A Preliminary Investigation into the Mass Transfer Properties of a Pesticide onto Abiotic Media
Z. Chen
W. F. McTernan
A. L. Hines
DOI: 10.2190/N45A-EKAK-PDCY-5X5H
Abstract
The effects of mass transfer properties on pesticide transport through a lab scale soil-water system were evaluated with alternative kinetically based model formulations. External and Internal Resistance as well as Surface Kinetic approaches were employed. Statistical procedures were used in subsequent data analysis to identify model conformance to collected data. The results of the experimtnal phase of the research indicated that the soil adsorptive capacity increased significantly with the removal of lipids and resins, suggesting that specific types rather than the sum of soil organics affected the adsorption process. While all three models satisfactorily predicted the ultimate capacity, only the Surface Kinetic approach simulated the shape of the breakthrough curves. The low soil organic contents and inherent surface heterogeneities apparently resulted in incomplete coatings of the soil particles and diminished the utility of the External and Internal Resistance Models. These are based upon the asusmption of constant adsoprtive potentials. The Surface-Kinetic Model effectively addressed this problem. In contrast to traditional adsorption theory, the transfer of an organic solute from liquid to soil may be due to several mechanisms resulting in the adsorption of solute onto the mineral surface as well as a partitioning of adsorbate into the soil humic materials themselves. Further studies on these processes are necessary for a better understanding of the solute transport process in the soil-water system.
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