Related Experiment Videos
Source apportionment modeling of volatile organic compounds in streams.
James F Pankow1, William E Asher, John S Zogorski
1Department of Environmental and Biomolecular Systems, OGI School of Science and Engineering, Oregon Health and Science University, 20000 NW Walker Rd., Beaverton, OR 97006-8921, USA. pankow@ebs.ogi.edu
Environmental Toxicology and Chemistry
|April 25, 2006
Summary
Understanding contaminant sources in streams is crucial. This study introduces two source apportionment rules for volatile organic compounds (VOCs), considering air-water interactions and different flux conventions for accurate water quality management.
Area of Science:
- Environmental Chemistry
- Water Quality Management
- Environmental Modeling
Background:
- Determining the relative importance of different contaminant sources in streams is essential for effective management.
- Volatile organic compounds (VOCs) introduce complexities in source apportionment due to air-water exchange.
- Existing source apportionment methods need to account for atmospheric absorption and volatilization of VOCs.
Purpose of the Study:
- To elaborate two source apportionment (SA) rules for VOCs in streams, considering air-water interface transport.
- To investigate the impact of different flux conventions (net flux F vs. individual fluxes J) on SA results.
- To provide a framework for comparing mitigation strategies for stream contamination.
Main Methods:
- Developed two SA rules: Rule 1 assigns air-water interface VOCs to the atmospheric source; Rule 2 distributes VOC losses proportionally.
- Applied these rules to four hypothetical stream cases with common VOCs (acetone, MTBE, benzene, chloroform, PCE).
- Analyzed the influence of net flux (F) and individual fluxes (J) conventions on SA outcomes.
- Introduced a characteristic time (τd) to predict differences between the two flux conventions.
Main Results:
- VOCs like acetone and MTBE can reach concerning levels in streams from atmospheric sources.
- For most VOCs, net outgassing (F > 0) occurs at typical water quality guideline concentrations.
- The net flux convention maintains source contributions (α values) while stream concentration decreases when F > 0.
- A characteristic time (τd) can predict when flux convention choice impacts SA results.
Conclusions:
- The proposed SA rules and analysis of flux conventions offer a robust framework for VOC source apportionment in streams.
- Source apportionment modeling is vital for evaluating and comparing contamination mitigation strategies.
- Understanding air-water exchange dynamics is critical for accurate assessment of VOC contamination in aquatic systems.