Short- and medium-chain chlorinated paraffins in urban soils of Shanghai: spatial distribution, homologue group patterns and ecological risk assessment

Chlorinated paraffins (CPs) are toxic, bioaccumulative, persistent, and ubiquitously present in the environment. Data on the presence of short- and medium-chain chlorinated paraffins (SCCPs and MCCPs) in urban areas with dense population are still scarce to date. SCCPs and MCCPs were measured in urban soils from Shanghai to comprehensively investigate their levels, spatial distribution, homologue group patterns and ecological risk. The concentrations of CPs in soils varied from ND to 615 ng g(-1) with a median value of 15.7 ng g(-1) for SCCPs and from 1.95 to 188 ng g(-1) with a median value of 7.98 ng g(-1) for MCCPs, respectively. The concentrations of SCCPs in most soils were higher than those of MCCPs. The total CP concentrations in soil samples were between 4.10 and 625 ng g(-1) with a median value of 26.4 ng g(-1). For different functional zones, the median concentrations of soil CPs were found higher in green land including park, greenbelt and campus than those in roadside. The highest concentrations of CPs in soils could be derived from sewage sludge application and wastewater irrigation for green land. Three types of soils were classified by hierarchical cluster analysis (HCA) for SCCPs and MCCPs, the most abundant homologue groups in the bulk of the soil samples were C11Cl5-7 and C13Cl5-7 for SCCPs, and C14Cl7-8 and C15Cl7-8 for MCCPs. Correlation analysis and PCA suggested that SCCPs and MCCPs in soils in the studied area derived from different sources. The preliminary ecological risk assessment indicates that soil CPs at present levels poses no significant ecological risk for soil-dwelling organisms.