USGS Fact Sheet FS-116-96
1Research Hydrologist
USGS, Water Resources Division
600 Fourth Street South
St. Petersburg, FL 33701
Internet: safitzge@usgs.gov
Phone: (813) 893-3100 x3082
2Hydrologist
USGS, Water Resources Division
8505 Research Way
Middleton, WI 53562-3581
Internet: jjsteuer@usgs.gov
Phone: (608) 821-3830
FAX: (608) 821-3817
Citation:
Fitzgerald, S.A. and Steuer, J.J., 1996, The Fox River PCB transport study -
Stepping stone to a healthy Great Lakes ecosystem: U.S. Geological Survey
Fact Sheet FS-116-96, 4 p.
The Lower Fox River is highly contaminated by PCBs and other toxic synthetic organic chemicals and trace metals. The Wisconsin Department of Natural Resources (WDNR) issued a fish consumption advisory (Sheffy, 1980) for the river in 1979 and a waterfowl consumption advisory in 1985. In 1984, more than 100 hazardous chemicals were identified in bottom sediments from the river (Sullivan and others, 1983). Both the fish and waterfowl advisories from Lake Winnebago to the mouth of the Fox River continue to this day (Amrhein and Anderson, 1994). It was from these earlier efforts that the Lower Fox River Study emerged. This fact sheet primarily summarizes study results from the Fox River study upstream of the DePere Dam as documented in the final report "A Deterministic PCB Transport Model for the Lower Fox River between Lake Winnebago and DePere, Wisconsin", by Jeffrey J. Steuer, Steven Jaeger, and Dale Patterson (WDNR PUBL 389-95). The dam at DePere, Wis., the last progressing downstream, is 11 km (6.8 miles) upstream from the mouth at Green Bay, Wis., and completes the 48-m (157 ft) drop in elevation from Lake Winnebago.
This study, conducted in concert with the larger Green Bay Mass Balance Study (GBMBS), was funded by the U.S. Environmental Protection Agency (USEPA), the WDNR, and the U.S. Geological Survey (USGS). Collection of the data necessary to answer the above questions was conducted primarily from May 1989 to April 1990 between Lake Winnebago and the DePere Dam. There were over 130 water column, 1,000 bottom sediment, 175 point-source effluent, 5 landfill wells, and 10 urban stormsewer samples that were analyzed for PCBs.
Using these data as a foundation, a mathematical, physical process-based model was constructed to help answer the PCB transport questions. The four-year modeling effort used the Water Quality Analysis Program (WASP4) (Ambrose and others, 1988) as a framework, and consisted of three major components: water column transport, solids mass balance (both suspended and bottom), and physiochemical processes.
A large reservoir of PCBs (25,000 kg) also is located in the bottom sediments between the DePere Dam and the Fox River mouth (Dale Patterson, Wisconsin Department of Natural Resources, written commun., 1993). This area is being investigated in 1996 to further understand the PCB distribution and the possibility of these PCBs being transported to Green Bay and Lake Michigan. Understanding the mobility of these sediments is critical because they contain three times as much PCBs than are presently in all of Green Bay (Manchester, 1993). These deposits represent a potential toxic legacy to present and future generations living along the Lower Fox River and Green Bay.
The study predicted that over the course of 25 years, 1,300 kg of PCB would be transported over the DePere Dam and 200 kg would be emitted to the atmosphere. Much of the PCB remaining in the Lower Fox River sediment would be in the semi-isolated deposits in LLBDM (900 kg) and immediately upstream of the DePere Dam (1,400 kg). Furthermore, the amount of PCB transported over the DePere Dam should decrease by 50% every 5 years (figure 4). This analysis assumed several factors, including that no intense short-duration rainfalls would occur in the vicinity of the Neenah Slough, nor would there be extreme high flows on the Fox River. For example, a theoretical high flow event in 1995 could have transported 2,100 kg of PCB instead of the 50 kg as predicted in figure 4, an effect that would linger for years after. Despite having to make several assumptions, bolstered with follow-up data the predictive model capabilities may be valuable for making management decisions about the future of the river.
Another study directly spawned from the Lower Fox River Study is the Milwaukee/Manitowoc Rivers Study, conducted at four sites along these two rivers in southeast Wisconsin. This study was co-funded by USEPA, WDNR, and the National Water Quality Assessment (NAWQA) Program of the USGS (see the "NAWQA" box). A major objective of this study was to further investigate the potential link seen initially in the Lower Fox River Study between the distribution, transport, and fate of PCBs and algae in these rivers (see the "PCBs and Algae" box). Specifically, the relation between the concentration of PCBs and the amount of algae present was examined. If true, refinements to the theoretical model that describes PCB concentration would be required to adequately represent transport of these contaminants in rivers.
In general, the amount of PCB transported (the mass in kilograms) increases as one proceeds downstream (figure 5). Water entering the Lower Fox River from Lake Winnebago had low, and sometimes immeasurable, concentrations of PCBs. By the time the water reached the DePere Dam, total PCB concentrations ranged from 50 to 90 ng/L (nanograms per liter = 10-9 grams per liter) in summer and about 10% of that amount in winter, showing a strong seasonal response. Maximum PCB concentrations occurred at high flow and during the summer. PCB concentrations in water exceeded 100 ng/L only under high flow conditions (that is, during storm events). Greater than 60% of the PCB transported over the DePere Dam occurred during only 20% of the year, times when discharge was above the annual mean of 120 m3/s (4,257 ft3/s). These events are represented as the steep increases in the cumulative PCB transport during the summer high flow-event and spring runoff in figure 5.
In contrast to the relatively high rate of PCB transport observed during the summer and during spring runoff, PCB transport during winter was significantly lower, even for water velocities greater than in the summer. These periods are represented by the relatively flat portions of the curves in figure 5. Also, reduced resuspension in winter increased the relative importance of porewater diffusion compared to the rest of the year. Thus, there is a strong seasonal component to PCB transport in the Fox River.
This apparent association between a phytoplankton indicator (chlorophyll-a) and PCB concentrations in the water was explored further in the Milwaukee/Manitowoc Rivers Study (see the "NAWQA" box). Here, the concentration of particulate PCB is positively related to chlorophyll-a at all sites, as it was in the Fox River (Fitzgerald and Steuer, USGS, unpublished data) (figure 6). PCBs, being only sparingly soluble in water, tend to associate with organic-rich particles such as phytoplankton cells. Thus the factors that control phytoplankton (for example, nutrient and light availability, predation, sinking, and resuspension, etc.) may indirectly control PCB distribution, transport, and fate in rivers.
Amrhein, J.F. and Anderson, H., 1994, Health guide for people who eat sportfish from Wisconsin waters: April 1994, Wisconsin Department of Natural Resources and Wisconsin Division of Public Health, Publ-IE-019.
House, L.B., 1995, Distribution and transport of polychlorinated biphenyls in Little Lake Butte Des Morts, Fox River, Wisconsin, 1987-88: Open File Report 93-31, 43 p.
Manchester, J.B., 1993, The role of porewater in the remobilization of sediment-bound polychlorinated biphenyl congeners: Ph.D. dissertation, University of Wisconsin, Madison, Wis.
Sheffy, T.B., St. Amant, J.R., 1980, Toxic substances survey of Lake Michigan, Superior, and tributary streams: First Annual Report, Wisconsin Department of Natural Resources Technical Publication, 107 p.
Steuer, J.J., Jaeger, S, and Patterson, D., 1995, A deterministic PCB transport model for the Lower Fox River between Lake Winnebago and DePere, Wisconsin: Wisconsin Department of Natural Resources, Publ. WR 389-95, 283 p.
Sullivan, J.R., Delfino, J.J., Beulow, C.R., and Sheffy, T.B., 1983, PCB concentrations in the Lower Fox river fish and sediments: Bulletin of Environmental Contamination and Toxicology, 30:58-64.
United States Environmental Protection Agency, 1989, Green Bay/Fox River mass balance study: U.S. Environmental Protection Agency, Great Lakes National Program Office, Chicago, Ill., EPA-905/8-89/001.
Wisconsin Department of Natural Resources, 1992, Wisconsin water quality assessment report to Congress - 1992: Wisconsin Department of Natural Resources, Publ. WR254-92-REV, 220 p.
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