HAZARD RANKING OF CONTAMINATED SEDIMENTS BASED ON CHEMICAL-ANALYSIS, LABORATORY TOXICITY TESTS, AND BENTHIC COMMUNITY COMPOSITION - PRIORITIZING SITES FOR REMEDIAL ACTION

The U.S. Environmental Protection Agency (U.S. EPA) organized a resear ch program to assess the extent of and possible methods for managing c ontaminated sediments. As part of this program, we developed a method by which multiple forms of information on sediment contamination (i.e. , chemistry, laboratory toxicity, and benthic community composition) c ould be combined to rank the relative hazard to aquatic life of a seri es of sediment samples. The process that was developed incorporates ch emistry and bioavailability into the ranking as toxic units in pore wa ter based on U.S. EPA Ambient Water Quality Criteria (AWQC). Laborator y toxicity is incorporated into the ranking process as mean response r elative to control response. Benthic community information is incorpor ated into the ranking process through the use of relative tolerance to pollution among benthic invertebrate tara, from which the mean tolera nce to pollution of the benthic community is calculated. The three res ulting ranks are then averaged to produce a relative ranking of risk t o aquatic life among sediment samples. Our results demonstrate that, a s long as a moderate list of laboratory toxicity test results are incl uded in the ranking process (i.e., tests from a fish, a zooplankter, a benthic invertebrate, a phytoplankter, and a microbe), the resultant rankings among samples does not significantly change with inclusion of more laboratory toxicity test results. Without any benthic community structure information, with only laboratory toxicity test results from Microfox,(R) and with only a short list of chemicals, relative rankin g among sites changes drastically. Our results demonstrate the general utility of the ranking process as one way of assessing the relative h azard among many sites when resource limitations necessitate prioritiz ation of sites for remediation.