SEDIMENT CONTAMINANTS IN CASCO BAY, MAINE - INVENTORIES, SOURCES, ANDPOTENTIAL FOR BIOLOGICAL IMPACT

An inventory-based approach to environmental assessment that determine s concentrations of sedimentary contaminants, defines their origins, a nd assesses the potential for biological impact is illustrated in Casc o Bay, ME. The most widespread contaminants in Casco Bay are petroleum and petroleum byproducts. The highest concentrations of contaminants are associated with population centers, effluent outfalls, and spills. The majority of PAH in sediments are the product of high-temperature combustion processes. PAH concentrations at sites in close proximity t o portland exceed values believed to produce toxic responses in marine benthic organisms. In contrast, PCB, DDTs, and chlordane concentratio ns in the sediments are below concentrations thought to produce toxic effects in marine organisms. Metal concentrations in sediments are als o below those that elicit biological responses. The geographic distrib ution of contaminants is initially controlled by the proximity to sour ces, and the regional differences in concentrations are the result of sediment accumulation patterns. Detrital (terrestrial), autochthonous marine, pyrogenic, and petroleum sources for PAH, alkanes, and trace m etals are defined.