Geographical patterns, sources, and ecological risks of short- and medium-chain chlorinated paraffins in mulching...

The broad utilization of chlorinated paraffins (CPs) as plasticizers has caused measurable soil pollution. However, the contribution of mulching films as a potential CPs source for agricultural soils remains inconclusive. This study revealed short- and medium-chain CP (SCCP and MCCP) concentrations in mulching cultivated soils from 29 provinces in China, ranging from 19 to 750, and 24-1580 ng/g dry weight (dw), respectively. CP concentrations in mulching cultivated soils from different regions varied, but their congener group profiles were all dominated with C_10-11Cl_7-8 and C₁₄Cl_7-8 for SCCPs and MCCPs, respectively. Mulching duration, cultivated crop types, and local rainfall might influence SCCP and MCCP concentrations in agricultural soils. Furthermore, mulching films were found with high CP contents, with biodegradable films showing higher concentrations (SCCPs: 20400 ng/g; MCCPs: 4410 ng/g) than polyethylene films (SCCPs: 11000 ng/g; MCCPs: 2350 ng/g). CP concentrations in biodegradable film mulched soils were also higher than polyethylene film mulched soils. Mulching films were identified as essential sources for CPs in agricultural soils. Although risk assessment indicated that current SCCP and MCCP concentrations in mulching cultivated soils posed relatively low direct health risks to residents in China, CPs in mulching films and soils should not be ignored and need further attention.