Short-chain chlorinated paraffins in the soils of two different Chinese cities: Occurrence, homologue patterns and vertical migration

Short-chain chlorinated paraffins (SCCPs) are candidate persistent organic pollutants (POPs) that are under review by the Stockholm Convention. China is currently the largest producer and consumer of chlorinated paraffins (CPs). To study the environmental behavior and fate of SCCPs in the soils of urban and suburban regions, the SCCP concentrations in 88 topsoils and 15 soil columns from land of different use types (e.g., woodland, vegetable field, paddy field and greenbelt) from Guangzhou and Chengdu have been determined. The SCCP concentrations in topsoils from Guangzhou (range: 1.45–25.5 ng g− 1 dry weight (dw), average: 10.3 ng g− 1 dw) were much higher than those from Chengdu (range: 0.218–3.26 ng g− 1 dw, average: 1.43 ng g− 1 dw). When compared to previously reported SCCP levels for topsoils from other areas, the SCCP concentrations measured in the present work were quite low. Much higher SCCP concentrations were observed in the greenbelt topsoils from Chengdu relative to the values measured from woodlands and vegetable and paddy fields. The composition profiles suggest that C10Cl6–10 and C11–13Cl6–8 were the major groups of SCCPs in topsoils from the woodlands and vegetable and paddy fields in Guangzhou and Chengdu. Vertical variations of the SCCP concentrations in the soil columns suggest that less chlorinated SCCPs (Cl5–6-SCCPs) are more capable of migrating to the deeper-layer soils than more chlorinated ones (Cl9–10-SCCPs). The SCCP concentrations displayed little dependence on organic matter (OM) for most topsoils (p > 0.05), indicating that OM is not the controlling factor in the distribution of SCCPs in the soils. This study analyzed the occurrence, homologue patterns and vertical migration of SCCPs in the topsoils of two Chinese cities with different industrial structures and climate conditions.