Approximating the Impact of Sorption on Biodegradation Kinetics in Soil-Water Systems
- A. P. Gamerdinger ,
- R. S. Achin and
- R. W. Traxler
Naphthalene sorption and biodegradation were quantified in three soils of varying organic C content using miscible displacement and batch incubation techniques. As anticipated, sorption increased with organic C content; the sorption rate coefficient and equilibrium sorption constant (Kd) were inversely related. Organic matter in solution (NOM) from the high-organic-matter soil decreased apparent sorption, which was also quantified using methanol as a cosolvent. A cosolvency power of 3.8 or 4.1 was determined. The initial biodegradation rate decreased with increasing sorption and was a function of naphthalene concentration in solution. The extent of biodegradation was greatest in the high-organic-matter soil and decreased when NOM was removed from the system. The observed dependence of biodegradation kinetics on sorption (this study and in the literature) prompted us to develop a simple approach for approximating a biodegradation rate constant for soil-water systems. This approach combines independently determined sorption parameters with the biodegradation rate constant determined for aqueous (soil-free) solution. The approach was applied to our data and to published data where sorption was shown to control naphthalene biodegradation. The approximated biodegradation rate constant was within 10% of the measured values for three cases, 20% for a fourth case, and was underestimated by five-to sevenfold for the high-organic-matter soil. The approach will be useful when applying management models for predicting contaminant fate and transport that require a degradation rate constant, or for estimating biodegradation rates in situations where cultured organisms are introduced for biodegradation.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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