Estimation of soil sorption coefficients using QSARs
- Utah State Univ., Logan, UT (United States). Utah Water Research Lab.
Sorption coefficients quantitatively describe the extent to which an organic chemical distributes itself between an environmental solid and the aqueous phase that it is contact with at equilibrium. Because of the difficulty and expense associated with measuring sorption coefficients, estimated values are often used in place of site specific, experimental values for fate modeling. Most reported methods for estimating the sorption of organic chemicals onto environmental solids are based on observation that for many organic chemicals, and in particular neutral hydrophobic organics, sorption is directly proportional to the quantity of organic matter associated with the solid. Normalizing soil or sediment specific sorption coefficients to the organic carbon content of the sorbent yields a new ``constant``, Koc, that is considered unique property of the organic chemical being sorbed. Values of Koc are then typically estimated from correlations between Koc and various descriptors of hydrophobicity such as octanol/water partition coefficients (Kow), aqueous solubility (S), molecular connectivity indices (MCIs) and retention times or capacity factors generated by reverse phase high performance liquid chromatography (RP-HPLC). Group contribution methods have also been described. While the so-called ``Koc approach`` for estimating sorption coefficients is most appropriate for neutral, hydrophobic organic chemicals on environmental solids containing a significant amount of organic matter, it has been applied to a wide variety of chemical and soil types. This presentation will focus on a discussion of the Koc approach, its applicability and limitations. A comparison of several widely used methods for estimating Koc will be presented.
- OSTI ID:
- 40120
- Report Number(s):
- CONF-9410273--
- Country of Publication:
- United States
- Language:
- English
Similar Records
Using QSAR to evaluate phenomenological models for sorption of organic compounds by soil
Sorption of 2,3,7,8-tetrachlorodibenzo-p-dioxin from water by surface soils