河湟谷地耕地土壤中有机氯农药残留特征及风险评价

Residual characteristics,health risks,and influencing factors of organochlorine pesticides in soil of cultivated land in Hehuang Valley

为了明确青藏高原典型农区耕地土壤中持久性有机污染物—有机氯农药(OCPs)的残留特征、健康风险及影响因素,本文采用网格布点法,在青海省河湟谷地的典型农区,分别采集不同种植类型耕地0~20 cm和20~40 cm土层土壤样品125个和14个,通过气相色谱和克里金插值法探讨六六六(HCHs)和滴滴涕(DDTs)的含量、空间分布特征和人体健康风险,并结合种植类型、气象条件和土壤理化性质分析农药残留分布的影响因素.结果表明,研究区域60%的土壤样点检出了HCHs,77.6%的土壤样点检出了DDTs.ΣHCHs与ΣDDTs的含量范围(平均值)分别为0.19~20.61 ng·g^(-1)(4.78 ng·g^(-1))和2.70~38.11 ng·g^(-1)(7.76 ng·g^(-1)),二者在互助县和乐都区的土壤样点中残留量较高,在同仁县的土壤样点残留量较低;20~40 cm土层中HCHs和DDTs残留较0~20 cm土层分别低53%和16%.种植类型对土壤中ΣHCHs的残留有一定影响,油菜和土豆土壤中的残留量显著高于玉米土壤.土壤中HCHs和DDTs残留量与土壤有机质、全氮、全磷、风速、降水量和日照时数呈正相关,HCHs与含水率和气温呈负相关.HCHs和DDTs残留主要来源于工业HCHs和DDTs的使用.河湟谷地土壤检出的HCHs和DDTs含量均低于我国环境标准规定的限值,其致癌与非致癌风险值均小于阈值,对研究区人群基本不会造成健康风险.

To understand the residues and health risks of persistent organic pollutants organochlorine pesticides(OCPs),as well as their influencing factors,in the soil of typical agricultural areas on the Qinghai-Tibet Plateau,this study surveyed soil via a grid-based approach from different cropping systems of Hehuang Valley in Qinghai Province,with 125 samples from 0~20 cm soil layer and 14 samples from the 20~40 cm soil layer.Gas chromatography was used to detect the content of hexachlorocyclohexane(HCHs)and dichlorodiphenyltrichloroethane(DDTs)and Kriging interpolation was applied to map their spatial distribution characteristics and human health risks.Factor analysis was conducted to sort out the influencing factors between the distribution of pesticide residues and crop types,meteorological conditions,and soil physicochemical properties.The results showed that there were 60%and 77.6%of HCHs and DDTs detected in soil samples,respectively.The ranges ofΣHCHs andΣDDTs content were 0.19~20.61 ng·g^(-1)(average 4.78 ng·g^(-1))and 2.70~38.11 ng·g^(-1)(average 7.76 ng·g^(-1)),respectively.The high level of both pesticides was detected in soils from Huzhu County and Ledu District,while the low level was found in soils from Tongren County.Residues of HCHs and DDTs in the 20~40 cm soil layer were lower than those in the 0~20 cm soil layer,reaching up to 53%and 16%of each,respectively.The significant difference was tested between crop type andΣHCHs residues,especially higher level ofΣHCHs being detected in rapeseed and potato planting soils than those in corn planting soils.HCHs and DDTs residues were positively correlated with soil organic matter,total nitrogen,total phosphorus,wind speed,precipitation,and sunlight hours,while HCHs residues showed a negative correlation with moisture content and air temperature.According to Chinese environmental standards,the content of HCHs and DDTs in the soil of the Hehuang Valley region was below the limit of the environment risk.Both carcinogenic and non-carcinogenic risk values were below the risk threshold,indicating no health risk for the population in the study area.