EFRAIM HALFON AND DON POULTON

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Concentrations of 89 toxic organic pollutants (25 contaminants, including Chlorobenzenes and pesticides, and 64 PCB Isomers) were measured In Lake Ontario along the Toronto Waterfront area during the spring, summer and fall of 1987. Data indicate that Humber Bay, the Inner harbour, and the areas near the Toronto Main Sewage Treatment Plant (STP) are the most polluted. While contaminant levels in some offshore areas are high. Average levels for most contaminants are similar to whole-lake levels. Lake Ontario receives large amounts of pollutants from atmospheric sources and the Niagara River. Consequently, the Impact of both local and whole-lake sources Is felt In the Toronto Waterfront Area. Thus, even if all local sources of pollution were removed, the Toronto Waterfront Area would probably remain affected by other sources, primarily the Niagara River. Concentrations of toxic pollutants would remain approximately the same as far as two kilometres from shore.

Key words: Toxic contaminants; spatial distribution; chlorobenzene; hexachloroethane; hexachlorobutadlene: toluene; BHC; chlordane; DDT; mirex; PCB; PCB Isomers.

As a component of the Ontario Ministry of the Environment's "Municipal-Industrial Strategy for Abatement" (MISA) program, the Ministry has conducted water quality studies at six pilot sites in Ontario. The purpose of these studies is to assess whether water quality conditions require higher levels of pollution control than those specified by BATEA (best available technology economically achievable). These site-specific, water quality-based effluent limits consider the environmental sensitivity of receiving water bodies. The Toronto Main Sewage Treatment Plant (STP) was selected as a pilot site. as it is one of the largest municipal STPs discharging to the Great Lakes, and receives influents from a large variety of sources (I.e. Industrial, domestic, storm overflow). Consequently, a series of studies encompassing all components of water quality (Poulton and Beak Consultants 1991), as well as various toxicity tests, have been undertaken.

A predictive link between effluent quality and specific effects on the aquatic environment can be established through the use of sophisticated modelling techniques, such as those described in the companion paper (Halfon 1994). By use of these techniques, water quality-based effluent limits can be derived and assessed relative to BATEA. in order to arrive at the final effluent requirements which adequately protect the aquatic environment in the Toronto area. Additionally, the results of this study are expected to contribute significantly to the development of the Toronto Waterfront Remedial Action Plan (RAP). The RAP is being prepared for the International Joint Commission by a combined federal-provincial work team, in cooperation with the municipalities and a formal public advisory committee, and will consider all possible measures of ecosystem quality restoration for the Metro Toronto Waterfront.

Large amounts of toxic contaminants enter Lake Ontario from the Niagara River, thus, lake waters contain measurable concentrations of hundreds of toxic pollutants. Nevertheless, concerns exist that the local input of toxic pollutants may result in Toronto drinking water containing contaminants in concentrations higher than the average in Lake Ontario. To this end, the National Water Research Institute (NWRI) and the Ontario Ministry of the Environment (MOE) in 1987 organized three cruises to sample the nearshore waters off the entire Metro Toronto Waterfront from Etobicoke to Scarborough as well as other sources. The purposes of this research are:

1. to provide baseline data on toxic contaminant concentrations across the Metro Toronto Waterfront In support of the Toronto RAP and Toronto MISA pilot site project;
2. (b) to Identify the relative contribution of Toronto sources and the Niagara River to organic contaminant pollution in the Toronto Waterfront; and
3. to document the concern that Toronto drinking water might contain toxic pollutants that enter the lake from nearby rivers and the STPs.

This report presents results on the first objective. A companion report (Halfon 1994) analyzes the last two, and Gore and Storrie

(1989) have developed a hydrodynamic model of the Toronto waterfront to study current movements. Data for all contaminants are available in spreadsheets.

Three cruises took place on May 26-June 11, July 27-August 7, and October 5-7. 1987; Table 1 and Figure 1 show the locations of all 29 stations. Two ships were used for data collection. The Advent, a small ship, could only work during daylight hours, and collected three to four samples a day. Thus, on average, each of the first two cruises took two weeks. The Limnos. a large ship, collected water samples on the last cruise. This ship worked 24 hours a day and needed only three days to sample all stations.

At all lake stations 200-L aqueous phase liquid-liquid extractor (APLLE) (Oliver and Nicol 1986) samples were collected. Coincidentally, during each cruise several 16-L samples were collected by the MOE at four STPs. The STPs that discharge directly into Lake Ontario are Highland (near the Rouge River). Toronto Main, Humber and Lakeview (Mississauga). The MOE also sampled river mouths during August and October with 200-L APLLE samplers.

Water samples were depth-integrated. During unstratified conditions, samples were collected from the surface to 40 m, or if shallower than 40 m. to 5 m from the bottom. During stratified conditions, samples were integrated from the surface to the top of

the thermocline. To integrate a sample, water was pumped at a rate of 5 L per minute from four equally spaced depths for ten minutes each, until the 200 L APLLE sampler was full. At six stations (2891 and the transect east of the Main STP, 2892 to 2897), the centrifuge bowl was cleaned and the particulate placed in the containers provided and stored at 4°C. Duplicate water samples were also collected at a few stations.

Nearshore water samples were collected along six transects. All transects include three stations representative of water depths of approximately 15, 30 and 60 m. except at the two central transects where 30 and 60 m contours are very close together. The two central transects include two further offshore locations at 8 km Distance intervals. In addition, samples were collected from stations 2891, about 3 km south of the Main STP outfall, and 2892, about 3 km east north-east of the outfall, since the draft of the Umnos prevented entry into shallow waters closer to the outfall. Samples were also collected at 2072 (Humber STP outfall), 2882 (Lakeview STP outfall), 2902 (Highland Creek STP outfall), 2029 (R.C. Harris filtration plant Intake). 1536 (Island filtration plant Intake), 2901 (easterly filtration plant intake). 2073 (Etoblcoke filtration plant Intake), and 1375 (inner harbour near the Don River mouth).

The following collections took place at each station:

1. an EBT profile to the bottom;
2. surface water temperature;
3. in daylight hours a Secchi disk reading from the shaded side of the vessel;
4. a transmissometer profile to the bottom with a 25-cm path length transmissometer;
5. a large volume water APLLE sample (200 L) collected with a March pump through a Westphalia continuous How centrifuge- and
6. at selected stations, particulates from the centrifuge were collected.

Extraction of the APLLE sample was undertaken in the field with 8 L of dichloromethane (DCM). Water samples in the APLLE extractor were spiked at the parts per trillion level with the following surrogate chemicals: 1,3-dlbromobenzene (1,3-DBB); 1.3,5-tribromobenzene (1,3.5-TBB); 1,2.4.5-tetrabromobenzene (1,2.4,5-TeBB); 2.3.5,6-tetrachloroblphenyl (PCB-65); and octachloronaphtalene (OCN). The surrogate enabled the laboratories to check the chemical recoveries both in the field sampling and in the laboratory cleanup/concentration for each sample; this extract was stored on the ship for the duration of the cruise, returned to the Canada Centre for Inland Waters (CCIW), and forwarded by truck to EU-Eco Laboratories in Rockwood, Ontario, for analysis. Some duplicate samples were sent to Zenon Laboratories in Burlington, Ontario.

At the four STPs, 16-L effluent samples (4 x 4 L) were collected by MOE. Dally composites were obtained by collecting 8 L in the morning and 8 L in the afternoon. These samples were also spiked with the five surrogates and sent to Zenon Laboratories for analysis. The river mouths were sampled by MOE using APLLE samplers. These were also sent to Zenon Laboratories for analysis.

Oliver and Nicol (1986) published the combined extraction and leanup/concentration procedures. The report from Ell-Eco Laboratories describes in detail the laboratory methodology. Detection limits for the 200-L water samples are 100 pg/L for dichlorobenzenes, 10 pg/L for trichlorobenzenes, 5 pg/L for tetrachlorobenzenes and 2 pg/L for pentachlorobenzene (QCB), hexachlorobenzene (HCB), most PCBs, and organochlorine pesticides.

The use of the APLLE sampler during the three 1987 sampling periods represents the first comprehensive analysis of the concentrations of PCBs. organochlorine pesticides and Chlorobenzenes undertaken in the Toronto Waterfront. Average concentrations of 11 Chlorobenzenes, 13 organochlorine pesticides including DDT and mirex. and total PCBs are given in Table 2 for each of the three survey periods. Sixty-four PCB congeners are also separated. These data indicate that few contaminants are present in relatively high concentrations (>1 ng/L). Such contaminants include the dichlorobenzenes (DCB), a-BHC. y-BHC (lindane), and, in October, total PCBs in 23 of 30 samples collected. This is most significant for total PCBs for which the provincial water quality objective (PWQO) is 1 ng/L. Levels of 1.2.4-trichlorobenzene (TCB). 1,2,3-TCB, and 1,2,3,4-tetrachlorobenzene (TeCB) were between 0.1 and 1 ng/L. Other contaminants averaged below 0.1 ng/L. These contaminants must nevertheless be taken into account in an analysis of relative impact because of possible additive and synergistic effects.

A set of 267 charts (three cruises x 89 chemicals made up of 25 contaminants and including 64 PCB congeners) is available on request. These charts show the concentrations of contaminants in Lake Ontario waters near Toronto; these data are also available on spreadsheets. This paper shows an analysis of the relations between water masses, identified by their temperature, contaminant concentrations and possible sources.

Upwelling episodes took place on the north shore of Lake Ontario. Lower temperature hypolimnetic water masses are brought to the surface by the upwelling process; hence, we can detect the different water masses present by their temperatures. Unfortunately, since all cruises progressed from west to east, we cannot state when each upwelling event began. Figure 2 shows the surface water temperature during the three cruises in 1987. Surface water temperatures in spring ranged from 12.3°C at station 2897 (midlake) to 7.4°C at station 2893 (nearshore). The temperature in the western part of the waterfront is three to seven degrees higher than off the Scarborough Bluffs. In July-August, water temperature was fairly uniform, except for an upwelling in Humber Bay. m October, with cooling air temperatures and moderate south-westerly winds of 5-20 knots, three water masses were Identified: an offshore epilimnetic mass at 14-15°C in Humber Bay, a mesolimnetic water mass of 6-8°C offshore from Picketing, and a hypolimnetic water mass at 4-5°C offshore from the Eastern Beaches.

In May-June 1987, two contaminated areas are observed: one located on the western zone of the Toronto Waterfront (which Includes Humber Bay, and Toronto inner and outer harbours) and one located near the Highland STP station, hi this area, the water temperature (Figure 2) is low and contaminants might have been diluted In cleaner, cooler hypolimnetic waters. In July-August, the pattern of pollution is similar to the one observed in May-June

Chlorobenzenes

Dichlorobenzenes are present in relatively high concentrations while the trichlorobenzenes, tetrachlorobenzenes, QCB and HCB occur at much lower concentrations (0.1 ng/L or less). While the relative toxicity of chlorinated benzene Isomers Increases in proportion to the number of chlorine atoms in the benzene molecule (thus making HCB potentially more hazardous than dichlorobenzene), all the observed chlorinated benzene levels were well below existing PWQOs. Concentrations of 1,2-dlchlorobenzene (DCB) (PWQO=2500 ng/L) are 0.7 to 1 ng/L in Humber Bay and 0-3 ng/L along the nearshore in May and August. In October, concentrations of the order of 2-4 ng/L still persist in Humber Bay while the offshore is below 1 ng/L. For 1.3-DCB (FWQO = 2500 ng/L), offshore concentrations in May are approximately 0.3-1 ng/L while nearshore concentrations are 1-2 ng/L; in July offshore concentrations are low and concentrations of 1-2 ng/L are only found In Humber Bay; in October concentrations are below 0.9 ng/L everywhere except for mean 1 ng/L levels along the western boundary of the study area (Figure 3). For 1,4-DCB (PWQO = 4000 ng/L), the May-June offshore concentrations are in the order of 2-3 ng/L". Higher concentrations are present in Humber Bay (about 35 ng/L near the Lakeview STP outfall) and relatively high concentrations of 5-15 ng/L are observed along the entire Toronto Waterfront nearshore. In July, concentrations are similar to those in June while in October no 1,4-DCB was detected anywhere, even offshore.

Higher chlorinated benzenes are present in low concentrations In Lake Ontario (Table 2). Only for 1.2.4-TCB were concentrations routinely above 0.1 ng/L; levels of all these compounds were far below their PWQOs. Highest levels of tri- and tetrachlorobenzenes were found In Humber Bay, near the Toronto Main STP outfall, in the Toronto inner harbour and along the western boundary of the study area. The maximum level ofQCB (PWQO=30 ng/L) was 0.18 ng/L in the inner harbour in August. HCB (PWQO=6.5 ng/L) was generally below 0.1 ng/L and showed a much weaker inshore-offshore gradient than the lower chlorinated benzenes.

Most organochlorine pesticides (Table 2) are in very low concentrations in the order of 0.1 ng/L or less. Exceptions are a-BHC and lindane (y-BHC), which are found in concentrations of 3-5 ng/L and 0.5-1 ng/L. respectively. In most months, concentrations of these contaminants are fairly uniform, except for October, where a mixing of different water masses of varying a-BHC concentration between 0 and 8 ng/L is observed. From May to August, a slightly higher concentration (2 ng/L) of lindane is observed in Humber Bay while in October concentrations are fairly uniform. Concentrations for the other pesticides Including DDT and mirex are fairly uniform over the lake and nearshore, and are less than 0.1 ng/L. No obvious sources exist for any of these compounds.

Figure 4 shows the concentrations of total PCBs. From May to June, concentrations are fairly uniform. Offshore concentrations are less than 0.5 ng/L while in the western part of the Toronto Waterfront, concentrations of 1-4 ng/L are observed. In July-August 1987 offshore concentrations are similar; concentrations of 1-4 ng/L are again found near the Humber River. In October, several water masses are present near the north shore of Lake Ontario and concentrations vary between 1 and 9 ng/L. No obvious PCB source is present nearshore.

This study represents the first time Toronto Waterfront samples have been analyzed for congener-specific PCBs. The main reason for this effort is to verify whether the same PCB sources were active during different periods in spring, summer and fall. Total PCB concentrations do not provide this level of resolution.

The analysis of PCBs Included 64 PCB congeners. A total of 209 PCB congeners exists; however. 31 congeners co-elute on the gas chromatography and we therefore report on 39 individual congeners, 14 pairs of congeners and one triplet. Most concentrations are very low and patterns cannot be easily identified. Nevertheless, this analysis is useful to point out whether any particular PCB congeners are in larger percentages than the others. Table 3 shows the percentages of all PCB congeners; the relative percentages vary more temporally than spatially. Six congeners are present in high percentages over time; they are PCB-52 (3-5 in all three cruises). PCB-70+76 (4-5), PCB-66+95 (5-7). PCB-84+92 (4-8). PCB-101 (2-8). and PCB-110 (2-3). In total they represent about 25 of all congeners. Other congeners appear in large percentages, but only once during the year: PCB-180 (19 in May-June), PCB-22 (29 in July-August) PCB-53 (27 in October) PCB-149 (10 in May^June), PCB-42 (9 in July-August). PCB-153+132+105 (8 in May-June), and PCB-6 and PCB-18 (6 each in October).

Overall we see that In May-June, 9 PCB congeners, out of 64account for 71 of all PCBs, in July-August, 8 PCB congeners account for 71, and in October, 9 congeners account for 63. All the other congeners are found in low percentages (less than 4 each). Oliver and Nlimi (1988) also did congener-specific PCB analyses in Lake Ontario, in a series of mid-lake samples more remote from Toronto. They found similar congeners to be present at relatively high percentages, though those found here in only one month were sometimes found in only very small amounts in their study (e.g. PCB-53 and 22). This raises the possibility of intermittent local sources, but further work would be required to confirm this.

Table 3: Percentages of total PCBs

One of the purposes of this study is to Identify any local sources of the contaminants and relate their presence with the water masses. Contaminant concentrations were measured in river mouths and in the final effluent from the four areas STPs: Poulton and Beak (1991) present the results of this sampling program. It was concluded that the main local sources of contaminants to the Toronto Waterfront are the STPs. The local rivers are only a minor source. The main problem of tracing the fate of toxic contaminants is the fact that Lake Ontario receives toxic contaminants from a variety of other sources, namely the atmosphere and the Niagara River. The lake is therefore full of contaminants and plumes from local sources can be followed only using mathematical models (Halfon 1994). This report deals mostly with data analysis rather than with simulations and therefore one way of tracing sources is to identify nearshore zones where concentrations are higher than average lake concentrations.

A method to trace the Impact of contaminants on the lake is to correlate the contaminant concentrations with the water temperature; this correlation verifies whether an association exists between water masses and Individual contaminants. Only large lake water masses can be identified since the sampling grid contains 26 stations per cruise. Water masses from the Humber River and the Don River, which enters the Toronto inner harbour, cannot be Identified in this analysis; Poulton and Beak Consultants (1991) showed the existence of relatively small impact zones near the major rivers and STPs, and in the inner and outer harbours using cluster analysis of station variations of conventional parameters. Table 4 shows the correlations of the water temperature and contaminant concentrations during the three cruises. A positive correlation between contaminant concentrations and surface water temperature implies that contaminants are associated with warm epilimnetic water. A negative correlation implies that high concentrations of contaminants are associated with cold hypolimnetic water that has upwelled near the north shore. The temporal trend in correlations is also important to detect whether the pollutants are associated with the water masses (sign of significant correlations does not change in the three cruises), or whether local sources are important (sign of significant correlations changes in time).

In May-June the overall correlation of the 25 contaminants (Including total PCBs but not all individual isomers) is 0.39. Since the water mass is warmer in Humber Bay than in the eastern shores, this correlation suggests pollution sources in Humber Bay. It should be noted that a significant con-elation factor does not imply a well-defined source but only a generalized area of contamination; Halfon (1994) identifies the source in Humber Bay as the Humber STP rather than the Humber River. 1,4-DCB has a correlation ofr=0.37 and 1,2-DCB a correlation ofr=0.40. These two contaminants have obvious sources nearshore. Other contaminants without well defined sources are 1.2,4.5-TeCB (r=0.35), HCE (r=0.42). lindane (r=0.43), and octachlorostyrene (r=-0.50). The negative correlation of octachlorostyrene Indicates higher onshore levels, suggesting a distant source such as the Niagara River. PCB isomers have no significant correlations with water temperature except for PCB-18 (r=0.34). PCB-118 (r=0.35) and PCB-138 (r=0.38).

Table 4: Correlation of contaminant concentration with temperature.

In July-August the overall correlation was r=-0.56. The negative correlation is significant with the location rather than with the water mass. As upwelling of cooler water has occurred In Humber Bay, this suggests pollution sources in this area. Large correlations can be observed for 1,4-DCB (r=-0.49), 1,2,4-TCB (r=-0.48), 1.2.3-TCB (r=-0.54), HCB (r=-0.44), 2.3,6-TCT (r=-0.62). Lindane (r==-0.37). -y-chlordane (r=-0.59), pp'-DDE (r=-0.44) and pp'-DDD (r=-0.44). Three PCB congeners are also significantly correlated and present in relatively high percentages of total PCBs: PCB-18 (r=-0.38; 2.1). PCB-99 (r=-0.43, 2.9) and PCB-153+132 (r=-0.69: 1.7).

In October the overall correlation is a non-significant r=0.11. The correlation analysis is less meaningful than for the other two previous cruises—as noted previously, three different water masses are present, low temperature water is present nearshore while the lake waters offshore are relatively warmer. Some individual contaminants, however, show significant correlations: 1.2,3-TCB (r==-0.40). 1,2,3.4-TeCB (r==-0.43). QCB (r=-0.49), pp'-DDD (r^-0.43) and mirex (r=0.35). The positive correlation for mirex shows that mirex is present in larger concentrations offshore, rather than inshore. Among the PCB isomers we can note PCB-44 (r=0.40; 3.7), PCB-70+76 (r=0.39; 4.1), PCB-66+95 (r=0.42: 5.7), PCB-84+92 (r=0.42; 3.8). PCB-101 (r=0.42; 2.5). PCB-87+97 (r=0.40; 2.3), and PCB-110 (r=0.41; 2.5). Total PCBs have a correlation of 0.38. again indicating higher levels in warmer onshore waters at this time.

Water concentrations of most contaminants are quite low and uniform. The presence of toxic contaminants in offshore waters shows that the lake is presently polluted by a variety of sources. Comparison of 1988-90 Niagara River loadings for water column plus particulate fractions (Data Interpretation Group 1990) with Toronto Waterfront STP loadings calculated from large-volume samples (Poulton and Beak 1991) indicates the Niagara River to be a major source for most contaminants, much larger than the local sources along the Toronto Waterfront. The only exception is for 1,4-DCB. for which the relative loadings are approximately equal. For other di- to tetrachlorobenzenes, the Toronto loadings are about 20 to 40 of the Niagara ones; relative Toronto loadings for other compounds such as PCBs are very low. Halfon (1994) drew similar conclusions regarding relative loadings. Elimination of chlorobenzene loadings from the Toronto Main STP would be quite beneficial to the Lake Ontario ecosystem. This action, however, might be impossible since low chlorinated benzenes are often use as disinfectants in urinals. Observability of the effect of removing these loads is discussed in Halfon (1994) by using simulation models.

Local sources of pollution with resulting concentrations higher than 1 ng/L have been identified only for 1,4-DCB (in May-June and July-August only), 1,2-DCB and total PCBs. All local sources of pollution are in Humber Bay; however, the exact location of each source has not been identified.

A correlation analysis between water temperature and contaminant concentrations has pointed out possible local sources of other contaminants, namely: in May-June. 1.2.4,5-TeCB. HCE. lindane and the PCB Isomers PCB-18, PCB-118 and PCB-138; in July-August. 1,4-DCB, 1.2.4-TCB. HCB, 2,3.6-TCT. lindane, gamma-chlordane, pp'-DDE, pp'-DDD and the three Isomers PCB-18, PCB-99 and PCB-153+132; in October, 1.2.3-TCB. 1,2,3.4-TeCB, QCB and pp'-DDD. The concentrations of these contaminants are quite low, <1 ng/L. and therefore the evidence from the correlation analysis is only circumstantial. Furthermore, the contaminant pattern varies with the sampling time, which points to intermittent sources of pollution.

Levels of most contaminants were similar to or slightly lower than averages for a series of Lake Ontario offshore locations surveyed using a similar technique in 1984 by Oliver and Niimi (1988). They are also within the ranges of concentrations given by Stevens and Neilson (1989) for a lakewide grid sampled in 1986 using a Goulden high-volume extractor which also extracts contaminants into dichloromethane. The latter failed to detect DDD. DDT and mirex in any of their samples; however, values found in this study were close to their detection limits. For many of the chlorinated benzenes, our values are near the lower end of their ranges, which is reasonable considering that their spatial analysis indicated highest concentrations near the Niagara River, again in agreement with the known higher loadings from this area. The dichlorobenzenes, and in particular, 1.4-DCB. showed higher concentrations in this study, also in agreement with the fact that high loadings are found in the Toronto Waterfront for these chemicals. Alpha-BHC is present in the Toronto Waterfront at relatively high concentrations (3-5 ng/L), similar to or slightly higher than values found by Oliver and Niimi (1988) and Stevens and Neilson (1989). This contaminant was observed uniformly distributed at concentrations higher than all other contaminants; many other studies have found it to be ubiquitous.

The distribution of some individual contaminants changed dramatically during the survey. Some contaminants, like the dichlorobenzenes. were present in large concentrations in May-June and July-August but disappeared almost completely in October. Others, like the isomer PCB-53. were not present In May-August but were present in low concentrations in October.

Even if Individual concentrations of contaminants change seasonally, the overall pattern of pollution is the same. Halfon (1994) has studied temporal trends in more detail with mathematical modelling techniques.

PCB water quality objectives (PWQO) of 1 ng/L are exceeded in many locations of the Toronto Waterfront. This observation reflects the fact that the average concentration of PCBs in Lake Ontario is 1.1 ng/L (Oliver and Niimi 1988). Local sources of PCBs do not have much impact on the nearshore waters. Other contaminants observed in concentrations between 1 and 5 ng/L, such as the three dichlorobenzenes, a-BHC and lindane. have higher water quality objectives (lindane is 10 ng/L and 1,2-DCB is 2500 ng/L) and therefore occur in concentrations unlikely to have a serious deleterious effect.

This study was funded by a grant from the Ontario Ministry of the Environment under the MISA and Toronto RAP programs. The crews of the ships Advent and Limnos did a wonderful Job in collecting the data and organizing the samples for analysis. Mr. Steve B. Smith led all the field experiments, and this report would not have been possible without his expert help. Mr. David de Jong helped in plotting the contaminant concentrations and organizing some of the information contained in this paper. Mr. David Brendon assisted with the editing and processing. Collin Gray. Marta Griffiths and Drs. Rod Allan and Klaus Kaiser reviewed drafts of the manuscript.

Data Interpretation Group, 1990. Joint evaluation of upstream/ downstream Niagara River Monitoring data for the period April 1988 to March 1989. Final Report, November 26. 1990. complied by K.W. Kuntz, WQB-OR.

Gore and Storrie. 1989. Toronto Waterfront RAP-RAND model simulation. Report on engineering services for Ministry of the Environment, Water Resources Branch, Great Lakes Section, August 1989.

Halfon, E. 1994. Simulation of the fate of toxic contaminants in the Toronto Waterfront. Wat. Poll. Res. J. Canada (In press).

Oliver, B.G. and K.D. Nicol. 1986. Field testing of a large volume liquid-liquid extraction device for halogenated organics in natural waters. Int. J. Env. Anal. Chem. 25: 275-285.

Oliver. B.G. and Niimi. A.J. 1988. Trophodynamic analysis of polychlorinated biphenyl congeners and other chlorinated hydrocarbons in the Lake Ontario ecosystem. Env. Sci. Tech. 22: 388-397.

Poulton. D.J. and Beak Consultants Ltd. 1991. Toronto Main STP MISA pilot site study component report: water quality. Great Lakes Section, Water Resources Branch. Ministry of the Environment

Stevens, R.J.J. and Neilson, MA. 1989. Inter- and Intralake distributions of trace organic contaminants in surface waters of the Great Lakes. J. Great Lakes Res. 15: 377-393.