Pollution Characteristics And Health Risk Assessment Of OCPs In The Weihe River Of Xi'an-Xianyang Section

Organochlorine pesticides(OCPs)have been extensively used as agricultural pesticides at home and abroad.Owing to their high toxicity,bioaccumulation and carcinogenicity,they still have potential human health risks and ecological environmental hazards.The Weihe River is a major river in Shaanxi Province.In recent years,the organic pollution situation has improved,but there are limited studies on the residual levels and risk assessment of OCPs in water bodies,In this study,water and surface sediaent samples were collected from 16 mam and tributary sections of Weihe River in different water periods,and 23 organochlorine pesticide residues were detected by GC-MS.The single factor environmental quality assessment,comprehensive pollution index and USEPA health risk assessment model were used to analyze the residual level,spatial distribution and risk level of OCPs in the Xi'an-Xianyang section of the Weihe River,and compared with statistical data and historical research data.Combined with statistical data and historical research data,the changes of OCPs in the.water of the Xi'an-Xianyang section of the Weihe River were compared.The following research results were obtained:1)Through on-site measurement and laboratory testing,the water pH of the Xi'an-Xianyang in the Weihe River is between 7 and 9 and is weakly alkaline;the water temperature is between 2.0 and 30.4 ?3 and the water temperature varies greatly;the conductivity is between 244 and 2121 S/m,ORP range is 158,8?201.5 mv,water ion content is high;COD is between 6 and 41 mg/L,DO is between 3.3 and 17.03 mg/L,TOC is between 0.3736 and 3.3889 mg/L,NH3-N is between 0.166 and 8.680 mg/L.Analysis by the comprehensive pollution index method shows that the pollution of Zaohe River and Xinhe River is the most serious.Compared with the environmental monitoring data of 2016?2018,the concentration of COD and NH3-N in the water of the Xi' an-Xianyang section of the Weihe River has decreased,the dissolved oxygen(DO)content has increased to some extent,and the water quality has gradually improved.2)The distribution characteristics of OCPs in the Xi'an-Xianyang section of the Weihe River are mainly the difference of the distribution of the mainstream and the tributary and the seasonal distribution.The pollution level of OCPs in the tributary water is higher than that in the mainstream,and the OCPs pollution level in the water during the flood period is higher than that in the dry season.The residual level of OCPs in the Xi' an-Xianyang section of the Weihe River wet season was ND?756.94 ng/L,and the detection rate of the section was 81.25%.The OCPs in the dry season were ND?326.52 ng/L,the detection rate of a section was 31.25%.The residual level of OCPs in sediments was ND?5.20 ng/g,the average value was 1.45 ng/g,and the detection rate of a section was 81.25%.DDTs are the most important OCPs contaminants in water and sediment.The residual levels of OCPs in water and sediments did not exceed the residue standard limits in?Environmental quality standards for surface water?(CB3 83 8-2002)and?Marine sediment quality?(GB18668-2002).Compared with other water in China,the pollution level of OCPs in the water body of the Xi' an-Xianyang section of the Weihe River is relatively high,and the pollution level of DDTs is relatively high,and the pollution level of HCHs is relatively low3)Compared with the existing OCPs research data,the HCHs pollution level of the water in the Xi'an-Xianyang section of the Weihe River is obviously reduced,but the DDTs content is increased.The content of HCHs in Tianjiang Rendu,Xinfengqiao,Zaohe River,Bahe River,Jinghe River,and Linhe River was no detected,and the section of Gengzhen Bridge was reduced by 94%.4)In the wet season,the value of DDT/(DDE+DDD)in the water of the Xi'an-Xianyang section in the Weihe River is 0.61?2.26.The ratio of Yangling and Nanning sections is less than l,indicating that the residual DDTs in the water mainly comes from the residues caused by the premature application of pesticides in the environment.The ratios of the four sections of Xingping,Fenghe,Zaohe and Gengzhen Bridge are all greater than 1,indicating that the four sections have DDT input recently.The ratio of ?-HCH/?-HCH in the section of Yangling and Gengzhen Bridge is close to 1,reflecting that the HCHs in water is mainly used in historical agricultural production in the dry season,the DDT/(DDE+DDD)value of the section of the Gengzhen Bridge is 1.61,demonstrating that the DDT has recently entered the section.5)The water health risk study shows that the non-carcinogenic health risk of OCPs in the water of the Xi'an-Xianyang section of the Weihe River is much less than 1,and the cancer risk is 1.69×10-5?1.92×10-7,the non-carcinogenic health risks and cancer risk health risks to the regional population are at a minimal level.The ecological risk assessment of sediments indicates that the residual DDTs in the sediments may have certain ecological risks to the ecological environment of the Xi' an-Xianyang section of the Weihe River.6)Correlation analysis showed that there was no significant correlation between HCHs and DDTs with COD,NH3-N,TOC,DO,TP,pH and conductivity in water,indicating that their distribution was not affected by the physical and chemical properties of water.Aldrin,hexachlorobenzene and endrin were significantly correlated with epoxy heptachloride and heptachloride,DDTs and DDT,respectively,suggesting similar sources of pollution.