Benthic Community and Sediment Quality Assessment of Port Hope Harbour, Lake Ontario

J. Great Lakes Res. 12(3):206-220 Internat. Assoc. Great Lakes Res., 1986

BENTHIC COMMUNITY AND SEDIMENT QUALITY ASSESSMENT OF PORT HOPE HARBOUR, LAKE ONTARIO

Donald R. Hart, Paul M. McKee, and Alan J. Burt

Beak Consultants Limited 6870 Goreway Drive Mississauga, Ontario L4V 1P1 Michael J. Goffin

EnvlfonmentCanada Environmental Protection Service 25 St. Clair A venue East Toronto, Ontario M4T 1M2 ABSTRACT. Sediments in Port Hope Harbour, Lake Ontario, have been heavily contaminated by radionuelides and heavy metals from a radium recovery plant, a uranium refinery, and other industrial activities. Spatial patterns in surficial sediment contamination, benthic community structure, and bioaccumulation ofcontaminants were assessed to determine possible relationships and potential environmental hazards in the event of dredging. Benthic community differences in species composition and density between inner and outer harbour areas corresponded with both habitat and sediment quality differences. Sediment loss-on-ignition, nitrogen, iron, copper, lead, chromium, zinc, and nickel concentrations in the inner harbour exceeded provincial guidelines for open water disposal of dredged spoils. Only iron exceeded those guidelines in the outer harbour. Tissue levels of radionuelides and heavy metals in benthic invertebrates were greatest at the most heavily contaminated stations in the inner harbour. Reduced benthic densities and maximum sediment contamination occurred near a refinery cooling water discharge. ADDITIONAL INDEX WORDS: Radioactive wastes, radioisotopes, metals, biological magnification.

INTRODUCTION

agement facility and some was returned to the plant for reprocessing. It is generally believed that the harbour was contaminated as a consequence of waste management practices during the period 1933 to 1948. Cooling and process water have been taken from the harbour and returned after use in refining since 1933. These discharges, as well as site run-off, have contributed to radioactive and non-radioactive contaminant loadings, primarily to the harbour turning basin. The Port Hope Harbour area has also served other industrial operations until very recently. Coal was stockpiled in the harbour area for shipment to inland markets until the late 1960s. The harbour also received site drainage from agricultural fertilizer and feed grain industries, as well as a metal

Port Hope Harbour on the north shore of Lake Ontario, approximately 80 km east of Toronto, Ontario, was the site of a Ra recovery plant from 1933 to 1952 and, since 1955, has been the site of a U refinery. The refinery included a U02/U03 production facility, which ceased operation in 1983, and a UF6 facility which has operated since 1970. Between 1933 and 1948, process wastes containing radionuclides of the U-238 and Th-232 decay chains and non-radioactive contaminants were stored at a number of locations within the town of Port Hope, including one area on the refinery site adjacent to the harbour. By 1948, much of the stored waste had been removed from the vicinity of the harbour. Some was relocated to a waste man206

207

PORT HOPE HARBOUR ASSESSMENT fabricating facility. The last of these operations has been discontinued since the 1970s. Other industries may have been important in earlier times. Thus, present environmental conditions in the harbour result not only from releases from Ra recovery and V refining, but may also reflect urban run-off and historic contaminant loadings from these antecedent industries. Port Hope Harbour has been dredged repeatedly since construction began in 1829. The harbour turning basin has not been dredged for at least two decades (Canada Department of Public Works, pers. comm.; Small Craft Harbours Directorate, Canada Department of Fisheries and Oceans, pers. comm.) although records of earlier dredging are difficult to interpret. Other areas of the harbour are dredged regularly. It is clear from decreasing water depths in the turning basin (Environmental Protection Service 1981) that additional dredging must soon be considered if the harbour turning basin is to remain functional. Dredging activities may result in resolubilization and resuspension of sediment-associated contaminants with possible transport out of the turning basin. Estimation of the potential impact requires characterization of existing sediment and water quality, biological communities, and community responses to environmental contamination. Recent radiological water quality in the harbour has been monitored by the Ontario Ministry of the Environment (MOE) and reviewed by the International Joint Commission (IJC 1983). These data indicate that V concentrations in the water of the harbour turning basin are generally in excess of 20 mg'L- 1 , the maximum acceptable concentration for drinking water set by Health and Welfare Canada (1980), although the turning basin is at present not a source of drinking water. Activities of Ra-226 in Port Hope Harbour from 1981 to 1982 were generally near or below the detection limit of 37 mBq'L- 1 , with Ra activities reported in the outer harbour being less than this limit. The recent V021 V03 plant closure has eliminated aqueous discharges of Ra-226. Thomas and Mudroch (1979) summarized trace metal concentrations of surficial sediments in the harbour, but did not determine radionuclide concentrations. Turning basin sediments showed significant contamination by P, Zn, Cu, Pb, and Hg, with concentrations exceeding the MOE guidelines for open-lake disposal of dredge spoils (Persuad and Wilkins 1976). Single samples exceeded guidelines for arsenic and PCBs. The Ontario Water

Resources Commission in 1968 and the MOE in 1976 analysed a series of sediment cores from the turning basin for V and Ra-226 (EPS 1981). Vranium concentrations measured in surficial sections in 1968 ranged from 120 to 18,000 p,g'g-I. Surficial activities of Ra-226, measured in both years, ranged from 19 to 260 Bq·g-I. Cook and Veal (1968) reported a benthic community in the turning basin characterized by high numbers of pollution-tolerant Tubificidae and Chironomidae. Species diversity was low and pollution-intolerant species were absent. Macroinvertebrates were absent near the former V021V03 cooling water outfall, suggesting toxic conditions. Low numbers of organisms (21 tubificids'm-Z) were found near a former aqueous waste outfall in the same vicinity on the west side of the turning basin. Previous studies have not described the biology in outer harbour areas or related the biology to the sediment chemistry. Nor has the biological uptake of contaminants been investigated. The objectives of the present study were to provide a more complete characterization of the physical, chemical, and radiochemical properties of the Port Hope Harbour sediments, from turning basin to outer harbour, and a corresponding characterization of the current benthic invertebrate community. Benthic community studies were designed to determine biological uptake of contaminants, changes in the turning basin community since 1968, and relationships between community structure and sediment quality. MATERIALS AND METHODS Study Area Figure 1 shows the study area and 20 sampling locations. Stations A to H correspond to those stations sampled by Cook and Veal (1968). Stations A to F and I to L are located in the turning basin, Stations M, N, and G in the west slip, Station H in the lower Ganaraska River, Station in the confluence, and Stations P to T in the outer harbour.

°

Field Survey Sampling was conducted on 20 to 23 and 27 November 1984, with surficial sediments collected from each of the 20 stations using a weighted 23 x 23-cm stainless steel Ekman grab. Surficial sediment samples were collected after removing the 200-p,m mesh top from the Ekman and allowing excess water to drain. The top 2 cm of sediment

208

HART et ale

LAKE ONTARIO N ..... 0

50

100

150

200

250m

- ..... F=Ld";;='L=g===j

FlG. 1. Locations of sampling stations in Port Hope Harbour.

was sampled, using a stainless steel spoon, and placed into polyethylene bags. Surficial sediments for PCB determination were placed in hexanewashed glass jars with hexane-rinsed foil cap liners. All samples were frozen within 12 h of collection. At each of the 20 stations, three replicate benthic macroinvertebrate samples were collected by

Ekman grab for community analysis. Each sample was sieved through a 200-p.m mesh screen, preserved in buffered 10070 formalin, and transported to the laboratory for sorting, identification, and enumeration. Additional benthic organism samples were collected from the harbour for radiochemical, metal, F, and PCB analyses of the tissues. Samples were

209

PORT HOPE HARBOUR ASSESSMENT collected by Ekman grab, sieved through a 500-J.tm screen, and the residue transferred into 20-L bu~k­ ets. Sufficient biomass was collected to provIde about 10 g (wet weight) for trace elements and PCB analysis at seven stations. Radiochemical analyses of tissues were carried out on samples from only six stations, due to insufficient biomass at one location. The samples were transported to the laboratory for hand-sorting of live animals. After sorting, these organisms were held at ambient temperature for 24 h in filtered Port Hope Harbour water to allow purging of the gut contents. Most organisms in the samples were oligochaetes. All organisms from each sample were composited for chemical and radiochemical analysis. Physical, Chemical, and Radiochemical Analyses The methylene blue method was used to determine sediment sulphide (Plumb 1981). Sediment carbon and N were determined by CHN elemental analyzer (Perkin Elmer Corp. 1977). Other elements, including Zn, Co, Cu, Fe, Pb, Cr, Ni, Cd, Mn, Ag, Ca, V, AI, Mg, Ba, K, Sr, Na, and Zr, were measured by plasma emission scan (SpectroMetrics, Inc., undated) of aqua regia sediment extracts (MOE 1983) and wet-ashed biological tissues (Smith 1965). Tissue determinations were performed on the first seven of these elements, as these were judged to be of the greatest toxicological concern. Fluoride in sediments was extracted with distilled water and analysed according to Standard Methods (APHA 1980). Polychlorinated biphenyl samples were extracted in 1:1 hexane/ acetone, purified using florisil clean-up reagent, and total PCBs measured by gas chromatography using electron capture. Loss on ignition was measured gravimetrically after ashing at 550°C. Moisture content was determined gravimetrically by drying to a constant weight at 105°C. The short pipette method of the FAST analysis (Rukavina and Duncan 1970) was applied to determine grain size in the inorganic (ash) fraction of surficial sediments. Total U was determined by delayed neutron activation (Chiu and Dean 1984). Samples for Ra-226 and Th isotope analysis were dissolved by KF-pyrosulphate fusion. The activity of each radionuclide was then determined by high resolution alpha spectrometry (Chiu and Dean 1984). Samples for Pb-210 and Po-21O analyses were digested in HF-HN0 3-HCI04 • Pb-21O was determined indirectly by measurement of bismuth-21O using a beta-counter (Chiu and Dean 1984).

Po-21O was determined following the method of Smithson (1979) with the use of Po-208 as a tracer (Chiu, pers. comm.). Benthic Analyses In the laboratory, benthic samples were washed in a 0.2 mm mesh sieve to remove remaining debris. Invertebrates were then sorted using a dissecting microscope and grouped by major taxa. Benthic identifications generally followed the classification scheme used by Pennak (1978) except for the Mollusca, Oligochaeta, and Chironomidae. Identification of Mollusca followed Clarke (1973) and Mackie et al. (1980), Oligochaeta followed Brinkhurst and Jamieson (1971) and Hiltunen and Klemm (1980), Chironomidae followed Oliver and Roussel (1983). Wiggins (1977) and Edmunds et al. (1976) were also used for Trichoptera and Ephemeroptera, respectively. Statistical Analyses Frequency distributions of physical, chemical, and radiochemical parameters in surficial sediments were examined and tested for goodness of fit to the normal distribution using the KolmogorovSmirnov test (Sokal and Rohlf 1969). All parameters not originally normal in distribution were normalized by log transformation. For these parameters the geometric mean (computed from log transformed data) is the appropriate measure of central tendency. Geometric means were also computed for other parameters in which normality was improved by log transformation, although the transformation was not strictly required. Arithmetic means were computed for all other parameters. Benthic communities were described in terms of species compositional similarities between stations. Squared Euclidean distance was used as an inverse similarity measure for this purpose, the distance formula for stations j and k (Norusis 1984) being: n

D2(j,k)

=

~(Xhj - Xhk)2 h-I

where Xhj = abundance of species h at statio~ j. All species abundances were log transformed pnor to computation. Similarity or distance information can be used to group stations into clusters of biologically similar stations. The grouping procedure, or cluster analysis , used in this study is a hierarchical .agglomera. tive technique. At each stage one statIon IS com-

HART et al.

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TABLE 1. Levels of radionuclides in surficial sediments of Port Hope Harbour. Geometric Mean and Range Turning Basin Outer Harbour and West Slip and Confluence Parameter U

Th-230 Ra-226 Pb-210 Po-210 Th-232 Th-228

Units JLg/g Bq/g Bq/g Bq/g Bq/g Bq/g Bq/g

Ganaraska Station

(N = 13)

(N = 6)

H

92.5 (3.5-1280) 6.78 (0.063-76.6) 1.56 (0.031-297) 6.54 (0.60-682) 5.79 (0.30-739) 0.20 (0.015-5.2) 0.10 (0.014-2.2)

1.77 (1.2-3.7) 0.42 (0.07-1.12) 0.06 (0.032-0.11) 0.33 (0.3-0.5) 0.33 (0.3-0.5) 0.02 (0.005-0.03) 0.04 (0.02-0.1)

4.2 0.36 0.17 0.70 0.50 0.058 0.022

bined either with another station or with an existing cluster of stations, according to its affinities, and the affinities of the newly formed cluster are recalculated. The process continues until all stations are accounted for. Distances between two clusters of stations were computed as the average of distances between pairs of stations in opposite clusters. This method is termed average linkage cluster analysis. Each cluster of stations so defined can be interpreted as a distinct benthic community. Discriminant analysis (Cooley and Lohnes 1971, Green 1979) was performed to examine overall sediment quality differences between communities. This multivariate technique combines the various physical-chemical and radiochemical parameters into a single composite measure of sediment quality. The composite index, or discriminant score, maximizes the ratio of between-community to within-community variance. Each station was assigned a discriminant score reflecting its place on the sediment quality scale. Species diversity was determined for each station using Brillouin's diversity index (Kaesler et al. 1978). The mean diversity and 95070 confidence intervals for each station were computed following Steel and Torrie (1960). Confidence intervals were compared with diversity values for corresponding stations (A to H) from the 1968 benthic survey .(Cook and Veal 1968) to evaluate change over time. Among-station differences in species diversity and total organism abundance in 1984 were examined by analysis of variance, followed by StudentNewman-Keuls tests for pair-wise interstation comparisons. Abundance was log transformed prior to analysis. Bartlett's test was used to test for homogeneity of variance between stations (Steel and Torrie 1960). Paired t-tests were used to com-

pare both species diversity and total organism abundance between 1968 and 1984, considering stations A-H as a group. An F-test of the variance ratio was used to compare variances of these parameters between years. Abundances computed for the single replicate per station in 1968 were compared to the 1984 confidence intervals at each station. RESULTS AND DISCUSSION Radiochemical Properties of Sediments Results of radiochemical analyses of surficial sediments are summarized in Table 1 for turning basin/west slip and outer harbour/confluence areas. Radionuclide levels in sediments were highly varied, with members of the U-238 decay chain ranging over three orders of magnitude in concentration among stations. The highest concentrations occurred at Station A in the turning basin, near the U refinery cooling water outfall, and the lowest concentrations in the sandy deposits of the outer harbour (Stations 0 to T). Concentrations at Station H, in the lower Ganaraska River, were generally as low as concentrations found in the outer harbour. High concentrations were found generally throughout the turning basin, with concentrations at Station A about an order of magnitude higher than other turning basin sediments. Concentrations in the west slip sediments were intermediate between those of the turning basin and those of the outer harbour and lower Ganaraska. Th-232 and its decay granddaughter Th-228 occurred with a spatial distribution similar to that of the U-238 series radionuclides, except that the range in Th-232 series activities was only two orders of magnitude.

PORT HOPE HARBOUR ASSESSMENT U-238 decay chain radionuclides did not occur in secular equilibrium. On an activity basis, U was depleted in all samples relative to other members of the decay chain. This deficiency may be due to the selective retention of U in the refining process or to the solubility of the U species discharged. NRCC (1983) reported U concentrations of 1.45 to 24.7 p,g_g-t in stream and lake sediments from across Canada, with a geometric mean of 5.6 p,g_g-I. UNSCEAR (1982) reported an average U-238 activity in soils throughout the world of 25 Bq-kg- t with a typical range of 10 to 50 Bq-kg- I. These values are equivalent to 2 p,g_g-t with a range of 0.8 to 4.1 p,g_g-I. Thus, surficial sediments from the turning basin and west slip are heavily contaminated with U, while sediments from the Ganaraska River and the outer harbour beyond the west slip appear close to the average for uncontaminated sediments. Concentrations of U previously reported in the surficial 2.5 cm of nine sediment cores from the Port Hope Harbour turning basin in 1968 ranged from 120 to 18,000 p,g_g-I (EPS 1981) in comparison to the range of 48.3 to 1,280 p,g_g-t in surficial sediments of the turning basin in this study. These data suggest a considerable decline in U concentrations in surficial sediments over 16 years, although the 1984 sampling stations were not coincident with the 1968 cores and spatial heterogeneity in U concentration may contribute to this apparent decline. The apparent decline is likely related to the decline in radionuclide inputs and burial of older, more contaminated sediment by relatively uncontaminated material. The average rate of burial appears to be on the order of 14 mm per year based on historical depth soundings (EPS 1981). At this rate of sedimentation, alJ~roximately 22 cm of fresh sediment would have accumulated in the turning basin between the 1968 and 1984 surveys. This accumulation is probably due to periodic flooding of the Ganaraska River, to shoreline filling and construction activities, and to inputs from other municipal drainage. Apparent dumping of refinery residues in the harbour in earlier decades also may have contributed to this longterm average sedimentation rate. Natural U is 99.275070 U-238, 0.72070 U-235, and 0.0057070 U-234 based on the proportion of atoms present. U-238 decays through several intermediates to U-234. Th-230 is the first long-lived decay daughter of U-234, and at secular equilibrium has the same activity as U-234. However, the activity of Th-230 measured in Port Hope Har-

211

bour was always greater than the activity of total U. Th shows a greater affinity for sediment than does U, with a log particulate/water partition'coefficient in freshwater systems of greater than 6.5 for Th and only about 4.0 for U (Santschi 1984). The affinity of Th for sediments, plus the preferential removal of U as a product of refining, apparently results in excess Th-230 levels in surficial sediments in the harbour. Ra-226 activities in the surficial 2.5 cm of cores collected from the turning basin by the OWRC in 1968 ranged from 19 to 260 Bq_g-I, with a geometric mean of 101 Bq-g-t (EPS 1981). A range of .81 to 297Bq-g-1 and a geometric mean of 2.95 Bq-g-t were found in surficial sediments of the turning basin in this study. Thus, like U, activities of Ra-226 in the turning basin appear to have declined since 1968. The decline may be attributed to declines in Ra loadings to the harbour and to burial of more contaminated sediments. With the exception of the sample collected at Station A, all surficial sediments showed a deficiency of Ra-226 relative to Th-230. A deficit of Ra-226 is consistent with the selective removal of Ra by past Ra refining activities, as well as the high solubility of Ra relative to Th (Snodgrass et al. 1983). Pb-21O and its granddaughter Po-21O appear to be in secular equilibrium in the surficial sediments of the harbour, as their activities are approximately the same. However, Pb-21O activity in the harbour is considerably greater than activity of its grandparent Ra-226. Pb is typically less soluble than Ra (e.g., Santschi 1984, Snodgrass et al. 1983); thus, an excess of Pb-21O relative to Ra-226 is reasonable for sediments. Pb-21O activity in Port Hope Harbour should fall over time since it is unsupported by similar activity of its grandparent in the sediment and since Ra-226 loadings have been eliminated from refinery operations. Other Sediment Properties Results of non-radiological analyses of surficial sediments are summarized in Table 2 for turning basin/west slip and outer harbour/confluence areas. Concentrations of the heavy metals which are most elevated in U and Ra refinery residues, such as Zn, Co, Cu, Pb, Fe, and Ni, were higher in the surficial sediments of Station A than elsewhere in the harbour (Table 3). This is consistent with the high radionuclide levels also found at this location. A metallic orange oxide colouration of the sediments at Station A probably reflects the high Fe

HART et ale

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TABLE 2. Physical-chemical properties of surficial sediments in Port Hope Harbour. Meanl,3 Concentration and Range (in brackets)

Parameter 1 Psize4* pH* Moisture* LOP* HzS N* C* Zn Cd6 Mn Fe* Co Cu Ag Pb Cr* Ni Ca

Units Z

070

% % % %

K

53.15 7.9 61.2

13.6 25 0.57 5.57 205.7

1.2 601 mg'g- I

32.1 57

122 mg'g- l

6 0.483 50

58 mg'g- l

V AF Mg Ba*

Turning Basin and West Slip (N = 13)

mg'g- l mg'g- l

114 33 10.9 9.1 179 2,036 178 446 69 12 45.7

(5.10-86.5) (7.0-8.0) (22.6-88.5) (1.4-26.7) (1-590) (0.05-1.28) (0.55-10.9) (30.0-780) (1-2) (112-1070) (12.4-51.0) (8-5800) (6-6600) (1-71) (0.01-34.0) (12-123) (5-6600) (74-135) (16-137) (3.7-16.8) (4.3-11.5) (35-670) (590-3100) (114-210) (260-570) (23-142) (3-76) (5.3-77.4)

Outer Harbour and Confluence (N = 6)

2.25 8.6 22.7 0.7 5 0.10 0.49 15.6 1 276

13.8 3 3 1 0.008 10.2 5 109 15 2.3 4.9 12 459 161 104 27 1 1.9

Ganaraska Station H

(0.0-6.70) (8.3-9.0) (16.7-28.4) (0.4-0.9) (1-211) (0.05-0.35) (0.10-0.95) (14.0-22.0) (280-330) (6.6-22.0) (2-4) (2-4) (0.004-0.019) (6-15) (3-7) (98-127) (6-30) (1.9-2.9) (4.0-6.1) (8-16) (390-570) (142-184) (240-300) (18-35) (1-2) (1-4.5)

Sr Na Zr F ng'g- l PCB* 1* indicates non-transformed parameters with arithmetic means; other means are geometric. z/Lg'g- unless otherwise indicated. . . . 3Italicized values exceed Ministry of Environment guidelines for open water disposal of dredged spoils (Persaud and Wilkms 1976). 4Psize = particle size, 070 less than 90 /Lm. sLOI = loss on ignition. 1 • 60ver-estimated due to inclusion of detection limit (l/Lg'g- ) for values less than detection. 7aqua regia digest probably does not capture total aluminum content.

content (5.1 %) and associated metal precipitates. The similarity of sediment chemistry at Station A to the chemistry of residues (Table 3) suggests that residue materials were at some point released directly into the harbour. The lack of a surface layer of less contaminated sediments on the apparent residue materials may be due to the current from nearby cooling water discharges preventing deposition of sediments. Sediment core profiles from Stations Band D show sediment chemistry in the deep sediments of the turning basin in general to be similar to surficial sediment chemistry at Station A (McKee et al. 1985). Former metal fabrica-

84.00 7.1 65.8

15.9 29 0.30 3.05 156.0 1 1,035 26.0 7 30 1 0.235

31 16 176 23 9.9 8.9 136 2,450 260 435 45 5

51.1

tion operations also may have contributed to metal contamination in the harbour sediments. In the turning basin and west slip, mean concentrations of N, loss on ignition, Fe, Cu, Pb, Cr, Zn, and Ni failed to meet MOE guidelines for the open water disposal of dredged materials (Persuad and Wilkins 1976). Among these parameters, mean Fe, Cu, Pb, and Ni concentrations in turning basin/west slip sediments exceeded the concentration ranges given for sediments of small craft harbours in the lower Great Lakes (Thomas and Mudroch 1979) or sediments at the mouths of 116 Great Lakes tributaries (Fitchko and Hutchinson

PORT HOPE HARBOUR ASSESSMENT

213

TABLE 3. Typical chemical characteristics of uranium/radium refinery residues} compared to sediment contamination at Station A. Parameter

U

Zn Mn Fe Co

Cu Ag Pb

Cr Ni Ca

V Al

Mg Na

Iron Residue l (0/0 dry weight)

Carbonate Residue l (% dry weight)

Station N (% dry weight)

0.36 1 0.5 10 2.3-2.4 2.0-2.1 <0.01 0.5 0.01 1.1-1.2 7 <0.1 5 5 5

0.36 1 0.3 10 0.3-1.0 1.0-1.4 0.05 1 0.01 0.4-0.9 7 <0.1 5

0.128 0.078 0.011

1 3

5.10 0.580 0.66 0.007 3.40 0.012 0.660 12.70 0.014 0.98 0.86 0.057

IFrom Golder Associates and James F. MacLaren Limited (1978); iron residue is from uranium recovery; carbonate residue from raduim recovery. 2Port Harbour maxima in italics.

1975). These concentrations indicate that the sediments of the turning basin/west slip of Port Hope Harbour are more heavily contaminated with several trace metals than most other sediments in the Great Lakes. In the outer harbour sediments (Stations 0 to T), only Fe concentrations exceeded the MOE guidelines. Trace metal concentrations in lower Ganaraska River sediments (Station H) were intermediate between those of the turning basin/west slip and outer harbour, although still in excess of MOE guidelines. PCB concentrations in Station H sediments also slightly exceeded the MOE guidelines (50 ngog- 1), and approached the highest levels found in the turning basin (Table 2).

Bioaccumulation of Contaminants Levels of radionuclides and heavy metals in tissues of benthic invertebrates are provided in Table 4. Comparison with corresponding levels of sediment contamination indicated that bioaccumulation factors were typically less than or nearly one for all radionuclides and heavy metals except Th-228. Bioaccumulation factors for this isotope ranged from 3.36 to 13.54 (mean 9.59 ± 4.31). Bioconcentration data for radionuclides relative to sediment are not common in the literature. However, Swanson (1985) and SENES (1984, 1985) have measured levels of U, Ra-226, and Pb-21O in

benthic insect larvae, and computed sedimentbased bioconcentration factors similar to those in Port Hope Harbour. The highest radionuclide bioconcentration factors reported in these studies were for Ra-226 and were approximately two orders of magnitude lower than typical waterbased bioconcentration factors given by NRCC (1983). This suggests that much of the radionuclide contamination in the sediments is not biologically available due to adsorption, complexation, and/or incorporation into the mineral matrix of the sediments. Chapman et al. (1982) have measured metal concentrations in surficial sediments and tubificids and reviewed data from four other studies of trace metals in sediments and oligochaetes (Mathis and Cummings 1973, Bindra and Hall 1978, Greichus et al. 1977, 1978). Sediment-based bioconcentration factors calculated from data in these studies for Cu, Zn, Pb, Fe, Ni and Co are in the same range as those in Port Hope (Table 4). Cook and Veal (1968) reported Ra-226 activities in tubificid oligochaetes, chironomids, isopods, and plankton from the turning basin in 1968. Ra-226 activities in tubificids were 2.5 to 17 Bqog-l (dry weight) at Stations B, D, E, and F, and 0.04 Bqog-l at Station H. These activities are similar to those reported in benthic tissues from the same harbour areas in this study (Table 4). There was an order of magnitude difference

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TABLE 4. Levels of radionuclides and heavy metals in tissues of benthic organismsI •

Parameter2 U

Th-230 (Bq·g-l) Ra-226 (Bq·g-l) Pb-210 (Bq'g-l) Po-21O (Bq·g-l) Th-232 (Bq·g-l) Th-228 (Bq·g-l) Zn Co Cu Fe (mg'g- l) Pb (mg'g- l) Cr Ni

Turning B 22.8 5.5 3.33 8.1 6.5 0.27 1.76 208 11 27 3.25 0.063 10 12

Basin/West Slip Stations C E M 40.9 17.3 1.7 7.6 1.50 0.188 13.6 0.732 0.40 25.0 2.0 2.6 17.8 3.2 1.2 0.27 0.54 0.033 2.3 1.04 0.34 220 181 120 72 7 2 82 34 10 3.10 3.15 1.62 0.250 0.029 0.004 9 3 5 77 8 6

IMainly Limnodrilus hoffm~isteri or T,ubifex tubifex. 2Tissue concentrations p.g'g- dry welgnt unless otherwise

between Th-232 and Th-228 activities in tissues (Table 4), but not in sediments (Table 1). Uptake and metabolism of two isotopes should be similar. However, Th-232 decays indirectly to Th-228 with Ra-228 as a relatively short-lived intermediate. Since Ra-228 is much more soluble than Th, it diffuses more readily out of the bottom sediments. Its Th-228 daughter precipitates rapidly; nevertheless, this process gives rise to excessive Th-228 activities relative to Th-232 in bottom waters (Nozaki et al. 1981, NRCC 1983). Since it is the dissolved Th which is primarily available for uptake by biota, an excess of Th-228 in benthos is reasonable. Moreover, a significant fraction of the Ra-228 concentrated in biota from interstitial water undergoes radioactive decay to the relatively short-lived Th-228 isotope (half-life = 1.9 years) over the lifespan of the organism. Tissue contamination levels (Table 4) showed the same spatial distribution as sediment contamination levels in the harbour. Benthos of Stations B and C, in the heavily contaminated southwest corner of the turning basin, had higher tissue levels of radionuclides and refinery residue metals than comparable benthic assemblages in other areas. All radionuclides and most of the metals showed lower tissue levels in the west slip (Station M) than in the turning basin. Radionuclide levels were invariably lowest in Ganaraska River benthos (Station H). However, heavy metal concentrations in the same

Ganaraska Station H :50.05 0.006 0.07 :50.3 0.12 0.014 0.074 129 3 14 5.00 0.005 11

4

Mean Bioconcentration Factors :50.136 0.157 1.94 :51.16 0.878 0.820 9.59 0.900 0.534 0.328 0.100 0.222 0.495 0.414

stated.

organisms at Station H equalled or exceeded tissue levels in the west-slip. Fe and Cr in Station H tissues exceeded tissue levels in the turning basin (Table 4), although this difference was not reflected in the sediments (Table 2). Benthic Communities Forty benthic invertebrate taxa were found in Port Hope Harbour sediments, including 17 oligochaetes and 14 chironomids. Coelenterates (Hydra sp.), nematodes, leeches (Erpobdella sp.), bivalves (Pisidium sp.), arachnids (Hydracarina), Crustacea (three genera), and beetle larvae (Dubiraphia sp.) were also represented in the collection. A detailed list of benthic species and densities is presented in Mckee et al. (1985). Figure 2 illustrates the biological relationships among sampling stations based on cluster analysis of their benthic faunas. Most turning basin/west slip stations cluster together, indicating that they form a biologicallydistinctive group. Similarly, the outer harbour/ confluence stations cluster together. Station G, in the west slip, is biologically more similar to the outer harbour/confluence area than to other stations in the turning basin/west slip. Stations Hand J are not closely related to either biological grouping, or to each other. Benthic densities in the turning basin/west slip group (Stations A-F, I, K-N) were high (9,600'm-2

215

PORT HOPE HARBOUR ASSESSMENT

>-

Z

o

~

~~

Vi

<.9Z

ow -10 I

(j)

T

I

EUCLIDEAN DISTANCE BETWEEN STATIONS

oI

5

10

I

I

15 I

20 I

25 I

r5TR- ~

0

Q- J G

o

P

•

•• • •

M N F I -W

e-

• •

I

Pl

DB L- W A E K H J

l-

I

FIG. 2. Cluster analysis of biological distances between Port Hope Harbour stations (e = increase in density or diversity from 1968 to 1984, 0 = decrease, p < 0.05; stations I to T were not sampled in 1968).

to 112,500om-2) (Table 5). They were slightly higher on average than reported by Cook and Veal (1968), although the average difference was not significant (paired t-test, p > 0.05). Comparison of densities at each station in 1968 with the corresponding 1984 confidence intervals suggests increased abundance in 1984 at Stations A, C, D, and E, and decreased abundance at Station G (Fig. 2). The 0.65-mm mesh used for sample sieving in 1968 was greater than the 0.2-mm mesh used in this study; thus, the greater densities observed at some stations in 1984 may be partially attributed to a greater retention of small benthic organisms in the samples. An apparent toxic response was suggested for Station A in 1968, since no organisms were found at that station. This was not obvious in 1984; however, densities were significantly lower at Station A (9,600om-2) than at any other station in the turning basin, except the adjacent Station B (SNK, p < 0.05). The surficial sediments at Station A were much more contaminated than at other locations in 1984, although habitat effects related to substrate scouring by the nearby cooling water dis-

charge may also be involved in the lower abundances at this station. McMurtry (1984) has shown that Limnodrilus hoffmeisteri and Tubifex tubifex actively avoid sediments contaminated with Cu at concentrations of 570 p,gog-I, about 10070 of the concentration at Station A. Benthic densities were typically lower in the outer harbour/confluence (Stations G, 0-T) than inner harbour areas (Table 5), ranging from 118 om-2 at Q to 19,I00om-2 at P. Sediments at these stations are fine to medium sands with low organic contents; thus, lower densities can be attributed to the effects of an unstable wave-washed substrate and a reduced food base. Total organism abundance in 1984 differed significantly among stations (ANOVA, p < 0.0001), primarily due to differences between the inner and outer harbour stations. Species diversities at Stations A through H were marginally greater in 1984 than in 1968 (paired ttest, p = 0.05). Higher diversities in 1984 were observed at six of the eight stations, with differences exceeding the 1984 confidence interval at Stations A, B, and F (Fig. 2). Species diversity in

HARTetal.

216

TABLE 5. Port Hope Harbour benthic community characteristics. Station Groups' A-F, I, K-N 0.57-1.40

H

1.41

J 1.69

2.68-3.75

3.80

3.87

Potamothrix moldaviensis (4) Limnodrilus hoffmeisteri (1)

L. hoffmeisteri (7) Quistadrilus multisetosus (3) Tubifex tubifex (1)

L. hoffmeisteri

Specaria josinae

Pisidium sp. (I) Nematoda (1)

other Tubificidae

Naididae

Asellus sp.

Characteristic Brillouin Diversity

G, O-T 0.37-1.20

Log,o Total Density3

0.77-2.98

Dominant Oligochaete Species2

Other Dominant Taxa 2

'Station groups defined by cluster analysis of species composition (see Fig. 2). 2Number of stations dominatsd by each taxon in parentheses. 3Based on mean densities (m- ) per station.

1984 was slightly greater on average in the turning basin/west slip than the outer harbour/confluence (Table 5). However, variance in diversity differed significantly from one station to another (Bartlett's test, p < 0.03), precluding any statistical test of diversity differences among stations. The dominant species in the turning basin/west slip area were, in the order of importance, the tubificids Limnodrilus hoffmeisteri, Quistadrilus multisetosus, and Tubifex tubi/ex (Table 5). Other tubificids (Limnodrilus cervix, Limnodrilus udekemianus, and Potamothrix vejdovskyl) were also abundant. Low numbers of chironomids (Chironomus spp., Dicrotendipes sp., Microtendipes sp., Cricotopus spp., and Procladius sp.), amphipods (Gammarus sp.), and Hydracarina were present at some stations. This oligochaete assemblage has been found in the polluted sediments of several harbour and nearshore areas in Lake Ontario, including Hamilton Harbour (Johnson and Matheson 1968), Toronto Harbour (Brinkhurst 1970), and Oswego Harbour (Boscor et al. 1974). Where this group dominates the community at high densities, eutrophic or organically enriched conditions are generally implicated (Brinkhurst et al. 1968, Cook and Johnson 1974). The dominant taxa in the outer harbour/ confluence area (Stations G, 0-T) in order of importance were the tubificids Potamothrix moldaviensis and L. hoffmeisteri, while nematodes and clams (Pisidium sp.), respectively, dominated

at the two most depauperate stations, 0 and Q (Table 5). Krieger (1984) found that Potamothrix was more frequent outside Lake Erie harbour areas than inside, suggesting a lower tolerance of environmental degradation. This pattern appears to apply in Port Hope Harbour. Other common species in the outer harbor were chironomids (Chironomus spp., Cryptochironomus sp., Paracladopelma sp., Polypedilum sp., Monodiamesa sp., Potthastia sp., and Psectrocladius) and amphipods (Pontoporeia sp.). This low density assemblage is similar to that described by Barton anq Hynes (1978) for the nearshore wave zone of Lake Ontario, and does not suggest severe pollution. The unique community at Station J was dominated by the naidid Specaria josinae, with other naidids (Ophidonais serpentina), tubificids (Q. multisetosus), isopods (Asellus sp.), and amphipods (Gammarus sp.) abundant. Chironomids included Chironomus spp., Dicrotendipes sp., and Cladotanytarsus sp. This diverse assemblage is typical of nearshore Lake Ontario communities associated with alga Cladophora (Nalepa and Thomas 1976), and is probably more indicative of the vegetation cover unique to this station than of underlying sediment quality. However, both oligochaete (Cook and Johnson 1974) and chironomid species present (Saether 1979) suggest eutrophic or polluted conditions. At Station H, in the Ganaraska River, the dominant oligochaete species was L. hoffmeisteri, as in

PORT HOPE HARBOUR ASSESSMENT

4

A,B,C,D,E, F,I,J,K,L,M,N

en z o

~ 3 t-.:: en ~ 2

217

I

G,o,p,a, R,S,T I

0::: W CD

~I

z

12

16

FIG. 3. Distribution of Port Hope Harbour benthic stations along a discriminant function of sediment parameters.

most of the turning basin. However, the additional presence of the naidids Amphichaeta sp., S. josinae, and Vejdovskyella intermedia, in association with decomposing vascular plants, was unique. All these naidids have been related to degraded sediment quality (Lafont 1984) perhaps suggesting some pollution in the lower river. The discriminant scores (Fig. 3) represent a composite index of sediment quality differences between inner and outer harbour biological communities. Station H in the Ganaraska River is intermediate between these communities, reflecting an intermediate level of overall sediment contamination. Station G is similar in sediment quality to the outer harbour stations, indicating a possible sediment quality basis for its biological affinities. However, Station J is not distinguishable from the other turning basin/west slip stations on this sediment quality basis. Its unique biota probably represents the independent influence of algal vegetation on species composition. Chemotoxic effects are likely more important than radiation effects in contributing to differences in species composition between inner and outer harbour communities. The dose rate to sediment-dwelling biota from the U series radionuelides was estimated at approximately 1 mGy/ day in the turning basin/west slip (Stations B-F, I-N), following IAEA (1976) calculations for a cylindrical body form and assuming uniform tissue concentrations of radionuelides equal to average sedi-

ment concentrations. Effects on invertebrate abundance and population performance have not been reported at dose rates of this order of magnitude, although cytogenetic effects in chironomid larvae (Blaylock 1966) and reproductive effects in aquatic snails (Cooley 1973) have been reported in White Oak Creek, Tennessee, at similar radiological dose rates. Investigations of possible genetic effects in Port Hope Harbour chironomids are in progress.

CONCLUSIONS The levels of U and Th series radionuelides, as well as the levels of trace elements associated with refinery residues, were higher in the Port Hope Harbour turning basin sediments compared to the outer harbour and lower Ganaraska River sediments. Loss on ignition, N, Fe, Cu, Pb, Cr, Zn, and Ni concentrations in the turning basin/west slip exceeded provincial guidelines for open water disposal of dredged spoils. Iron, Cu, Pb, and Ni concentrations in the turning basin/west slip were higher than reported in surveys of contaminated sediments from throughout the Great Lakes. Conversely, only Fe exceeded dredging guidelines in the sediments from the outer harbour/confluence. The greatest contamination of surficial sediments occurred at Station A in the turning basin near the U refinery cooling water discharge.

HART et al.

218

The turning basin/west slip and outer harbour/ confluence benthic communities were distinctive from each other in terms of species composition and overall density, although tubificids dominated both communities. The differences can be attributed either to differences in contamination or habitat or both. The species composition was unique at Station J in the turning basin, where species associated with algal vegetation were abundant, and at Station H in the lower Ganaraska River where decomposing vascular vegetation may influence the benthic fauna. Tissue levels of V and Th series radionuclides and heavy metals in benthic invertebrates were greatest at the most heavily contaminated stations. Sediment-based benthic bioaccumulation factors were highest for Th-228, and typically less than or near one for other radionuclides and heavy metals. A relatively low invertebrate density occurred at the most contaminated location (Station A), suggesting that the benthic community of the turning basin would be adversely affected by dredging in the turning basin if the more heavily contaminated deeper sediments became directly exposed at the sediment water interface after dredging. Complete removal of the deep contaminated layer would prevent this impact. Mobilization of contaminants from the sediment to the water column during dredging may result in temporary toxic conditions in the water column of the turning basin. ACKNOWLEDGMENTS This work was jointly sponsored and reviewed by the Environmental Protection Service, Ontario Region, and the Atomic Energy Control Board of Canada. Radiochemical analyses were performed by Monenco Analytical Laboratories Ltd, under the direction of Drs. N. Chiu and J. Dean. Field support was provided by R. Jonczyk and J. Sferrazza. Mr. P. Mark Green drafted the figures. REFERENCES American Public Health Association (APHA). 1980.

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