The effect of anthropogenic activities on the environmental fate of chlorinated paraffins in surface soil in an urbanized zone of northern China

Abstract

Chlorinated paraffins (CPs) have been widely used as halogenated flame retardants and plasticizers since the mid-20th century. The prevalence of CPs in soil has been widely reported, but the distribution pattern of CPs in urbanized zones and their association with multiple socioeconomic variables have not been adequately explored. Herein, short-chain and medium-chain chlorinated paraffins (SCCPs and MCCPs) were investigated in surface soil samples from Tianjin, China, a typical urbanized area. The concentration distributions of SCCPs and MCCPs showed similar trends in different administrative divisions and land use types: urban areas > suburbs > outer suburbs (p < 0.001) and residential areas > greenbelts > agricultural areas (p < 0.001). The CP congeners in residential surface soils mainly included those with longer carbon chains and high degree of chlorination, while the CP congeners in agricultural surface soils mainly consisted of those with shorter carbon chains and fewer chlorine substituents. Multiple statistical approaches were used to explore the association between socioeconomic factors and CP distribution. CP concentration was significantly correlated to population density and gross domestic product (GDP) (p < 0.001), and structural equation models incorporating administrative regional planning showed an indirect impact on the distribution of MCCP concentration due to the influence of regional planning on population density. These results highlight the association between CP contamination and the degree of urbanization, and this paper provides useful information toward mitigating the exposure risk of CPs for urban inhabitants.