Lake Michigan Mass Balance

U.S. Environmental Protection Agency Great Lakes National Program Office (G-17J) 77 West Jackson Boulevard Chicago, IL 60604 EPA 905 R-01-011 entire report (PDF 5.2 Mb) Results of the Lake Michigan Mass Balance Study: Polychlorinated Biphenyls and trans-Nonachlor Data Report Prepared for: USEPA Great Lakes National Program Office 77 West Jackson Boulevard Chicago, IL 60604 Prepared by: Harry B. McCarty, Ph.D. Judy Schofield, Ken Miller, and Robert N. Brent, Ph.D. DynCorp – A CSC Company 6101 Stevenson Avenue Alexandria, Virginia 22304 and Patricia Van Hoof, Ph.D. and Brian Eadie, Ph.D. April 2004

Cover (PDF) 0.74Mb Chapter 1 (PDF) 0.35Mb Chapter 2 (PDF) 0.65Mb Chapter 3 (PDF) 0.61Mb Chapter 4 (PDF) 0.59Mb Chapter 5 (PDF) 1.49 Mb Chapter 6 (PDF) 0.88Mb Chapter 7 (PDF) 0.47Mb Chapter 8 (PDF) 0.37Mb Chapter 9 (PDF) 0.79Mb Reference section (PDF) 0.12Mb Entire Report  (PDF) 5.2Mb

Results of the Lake Michigan Mass Balance Study: Polychlorinated Biphenyls and trans-Nonachlor Data Report

April 2004

The U.S. Environmental Protection Agency’s Great Lakes National Program Office (GLNPO) and its partners instituted the Lake Michigan Mass Balance (LMMB) Study to measure and model the concentrations of representative pollutants within important compartments of the Lake Michigan ecosystem. The goal of the LMMB Study was to develop a sound, scientific base of information to guide future toxic load reduction efforts at the Federal, State, Tribal, and local levels. Objectives of the study were to:

1. Estimate pollutant loading rates,
2. Establish a baseline to gauge future progress,
3. Predict the benefits associated with load reductions, and
4. Further understand ecosystem dynamics.

The LMMB Study measured the concentrations of mercury, polychlorinated biphenyls (PCBs), transnonachlor, and atrazine in the atmosphere, tributaries, lake water, sediments, and food webs of Lake Michigan. This document summarizes the PCB and trans-nonachlor data collected as part of the LMMB Study, and is one in a series of data reports that documents the project.

PCBs are synthetic organic chemicals that are chemically inert, nonflammable, and do not transmit electrical current. These properties, combined with high melting and boiling points, made PCBs useful in a wide variety of industrial applications, particularly as dielectric fluids in electrical transformers and capacitors. In the United States, the Monsanto Company produced commercial mixtures of PCBs by chlorinating biphenyl and sold the mixtures under the trade name Aroclor. The parent compound, biphenyl, consists of two six-membered aromatic carbon rings joined by a single carbon-carbon bond. Chlorination of biphenyl attaches one or more chlorine atoms to carbon atoms in the two ring structures. PCB production and export in the U.S. was halted in October 1977 under the auspices of the Toxic Substances Control Act (TSCA).

There are 209 possible arrangements of chlorine atoms, and each of the arrangements is referred to as a PCB “congener.” The formal chemical name of each congener identifies the specific positions and the total number of chlorine atoms in the congener. However, individual PCB congeners are often referred to simply by “congener number,” e.g., PCB 1 to PCB 209. This report focuses on the results for three congeners, PCB 33, PCB 118, and PCB 180 in all of the samples except sediments. For sediments (Chapter 6), the report focuses on the results for the sum of PCBs 28 and 31, PCB 118, and PCB 180.

trans-Nonachlor is the common name for 1,2,3,4,5,6,7,8,8-nonachloro-3a,4,7,7a-tetrahydro-4,7-methanoindan, a member of the class of cyclodiene pesticides. trans-Nonachlor was not produced as a pure compound, but was a major component of the pesticide “technical chlordane,” which is a mixture of at least 140 related compounds. Chlordane mixtures were first produced in the U.S. in 1948 and various formulations of chlordane were widely used as pesticides on food crops and lawns, and for termite control from 1948 to 1988. In April 1988, EPA canceled all commercial uses of chlordane in the U.S.

Study Design

Lake Michigan Mass Balance Study Sampling Locations

In the LMMB Study, PCBs and trans-nonachlor were measured in atmospheric, tributary, open-lake water column samples, sediments, lower pelagic food web organisms, and fish. From March 1994 through October 1995, over 1000 samples were collected from locations in and around Lake Michigan (see Figure 1-2 in Chapter 1) and analyzed by gas chromatography with either electron capture or mass spectrometry detectors. Atmospheric vapor, particulate, and precipitation samples were collected from eight stations surrounding Lake Michigan and three background stations outside the Lake Michigan basin. Tributary samples were collected from 11 rivers that flow into Lake Michigan. Open-lake water column samples were collected from 38 sampling stations in Lake Michigan, 2 stations in Green Bay, and 1 station in Lake Huron. Sediment samples were collected from over 100 stations in Lake Michigan and Green Bay. Samples of particulate matter were collected in sediment traps deployed at eight stations in Lake Michigan. Samples of phytoplankton and zooplankton were collected from 12 stations in Lake Michigan. Samples of Mysis and Diporeia were collected at 10 stations in Lake Michigan. Specimens of lake trout, coho salmon, bloater chub, alewife, smelt, deepwater sculpin, and slimy sculpin were collected from three to 79 locations around the lake, depending on the species.

PCBs and trans-Nonachlor in Atmospheric Components

Vapor-phase PCB congeners were detected in the vast majority of the samples collected from all LMMB Study stations. Monthly composite concentrations of vapor-phase total PCBs ranged from 0 pg/m3 at Beaver Island and Brule River stations to 6300 pg/m3 at the IIT Chicago station. Vapor-phase PCB results exhibited a seasonal trend, with higher concentrations occurring in summer months and lower concentrations occurring in winter months and may be a result of the interaction of the vapor pressures of the PCBs and the increased temperatures during summer months. Vapor-phase PCB congener and total PCB concentrations varied by sampling station. Urban and urban-influenced sites had higher mean monthly composite concentrations for the duration of the study period than rural sites.

Vapor-phase trans-nonachlor was detected much less frequently than PCB congeners. Vapor-phase trans-nonachlor was not detected in the samples from two over-water stations. Of the 28 sampling stations, 13 stations had 13% to 50% of the individual samples below detection limits. Only one sample was collected at Stations 380 and 19M and each had a result of zero. Concentrations of vapor-phase trans-nonachlor ranged from 0 pg/m3 at over-water stations 380 and 19M to 118 pg/m3 at Bondville. Non-zero mean monthly composite concentrations of trans-nonachlor for each sampling station ranged from 2.1 pg/m3 measured at Brule River to 43 pg/m3 measured at Bondville. Vapor-phase transnonachlor results showed an even stronger seasonal variation than the vapor-phase PCB results. All of the sites exhibited similar trends in vapor phase trans-nonachlor concentrations, with higher concentrations generally occurring in the summer and lower concentrations in the winter, despite differences between sites of an order of magnitude or more. For the urban site IIT Chicago, concentrations of vapor-phase trans-nonachlor were 1.5 pg/m3 in February 1995 and were 50 times higher in July 1995, at 80 pg/m3. For the rural Bondville station, vapor-phase trans-nonachlor was 2 pg/m3 in February 1995 and was 60 times higher in July 1995 at 120 pg/m3.

Particulate-phase PCB congeners were detected in the majority of the samples collected from all LMMB Study stations. Concentrations of particulate-phase total PCBs ranged from 0 pg/m3 at the Beaver Island station to 250 pg/m3 at the IIT Chicago station. Particulate-phase PCB congener and total PCB concentrations varied by sampling station. Urban and urban-influenced sites had higher mean monthly composite concentrations for the duration of the study period than rural sites, consistent with the hypothesis that urban and urban-influenced areas contain significant sources of particulate-phase PCBs.

Particulate-phase trans-nonachlor was detected much less frequently than PCB congeners in the samples. Except for the samples collected at the Empire Michigan station, trans-nonachlor was reported as being below the sample-specific detection limit in 20 - 100% of the particulate-phase samples from the other 16 stations. Concentrations of particulate-phase trans-nonachlor ranged from 0 pg/m3 at 12 stations to 2.6 pg/m3 at Bondville. Mean monthly composite concentrations of trans-nonachlor for each sampling station ranged from 0.16 pg/m3 measured at GB24M to 1.2 pg/m3 measured at IIT Chicago, with a concentration of 1.8 pg/m3 for the only sample collected at over-water Station 1.

PCB congeners were detected in many of the precipitation samples collected from the LMMB Study stations. However, the overall frequency of occurrence of PCBs in the precipitation samples was lower than for the vapor-phase and particulate-phase samples. For total PCBs, the mean concentrations in precipitation ranged from 290 pg/L at the Eagle Harbor station to 16,000 pg/L at the IIT Chicago station.

trans-Nonachlor was detected even less frequently than the PCB congeners in the precipitation samples. Except for the samples collected at the IIT Chicago station, trans-nonachlor was reported as being below the sample-specific detection limit in 75 to 100% of the precipitation samples from all stations. The concentrations of trans-nonachlor in the precipitation samples ranged from 0 pg/L at every site to a high of 630 pg/L at the Chiwaukee Prairie site.

PCBs and trans-Nonachlor in Tributaries

The dissolved total PCB concentrations ranged from not detected in four tributaries to 48 ng/L in the Grand Calumet, while particulate total PCB concentrations ranged from not detected in four tributaries to 120 ng/L in the Sheboygan River. Mean dissolved total PCB concentrations ranged from 0.43 ng/L in the Pere Marquette River to 35 ng/L in the Grand Calumet, while mean particulate concentration ranged from 0.25 ng/L in the Muskegon River to 55 ng/L in the Sheboygan River.

The concentrations of dissolved and particulate total PCBs exhibited a seasonal trend for many of the tributaries, with higher mean concentrations occurring in summer months and lower mean concentrations occurring in winter months. There were significant differences between seasons for the dissolved total PCB concentrations in nine of the eleven tributaries, and significant differences between season for the particulate total PCB concentration in six of the eleven tributaries. However, the trend was not consistent across all of the tributaries. The mean seasonal concentrations of dissolved and particulate total PCBs across all 11 tributaries span at least two orders of magnitude.

Concentrations of dissolved trans-nonachlor ranged from not detected in seven tributaries to 0.19 ng/L in the Manistique River, while particulate trans-nonachlor ranged from not detected in five tributaries to 0.38 ng/L in the Manistique River. Mean dissolved trans-nonachlor concentrations ranged 0.0033 ng/L in the Menominee River to 0.026 ng/L in the St. Joseph River, while mean particulate trans-nonachlor concentrations ranged from 0.0028 ng/L in the Menominee River to 0.074 ng/L in the St. Joseph River.

The mean concentrations of dissolved and particulate trans-nonachlor show fewer significant differences than the total PCB results. Eight of the eleven tributaries exhibit no statistically significant differences in mean dissolved trans-nonachlor concentrations among the seasons. Of the other three tributaries, the mean dissolved trans-nonachlor in the Kalamazoo River is never the lowest in spring or summer, and never the highest in autumn, while in the Sheboygan River, mean dissolved trans-nonachlor is never the lowest in the summer, or the highest in the winter. The dissolved trans-nonachlor results for the Manistique River are characterized by a very high mean concentration in the winter which is significantly different from the other three seasons, which in turn, are not significantly different from one another. The very high winter mean concentration is repeated in the particulate trans-nonachlor results in this tributary.

PCBs and trans-Nonachlor in Open-lake Water

The concentrations of dissolved PCB congeners are generally lowest in the far northern areas of the lake that are removed from urban influences. The highest dissolved concentrations generally are found in the southwest area of the lake, near the urban areas of Chicago and Milwaukee.

The particulate PCB concentrations are highest in Green Bay, at Station GB 17, with much lower particulate PCB concentrations in the remainder of the lake. The particulate concentrations of PCBs 118 and 180 show a slight increase in the southeast portion of the lake, in the area between the mouths of the St. Joseph and Kalamazoo Rivers. However, the concentrations of particulate PCBs 118 and 180 in that area are still 2 to 5 times lower than in the upper reaches of Green Bay.

The dissolved concentrations of trans-nonachlor are similar to those of the dissolved PCB congeners, with an apparent increase in concentration in the southwest portion of the lake, near Chicago. The particulate concentrations of trans-nonachlor are similar to those of the particulate PCB congeners, with the highest concentrations in Green Bay, near Station GB 17. However, particulate trans-nonachlor concentrations appear to increase in areas of the lake adjacent to most of the major urban areas around the lake. Similar increases occur near the discharges of the Manistique and Pere Marquette Rivers, which are not associated with urban areas, suggesting that the increases near the urban area may be a function of river-borne sources of particulate trans-nonachlor, including resuspension of contaminated sediments.

PCBs and trans-Nonachlor in Sediments

The mean concentrations of the PCB congeners and total PCBs exhibit a general trend of decreasing concentrations from south to north, with the lowest concentrations in the Straits region. In contrast, the mean concentrations of trans-nonachlor, while lowest in the Straits region, exhibit no south to north trend. The organic carbon content data exhibit a pattern similar to that for trans-nonachlor.

Total PCBs exhibit a wide range in concentration. Although not a true bimodal distribution, two distinct groups are evident within the total PCB distribution. The first group of samples, from nondepositional and transitional stations, has very low concentrations that exponentially decline in number with increasing concentration (0 - 30 ng/g). The second group of samples taken mainly from depositional sites (35 - 225 ng/g) is more normally distributed, though tailing toward higher levels is evident.

Concentrations of PCBs and trans-nonachlor in surficial sediments increase with increasing organic carbon (OC) content. The spread in the data suggest that the southern basin stations were significantly higher in contamination. This finding was expected as hydrophobic compounds are known to partition strongly to organic matter. The southern basin the relationships of the PCB congeners and organic carbon content exhibited an additional feature not seen in other basins. A peak in PCB concentration was observed at ~25 mg/g OC for PCB 28+31 and at ~35 mg/g for PCB 118 and PCB 180. The relationship of trans-nonachlor with OC did not follow the same pattern as any particular PCB congener.

PCBs and trans-Nonachlor in Lower Pelagic Food Web Organisms

PCB and trans-nonachlor concentrations measured in the lower pelagic food web differed significantly among phytoplankton, zooplankton, Mysis spp., and Diporeia spp. Concentrations of total PCBs and trans-nonachlor were highest in samples of Diporeia spp., followed by Mysis spp., zooplankton, and phytoplankton, respectively. Total PCB concentrations were 9 times higher in Diporeia spp. than in phytoplankton, averaging 420, 250, 170, and 49 ng/g dry weight in Diporeia spp., Mysis spp., zooplankton, and phytoplankton samples, respectively. Trans-Nonachlor concentrations were 19 times higher in Diporeia spp. than in phytoplankton, averaging 32, 25, 16, and 1.7 ng/g dry weight in Diporeia spp., Mysis spp., zooplankton, and phytoplankton samples, respectively.

A portion of the difference in PCB and trans-nonachlor concentrations among lower pelagic food web sample types is likely due to variations in the lipid content of the samples. Hydrophobic organic contaminants such as PCBs and trans-nonachlor preferentially concentrate in the fatty tissues of organisms, so those organisms with higher lipid content will likely concentrate more of these contaminants. The differences in lipid content among the sample types, however, explained only a quarter to less than half of the variability in total PCB and trans-nonachlor concentrations. Even when total PCB and trans-nonachlor concentrations were normalized by lipid content, the trends in PCB and trans-nonachlor concentrations among the sample types were almost always the same. Normalized total PCB and trans-nonachlor concentrations in Diporeia spp. and Mysis spp. were significantly higher than in zooplankton and phytoplankton, and normalized trans-nonachlor concentrations in zooplankton were significantly higher than in phytoplankton. Normalized total PCB concentrations in zooplankton, however, were not significantly different than in phytoplankton.

PCBs and trans-Nonachlor in Fish

PCB and trans-nonachlor concentrations differed significantly among species. Significantly higher levels of total PCBs and trans-nonachlor were observed in Lake trout, a top predator in the Lake Michigan pelagic food web, than in any other fish species. Mean wet-weight concentrations of total PCBs and trans-nonachlor in lake trout were 3.6 and 2.9 times higher than for any other species. This trend was similar for dry-weight basis PCB and trans-nonachlor concentrations. Mean dry-weight basis total PCB concentrations in lake trout were from 1.2 to 16 times higher than in other species, and mean dry-weight basis trans-nonachlor concentrations were 2.4 to 34 times higher in lake trout than in other species.

When PCB and trans-nonachlor concentrations were compared among fish species on a lipid-normalized basis, lake trout still contained higher levels of contamination than all other species with the exception of adult coho salmon. Mean lipid-normalized total PCB and trans-nonachlor concentrations were highest in adult coho salmon and second highest in lake trout. Lipid-normalized total PCB and trans-nonachlor concentrations in these two top predator fish species were significantly higher than in any of the forage fish species. The higher mean concentrations of lipid-normalized contaminants in adult coho salmon were due to the relatively low lipid content in this species. Lipid content in adult coho salmon averaged only 4%, compared to 16% in lake trout. Of the species analyzed in this study, only smelt contained lower lipid content (3.6%) than adult coho salmon.

The lowest total PCB and trans-nonachlor concentrations on a wet-weight, dry-weight, or lipid-weight basis were consistently found in hatchery and yearling coho salmon. This species is raised in hatcheries and annually stocked in Lake Michigan. Hatchery samples consisted of immature coho collected directly from the Platte River hatchery, and yearling samples consisted of immature coho collected in Lake Michigan. The reduced contamination in these sample types most likely reflects both the young age of the fish and reduced contaminant exposure from hatchery food and water sources.

The Great Lakes Fish Consumption Advisory Task Force has set a fish advisory category of “no consumption” at PCB levels above 2000 ng/g, and established four lesser consumption categories ranging form unrestricted consumption to no more than 6 meals per year. Of the Lake Michigan fish analyzed in the LMMB Study, only lake trout contained PCBs above the 2000 ng/g level. In fact, 56% of lake trout samples exceeded this tolerance level, and the mean total PCB concentration for Lake Michigan lake trout was 3000 ng/g (or 3 ppm), which is 50% above the 2000 ng/g tolerance level. No coho salmon or lake trout samples fell into the unrestricted consumption category. Coho salmon primarily fell into the 1 meal/mo and 6 meals/yr categories. These categories contained 46% and 44% of coho salmon samples, respectively, with only 9% of coho salmon samples falling into the 1 meal/wk category. Lake trout primarily fell into the no consumption category (56%), with only 0.4%, 17%, and 26% in the 1 meal/wk, 1 meal/mo, and 6 meals/yr categories, respectively.

Mass Balance and Modeling Efforts

The data collection and quality assurance efforts described in this report were designed to support the LMMB Study and related efforts to model the concentrations of pollutants in the Lake Michigan ecosystem. However, the mass balance itself and the associated modeling efforts are beyond the scope of this data report but will be described in later documents from GLNPO.

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