Differential Accumulation of Polychlorinated Biphenyl Congeners in the Terrestrial Food Web of the Kalamazoo River Superfund Site, Michigan ALAN L. BLANKENSHIP,* ,†,# MATTHEW J. ZWIERNIK, #,‡ KATHERINE K. COADY, † DENISE P. KAY, † JOHN L. NEWSTED, †,#,‡ KARL STRAUSE, † CYRUS PARK, ‡ PATRICK W. BRADLEY, † ARIANNE M. NEIGH, ‡ STEPHANIE D. MILLSAP, ‡,§, | PAUL D. JONES, #,‡ AND JOHN P. GIESY #,‡, ⊥ ENTRIX, Inc., 4295 Okemos Road, Suite 101, Okemos, Michigan 48864, National Food Safety and Toxicology Center, Center for Integrative Toxciology, and Department of Zoology, Michigan State University, East Lansing, Michigan 48824, Department of Fisheries and Wildlife, Michigan State University, East Lansing, Michigan 48824, U.S. Fish and Wildlife Service, Grosse Ile, Michigan 48138, and Department of Biology and Chemistry, City University of Hong Kong, Kowloon, Hong Kong SAR, China A series of field studies was conducted to determine the bioaccumulation of polychlorinated biphenyl (PCB) congeners in the terrestrial food web of the Kalamazoo River flood plain. Samples included colocated soils, native plants likely to be consumed by wildlife, several taxa of terrestrial invertebrates, small mammals, passerine bird eggs, nestlings, and adults, and great horned owl plasma and eggs. Mean concentrations of total PCBs in samples from the former Trowbridge impoundment were 6.5 mg/kg dry weight for soils and 0.023, 0.13, 1.3, 1.3, 1.6, and 8.2 mg/kg wet weight for plants, small herbivorous mammals, depurated earthworms, shrews, great horned owl eggs, and house wren eggs, respectively. Historical data from the Kalamazoo River have reported Aroclor-equivalent total PCB concentrations in the terrestrial food web; however, the degree of environmental weathering of the parent PCB mixtures was unknown. In this study, earthworms and composite samples of coleoptera exhibited PCB congener patterns that were similar to patterns in colocated soils. However, in plants, less chlorinated PCBs (e.g., mono-, di-, tri-, and tetrachlorinated biphenyls) were predominant, and in small mammals, there was a notable enrichment of PCBs 153, 180, 138, 118, and 99. In general, concentrations of PCBs were lower in most biota than in soil from the Kalamazoo River Area of Concern (KRAOC) although there was a modest biomagnification of PCBs from lower trophic level biota to higher trophic levels. As a consequence of environmental weathering of PCBs in the terrestrial food web of the KRAOC, the relative potency of the PCBs (expressed as mg TEQs/kg PCBs) decreased from soil to most biota. While there was a general trend, as expected, in which concentrations of 2,3,7,8-tetrachlorodibenzo-p- dioxin equivalents (TEQs) increased with total PCBs, this relationship was rather poor (R 2 ) 0.13). Taken together, these data suggest that the differential accumulation of PCB congeners in the terrestrial food web can be explained by congener-specific differences in bioavailability from soil, exposure pathways, and metabolic potential of each of the food web components. Introduction In 1990, approximately 80 miles of the Kalamazoo River was designated a Superfund site, referred to as the Kalamazoo River Area of Concern (KRAOC). The site extends from Morrow Dam in Kalamazoo County to Lake Michigan (Figure 1). The release of polychlorinated biphenyls (PCBs), the primary contaminants of potential ecological concern (COPECs), resulted from PCB-contaminated waste dis- charged from the recycling and processing of carbonless copy paper (1). During the period from 1957 to 1971, the ink solvent used in carbonless copy paper contained mixtures of PCBs, primarily Aroclor 1242 (2). Aroclor 1254 may also have been added to inks and other additives in lesser amounts (2). The majority of PCBs in the Kalamazoo River watershed are associated with sediment deposits in a series of impound- ments. However, partial removal of three dams (e.g., Plain- well, Otsego, and Trowbridge) to their sill levels in the 1970s allowed substantial amounts of sediments to be transported downstream, lowered the water levels to the sill of the dams’ spillways, and exposed former sediments in the former impoundments. Much of the exposed former sediment is within the flood plain and thus becomes periodically inundated during high flow events. PCBs are an environmentally ubiquitous, complex mixture of individual compounds that are chlorinated with 1-10 chlorines in various combinations of positions to create a total of 209 possible congeners. Historically, site-specific PCB data from samples collected from the KRAOC have been quantified as Aroclors 1016, 1242, 1248, 1254, and/or 1260 (1). However, the analytical methodologies used in these investigations (i.e., EPA Methods 8080 and 8081) do not measure “Aroclors” but rather a pattern of PCB congeners. The analyst then determines the Aroclor pattern that most closely approximates that mixture of PCB congeners. In some cases, the PCBs were quantified as a particular Aroclor simply because that Aroclor or mixture of Aroclors was used as the standard. Each Aroclor is a complex mixture of numerous PCB congeners, and each congener behaves independently once released to the environment. Due to selective volatilization, degradation, accumulation, sorption, and metabolism (i.e., collectively termed “environmental weathering”), the relative concentrations of congeners in a mixture or matrix change as a function of time. Limitations associated with Aroclor- based determination of PCBs in environmental samples have been recognized for a long time (3-6) and have been acknowledged by the U.S. EPA (7, 8) and the National * Corresponding author phone: (517)381-1434; fax: (517)381-1435; e-mail: ablankenship@entrix.com. † ENTRIX, Inc. # National Food Safety and Technology Center and Center for Integrative Toxicology, Michigan State University. ‡ Department of Zoology, Michigan State University. § Department of Fisheries and Wildlife, Michigan State University. | U.S. Fish and Wildlife Service. ⊥ Department of Biology and Chemistry, City University of Hong Kong. Environ. Sci. Technol. 2005, 39, 5954-5963 5954 9 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 39, NO. 16, 2005 10.1021/es0483185 CCC: $30.25  2005 American Chemical Society Published on Web 07/16/2005