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Temperature dependence of atmospheric PCB concentrations
Daniel L Carlson1, Ronald A Hites
1School of Public and Environmental Affairs, Indiana University, Bloomington, Indiana 47405, USA.
Environmental Science & Technology
|March 11, 2005
Summary
Temperature dependence of atmospheric PCBs is similar across sites, challenging source identification. A new model using the Clausius-Clapeyron equation improves accuracy for polychlorinated biphenyls (PCBs) analysis.
Area of Science:
- Environmental Chemistry
- Atmospheric Science
- Ecotoxicology
Background:
- Polychlorinated biphenyls (PCBs) are persistent organic pollutants with complex atmospheric transport patterns.
- Understanding the temperature dependence of atmospheric PCB concentrations is crucial for source apportionment and risk assessment.
- Existing models for PCB temperature dependence have limitations in accurately reflecting real-world conditions.
Purpose of the Study:
- To investigate the reliability of using temperature dependence to differentiate between long-range transport and local sources of atmospheric PCBs.
- To identify factors influencing the observed temperature dependence of atmospheric PCBs.
- To develop a more accurate model for predicting atmospheric PCB concentrations based on temperature.
Main Methods:
- Analysis of data from the U.S. Integrated Atmospheric Deposition Network (IADN) near the Great Lakes.
- Review of existing literature on atmospheric PCB concentrations and temperature relationships.
- Development and application of a modified Clausius-Clapeyron equation model.
Main Results:
- Temperature dependence of atmospheric PCBs cannot reliably distinguish between local and long-distance sources.
- Short-term data sets (approx. 25 measurements/year) yield unreliable temperature dependence indicators.
- Temperature independence of PCBs observed below freezing point (273 K).
- Increasing PCB chlorination correlates with increased temperature dependence.
- A new model, adjusting temperatures below 273 K to 273 K, effectively explains observed temperature dependence phenomena.
Conclusions:
- The temperature dependence of atmospheric PCBs exhibits similar patterns across different IADN sites, irrespective of source type.
- Factors such as short data duration and low concentrations can significantly bias temperature dependence analyses.
- A refined model incorporating temperature adjustments and the Clausius-Clapeyron equation provides a more robust framework for understanding atmospheric PCB behavior.
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