Predicting organic carbon–water partitioning of hydrophobic organic chemicals in soils and sediments based on water solubility

For predicting organic carbon–water partitioning of organic pollutants in soils and sediments, a simple empirical relationship is derived from Raoult's law and fitted to data sets of experimental organic carbon normalized partition coefficients (Koc) and aqueous solubilities (Si) of 64 hydrophobic organic chemicals (HOCs) from literature including mono- and polycyclic aromatic hydrocarbons, halogenated monoaromatic and alkyl hydrocarbons, and polychlorinated biphenyls. Although over 5 orders of magnitude are covered in sorptivity (log Koc), the new relationship (log Koc = − 0.85 log Si − 0.55) predicts Koc with an average absolute deviation of only 0.23 log units. The relationship between Koc and Si is inverse and slightly nonlinear. The product of Koc times Si (= Koc∗, which indicates the theoretical maximum contaminant loading at its solubility limit per unit mass of organic carbon) is 0.098 kg kg−1 and 0.012 kg kg−1 for compounds with water solubilities of 1 g L−1 and 1 μg L−1, respectively.