Water Quality Management - River Dynamics and Integrated River Management - page 609

walleye, and Chinook salmon have been found to bioaccumulate PCB concentrations 100,000 to one million
times greater than the concentrations in surrounding waters (Smith et al., 1988). The No Observable
Adverse Effect Level standard for Forster's Tern is 2,000,000 ppt. Harris and Kraft (1993) reported that
in order to achieve this at the mouth of the Fox River (which feeds into Green Bay), the following
biomagnifications would be needed: sediment—2 ppt, algae—20,000 ppt, forage fish—200,000 ppt, and
Forster's tern egg—2,000,000 ppt. Since a typical goal for PCB clean-up/remediation is 0.25 ppm (e.g.,
Fox River cleanup in Wisconsin, U.S.), the current “State of the Art” in sediment remediation is not fully
protective of wildlife health. In the following section one approach to evaluate the toxicity of pollutants
in sediment is described.
9.5.1 Assessment of Sediment Toxicity
The Wisconsin Department of Natural Resources (WDNR, 2003) has established a system for evaluating
the toxic effects of pollutants in sediment on the benthic organisms. The WDNR recommends the use of this
system for establishing levels of concern for prioritizing sites for additional study and possible cleanup.
This system uses three criteria based on the likely effects on benthic organisms as follows. The Threshold
Effect Concentration (TEC) indicates contaminant concentrations below which adverse effects to benthic
organisms are considered to be unlikely. The Probable Effect Concentration (PEC) indicates contaminant
concentrations at which adverse effects to the benthic organisms are highly probable or frequently seen.
The Midpoint Effect Concentration (MEC) is derived from the TEC and PEC values for the purpose of
interpreting the effects of pollutant concentrations that fall between the TEC and PEC. Table 9.14 lists
the TEC, MEC, and PEC values for some pollutants of concern commonly encountered in sediments, a
more complete list of pollutants is included in WDNR (2003).
Table 9.14 Threshold Effect Concentration (TEC), Midpoint Effect Concentration (MEC), and Probable Effect
Concentration (PEC) for selected contaminants that have commonly been found by the Wisconsin Department of
N atural Resources (WDNR) at contaminated sites in Wisconsin
Substance TEC MEC PEC
Metals
Arsenic 9.80 21.40 33.0
Cadmium 0.99 3.00 5.0
Chromium 43.00 76.50 110.0
Copper 32.00 91.00 150.0
Mercury 0.18 0.64 1.1
Nickel 23.00 36.00 49.0
Lead 36.00 83.00 130.0
Zinc 120.00 290.00 460.0
Nonpolar organic compounds
Total Polycyclic Aromatic Hydrocarbons (PAHs) 1610.00 12,205.00 22,800.0
Total Polychlorinated Biphenyls (PCBs) 60.00 368.00 676.0
Chlordane 3.20 10.60 18.0
Sum o,p￿ + p,p￿ DDT 4.20 33.60 63.0
Sum DDD+DDE+DDT 5.30 289.00 572.0
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) 0.85 11.20 21.5
Note: TEC, MEC, and PEC values are from WDNR (2003), while the list of commonly found contaminants was
provided by Dr. X. Zhang, WDNR. Metal values are in milligrams per kilogram, dry weight; nonpolar organic compound
values are expressed on a dry weight basis normalized to a total organic carbon level of 1 percent and the units are
micrograms per kilogram.