, P., Feeley, M., Giesy, J.P., Hanberg, A., Hasegawa, R., Kennedy, S.W., Kubiak, T., Larsen, J.C., Rolaf van Leeuwen, F.X., Liem, A.K.D., Nolt, C., Peterson, R.E., Poellinger, L., Safe, S., Schrenk, D., Tillitt, D., Tysklind, M., Younes, M., Waern, F., and Zacharewski, T. 1998. Toxic equivalency factors (TEFs) for PCBs, PCDDs, PCDFs for humans and wildlife. Environ. Health Perspect. 106:775–792. Van Hove Holdrinet, M., Frank, R., Thomas, R.L., and Hetling, L.J. 1978. Mirex in the sediments of Lake Ontario. J. Great Lakes Res. 4:69–74. Warry, N.D., and Chan, C.H. 1981. Organic contaminants in the suspended sediments of the Niagara River. J. Great Lakes Res. 7:394–403.
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Whittle, D.M., and Fitzsimons, J.D. 1983. The influence of the Niagara River on contaminant burdens of Lake Ontario biota. J. Great Lakes Res. 9:295–302. Wong, C.S., Sanders, G., Engstrom, D.R., Long, D.T., Swackhamer, D.L., and Eisenreich, S.J. 1995. Accumulation, inventory, diagenesis of chlorinated hydrocarbons in Lake Ontario sediments. Environ. Sci. Technol. 29:2661–2672. Woodfield, K., and Estabrooks, F. 1999. Dioxin/furan in Lake Ontario tributaries 1995–1997. Bureau of Watershed Assessment and Research, Division of Water, New York State Department of Environmental Conservation, Albany, New York. Submitted: 16 September 2002 Accepted: 27 February 2003 Editorial handling: Ronald Rossmann