Accumulation and recycling of PCBs and PAHs in artificially eutrophied Lake 227

The influence of lake trophic status on the cycling and burial of polychlor inated biphenyls (PCB's) and poly-cyclic aromatic hydrocarbons (PAH's) was examined in Lake 227 (L227), an artificially eutrophied lake in the Experim ental Lakes Area, northwestern Ontario, Canada. Sedimentary accumulation of PCB's, PAH's, and organic carbon (OC) was determined pre- and post-eutroph ication in L227 and compared with accumulation in other regional lakes. Mas s and OC accumulation increased an average of 1.4 and 2.0 times, respective ly, since nutrient addition began in June 1969. Sigma PCB and Sigma PAH sed iment accumulation rates and profiles in L227 were similar to those in Lake Superior and other proximate and midlatitude lakes unimpacted by point sou rces. Eutrophication did not increase contaminant accumulation. In general, individual PAH accumulation rates declined following eutrophication, which coincided with similar signals elsewhere. Perylene declined markedly (4 ti mes) since eutrophication as a result of decreased in situ formation. An in crease in OC accumulation did not enhance contaminant accumulation in L227 because phytoplankton community structure shifted to species characterized by lower bioaccumulation factors, and water column recycling rates were hig h. Accumulation rates of mass, OC, PCB's, and PAH's, when compared with ice -free settling fluxes in 1993 and 1994, exhibited similar recycling ratios in eutrophic L227 and oligotrophic L110 due to the efficient preservation o f organic matter in sediments.