- Email: [email protected]
Pesticides in Sediments From Queensland Irrigation Channels and Drains
PII:
Marine Pollution Bulletin Vol. 41, Nos. 7±12, pp. 294±301, 2000 Ó 2000 Elsevier Science Ltd. All rights reserved Printed in Great Britain S0025-326X(00)00095-3 0025-326X/00 $ - see front matter
Pesticides in Sediments From Queensland Irrigation Channels and Drains JOCHEN F. MULLER *, SABINE DUQUESNE , JACK NG , GLEN R. SHAW , K. KRRISHNAMOHAN , K. MANONMANII , MARY HODGEà and GEOFF K. EAGLESHAMà National Research Center For Environmental Toxicology, University of Queensland, 39 Kessels Road, Coopers Plains, Qld 4108, Australia àQueensland Health Scienti®c Services, University of Queensland, 39 Kessels Rd, Coopers Plains, Qld 4108, Australia Pesticide concentration in sediment from irrigation areas can provide information required to assess exposure and fate of these chemicals in freshwater ecosystems and their likely impacts to the marine environment. In this study, 103 sediment samples collected from irrigation channels and drains in 11 agricultural areas of Queensland were analysed for a series of past and presently used pesticides including various organochlorines, synthetic pyrethroids, benzoyl ureas, triazines and organophosphates. The most often detected compounds were endosulphans (a, b and/or endosulphan sulphate) which were detectable in 78 of the 103 samples and levels ranged from below the limit of quanti®cation (0.1 ng gÿ1 dw) up to 840 ng gÿ1 dw. DDT and its metabolites were the second most often detected pesticide investigated (74 of the 103 samples) with concentrations up to 240 ng gÿ1 dw of +DDTs. Mean +endosulphan and +DDT concentrations were 1±2 orders of magnitude higher in sediments from the irrigation areas which are dominated by cotton cultivation compared to those which are dominated by sugarcane cultivation. In contrast to these insecticides, the herbicides diuron, atrazine and ametryn were the compounds which were most often detected in sediments from irrigation drains in sugarcane areas with maximum concentrations in areas of 120, 70 and 130 ng gÿ1 dw, respectively. In particular during ¯ood events, when light is limiting, transport of these photosynthesis inhibiting herbicides from the sugarcane cultivation areas to the marine environment may result in additional stress of marine plants. Ó 2000 Elsevier Science Ltd. All rights reserved.
Introduction Sediment can be an important sink for persistent organic pollutants including many pesticides in present and past uses. Analytical results from sediments have been used to evaluate pollutant sources (Eitzer, 1993), historical trends (Jones et al., 1992) and to predict water and thus exposure concentrations of biota in the aquatic environment (Mackay, 1991; Connell, 1990). AustraliaÕs north-eastern state, Queensland, is located in a subtropical to tropical region and has a relatively low population density when compared to other industrialized countries. Agriculture is one of the StateÕs most important industries and is dominated by sugarcane and cotton cultivation which to date rely on intensive plant protection using pesticides. Depending on the physicalchemical properties of the compounds, local properties of the soil, topographical parameters and the climate, a fraction of the applied pesticide is transported into the irrigation drains and ultimately downstream into the marine environment and into the Great Barrier Reef Marine Park (GBRMP). The channels and drains in irrigation areas are subject to periodical desilting in which accumulated sediment and associated contaminants from the irrigation channels and drains are dug out and deposited along the banks of the water channel. The results presented here are part of a study which focussed on pesticide contamination in the desilted sediments including the potential for accumulation in grazing cattle.
Material and Methods
*Corresponding author. Tel.: +61-7-3274-9009; fax: +61-7-32749003. E-mail address: [email protected] (J. F. MuÈller).
294
Sampling areas The sediments were collected from 11 irrigation areas in Queensland (Fig. 1). The regions can be dierentiated into those which are dominated by either sugarcane or cotton cultivation. In some regions, samples were collected almost exclusively from irrigation drains, whereas
Volume 41/Numbers 7±12/July±December 2000
demonstration of the sampling protocol. Samples were collected between July and November 1998. Samples were collected from either the wet or dry bed in the irrigation drain or from the banks beside the channel and drains if fresh silt was deposited within the last seven days from the sampling date. Each sample consisted of a homogenized composite made of equal fractions of eight subsamples collected at a distance of approximately 10 m from all other subsamples. Samples were collected from the wet bed using a Van±Veen sampler or from the dry bed or the desilted mound using a stainless steel spade. Surface sediment of the top 2 cm layer was removed and discarded if samples were collected from the dry bed or the silt mound. All samples were refrigerated and transported to the laboratory within 48 h and stored at ±20°C until extraction.
Fig. 1 Map of Queensland showing the capital city, the major cotton and sugarcane cultivation areas and sampling regions where sediments were obtained for analysis in this study. (Note that samples were collected only in selected areas marked with an arrow and the regions name.)
in other regions only supply channels exist and were sampled (Table 1). The majority of samples originated from either the Emerald irrigation area which is dominated by cotton cultivation (26 samples) or the Burdekin irrigation area (BRIA) dominated by sugarcane production (21 samples). Sampling Sampling was carried out by ®eld ocers from the Department of Natural Resources, Queensland, who received detailed instructions including an audiovisual
Analysis Samples were thawed, homogenized and a subsample (15 g) was extracted with 100 ml acetone (all solvents used were nanograde) in a mechanical shaker overnight. Samples were then centrifuged and the supernatant was subjected to liquid/liquid extraction after the addition of 50 ml of saturated NaCl solution and about 200±300 ml dichloromethane (as much as was required for the aqueous phase to rise to the top). The nonpolar fraction was ®ltered through anhydrous sodium sulphate and concentrated using a rotary evaporator and transferred into n-hexane. The extracts were puri®ed on a column (18 mm I.D.) ®lled with 20 cm of Florisilä deactivated with 5% H2 O. Compounds of interest were eluted in three separate fractions using 120 ml of n-hexane/diethylether (94/6 V/V), followed by 90 ml of n-hexane/ acetone (90/10 V/V) and ultimately 120 ml n-hexane/ acetone (50/50 V/V). The ®rst two fractions were then concentrated to 1 ml and analysed for the organophosphorus pesticides using GC±FPD and GC±NPD. The ®rst fraction (n-hexane/ diethylether eluate) was subjected to a sulphur removal clean-up. Samples were transferred to test tubes and 1 ml of tetrabutyl ammonium hydroxide, 2 ml isopropanol
TABLE 1 Areas covered by the various regions where the study sites were located, number of samples collected from each region, major land use and type of irrigation system which has been sampled in the study. Region (abbreviation) Burdekin (BRIA) Emerald Dawson Valleyb St George Mareeba-Dimbulah (MDIA) Bundaberg Callide Valleyb Warrill Valleyb Lockyer Valleyb Eton Lower Mary a b
Sample No. 22 26 14 12 10 4 4 3 3 3 2
Area (in 1000 ha) 33 20 7.9 14 17 58 5.6 19 6.2
Major crops
Irrigation system sampleda
Sugarcane/horticulture Cotton/horticulture Cotton Cotton Horticulture/sugarcane Sugarcane/horticulture Cotton/horticulture Horticulture/fodder Horticulture Sugarcane Horticulture/fodder
Mainly drains Mainly drains Mainly drains Mainly drains Mainly drains Channels Channels Channels Channels Channels Channels
The term channel refers to water supply channels while the term drain refers to the irrigation drains. Abbreviated as Dawson, Warrill, Lockyer and Callide, respectively, in Fig. 1.
295
Marine Pollution Bulletin
and small amounts of anhydrous sodium sulphite were added. After shaking (60 s) 5 ml of H2 O was added and the samples were again shaken (60 s). The top layer was carefully transferred using an extra 2 ml of n-hexane and concentrated under a gentle stream of nitrogen to 1 ml. Both the ®rst fraction (after sulphur clean-up) and the second fraction from the Florisilä column were then analysed for organochlorines and selected organophosphates using dual column GC±ECD. A selection of the samples in which concentrations were found to be relatively high were analysed using GC±MS (full ion scan) for structural con®rmation of the analytes. Once the results were evaluated, all three fractions from the Florisilä column were combined and a solvent exchange to methanol was undertaken. Then the samples were analysed using multiple reaction monitoring with a triple stage quadrupole LC-MS/MS system (API 300 PE/ Sciex Instruments). The analytical method was subject to standard QA/ QC procedures. Blanks and a series of spikes, which contained known quantities of the analytes, were included in each batch (usually 12 samples). The reporting limit was de®ned as ®ve times the average values of the baseline noise signals and/or three times the concentration in a representative blank.
Results Pesticides were found in most of the 103 sediment samples. The most widely detected compounds were p,p0 -DDE, diuron, endosulphan-SO4 , atrazine and bendosulphan, all of which were detected in more than 50% of the sediment samples collected. Endosulphan (present as a, b and/or endosulphan sulphate) was detectable in 76% P of the 103 samples and the mean concentration of endosulphan in the 78 samples in which P it was detected was 42 ng gÿ1 dw. The endosulphan concentrations ranged from below the quanti®cation limit (0.l ng gÿ1 dw) to 840 ng gÿ1 dw in a sample from a drain in the Emerald irrigation area. DDT and its metabolites were the second most often detected pesticide investigated since in 74% samples P one or more of the DDTs were detected. The mean DDT concentration in these 76 samples was 32 ng gÿ1 dw. The highest P DDT concentration was 240 ng gÿ1 dw and was determined in a sediment sample collected from a drain in the Dawson irrigation area. The herbicide diuron was detected in 72% of the samples and the mean detected concentration was 30 ng gÿ1 dw with the highest concentration (340 ng gÿ1 dw) observed in sediments from a drain in the Dawson irrigation area. Atrazine was the pesticide which was the fourth most often detected (55% of the samples) with a mean detected concentration of 6.5 ng gÿ1 dw. Herbicides such as prometryn, ¯uometuron and ametryn were also detected in 30±50% of the samples and the mean detected concentration was 3.2, 12 and 9.7 ng gÿ1 dw, respectively. Chlorpyrifos was found in 39% of the samples and the mean detected 296
concentration was 4.8 ng gÿ1 dw. Other pesticides investigated were found in only a few samples and usually at concentrations of less than 5 ng gÿ1 dw. Hexachlorobenzene for example, which was detectable in 22 samples, did not exceed 1 ng gÿ1 dw in any of the samples analysed. Dierences between sampling regions A comparison of the results with respect to dierences between the various sampling regions is given in Table 2. Highest concentrations of almost all insecticides studied were found in sediments from drains in cotton growing regions (Emerald, Dawson and St George).PBoth the maximum P and the mean concentrations of endosulphan and DDT in sediments from irrigation drains in cotton growing areas were 1±2 orders of magnitude higher than those from areas dominated by sugarcane cultivation. Endosulphan was found in each sample from the Emerald, Dawson and St George regions, while it was not detected in about half of all other samples. Similarly, DDTs were more often detected in samples from drains in cotton growing areas than all other samples. Chlorpyrifos was almost exclusively found in drain sediment samples from the cotton growing regions with a maximum concentration of 94 ng gÿ1 dw in a sample from Dawson. In contrast to the insecticides being the dominant contaminants of interest in the sediments from cotton growing areas, the herbicides diuron, atrazine and ametryn were the compounds most frequently detected in sediments from irrigation drains in sugarcane areas. Atrazine and ametryn were, for example, detected in all 21 sediment samples and diuron in 20 of the 21 sediment samples collected in the Burdekin irrigation area. The mean and maximum concentrations of diuron, atrazine and ametryn in sediments from the Burdekin irrigation area were in the range of 13±25 ng gÿ1 dw (mean of detectables) and 70±130 ng gÿ1 dw (maximum). Within a given region, the compound concentrations in sediment samples varied substantially P from site to P site. For example, the endosulphan or DDT concentration in drains from Emerald varied over more than three orders of magnitude despite the latter being banned for use in Australia for more than a decade. The great variability of compound concentration between samples from a given site appears to be similar for most compounds investigated, although it is not possible to assess this for compounds which barely exceeded detection limits. In comparison to endosulphans, DDTs, or the three dominant herbicides diuron, atrazine and ametryn, the concentrations of many banned organochlorine compounds including hexachlorobenzene, lindane, heptachlor, aldrin and dieldrin were relatively low. The mean concentrations of these latter compounds in any of these regions were less than 1 ng gÿ1 dw and only dieldrin and aldrin were found to exceed 1 ng gÿ1 dw in samples from individual sites (Table 2).
TABLE 2
100 (0.91±360) [15/15] 52 (<0.07±240) [13/15] 80 (8.8±340) [15/15] 5.1 (<0.5±41) [11/15] 0.14 (<0.07±0.27) [4/15] <0.05 [0/15] 0.15 (<0.05±0.24) [6/15] <0.05 [0/15] <0.1 [0/15] 0.39 (<0.07±0.69) [3/15] 4.2 (<0.5±6) [2/15] <1 [0/15] <0.5 [0/15] 8.1 (0.09±94) [15/15] <1 [0/15] 0.09 (<0.09±0.1) [1/15] <0.5 [0/15] 4.7 (<0.2±18) [4/15] 3.2 (0.21±10) [6/15] 17 (<1±61) [14/15] 0.98 (<0.5±0.98) [1/15] 0.23 (<0.2±0.23) [1/15]
Dawson cotton 1.0 (<0.27±1.7) [5/10] 1.9 (<0.3±5.9) [5/10] 9.1 (<0.36±37) [5/10] 0.23 (<0.5±0.23) [1/10] 0.2 (<0.1±0.2) [1/10] <0.05 [0/10] <0.05 [0/10] <0.05 [0/10] <0.1 [0/10] 0.06 (<0.05±0.07) [2/10] <0.5 [0/10] <1 [10/10] <0.5 [10/10] <0.1 [0/10] <1 [0/10] <0.5 [0/10] <0.5 [0/10] 15 (<0.2±30) [2/10] 0.45 (<0.2±0.45) [1/10] <1 [0/10] <0.5 [0/10] 0.17 (<0.15±0.17) [1/10]
MDIA sugarcane 2.0 (<0.05±13) [14/21] 2.6 (<0.07±6) [10/21] 25 (<1±120) [20/21] 13 (0.46±70) [21/21] 0.03 (<0.03±0.03) [2/21] 0.037 (<0.05±0.04) [1/21] <0.05 [0/21] 0.053 (<0.04±0.06) [3/21] 0.13 (<0.1±0.13) [1/21] 0.09 [1/21] <0.5 [0/21] <1 [0/21] 2.0 (<0.5±2) [1/21] 1.2 (<0.27±2.8) [3/21] <1 [0/21] 0.25 (<0.5±0.25) [1/21] <0.5 [0/21] 14 (0.11±130) [21/21] 0.53 (<0.18±1.6) [5/21] <1 [0/21] 0.61 (0.46±0.71) [3/21] 0.38 (<0.15±0.38) [1/21]
0.74 (0.14±1.3) [3/4] 0.56 (0.09±1.3) [4/4] 0.56 (<0.4±0.56) [1/4] 0.40 (<0.25±0.54) [2/4] 0.073 (<0.03±0.1) [3/4] <0.05 [0/4] 0.12 (<0.05±0.12) [1/4] <0.05 [0/4] 0.21 (<0.1±0.21) [2/4] <0.04 [0/4] <0.5 [0/4] <1 [0/4] <0.5 [0/4] <0.5 [0/4] <1 [0/4] <0.5 [0/4] <0.5 [0/4] 0.25 (0.14±0.37) [4/4] <0.5 [0/4] <1 [0/4] <0.5 [0/4] <0.5 [0/4]
0.10 [1/4] 0.28 (0.05±0.85) [4/4] 2 (<1±2) [1/4] <0.5 [0/4] <0.03 [0/4] 0.05 (<0.05±0.05) [1/4] 0.1 (<0.05±0.1) [1/4] <0.05 [0/4] 0.05 (<0.05±0.05) [1/4] 0.09 (<0.04±0.09) [1/4] <0.5 [0/4] <1 [0/4] <0.5 [0/4] <0.5 [0/4] <1 [0/4] <0.5 [0/4] <0.5 [0/4] 0.4 (<0.1±0.4) [1/4] <0.5 [0/4] <1 [0/4] <0.5 [0/4] <0.5 [0/4]
0.11 [1/3] 0.47 [3/3] <0.4 [0/3] <0.5 [0/3] <0.03 [0/3] 0.7 [1/3] <0.05 [0/3] <0.05 [0/3] <0.1 [0/3] <0.04 [0/3] <0.5 [0/3] <1 [0/3] <0.5 [0/3] <0.5 [0/3] <1 [0/3] <0.5 [0/3] <0.5 [0/3] <0.2 [0/3] <0.5 [0/3] <1 [0/3] <0.5 [0/3] <0.5 [0/3]
BRIA sugarcane Callide sugarcane Bundaberg sugarcane Lockyer 2.4 [1/3] 2.8 [2/3] <0.4 [0/3] 1.1 [1/3] <0.03 [0/3] <0.05 [0/3] <0.05 [0/3] <0.05 [0/3] <0.1 [0/3] <0.04 [0/3] <0.5 [0/3] <1 [0/3] <0.5 [0/3] <0.5 [0/3] <1 [0/3] <0.5 [0/3] <0.5 [0/3] <0.2 [0/3] <0.5 [0/3] <1 [0/3] <0.5 [0/3] <0.5 [0/3]
<0.3 [0/2] <0.05 [0/2] 7.9 [1/2] <0.5 [0/2] <0.03 [0/2] <0.05 [0/2] 0.29 [1/2] <0.05 [0/2] <0.1 [0/2] 0.42 [1/2] <0.5 [0/2] <1 [0/2] <0.5 [0/2] <0.5 [0/2] <1 [0/2] <0.5 [0/2] <0.5 [0/2] <0.2 [0/2] <0.5 [0/2] <1 [0/2] <0.5 [0/2] <0.5 [0/2]
Warrill Lower Mary
<0.3 [0/3] <0.05 [0/3] <0.4 [0/3] <0.5 [0/3] <0.03 [0/3] <0.05 [0/3] <0.05 [0/3] <0.05 [0/3] <0.1 [0/3] 0.19 [1/3] <0.5 [0/3] <1 [0/3] <0.5 [0/3] <0.5 [0/3] <1 [0/3] <0.5 [0/3] <0.5 [0/3] <0.2 [0/3] <0.5 [0/3] <1 [0/3] <0.5 [0/3] <0.5 [0/3]
Eton
Samples in which the compounds were not detectable were not included in the calculation of the mean. The minimum and maximum concentrations are given in ( ) while the number of samples in which compounds were detected and the number of samples analysed from the respective irrigation area are given in [ ]. Samples were also analysed for fenthion, cyhalothrin, deltamethrin, cypermethrin and ¯uazuron but none of these compounds were detectable in any of the samples.
a
84 (0.46±840) 43 (4.1±100) [26/26] [12/12] Total DDT 35 (<0.1± 160) 79 (2±230) [23/26] [12/12] Diuron 17 (<1±54) 6.3 (<0.4±14) [25/26] [7/12] Atrazine 2.4 (<0.5±11) 1.1 (<0.5±1.1) [20/26] [1/12] HCB 0.068 (<0.03±0.16) <0.03 [12/26] [0/12] HCH <0.05 <0.05 [0/26] [0/12] Aldrin 0.32 (<0.04±2.2) <0.05 [9/26] [0/12] Heptachlor 0.10 (<0.03±0.18) <0.05 [6/26] [0/12] Heptachlorepoxide 0.10 (<0.1±0.1) 0.08 (<0.1±0.08) [1/26] [1/12] Dieldrin 0.90 (<0.04±3.3) <0.05 [4/26] [0/12] Diazinon <0.5 2.2 (<0.5±4.2) [0/26] [2/12] Fenitrothion 1.3 (<1±1.3) <1 [1/26] [0/12] Parathion 3.4 (<0.5±6.3) <0.5 [2/26] [0/12] Chlorpyrifos 0.89 (<0.2±3.2) 8.5 (<0.02±49) [16/26] [6/12] Bifenthrin <1 10 (<0.2±29) [0/26] [3/12] Chlor¯uazuron 0.86 (<0.5±1.3) <0.5 [7/26] [0/12] Tri¯uaraline <0.5 0.24 (0.13±0.43) [0/26] [3/12] Ametryn 0.33 (<0.2±0.38) <0.2 [3/26] [0/12] Prometryn 2.0 (<0.2±5.2) 8.2 (<0.5±40) [22/26] [8/12] Flumeturon 9.8 (<0.43±58) 7.9 (<1.0±23) [18/26] [5/12] Simazine <0.5 <0.5 [0/26] [0/12] Hexazinone 0.25 (<0.2±0.3) <0.2 [3/26] [12/12]
Total endosulphan
Emerald cotton St George cotton
Mean of detectable concentrations, and maximum and minimum pesticide concentrations (ng gÿ1 dw) as well as the number of samples in which the compound was detected and the number of samples analysed for the sediments from irrigation channels and drains in Queenslands irrigation areas.a
Volume 41/Numbers 7±12/July±December 2000
297
Marine Pollution Bulletin
gradation products DDE has been used to assess recent usage of DDT (Tinsley, 1979; Umlauf, 1994). In this study, DDE was quanti®ed in 74% of the 103 samples and the mean DDE concentration was 33 ng gÿ1 dw. DDT could be quanti®ed in 41% of the samples and the mean concentration in these 42 samples was 1.6 ng gÿ1 dw. Furthermore, a relationship between the logarithms of concentrations of DDT and DDE had a shallow slope (0.36) suggesting that the concentration of DDE varies to a greater extent than the concentration of the parent compound DDT (Fig. 3). P Fig. 2 P Comparison of the mean concentrations of endosulphan, DDT, diuron and chlorpyrifos in run-o drains and supply channels of the St George irrigation area. (Note that diuron and chlorpyrifos were not detected in all channels and drains and the mean and standard deviation were calculated from only those samples in which the pesticides were quanti®able.)
Channels versus drains Sediment samples were collected from either supply channels or the run-o drains in the irrigation areas. For most areas the sampling was limited to either channels or drains. However, in the St George and the Burdekin irrigation areas, sediment samples from both run-o drains and supply channels were collected. A comparison of the mean concentrations of the four most frequently detected pesticides in the St George regions shows that higher concentrations were present in drains than in channels (Fig. 2). The result is supported by those from the Burdekin irrigation area where the P P mean concentrations of atrazine, endosulphan or DDTs were also an order of magnitude higher in the drain samples compared to those from the channels. Ratios of parent compounds to degradation products In order to assess the historical usage of a particular pesticide, the ratio of the applied parent compound to its degradation products can provide valuable information. For example, the ratio of DDT to one of its de-
Fig. 3 Plot of the logarithm of the concentrations of DDT in sediment samples versus the logarithm of the concentrations of DDE in the respective sediments. Data were expressed in ng gÿ1 dw prior to log transformation.
298
Discussion The results from this study demonstrate that pesticide contamination is widespread in sediments of irrigation channels and drains in Queensland. The detection of pesticides in these sediments is mainly limited to a few pesticides which are currently, or have been used heavily in the past. These pesticides include the insecticides endosulphan and DDT (including their degradation products) and the herbicides diuron and atrazine. These pesticides were found in more than 50% of the samples. Further, prometryn and chlorpyrifos and ametryn were detected in about 40% of the samples. The percentage of samples in which compounds were detected and the mean concentrations of the respective compounds in these samples were in agreement. For example, ranking of the compounds according to either their mean or maximum concentrations or the percentage of samples in which they were detected results in top ranks for endosulphans, DDTs and diuron. On the other hand, more than half of the pesticides investigated were either not detected in any of the samples or found in less than 10% of the samples. These included various pyrethroids including compounds such as cyhalomethrin. Dieldrin and lindane, two insecticides which were widely used in the 1980s and even later, were also rarely detected in the sediment samples and their maximum concentrations detected P in this study were relatively low when compared to DDTs. The results obtained from cotton cultivation areas are in good agreement with data from previous investigations. Total DDTs and endosulphans were also reported as pesticides of particular concern in the sediment from the Emerald irrigation area, and concentrations of endosulphan above the ANZEC environmental guidelines (0.01 lg lÿ1 ) were also detected elsewhere (DNR, 1998; Simpson, 1998). P The concentrations of DDT measured in samples of this study were in the same range or exceeding those which were found in sediments collected from tobacco cultivation areas in North Eastern Victoria, Australia (with maximum concentrations of 32 ng gÿ1 in the fraction below 250 lm size) (McKenzie-Smith et al., 1994). Elsewhere, DDT concentrations up to 561 ng gÿ1 were found in sediment samples from Moon Lake and its watershed in Mississippi (Cooper, 1993). DDT
Volume 41/Numbers 7±12/July±December 2000
P ( DDT) in mud samples collected during 1970 in Ontario were contaminated with maximum concentrations of up to 441 ng gÿ1 in samples from Big Creek and 1730 ng gÿ1 in samples from drainage ditches at Erieau (Kent County) (Miles and Harris, 1971). Interestingly, after restricting the use of DDT in January 1970, the concentration in Big Creek was found to have decreased to 22 ng gÿ1 (Miles and Harris, 1973). Compared to the maximum concentrations found in agricultural P streams from overseas, the maximum concentrations of DDT in samples collected in irrigation areas from Queensland are usually much lower. Nevertheless it is noteworthy that the concentrations found in samples from this study did exceed sediment quality guidelines. For example, the Ontario Ministry of Environment Screening Level Guidelines adopted a value of 120 ng gÿ1 as Ôsevere levelÕ (concentration that can eectively eliminate most benthic organisms) (Persaud et al., 1990 cited in ANZECC and ARMCANZ, 1999). Also the values which are proposed in the Australian and New Zealand Guidelines for Fresh and Marine Water Quality draft for Interim Sediment Quality Guideline (ISQG) were substantially exceeded (ANZECC and ARMCANZ, 1999) for various compounds and regions. In selected samples the levels of DDE and/or dieldrin were more than two orders of magnitudes higher than the corresponding guideline values speci®ed in the draft ISQG. (Note that the draft ISQG is primarily adapted from Long et al. (1995) using the biological eect database compiled by the National Oceanographic and Atmospheric Administration; forPdetails see ANZECC and ARMCANZ, 1999.) The DDT concentrations measured in this study remain, however, well below the background levels reported in the environmental soil quality guidelines (970 ng gÿ1 ) (Ng et al., 1999). The mean concentration of endosulphan measured in the irrigation areas in Queensland is 42 ng gÿ1 and the maximum concentration detected is 840 ng gÿ1 . In Ontario, maximum concentrations of 3 and 62 ng gÿ1 were measured in sediments of Big Creek and in drainage ditches at Erieau, respectively (Miles, 1976; Miles and Harris, 1971). Concentrations ranging from 5 to 2460 ng gÿ1 were reported from Lower Fraser Valley of British Columbia (Wan et al., 1995). In Australia, despite the fact that a series of ®sh kills could be attributed to endosulphan contamination (Nowak, 1996), no sediment quality guideline value has been included in the ISQG (ANZECC and ARMCANZ, 1999). Although it is thus not possible to assess the concentrations found in this study with respect to guideline values, the relative high toxicity of endosulphan compared to various other pesticides suggests that this compound may pose the highest risk to the aquatic ecosystem in irrigation drains of areas dominated by cotton cultivation (Ng et al., 1999). Highest pesticide concentrations were present in the irrigation drains rather than channels which suggests that the sediment concentration is mainly a function of
post-application processes such as surface run-o. Furthermore, a shallow slope of a regression between the concentrations of the logarithm of DDE and DDT was observed, and thus the variation in the DDE concentrations in sediment samples was much greater than the variation in the DDT concentrations. If DDT had been applied recently, a relatively high DDT concentration and high DDT-to-DDE concentration ratio would be expected when compared to applications in the distant past. However the DDT/DDE ratios were highest in samples with relatively low concentrations of DDE and/or DDT. This can be interpreted as a strong indication that the DDT (and consequently DDE) are remnants from past usage or to some extent may be the result of long range transport to the sampling sites. A comparison of the pesticide concentrations in sediments from dierent regions demonstrates that dierences in pesticide residues can be related to the cultivation of speci®c crops and pesticide usage. Both insecticides, (the currently used endosulphan and the long banned DDT) were, on average, found at much higher concentrations in sediments from the cotton growing areas compared with those from sugarcane cultivation areas. Chlorpyrifos was also detected in more than 60% of the samples from the key cotton growing areas, while the concentration of chlorpyrifos in sediments from sugarcane areas were usually below the quanti®cation limit. In contrast, the herbicides diuron, atrazine and ametryn were the dominant compounds detected in sediments collected from sugarcane cultivation areas. Transport of insecticide residues from cotton growing areas to the marine environment is believed to be of little relevance since: (i) in Queensland the cotton growing areas are relatively distant from the marine environment and (ii) cotton growing areas are located in the more arid areas of the State, and the irrigation drains in these areas are only infrequently ¯ushed. Hence it seems unlikely that the high insecticide concentrations observed in drains from the cotton growing areas pose a major risk to biota in the marine environment. In addition, the insecticide concentrations in the sugarcane growing areas are relatively low so that it seems unlikely that these compounds are a key risk to the marine environment. This conclusion is supported by recent surveys of pesticide concentrations in the near-shore regions of the Great Barrier Reef (Haynes et al., 1999). The only contaminants investigated which are likely to reach the marine environment in signi®cant quantities are the herbicides which were found at relatively high concentrations in the sediments of the sugarcane areas. Their concentrations in water of the irrigation areas is probably elevated as the hydrophobicity of these herbicides is relatively low (e.g. their solubility in water high when compared with many of the insecticides investigated). Thus the herbicides enter the marine environment both in the dissolved phase or associated with suspended 299
Marine Pollution Bulletin
sediments. In addition, sugarcane is cultivated in areas with at least 1000 mm annual rainfall and ¯ood events are regular in these areas. Thus it is feasible to assume that a signi®cant portion of the applied herbicides could enter the marine environment. A recent US study suggested that, for example, almost 1% of the herbicides atrazine which is applied in the huge Mississippi basin is ultimately transported and deposited in the Gulf of Mexico (Clark et al., 1999). In the case of the sugarcane areas, the distances between the sugarcane growing areas and the marine environment in Queensland are much shorter compared to those in the Mississippi basin. Also ¯ood events are common along QueenslandÕs coastal plains. Thus it is likely that a signi®cant higher portion of the respective herbicides could enter the marine environment. If it is assumed that 5% of diuron and atrazine which has been applied in agricultural catchments between the Burdekin and the Mareeba region is transported to the marine environment, the total annual load is estimated to be approximately 3 t of diuron and 10 t of atrazines (active ingredient using annual estimates of usage in the respective areas provided by Hamilton and Haydon, 1996). It is noteworthy that herbicides including diuron and atrazine have already been found in marine sediments from Queensland (Haynes et al., 1999). Seagrass beds are an important component of the marine ecological system in Queensland coastal waters, and the loss of seagrass has been recognized as a key environmental issue in Queensland (Dennison and Abal, 1999). While the main focus has been on light limitations recent laboratory based experiments suggested that, for example, diuron, at levels of less than 10 lg lÿ1 inhibits photosynthesis in seagrass (Ralph et al., 1999). Herbicide transport is highest when the drains are ¯ushed during ¯ood events when the light limitations are also greatest. Hence seagrass decline following ¯ood events may result from additive photosynthesis inhibition due to decreased light penetration and the eects of herbicide contamination.
Conclusion Pesticides such as endosulphan are widely distributed in sediments from irrigation areas of Queensland. Only a few compounds were found in the majority of the samples and the most prominent compounds investigated were the insecticides endosulphan and DDT (including degradation products) and the herbicides diuron and atrazine. Concentrations of endosulphan and DDT were highest in drains from cotton growing areas while the herbicides were the key contaminants in the sediments from the sugarcane cultivation areas. A signi®cant proportion of these herbicides is likely to enter the marine environment. The risk of herbicide exposure to seagrass, particularly under light limiting conditions needs to be assessed. 300
Work presented in this study was carried out for the Queensland Department of Natural Resources (QDNR) and its ®nancial support is kindly acknowledged. The authors wish to acknowledge the ®eld scientists and in particular Brian Bycroft of the QDNR for organizing the collection of sediment samples, Steve Carter (QHSS) for assistance with sample analysis and Dave Haynes (GBRMPA) for helpful comments with the manuscript. NRCET is funded by NHMRC, Queensland Health, Grith University and the University of Queensland.
ANZECC and ARMCANZ (1999) Australian and New Zealand guidelines for fresh and marine water quality ± public comment draft ± not yet endorsed by either Council, released, July 1999. Clark, G. M., Goolsby, D. A. and Battaglin, W. A. (1999) Seasonal and annual load of herbicides from the Mississippi River basin to the Gulf of Mexico. Environmental Science and Technology 33, 981± 986. Connell, D. W. (1990) Bioaccumulation of Xenobiotic Compounds. CRC Press, Boca Raton, FL. Cooper, C. M. (1993) Biological eects of agriculturally derived surface-water pollutants on aquatic systems ± A review. Journal of Environmental Quality 22, 402±408. Dennison, W. C. and Abal, E. G. (1999) Moreton Bay Study ± A Scienti®c Basis for the Healthy Waterways Campaign. South East Queensland Regional Water Quality Management Strategy, Brisbane. DNR ± Department of Natural Resources, Queensland (1998) Emerald irrigation area, drainage management study. Project report, available at DNR, State Water Project, Mary Street, Brisbane, Qld 4000, Australia. Eitzer, B. D. (1993) Comparison of point and non-point sources of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans to sediments of the Housatonic River. Environmental Science and Technology 27, 1632±1637. Hamilton, D. and Haydon, G. (1996) Pesticides and fertilisers in the Queensland sugar industry ± estimates of usage and likely environmental fate (Report No. ICM-R&D.94.01 Vol. 1: Pesticides). Department of Primary Industries, Queensland. Haynes, D., M uller, J. F. and Carter, S. (1999) Pesticide and herbicide residues in sediments and seagrasses from the Great Barrier Reef World Heritage Area and Queensland coast. In Sources, Fates and Consequences of Pollutants in the Great Barrier Reef and Torres Strait. Conference abstracts compiled by D. Kellaway. Jones, K. C., Sanders, G., Wild S. R, Burnett, V. and Johnston, A. E. (1992) Evidence for a decline of PCBs and PAHs in rural vegetation and air in the United Kingdom. Nature 356, 1370±140. Long, E. R., MacDonald, D. D., Smith, S. L. and Calder, E. D. (1995) Incidence of adverse biological eects within ranges of chemical concentrations in marine and estuarine sediments. Environment Management 19, 81±97. Mackay, D. (1991) Multimedia Environmental Models: The Fugacity Approach. Lewis Publisher, Chelsea. McKenzie-Smith, F., Tiller, D. and Allen, D. (1994) Organochlorine pesticide residues in water and sediments from the Ovens and King Rivers, north-east Victoria, Australia. Archives of Environmental Contamination and Toxicology 26, 483±490. Miles, J. R. W. (1976) Insecticide residues on stream sediments in Ontario, Canada. Pesticide Monitoring Journal 10 (3), 87±91. Miles, J. R. W. and Harris, C. R. (1971) Insecticide residues in a stream and a controlled drainage system in agricultural areas of southwestern Ont., Canada. Pesticide Monitoring Journal 5 (3), 289±294. Miles, J. R. W. and Harris, C. R. (1973) Organochlorine insecticide residues in streams draining agricultural, urban-agricultural, and resort areas of Ont., Canada. Pesticide Monitoring Journal 6 (4), 363±368. Nowak, B. (1996) Toxicants causing ®shkills. In Fishkills ± Causes and Investigations in Australia, ed. D. OÔSullivan, Aquaculture Source Book 13; Aquaculture Department, University of Tasmania, Launceston. Ng, J. C., Duquesne, S., M uller, J. F., Eaglesham, G., Shaw, G. R., Connell, D. W., Sadler, R., Garnett, C., Krrishnamohan, K. and Manonmanii, M. (1999) The Identi®cation of Areas Subject to Pesticide Contamination as a Result of Desilting Activities from Channels and Drains in Queensland. Report to the State Water Project, Department of Natural Resources, Queensland, Australia.
Volume 41/Numbers 7±12/July±December 2000 Ralph, P. J., Prange, J., Haynes, D. and Dennison, W. C. (1999) Impact of diuron exposure to tropical seagrasses assessed by chlorophyll ¯uorescence. In Sources, Fates and Consequences of Pollutants in the Great Barrier Reef and Torres Strait. Conference abstracts compiled by D. Kellaway. Simpson, B. (1998) Pesticide Transport from Cotton Production Systems at Queensland Sites. Project QP323, Queensland Department of Natural Resources, available from DNR, Meiers Road, Indooroopilly, Qld, Australia.
Tinsley, I. (1979) Chemical Concepts in Pollutant Behaviour. Wiley, New York. Umlauf, G. (1994) Atmosphaerische deposition lipophiler organischer Verbindungen auf P¯anzen am Beispiel von Picea Abies. Doctoral Thesis published in Shaker Verlag, Aachen, Germany. Wan, M. T., Szeto, S., and Price, P. (1995) Distribution of endosulphan residues in the drainage waterways of the Lower Fraser Valley of British Columbia. Journal of Environmental Science and Health B 30 (3), 401±433.
301
Marine Pollution Bulletin Vol. 41, Nos. 7±12, pp. 294±301, 2000 Ó 2000 Elsevier Science Ltd. All rights reserved Printed in Great Britain S0025-326X(00)00095-3 0025-326X/00 $ - see front matter
Pesticides in Sediments From Queensland Irrigation Channels and Drains JOCHEN F. MULLER *, SABINE DUQUESNE , JACK NG , GLEN R. SHAW , K. KRRISHNAMOHAN , K. MANONMANII , MARY HODGEà and GEOFF K. EAGLESHAMà National Research Center For Environmental Toxicology, University of Queensland, 39 Kessels Road, Coopers Plains, Qld 4108, Australia àQueensland Health Scienti®c Services, University of Queensland, 39 Kessels Rd, Coopers Plains, Qld 4108, Australia Pesticide concentration in sediment from irrigation areas can provide information required to assess exposure and fate of these chemicals in freshwater ecosystems and their likely impacts to the marine environment. In this study, 103 sediment samples collected from irrigation channels and drains in 11 agricultural areas of Queensland were analysed for a series of past and presently used pesticides including various organochlorines, synthetic pyrethroids, benzoyl ureas, triazines and organophosphates. The most often detected compounds were endosulphans (a, b and/or endosulphan sulphate) which were detectable in 78 of the 103 samples and levels ranged from below the limit of quanti®cation (0.1 ng gÿ1 dw) up to 840 ng gÿ1 dw. DDT and its metabolites were the second most often detected pesticide investigated (74 of the 103 samples) with concentrations up to 240 ng gÿ1 dw of +DDTs. Mean +endosulphan and +DDT concentrations were 1±2 orders of magnitude higher in sediments from the irrigation areas which are dominated by cotton cultivation compared to those which are dominated by sugarcane cultivation. In contrast to these insecticides, the herbicides diuron, atrazine and ametryn were the compounds which were most often detected in sediments from irrigation drains in sugarcane areas with maximum concentrations in areas of 120, 70 and 130 ng gÿ1 dw, respectively. In particular during ¯ood events, when light is limiting, transport of these photosynthesis inhibiting herbicides from the sugarcane cultivation areas to the marine environment may result in additional stress of marine plants. Ó 2000 Elsevier Science Ltd. All rights reserved.
Introduction Sediment can be an important sink for persistent organic pollutants including many pesticides in present and past uses. Analytical results from sediments have been used to evaluate pollutant sources (Eitzer, 1993), historical trends (Jones et al., 1992) and to predict water and thus exposure concentrations of biota in the aquatic environment (Mackay, 1991; Connell, 1990). AustraliaÕs north-eastern state, Queensland, is located in a subtropical to tropical region and has a relatively low population density when compared to other industrialized countries. Agriculture is one of the StateÕs most important industries and is dominated by sugarcane and cotton cultivation which to date rely on intensive plant protection using pesticides. Depending on the physicalchemical properties of the compounds, local properties of the soil, topographical parameters and the climate, a fraction of the applied pesticide is transported into the irrigation drains and ultimately downstream into the marine environment and into the Great Barrier Reef Marine Park (GBRMP). The channels and drains in irrigation areas are subject to periodical desilting in which accumulated sediment and associated contaminants from the irrigation channels and drains are dug out and deposited along the banks of the water channel. The results presented here are part of a study which focussed on pesticide contamination in the desilted sediments including the potential for accumulation in grazing cattle.
Material and Methods
*Corresponding author. Tel.: +61-7-3274-9009; fax: +61-7-32749003. E-mail address: [email protected] (J. F. MuÈller).
294
Sampling areas The sediments were collected from 11 irrigation areas in Queensland (Fig. 1). The regions can be dierentiated into those which are dominated by either sugarcane or cotton cultivation. In some regions, samples were collected almost exclusively from irrigation drains, whereas
Volume 41/Numbers 7±12/July±December 2000
demonstration of the sampling protocol. Samples were collected between July and November 1998. Samples were collected from either the wet or dry bed in the irrigation drain or from the banks beside the channel and drains if fresh silt was deposited within the last seven days from the sampling date. Each sample consisted of a homogenized composite made of equal fractions of eight subsamples collected at a distance of approximately 10 m from all other subsamples. Samples were collected from the wet bed using a Van±Veen sampler or from the dry bed or the desilted mound using a stainless steel spade. Surface sediment of the top 2 cm layer was removed and discarded if samples were collected from the dry bed or the silt mound. All samples were refrigerated and transported to the laboratory within 48 h and stored at ±20°C until extraction.
Fig. 1 Map of Queensland showing the capital city, the major cotton and sugarcane cultivation areas and sampling regions where sediments were obtained for analysis in this study. (Note that samples were collected only in selected areas marked with an arrow and the regions name.)
in other regions only supply channels exist and were sampled (Table 1). The majority of samples originated from either the Emerald irrigation area which is dominated by cotton cultivation (26 samples) or the Burdekin irrigation area (BRIA) dominated by sugarcane production (21 samples). Sampling Sampling was carried out by ®eld ocers from the Department of Natural Resources, Queensland, who received detailed instructions including an audiovisual
Analysis Samples were thawed, homogenized and a subsample (15 g) was extracted with 100 ml acetone (all solvents used were nanograde) in a mechanical shaker overnight. Samples were then centrifuged and the supernatant was subjected to liquid/liquid extraction after the addition of 50 ml of saturated NaCl solution and about 200±300 ml dichloromethane (as much as was required for the aqueous phase to rise to the top). The nonpolar fraction was ®ltered through anhydrous sodium sulphate and concentrated using a rotary evaporator and transferred into n-hexane. The extracts were puri®ed on a column (18 mm I.D.) ®lled with 20 cm of Florisilä deactivated with 5% H2 O. Compounds of interest were eluted in three separate fractions using 120 ml of n-hexane/diethylether (94/6 V/V), followed by 90 ml of n-hexane/ acetone (90/10 V/V) and ultimately 120 ml n-hexane/ acetone (50/50 V/V). The ®rst two fractions were then concentrated to 1 ml and analysed for the organophosphorus pesticides using GC±FPD and GC±NPD. The ®rst fraction (n-hexane/ diethylether eluate) was subjected to a sulphur removal clean-up. Samples were transferred to test tubes and 1 ml of tetrabutyl ammonium hydroxide, 2 ml isopropanol
TABLE 1 Areas covered by the various regions where the study sites were located, number of samples collected from each region, major land use and type of irrigation system which has been sampled in the study. Region (abbreviation) Burdekin (BRIA) Emerald Dawson Valleyb St George Mareeba-Dimbulah (MDIA) Bundaberg Callide Valleyb Warrill Valleyb Lockyer Valleyb Eton Lower Mary a b
Sample No. 22 26 14 12 10 4 4 3 3 3 2
Area (in 1000 ha) 33 20 7.9 14 17 58 5.6 19 6.2
Major crops
Irrigation system sampleda
Sugarcane/horticulture Cotton/horticulture Cotton Cotton Horticulture/sugarcane Sugarcane/horticulture Cotton/horticulture Horticulture/fodder Horticulture Sugarcane Horticulture/fodder
Mainly drains Mainly drains Mainly drains Mainly drains Mainly drains Channels Channels Channels Channels Channels Channels
The term channel refers to water supply channels while the term drain refers to the irrigation drains. Abbreviated as Dawson, Warrill, Lockyer and Callide, respectively, in Fig. 1.
295
Marine Pollution Bulletin
and small amounts of anhydrous sodium sulphite were added. After shaking (60 s) 5 ml of H2 O was added and the samples were again shaken (60 s). The top layer was carefully transferred using an extra 2 ml of n-hexane and concentrated under a gentle stream of nitrogen to 1 ml. Both the ®rst fraction (after sulphur clean-up) and the second fraction from the Florisilä column were then analysed for organochlorines and selected organophosphates using dual column GC±ECD. A selection of the samples in which concentrations were found to be relatively high were analysed using GC±MS (full ion scan) for structural con®rmation of the analytes. Once the results were evaluated, all three fractions from the Florisilä column were combined and a solvent exchange to methanol was undertaken. Then the samples were analysed using multiple reaction monitoring with a triple stage quadrupole LC-MS/MS system (API 300 PE/ Sciex Instruments). The analytical method was subject to standard QA/ QC procedures. Blanks and a series of spikes, which contained known quantities of the analytes, were included in each batch (usually 12 samples). The reporting limit was de®ned as ®ve times the average values of the baseline noise signals and/or three times the concentration in a representative blank.
Results Pesticides were found in most of the 103 sediment samples. The most widely detected compounds were p,p0 -DDE, diuron, endosulphan-SO4 , atrazine and bendosulphan, all of which were detected in more than 50% of the sediment samples collected. Endosulphan (present as a, b and/or endosulphan sulphate) was detectable in 76% P of the 103 samples and the mean concentration of endosulphan in the 78 samples in which P it was detected was 42 ng gÿ1 dw. The endosulphan concentrations ranged from below the quanti®cation limit (0.l ng gÿ1 dw) to 840 ng gÿ1 dw in a sample from a drain in the Emerald irrigation area. DDT and its metabolites were the second most often detected pesticide investigated since in 74% samples P one or more of the DDTs were detected. The mean DDT concentration in these 76 samples was 32 ng gÿ1 dw. The highest P DDT concentration was 240 ng gÿ1 dw and was determined in a sediment sample collected from a drain in the Dawson irrigation area. The herbicide diuron was detected in 72% of the samples and the mean detected concentration was 30 ng gÿ1 dw with the highest concentration (340 ng gÿ1 dw) observed in sediments from a drain in the Dawson irrigation area. Atrazine was the pesticide which was the fourth most often detected (55% of the samples) with a mean detected concentration of 6.5 ng gÿ1 dw. Herbicides such as prometryn, ¯uometuron and ametryn were also detected in 30±50% of the samples and the mean detected concentration was 3.2, 12 and 9.7 ng gÿ1 dw, respectively. Chlorpyrifos was found in 39% of the samples and the mean detected 296
concentration was 4.8 ng gÿ1 dw. Other pesticides investigated were found in only a few samples and usually at concentrations of less than 5 ng gÿ1 dw. Hexachlorobenzene for example, which was detectable in 22 samples, did not exceed 1 ng gÿ1 dw in any of the samples analysed. Dierences between sampling regions A comparison of the results with respect to dierences between the various sampling regions is given in Table 2. Highest concentrations of almost all insecticides studied were found in sediments from drains in cotton growing regions (Emerald, Dawson and St George).PBoth the maximum P and the mean concentrations of endosulphan and DDT in sediments from irrigation drains in cotton growing areas were 1±2 orders of magnitude higher than those from areas dominated by sugarcane cultivation. Endosulphan was found in each sample from the Emerald, Dawson and St George regions, while it was not detected in about half of all other samples. Similarly, DDTs were more often detected in samples from drains in cotton growing areas than all other samples. Chlorpyrifos was almost exclusively found in drain sediment samples from the cotton growing regions with a maximum concentration of 94 ng gÿ1 dw in a sample from Dawson. In contrast to the insecticides being the dominant contaminants of interest in the sediments from cotton growing areas, the herbicides diuron, atrazine and ametryn were the compounds most frequently detected in sediments from irrigation drains in sugarcane areas. Atrazine and ametryn were, for example, detected in all 21 sediment samples and diuron in 20 of the 21 sediment samples collected in the Burdekin irrigation area. The mean and maximum concentrations of diuron, atrazine and ametryn in sediments from the Burdekin irrigation area were in the range of 13±25 ng gÿ1 dw (mean of detectables) and 70±130 ng gÿ1 dw (maximum). Within a given region, the compound concentrations in sediment samples varied substantially P from site to P site. For example, the endosulphan or DDT concentration in drains from Emerald varied over more than three orders of magnitude despite the latter being banned for use in Australia for more than a decade. The great variability of compound concentration between samples from a given site appears to be similar for most compounds investigated, although it is not possible to assess this for compounds which barely exceeded detection limits. In comparison to endosulphans, DDTs, or the three dominant herbicides diuron, atrazine and ametryn, the concentrations of many banned organochlorine compounds including hexachlorobenzene, lindane, heptachlor, aldrin and dieldrin were relatively low. The mean concentrations of these latter compounds in any of these regions were less than 1 ng gÿ1 dw and only dieldrin and aldrin were found to exceed 1 ng gÿ1 dw in samples from individual sites (Table 2).
TABLE 2
100 (0.91±360) [15/15] 52 (<0.07±240) [13/15] 80 (8.8±340) [15/15] 5.1 (<0.5±41) [11/15] 0.14 (<0.07±0.27) [4/15] <0.05 [0/15] 0.15 (<0.05±0.24) [6/15] <0.05 [0/15] <0.1 [0/15] 0.39 (<0.07±0.69) [3/15] 4.2 (<0.5±6) [2/15] <1 [0/15] <0.5 [0/15] 8.1 (0.09±94) [15/15] <1 [0/15] 0.09 (<0.09±0.1) [1/15] <0.5 [0/15] 4.7 (<0.2±18) [4/15] 3.2 (0.21±10) [6/15] 17 (<1±61) [14/15] 0.98 (<0.5±0.98) [1/15] 0.23 (<0.2±0.23) [1/15]
Dawson cotton 1.0 (<0.27±1.7) [5/10] 1.9 (<0.3±5.9) [5/10] 9.1 (<0.36±37) [5/10] 0.23 (<0.5±0.23) [1/10] 0.2 (<0.1±0.2) [1/10] <0.05 [0/10] <0.05 [0/10] <0.05 [0/10] <0.1 [0/10] 0.06 (<0.05±0.07) [2/10] <0.5 [0/10] <1 [10/10] <0.5 [10/10] <0.1 [0/10] <1 [0/10] <0.5 [0/10] <0.5 [0/10] 15 (<0.2±30) [2/10] 0.45 (<0.2±0.45) [1/10] <1 [0/10] <0.5 [0/10] 0.17 (<0.15±0.17) [1/10]
MDIA sugarcane 2.0 (<0.05±13) [14/21] 2.6 (<0.07±6) [10/21] 25 (<1±120) [20/21] 13 (0.46±70) [21/21] 0.03 (<0.03±0.03) [2/21] 0.037 (<0.05±0.04) [1/21] <0.05 [0/21] 0.053 (<0.04±0.06) [3/21] 0.13 (<0.1±0.13) [1/21] 0.09 [1/21] <0.5 [0/21] <1 [0/21] 2.0 (<0.5±2) [1/21] 1.2 (<0.27±2.8) [3/21] <1 [0/21] 0.25 (<0.5±0.25) [1/21] <0.5 [0/21] 14 (0.11±130) [21/21] 0.53 (<0.18±1.6) [5/21] <1 [0/21] 0.61 (0.46±0.71) [3/21] 0.38 (<0.15±0.38) [1/21]
0.74 (0.14±1.3) [3/4] 0.56 (0.09±1.3) [4/4] 0.56 (<0.4±0.56) [1/4] 0.40 (<0.25±0.54) [2/4] 0.073 (<0.03±0.1) [3/4] <0.05 [0/4] 0.12 (<0.05±0.12) [1/4] <0.05 [0/4] 0.21 (<0.1±0.21) [2/4] <0.04 [0/4] <0.5 [0/4] <1 [0/4] <0.5 [0/4] <0.5 [0/4] <1 [0/4] <0.5 [0/4] <0.5 [0/4] 0.25 (0.14±0.37) [4/4] <0.5 [0/4] <1 [0/4] <0.5 [0/4] <0.5 [0/4]
0.10 [1/4] 0.28 (0.05±0.85) [4/4] 2 (<1±2) [1/4] <0.5 [0/4] <0.03 [0/4] 0.05 (<0.05±0.05) [1/4] 0.1 (<0.05±0.1) [1/4] <0.05 [0/4] 0.05 (<0.05±0.05) [1/4] 0.09 (<0.04±0.09) [1/4] <0.5 [0/4] <1 [0/4] <0.5 [0/4] <0.5 [0/4] <1 [0/4] <0.5 [0/4] <0.5 [0/4] 0.4 (<0.1±0.4) [1/4] <0.5 [0/4] <1 [0/4] <0.5 [0/4] <0.5 [0/4]
0.11 [1/3] 0.47 [3/3] <0.4 [0/3] <0.5 [0/3] <0.03 [0/3] 0.7 [1/3] <0.05 [0/3] <0.05 [0/3] <0.1 [0/3] <0.04 [0/3] <0.5 [0/3] <1 [0/3] <0.5 [0/3] <0.5 [0/3] <1 [0/3] <0.5 [0/3] <0.5 [0/3] <0.2 [0/3] <0.5 [0/3] <1 [0/3] <0.5 [0/3] <0.5 [0/3]
BRIA sugarcane Callide sugarcane Bundaberg sugarcane Lockyer 2.4 [1/3] 2.8 [2/3] <0.4 [0/3] 1.1 [1/3] <0.03 [0/3] <0.05 [0/3] <0.05 [0/3] <0.05 [0/3] <0.1 [0/3] <0.04 [0/3] <0.5 [0/3] <1 [0/3] <0.5 [0/3] <0.5 [0/3] <1 [0/3] <0.5 [0/3] <0.5 [0/3] <0.2 [0/3] <0.5 [0/3] <1 [0/3] <0.5 [0/3] <0.5 [0/3]
<0.3 [0/2] <0.05 [0/2] 7.9 [1/2] <0.5 [0/2] <0.03 [0/2] <0.05 [0/2] 0.29 [1/2] <0.05 [0/2] <0.1 [0/2] 0.42 [1/2] <0.5 [0/2] <1 [0/2] <0.5 [0/2] <0.5 [0/2] <1 [0/2] <0.5 [0/2] <0.5 [0/2] <0.2 [0/2] <0.5 [0/2] <1 [0/2] <0.5 [0/2] <0.5 [0/2]
Warrill Lower Mary
<0.3 [0/3] <0.05 [0/3] <0.4 [0/3] <0.5 [0/3] <0.03 [0/3] <0.05 [0/3] <0.05 [0/3] <0.05 [0/3] <0.1 [0/3] 0.19 [1/3] <0.5 [0/3] <1 [0/3] <0.5 [0/3] <0.5 [0/3] <1 [0/3] <0.5 [0/3] <0.5 [0/3] <0.2 [0/3] <0.5 [0/3] <1 [0/3] <0.5 [0/3] <0.5 [0/3]
Eton
Samples in which the compounds were not detectable were not included in the calculation of the mean. The minimum and maximum concentrations are given in ( ) while the number of samples in which compounds were detected and the number of samples analysed from the respective irrigation area are given in [ ]. Samples were also analysed for fenthion, cyhalothrin, deltamethrin, cypermethrin and ¯uazuron but none of these compounds were detectable in any of the samples.
a
84 (0.46±840) 43 (4.1±100) [26/26] [12/12] Total DDT 35 (<0.1± 160) 79 (2±230) [23/26] [12/12] Diuron 17 (<1±54) 6.3 (<0.4±14) [25/26] [7/12] Atrazine 2.4 (<0.5±11) 1.1 (<0.5±1.1) [20/26] [1/12] HCB 0.068 (<0.03±0.16) <0.03 [12/26] [0/12] HCH <0.05 <0.05 [0/26] [0/12] Aldrin 0.32 (<0.04±2.2) <0.05 [9/26] [0/12] Heptachlor 0.10 (<0.03±0.18) <0.05 [6/26] [0/12] Heptachlorepoxide 0.10 (<0.1±0.1) 0.08 (<0.1±0.08) [1/26] [1/12] Dieldrin 0.90 (<0.04±3.3) <0.05 [4/26] [0/12] Diazinon <0.5 2.2 (<0.5±4.2) [0/26] [2/12] Fenitrothion 1.3 (<1±1.3) <1 [1/26] [0/12] Parathion 3.4 (<0.5±6.3) <0.5 [2/26] [0/12] Chlorpyrifos 0.89 (<0.2±3.2) 8.5 (<0.02±49) [16/26] [6/12] Bifenthrin <1 10 (<0.2±29) [0/26] [3/12] Chlor¯uazuron 0.86 (<0.5±1.3) <0.5 [7/26] [0/12] Tri¯uaraline <0.5 0.24 (0.13±0.43) [0/26] [3/12] Ametryn 0.33 (<0.2±0.38) <0.2 [3/26] [0/12] Prometryn 2.0 (<0.2±5.2) 8.2 (<0.5±40) [22/26] [8/12] Flumeturon 9.8 (<0.43±58) 7.9 (<1.0±23) [18/26] [5/12] Simazine <0.5 <0.5 [0/26] [0/12] Hexazinone 0.25 (<0.2±0.3) <0.2 [3/26] [12/12]
Total endosulphan
Emerald cotton St George cotton
Mean of detectable concentrations, and maximum and minimum pesticide concentrations (ng gÿ1 dw) as well as the number of samples in which the compound was detected and the number of samples analysed for the sediments from irrigation channels and drains in Queenslands irrigation areas.a
Volume 41/Numbers 7±12/July±December 2000
297
Marine Pollution Bulletin
gradation products DDE has been used to assess recent usage of DDT (Tinsley, 1979; Umlauf, 1994). In this study, DDE was quanti®ed in 74% of the 103 samples and the mean DDE concentration was 33 ng gÿ1 dw. DDT could be quanti®ed in 41% of the samples and the mean concentration in these 42 samples was 1.6 ng gÿ1 dw. Furthermore, a relationship between the logarithms of concentrations of DDT and DDE had a shallow slope (0.36) suggesting that the concentration of DDE varies to a greater extent than the concentration of the parent compound DDT (Fig. 3). P Fig. 2 P Comparison of the mean concentrations of endosulphan, DDT, diuron and chlorpyrifos in run-o drains and supply channels of the St George irrigation area. (Note that diuron and chlorpyrifos were not detected in all channels and drains and the mean and standard deviation were calculated from only those samples in which the pesticides were quanti®able.)
Channels versus drains Sediment samples were collected from either supply channels or the run-o drains in the irrigation areas. For most areas the sampling was limited to either channels or drains. However, in the St George and the Burdekin irrigation areas, sediment samples from both run-o drains and supply channels were collected. A comparison of the mean concentrations of the four most frequently detected pesticides in the St George regions shows that higher concentrations were present in drains than in channels (Fig. 2). The result is supported by those from the Burdekin irrigation area where the P P mean concentrations of atrazine, endosulphan or DDTs were also an order of magnitude higher in the drain samples compared to those from the channels. Ratios of parent compounds to degradation products In order to assess the historical usage of a particular pesticide, the ratio of the applied parent compound to its degradation products can provide valuable information. For example, the ratio of DDT to one of its de-
Fig. 3 Plot of the logarithm of the concentrations of DDT in sediment samples versus the logarithm of the concentrations of DDE in the respective sediments. Data were expressed in ng gÿ1 dw prior to log transformation.
298
Discussion The results from this study demonstrate that pesticide contamination is widespread in sediments of irrigation channels and drains in Queensland. The detection of pesticides in these sediments is mainly limited to a few pesticides which are currently, or have been used heavily in the past. These pesticides include the insecticides endosulphan and DDT (including their degradation products) and the herbicides diuron and atrazine. These pesticides were found in more than 50% of the samples. Further, prometryn and chlorpyrifos and ametryn were detected in about 40% of the samples. The percentage of samples in which compounds were detected and the mean concentrations of the respective compounds in these samples were in agreement. For example, ranking of the compounds according to either their mean or maximum concentrations or the percentage of samples in which they were detected results in top ranks for endosulphans, DDTs and diuron. On the other hand, more than half of the pesticides investigated were either not detected in any of the samples or found in less than 10% of the samples. These included various pyrethroids including compounds such as cyhalomethrin. Dieldrin and lindane, two insecticides which were widely used in the 1980s and even later, were also rarely detected in the sediment samples and their maximum concentrations detected P in this study were relatively low when compared to DDTs. The results obtained from cotton cultivation areas are in good agreement with data from previous investigations. Total DDTs and endosulphans were also reported as pesticides of particular concern in the sediment from the Emerald irrigation area, and concentrations of endosulphan above the ANZEC environmental guidelines (0.01 lg lÿ1 ) were also detected elsewhere (DNR, 1998; Simpson, 1998). P The concentrations of DDT measured in samples of this study were in the same range or exceeding those which were found in sediments collected from tobacco cultivation areas in North Eastern Victoria, Australia (with maximum concentrations of 32 ng gÿ1 in the fraction below 250 lm size) (McKenzie-Smith et al., 1994). Elsewhere, DDT concentrations up to 561 ng gÿ1 were found in sediment samples from Moon Lake and its watershed in Mississippi (Cooper, 1993). DDT
Volume 41/Numbers 7±12/July±December 2000
P ( DDT) in mud samples collected during 1970 in Ontario were contaminated with maximum concentrations of up to 441 ng gÿ1 in samples from Big Creek and 1730 ng gÿ1 in samples from drainage ditches at Erieau (Kent County) (Miles and Harris, 1971). Interestingly, after restricting the use of DDT in January 1970, the concentration in Big Creek was found to have decreased to 22 ng gÿ1 (Miles and Harris, 1973). Compared to the maximum concentrations found in agricultural P streams from overseas, the maximum concentrations of DDT in samples collected in irrigation areas from Queensland are usually much lower. Nevertheless it is noteworthy that the concentrations found in samples from this study did exceed sediment quality guidelines. For example, the Ontario Ministry of Environment Screening Level Guidelines adopted a value of 120 ng gÿ1 as Ôsevere levelÕ (concentration that can eectively eliminate most benthic organisms) (Persaud et al., 1990 cited in ANZECC and ARMCANZ, 1999). Also the values which are proposed in the Australian and New Zealand Guidelines for Fresh and Marine Water Quality draft for Interim Sediment Quality Guideline (ISQG) were substantially exceeded (ANZECC and ARMCANZ, 1999) for various compounds and regions. In selected samples the levels of DDE and/or dieldrin were more than two orders of magnitudes higher than the corresponding guideline values speci®ed in the draft ISQG. (Note that the draft ISQG is primarily adapted from Long et al. (1995) using the biological eect database compiled by the National Oceanographic and Atmospheric Administration; forPdetails see ANZECC and ARMCANZ, 1999.) The DDT concentrations measured in this study remain, however, well below the background levels reported in the environmental soil quality guidelines (970 ng gÿ1 ) (Ng et al., 1999). The mean concentration of endosulphan measured in the irrigation areas in Queensland is 42 ng gÿ1 and the maximum concentration detected is 840 ng gÿ1 . In Ontario, maximum concentrations of 3 and 62 ng gÿ1 were measured in sediments of Big Creek and in drainage ditches at Erieau, respectively (Miles, 1976; Miles and Harris, 1971). Concentrations ranging from 5 to 2460 ng gÿ1 were reported from Lower Fraser Valley of British Columbia (Wan et al., 1995). In Australia, despite the fact that a series of ®sh kills could be attributed to endosulphan contamination (Nowak, 1996), no sediment quality guideline value has been included in the ISQG (ANZECC and ARMCANZ, 1999). Although it is thus not possible to assess the concentrations found in this study with respect to guideline values, the relative high toxicity of endosulphan compared to various other pesticides suggests that this compound may pose the highest risk to the aquatic ecosystem in irrigation drains of areas dominated by cotton cultivation (Ng et al., 1999). Highest pesticide concentrations were present in the irrigation drains rather than channels which suggests that the sediment concentration is mainly a function of
post-application processes such as surface run-o. Furthermore, a shallow slope of a regression between the concentrations of the logarithm of DDE and DDT was observed, and thus the variation in the DDE concentrations in sediment samples was much greater than the variation in the DDT concentrations. If DDT had been applied recently, a relatively high DDT concentration and high DDT-to-DDE concentration ratio would be expected when compared to applications in the distant past. However the DDT/DDE ratios were highest in samples with relatively low concentrations of DDE and/or DDT. This can be interpreted as a strong indication that the DDT (and consequently DDE) are remnants from past usage or to some extent may be the result of long range transport to the sampling sites. A comparison of the pesticide concentrations in sediments from dierent regions demonstrates that dierences in pesticide residues can be related to the cultivation of speci®c crops and pesticide usage. Both insecticides, (the currently used endosulphan and the long banned DDT) were, on average, found at much higher concentrations in sediments from the cotton growing areas compared with those from sugarcane cultivation areas. Chlorpyrifos was also detected in more than 60% of the samples from the key cotton growing areas, while the concentration of chlorpyrifos in sediments from sugarcane areas were usually below the quanti®cation limit. In contrast, the herbicides diuron, atrazine and ametryn were the dominant compounds detected in sediments collected from sugarcane cultivation areas. Transport of insecticide residues from cotton growing areas to the marine environment is believed to be of little relevance since: (i) in Queensland the cotton growing areas are relatively distant from the marine environment and (ii) cotton growing areas are located in the more arid areas of the State, and the irrigation drains in these areas are only infrequently ¯ushed. Hence it seems unlikely that the high insecticide concentrations observed in drains from the cotton growing areas pose a major risk to biota in the marine environment. In addition, the insecticide concentrations in the sugarcane growing areas are relatively low so that it seems unlikely that these compounds are a key risk to the marine environment. This conclusion is supported by recent surveys of pesticide concentrations in the near-shore regions of the Great Barrier Reef (Haynes et al., 1999). The only contaminants investigated which are likely to reach the marine environment in signi®cant quantities are the herbicides which were found at relatively high concentrations in the sediments of the sugarcane areas. Their concentrations in water of the irrigation areas is probably elevated as the hydrophobicity of these herbicides is relatively low (e.g. their solubility in water high when compared with many of the insecticides investigated). Thus the herbicides enter the marine environment both in the dissolved phase or associated with suspended 299
Marine Pollution Bulletin
sediments. In addition, sugarcane is cultivated in areas with at least 1000 mm annual rainfall and ¯ood events are regular in these areas. Thus it is feasible to assume that a signi®cant portion of the applied herbicides could enter the marine environment. A recent US study suggested that, for example, almost 1% of the herbicides atrazine which is applied in the huge Mississippi basin is ultimately transported and deposited in the Gulf of Mexico (Clark et al., 1999). In the case of the sugarcane areas, the distances between the sugarcane growing areas and the marine environment in Queensland are much shorter compared to those in the Mississippi basin. Also ¯ood events are common along QueenslandÕs coastal plains. Thus it is likely that a signi®cant higher portion of the respective herbicides could enter the marine environment. If it is assumed that 5% of diuron and atrazine which has been applied in agricultural catchments between the Burdekin and the Mareeba region is transported to the marine environment, the total annual load is estimated to be approximately 3 t of diuron and 10 t of atrazines (active ingredient using annual estimates of usage in the respective areas provided by Hamilton and Haydon, 1996). It is noteworthy that herbicides including diuron and atrazine have already been found in marine sediments from Queensland (Haynes et al., 1999). Seagrass beds are an important component of the marine ecological system in Queensland coastal waters, and the loss of seagrass has been recognized as a key environmental issue in Queensland (Dennison and Abal, 1999). While the main focus has been on light limitations recent laboratory based experiments suggested that, for example, diuron, at levels of less than 10 lg lÿ1 inhibits photosynthesis in seagrass (Ralph et al., 1999). Herbicide transport is highest when the drains are ¯ushed during ¯ood events when the light limitations are also greatest. Hence seagrass decline following ¯ood events may result from additive photosynthesis inhibition due to decreased light penetration and the eects of herbicide contamination.
Conclusion Pesticides such as endosulphan are widely distributed in sediments from irrigation areas of Queensland. Only a few compounds were found in the majority of the samples and the most prominent compounds investigated were the insecticides endosulphan and DDT (including degradation products) and the herbicides diuron and atrazine. Concentrations of endosulphan and DDT were highest in drains from cotton growing areas while the herbicides were the key contaminants in the sediments from the sugarcane cultivation areas. A signi®cant proportion of these herbicides is likely to enter the marine environment. The risk of herbicide exposure to seagrass, particularly under light limiting conditions needs to be assessed. 300
Work presented in this study was carried out for the Queensland Department of Natural Resources (QDNR) and its ®nancial support is kindly acknowledged. The authors wish to acknowledge the ®eld scientists and in particular Brian Bycroft of the QDNR for organizing the collection of sediment samples, Steve Carter (QHSS) for assistance with sample analysis and Dave Haynes (GBRMPA) for helpful comments with the manuscript. NRCET is funded by NHMRC, Queensland Health, Grith University and the University of Queensland.
ANZECC and ARMCANZ (1999) Australian and New Zealand guidelines for fresh and marine water quality ± public comment draft ± not yet endorsed by either Council, released, July 1999. Clark, G. M., Goolsby, D. A. and Battaglin, W. A. (1999) Seasonal and annual load of herbicides from the Mississippi River basin to the Gulf of Mexico. Environmental Science and Technology 33, 981± 986. Connell, D. W. (1990) Bioaccumulation of Xenobiotic Compounds. CRC Press, Boca Raton, FL. Cooper, C. M. (1993) Biological eects of agriculturally derived surface-water pollutants on aquatic systems ± A review. Journal of Environmental Quality 22, 402±408. Dennison, W. C. and Abal, E. G. (1999) Moreton Bay Study ± A Scienti®c Basis for the Healthy Waterways Campaign. South East Queensland Regional Water Quality Management Strategy, Brisbane. DNR ± Department of Natural Resources, Queensland (1998) Emerald irrigation area, drainage management study. Project report, available at DNR, State Water Project, Mary Street, Brisbane, Qld 4000, Australia. Eitzer, B. D. (1993) Comparison of point and non-point sources of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans to sediments of the Housatonic River. Environmental Science and Technology 27, 1632±1637. Hamilton, D. and Haydon, G. (1996) Pesticides and fertilisers in the Queensland sugar industry ± estimates of usage and likely environmental fate (Report No. ICM-R&D.94.01 Vol. 1: Pesticides). Department of Primary Industries, Queensland. Haynes, D., M uller, J. F. and Carter, S. (1999) Pesticide and herbicide residues in sediments and seagrasses from the Great Barrier Reef World Heritage Area and Queensland coast. In Sources, Fates and Consequences of Pollutants in the Great Barrier Reef and Torres Strait. Conference abstracts compiled by D. Kellaway. Jones, K. C., Sanders, G., Wild S. R, Burnett, V. and Johnston, A. E. (1992) Evidence for a decline of PCBs and PAHs in rural vegetation and air in the United Kingdom. Nature 356, 1370±140. Long, E. R., MacDonald, D. D., Smith, S. L. and Calder, E. D. (1995) Incidence of adverse biological eects within ranges of chemical concentrations in marine and estuarine sediments. Environment Management 19, 81±97. Mackay, D. (1991) Multimedia Environmental Models: The Fugacity Approach. Lewis Publisher, Chelsea. McKenzie-Smith, F., Tiller, D. and Allen, D. (1994) Organochlorine pesticide residues in water and sediments from the Ovens and King Rivers, north-east Victoria, Australia. Archives of Environmental Contamination and Toxicology 26, 483±490. Miles, J. R. W. (1976) Insecticide residues on stream sediments in Ontario, Canada. Pesticide Monitoring Journal 10 (3), 87±91. Miles, J. R. W. and Harris, C. R. (1971) Insecticide residues in a stream and a controlled drainage system in agricultural areas of southwestern Ont., Canada. Pesticide Monitoring Journal 5 (3), 289±294. Miles, J. R. W. and Harris, C. R. (1973) Organochlorine insecticide residues in streams draining agricultural, urban-agricultural, and resort areas of Ont., Canada. Pesticide Monitoring Journal 6 (4), 363±368. Nowak, B. (1996) Toxicants causing ®shkills. In Fishkills ± Causes and Investigations in Australia, ed. D. OÔSullivan, Aquaculture Source Book 13; Aquaculture Department, University of Tasmania, Launceston. Ng, J. C., Duquesne, S., M uller, J. F., Eaglesham, G., Shaw, G. R., Connell, D. W., Sadler, R., Garnett, C., Krrishnamohan, K. and Manonmanii, M. (1999) The Identi®cation of Areas Subject to Pesticide Contamination as a Result of Desilting Activities from Channels and Drains in Queensland. Report to the State Water Project, Department of Natural Resources, Queensland, Australia.
Volume 41/Numbers 7±12/July±December 2000 Ralph, P. J., Prange, J., Haynes, D. and Dennison, W. C. (1999) Impact of diuron exposure to tropical seagrasses assessed by chlorophyll ¯uorescence. In Sources, Fates and Consequences of Pollutants in the Great Barrier Reef and Torres Strait. Conference abstracts compiled by D. Kellaway. Simpson, B. (1998) Pesticide Transport from Cotton Production Systems at Queensland Sites. Project QP323, Queensland Department of Natural Resources, available from DNR, Meiers Road, Indooroopilly, Qld, Australia.
Tinsley, I. (1979) Chemical Concepts in Pollutant Behaviour. Wiley, New York. Umlauf, G. (1994) Atmosphaerische deposition lipophiler organischer Verbindungen auf P¯anzen am Beispiel von Picea Abies. Doctoral Thesis published in Shaker Verlag, Aachen, Germany. Wan, M. T., Szeto, S., and Price, P. (1995) Distribution of endosulphan residues in the drainage waterways of the Lower Fraser Valley of British Columbia. Journal of Environmental Science and Health B 30 (3), 401±433.
301