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Quantification of contaminant sorption-desorption time scales from batch experiments
Jeffrey A Cunningham1, James J Deitsch, James A Smith
1Department of Civil and Environmental Engineering, University of South Florida, Tampa, Florida 33620, USA. cunning@eng.usf.edu
Environmental Toxicology and Chemistry
|October 1, 2005
Summary
This study introduces a novel method to calculate contaminant sorption-desorption time scales directly from batch experimental data, improving bioavailability and risk assessment. The approach offers a more accurate understanding of contaminant transport in the environment.
Area of Science:
- Environmental Chemistry
- Geochemistry
- Environmental Science
Background:
- Accurate prediction of contaminant sorption and desorption rates is crucial for assessing environmental bioavailability, fate, transport, and risk.
- Existing methods for determining these rates often rely on complex model fitting and assumptions about parameter distributions.
Purpose of the Study:
- To present a new, direct method for determining contaminant sorption-desorption time scales from temporal moments of batch experimental data.
- To provide a method that is independent of arbitrary distribution choices and directly calculable without best-fitting.
Main Methods:
- The method utilizes temporal moments of batch experimental data to calculate time scales.
- It can be implemented with diffusion-based (t(diff)) or linear-driving-force (t(LDF)) kinetic models.
- The approach accommodates both discrete and continuous distributions of rate parameters.
Main Results:
- The new method allows direct calculation of sorption-desorption time scales (t(diff) or t(LDF)) without requiring best-fitting of experimental data.
- Calculated time scales are independent of arbitrarily chosen distribution functions (e.g., gamma, lognormal).
- Application to 1,2-dichlorobenzene (DCB) sorption on four natural sorbents revealed a different sorption rate order compared to previous studies.
Conclusions:
- The developed method offers a robust and direct way to determine sorption-desorption time scales, enhancing environmental risk assessment.
- This approach provides time scales consistent with experimental duration and independent of model assumptions.
- The findings highlight the importance of accurate kinetic parameter determination for understanding contaminant behavior in natural sorbents.