通辽地区农田土壤中多氯联苯分布特征及生态风险评价

Distribution characteristics and ecological risk assessment of polychlorinated biphenyls in farmland soil of Tongliao City

为揭示污灌区农田土壤中多氯联苯(PCBs)的污染水平,解析不同再生水对土壤中PCBs的影响,选取通辽地区6个不同灌区,分析土壤样品中的48种PCBs,采用环境质量标准和毒性当量因子法进行生态风险评价.结果表明:PCBs总浓度为0.36~2.44ng獉g-1,7种指示性PCBs浓度范围在0.05~0.38ng獉g-1,其中处理后工业废水灌溉区PCBs污染程度最大.土壤中PCBs同系物组成以三、四氯联苯所占比例最高,其次是二氯联苯及五氯联苯.土壤样品中PCBs浓度呈现深层土壤低于表层土壤的趋势.主成分分析发现,污灌农田土壤主要来源于变压油的泄漏及大气的干湿沉降.从整体上看,通辽农田土壤污染水平或毒性当量处于较低生态污染水平,生态环境评价结果表明,研究区域生态风险小,但污水的长期灌溉会增大土壤的生态风险.

In order to investigate the residues of polychlorinated biphenyls（PCBs）in the agricultural soil of sewage irrigation areas,and analyze the effects of different reclaimed wastewater on PCBs in soil,we analyzed 48 types of PCBs congeners of soil samples from 6irrigation areas of Tongliao City,and assessed the ecological risks by using environmental quality standard and toxicity equivalent factors method.The results showed that the total concentrations of PCBs were between 0.36ng獉g-1 and 2.44ng獉g-1,the total concentrations of seven indicative PCBs ranged from 0.05ng獉g-1 to 0.38ng獉g-1,and the total concentrations of PCBs in soil from the treated industrial wastewater irrigation areas were the highest.Tri-CBs and tetra-CBs took up the max proportion of the homologues of PCBs,and di-CBs and penta-CBs were in the next place respectively.It showed a trend that the concentration of PCBs in deep soil samples was lower than that in surface soil samples.Principal component analysis revealed that PCBs in farmland soil was mainly from domestic transformer oil leakage and atmosphere deposition.Overall,the pollution level and toxic equivalence of PCBs in farmland soil of Tongliao City were at a lower level.Risk assessment indicated that the environmental risk in farmland soil of Tongliao City was at a lower level,but the long-term irrigation of wastewater can increase the ecological risk of soil.