On the influence of the polarity index of organic matter in predicting environmental sorption of chemicals

Data on the correlation of partition coefficients and the polarity index (PI = (O+N)/C) of sorbents is compiled from literature and discussed with respect to the possible influence on the calculation of predicted environmental concentrations in risk assessment. When artificial substrates are used a linear correlation between PI and sorption of chemical substances is observed. However, sorption to natural organic matter extracted from soil and water is not correlated to the PI of the sorbert. Therefore, the origin of the sorbent should be taken in account when estimating the sorption from the log Pow of the substance. In term of risk assessment purposes the equation log Koc log Pow − 1 is adequate for estimating the sorption to organic matter extracted from soil, and the equation log Koc log Pow − 2 is adequate for estimating the sorption to organic matter in surface waters.