Recovery of Lake Superior from historical PCB pollution

Session: 07. - Effects of Environmental Contamination on Fish Communities

Noel Urban, Dept. Civil & Environment Eng., Michigan Technological Univ., [email protected]
Judith Perlinger, Michigan Tech. University, Civil & Environmental Engineering Dept., [email protected]
Tanvir Khan, Michigan Tech. University, [email protected]
Mugdha Priyadarshini, Michigan Technological Univ., [email protected]
Carey Friedman, Maine Maritime Academy, [email protected]
Alan Labisch, Michigan Technological University, [email protected]
Hongyi Lin, Michigan Technological University, [email protected]

Abstract

Despite bans on PCB production, PCBs remain a prevalent contaminant.  Rates of PCB decline in Lake Superior fish are slower (20-100 yr half-lives) than rates of decline in air (12-yr half-life).  Recycling from sediments is often invoked to explain slow recovery.  In this study, we analyzed congener fingerprints in air, water, fish and sediments to evaluate sources of PCBs.  To estimate the timescale for PCB recycling from sediments and for recovery from legacy inputs, we developed a dynamic, congener-specific model of PCB cycling.  We used a global transport model for PCBs to differentiate contributions from primary and secondary emissions.  Congener fingerprints indicated that fish currently receive significant PCB inputs from sediment recycling.  Since the 1990s, there has been a shift toward heavier congeners in the lake and fish.  For light congeners, recycling from sediments was unimportant.  For heavier congeners, recycling from sediments increased the half-life in the lake to ~20 years.  Under different scenarios for future air concentrations, the model predicts that concentrations in fish will decline below 100 ppb in a few decades.  Model predictions are not consistent with observed trends in fish and suggest that food web changes in the lake may be affecting trajectories of contaminant concentrations.

1. Keyword
PCBs

2. Keyword
Lake Superior

3. Keyword
fish

4. Additional Keyword
recovery