Temperature-dependence of soil/air partition coefficient for polychlorinated biphenyls at subzero temperatures

Soil/air partition coefficients (KSA) were measured experimentally on a silty clay loam soil spiked with polychlorinated biphenyls (PCBs) over a wide range of environmentally relevant temperatures (−30 to +30 °C). Measured KSA-values ranged over 6.4 orders of magnitude, with log KSA from 4.3 for PCBs 10/4 at +30 °C to 10.7 for PCBs 77/110 at −30 °C. Higher than expected, KSA-values were observed at subzero temperatures (by up to one order of magnitude, at −30 °C). The plots of log KSA vs. reciprocal absolute temperature show a change in slope at 0 °C. A log–log linear regression of KSA vs. octanol/air partition coefficient (KOA) has a slope close to 1, indicating that KOA is a good descriptor of the interchemical variability in KSA. Further study showed that KOA-based Karickhoff-type equations can perfectly fit experimental KSA-values.