Effects of temperature and relative humidity on soil−air partition coefficients of organophosphate flame retardants and polybrominated diphenyl ethers

The soil−air partition coefficients (K_SA) of polybrominated diphenyl ethers (PBDEs) and organophosphate flame retardants (OPFRs) is important for determining their fate in soil and air media. However, K_SA values of OPFRs and PBDEs are not available from the current literature, and the effects of environmental factors such as temperature and relative humidity (RH) on K_SA values are not clear. In this study, a solid-phase fugacity meter was used to measure the K_SA values of PBDEs and OPFRs at different temperatures (25, 30, 35, 40, and 45 °C) and relative humidity (RH) conditions (<3 and 100% RH), the relationships between K_SA and octanol−air partition coefficients (K_OA) for OPFRs and PBDEs were analyzed. The results showed that an increase in temperature and RH resulted in a decrease of all K_SA values for PBDEs and OPFRs. Furthermore, the effects of RH on the soil−air partitioning behavior of PBDEs were larger than that of OPFRs. In addition, a significant correlation (p < 0.0001) was observed between log K_SA and log K_OA. The experimental K_SA values of OPFRs and PBDEs were quite different from the predicted K_SA, when calculated with their K_OA values. Overall, this study provides a better understanding for predicting the behavior and fate of OPFRs and PBDEs in soil−air systems.