Correlations between Experimental and Predicted Equilibrium Distribution Coefficient of Chlorobezene and Chlorophenol Compounds in Soil-Water System Using Partial Solubility Parameters

Ching-Guang Jaw¹, Kuo-Hsiung Lin¹, Jui-Hung Yen², Yei-Shung Wang²*

¹Department of Environmental Engineering and Science, Fooyin University, Kaohsiung, Taiwan; ²Department of Agricultural Chemistry, National Taiwan University, Taipei, Taiwan

Abstract

Many pesticides are degraded to become chlorinated aromatic compounds in soils.  Equilibrium distribution of chlorobenzene and chlorophenol compounds in soil-water systems of Yangmingshan loam, Pingcheng silty clay loam and Annei silty loam was studied with the integral distribution equilibrium equation involving the partial solubility parameters of the chemicals.  Supposing that adsorption of chemicals on soils is partitioning in soil organic matter surrounding the soil mineral particles.  The absorption constant (K_d) of a chemical in soil-water system could be stated as the distribution coefficient (or partition constant, K_oc) of the chemical in the two adjunct immiscible phases --- water and soil organic matter.  The distribution coefficient (K_oc) of chemicals calculated from the integral distribution equilibrium equation agrees well with the experimental adsorption coefficient (K_d , or experimental K_oc ) of chemicals determined in this study, for all the three different types of soils in water according to multiple-regression analysis.  Reference data of Karger or Tijssen are employed to estimate the K_oc for both polar and non-polar chemicals.  The integral distribution equilibrium equation can exactly describe the distribution behavior of nonionic compound of chlorobenzenes and chlorophenols in soil-water system.