Sediment quality in Burlington Harbor, Lake Champlain, USA

Surface samples and cores were collected in 1993 from the Burlington Harbor region of Lake Champlain. Sediment samples were analyzed for trace metals (cadmium, copper, lead, nickel, silver and zinc), simultaneously extracted metal/acid volatile sulfide (SEM-AVS), grain size, nutrients (carbon and ni trogen) and organic contaminants (polycyclic aromatic hydrocarbons (PAHs) a nd polychlorinated biphenyls (PCBs)). The concentrations of cadmium, copper , silver and zinc from the partial sediment digestion of the surface sample s correlated well with each other (r(2)>0.60) indicating that either a comm on process, or group of processes determined the sediment concentrations of these metals. In an analysis of the spatial distribution of the trace meta ls and PAHs, high surficial concentrations were present in the southern por tion of the Harbor. The trace metal trend was strengthened when the concent rations were normalized by grain size. A sewage treatment plant outfall dis charge was present in the southeastern portion of the Harbor at the time of this study and is the major source of trace metal and PAH contamination. E valuation of sediment cores provides a proxy record of historical trace met al and organic inputs. The peak accumulation rate for copper, cadmium, lead , and zinc was in the late 1960s and the peak silver accumulation rate was later. The greatest accumulation of trace metals occurred in the late 1960s after discharges from the STP began. Subsequent declines in trace metal co ncentrations may be attributed to increased water and air regulations. The potential toxicity of trace metals and organic contaminants was predicted b y comparing contaminant concentrations to benchmark concentrations and pote ntial trace metal bioavailability was predicted with SEM-AVS results. Surfa ce sample results indicate lead, silver, Sigma PAHs and Sigma PCBs are pote ntially toxic and/or bioavailable. These predictions were supported by stud ies of biota in the Burlington Harbor watershed. There is a clear trend of decreasing PAH and trace metal contaminant concentrations with distance fro m the STP outfall.