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Watershed processing of atmospheric polychlorinated biphenyl inputs
Amy A Rowe1, Lisa A Totten, Gregory I Cavallo
1Department of Environmental Sciences, Rutgers University, 14 College Farm, Road, New Brunswick, New Jersey 08901, USA.
Environmental Science & Technology
|April 19, 2007
Summary
Polychlorinated biphenyls (PCBs) transfer from air to rivers via watersheds. Higher molecular weight PCBs are transferred more efficiently, suggesting watersheds may be near equilibrium for lower molecular weight PCB exchange.
Area of Science:
- Environmental Chemistry
- Environmental Science
- Atmospheric Chemistry
Background:
- Polychlorinated biphenyls (PCBs) are persistent organic pollutants with significant environmental implications.
- Atmospheric deposition is a key pathway for PCBs entering aquatic ecosystems.
- Understanding PCB transport from air to water is crucial for effective environmental management.
Purpose of the Study:
- To investigate the indirect atmospheric deposition of PCBs in Delaware River Estuary subwatersheds.
- To quantify PCB transfer efficiencies from the atmosphere to river systems.
- To develop a new metric, the watershed delivery rate (vws), for assessing PCB atmospheric deposition.
Main Methods:
- Analysis of tributary PCB loads and atmospheric PCB concentrations.
- Calculation of pass-through efficiency (E) using deposition fluxes.
- Development and application of the watershed delivery rate (vws) to relate watershed export to atmospheric concentrations.
- Examination of PCB congener-specific transfer efficiencies.
Main Results:
- Watershed delivery rate (vws) increases with PCB chlorination and correlates with vapor pressure.
- Higher molecular weight PCBs show more efficient transfer from atmosphere to river.
- Calculated pass-through efficiency (E) is approximately 3% when congener-specific deposition velocities are used.
- Lower molecular weight PCBs may undergo revolatilization after deposition, indicating potential disequilibrium.
Conclusions:
- Watershed processes significantly influence PCB transfer from the atmosphere to rivers.
- PCB transfer efficiency is dependent on molecular weight and volatility.
- The watershed delivery rate (vws) provides a valuable metric for assessing atmospheric PCB inputs.
- Delaware River Estuary subwatersheds may be near equilibrium for gaseous exchange of lower molecular weight PCBs.
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