短链及中链氯化石蜡在上海市松江区农田土壤中的污染渗透及生态风险

土壤是氯化石蜡重要的"源"和"汇"，为了评估上海市松江区某农业区土壤中短链氯化石蜡（SCCPs）及中链氯化石蜡（MCCPs）的污染水平及渗透潜能，利用超声提取-复合硅胶柱一步净化-GC-ECNI-LRMS方法监测农田表层及不同深度（0~15、15~30、30~45 cm）土柱样品中SCCPs及MCCPs的含量水平、组成特征及潜在风险.结果表明:①表层土壤中SCCPs和MCCPs含量范围分别为52.58~237.56和417.21~1 690.82 ng/g，二者对应的氯含量分别为58.98%~63.85%和51.23%~56.50%.SCCPs同系物主要以C₁₀Cl_5~7为主，MCCPs同系物以C₁₄Cl_6~7为主.②单因素方差分析发现，MCCPs含量沿土柱深度变化显著（P < 0.01），其同系物在上层、中层和深层的占比分别为60.5%、25.4%和14.1%.SCCPs同系物含量沿土柱深度分布均匀，MCCPs同系物含量沿土柱深度呈指数递减趋势.垂直分布曲线表明，低氯化、短碳链的氯化石蜡同系物（CPs）具有更高的土壤渗透潜力.③皮尔逊相关性分析发现，CPs含量和总有机碳（TOC）含量之间不存在显著相关性（P>0.05）.主成分分析表明，研究区土壤中SCCPs和MCCPs的来源不同，可能与环境条件以及不同商业CPs混合物的生产技术、原材料差异等有关.④风险商值法评价表明，土壤SCCPs和MCCPs的风险商（risk quotients，RQ）范围分别为0.01~0.05和0.01~0.06，均处于低风险水平（0.01~0.1）.应用人体暴露模型对儿童和成人的人体暴露值进行估算，两类人群的CPs日均暴露值均低于每日可耐受摄入量（TDI，10 μg/kg），非饮食暴露导致的健康风险较低.研究显示，上海市松江区农田土壤中CPs污染含量处于中等水平，SCCPs沿土柱的渗透能力较强，该地区土壤生物风险商和人体健康暴露值均较低，产生的生态风险可忽略，但农作物富集造成的潜在健康威胁需要引起注意. 

Contamination,Penetration and Ecological Risk Assessment of Short and Medium-Chain Chlorinated Paraffins in Agricultural Soils in Songjiang District,Shanghai

Soil is considered to be a gigantic sink and source of chlorinated paraffins. In order to investigate the pollution level and penetration potential of short-chain and medium-chain chlorinated paraffins (SCCPs and MCCPs) in the Songjiang District agricultural area of Shanghai, the contamination, composition characteristics and potential risks of SCCPs and MCCPs were identified in the surface and core soils (0-15, 15-30, 30-45 cm) by ultrasonic extraction, composite packing column one-step purification coupled and GC-ECNI-LRMS. The results show that: (1) The concentrations of SCCPs and MCCPs in surface soils were 52.58-237.56 and 417.21-1690.82 ng/g dry weight, respectively, and the chlorine content was 58.98%-63.85% and 51.23%-56.50%, respectively. C₁₀Cl_5-7 and C₁₄Cl_6-7 were the predominant congener groups. (2) The concentration of MCCPs decreased significantly with the depth of the soil column (P < 0.01), and the abundance percentages from top to bottom were 60.5%, 25.4% and 14.1%, respectively. The level of SCCP co-ethnic group along the depth of the soil column was relatively uniform, and the level of MCCP co-ethnic group decreased exponentially. The vertical distributions further showed that the shorter carbon chain congener groups with smaller K_ow and higher water solubility tended to penetrate deeper into the soil. (3) Pearson correlation analysis showed that there was not significant correlation between CPs content and TOC content (P>0.05). Principal component analysis showed that the sources of SCCPs and MCCPs were different, which may be related to environmental conditions and the differences in the production process and raw materials of different commercial CPs mixtures. (4) The risk quotient model (RQ) was used to assess the potential risks of SCCPs and MCCPs in the agricultural soils. RQ values for SCCPs and MCCPs in soil were 0.01-0.05 and 0.01-0.06, respectively, indicating that their ecological risks were low (0.01-0.1). The daily exposure level of CPs in children and adults did not exceed the Tolerable Daily Intake (TDI) (10 μg/kg), indicating that there were no risks caused by non-dietary exposure. The studies has shown that the contents of CPs in Songjiang District agricultural area were at a medium level, and SCCPs have strong permeability along the soil column. The biological risk quotient and human health exposure values in this area are low. Therefore, the ecological risks are negligible, but the potential health threat caused by the pollution enrichment of crop should arouse our attention.