Heavy Metal Pollution Assessment And Health Risk Assessment Of Cultivated Land Based On Soil-crop-human System

Cultivated land is the foundation of economic and social development,and food security is the basic demand of human survival and development.However,due to the development of industry,science and technology,heavy metal pollution has begun to affect soil quality.And further through the plant roots and food chain into crops and human body,to human health.Therefore,further study on the risk of heavy metal pollution in soil-crop-human system is of theoretical and practical significance on the premise of soil heavy metal pollution.In this paper,eight districts under the jurisdiction of Prefecture X were selected as the study area,based on the heavy metal content data of eight heavy metals(Cr,Pb,Cd,Hg,As,Cu,Zn,Ni)and four main crops(grain,fruit,vegetable,tea).Four methods of heavy metal pollution risk assessment were used to determine the accumulation of heavy metal pollution in soil and the main polluted heavy metal elements,and the relationship between heavy metal content in soil and heavy metal content in crops was analyzed.The characteristics of migration and accumulation of heavy metal pollutants in soil-crop system and the risk of synergistic pollution were discussed,and the risk assessment model of human health and the method of target hazard coefficient were used.On the basis of evaluating the carcinogenic risk and non-carcinogenic risk of heavy metals in cultivated soil and crops respectively,the risk control value and risk control measures of heavy metal elements of potential risk in the study area were determined.The main conclusions of this paper are as follows:(1)the accumulation of heavy metal Hg and Cd in cultivated soil i's the most serious,and they should be regarded as potential risk heavy metals,and mainly distributed in the southeast-central region.The decreasing order of accumulation of eight heavy metals is:Hg>Cd>Cu>Pb>Zn>Cr>Ni>As.(2)The pollution of As,Ni,Cr,Pb,Zn,Cd in heavy metals of crops was the most serious.Among the four crops,the food crops exceeded the standard most seriously,which reached grade ?.The decreasing order of the eight heavy metal pollution indexes was As>Ni>Cr>Pb>Zn>Cd>Cu>Hg.the order of the index of heavy metal pollution was As>Ni>Cr>Pb>Zn>Cd>Cu>Hg..The risk assessment results of heavy metal pollution in crops are different from those in soil,which may be due to the direct or indirect effects of many external factors on the content of heavy metals in crops.(3)There is a strong correlation between the heavy metal content in crops and the heavy metal content in soil,among which the heavy metal content in food crops is the strongest with the heavy metal content in soil,followed by vegetables and fruits.The contents of heavy metals in soil have certain synergistic and inhibitory effects on the absorption of heavy metals by crops.There is a significant correlation between CB,Cu(crop and Cd,Cu(soil)respectively.The Cd,Cu in soil may be in crop and Cd,in soil.The main source of Cu,in addition to mercury,heavy metals in other crops also have positive and negative correlation with non-self-elements in soil.(4)The absorption capacity of different crops to different heavy metals was different,and the cumulative index of grain was higher than that of other crops.Among the eight heavy metal elements,Cd is the most easily absorbed by crops,and Pb is the most difficult heavy metal element to migrate in soil-crop system.The results showed that there was at least one excess in soil and crop,and the seriously polluted samples were mainly distributed in the southwest-central part of the study area,and the samples mainly came from grain crops.(5)The comprehensive non-carcinogenic risk control values of children and adults with soil heavy metal Cr were 0.76mg/kg and 0.28mg/kg.The comprehensive carcinogenic risk control values of children and adults with soil heavy metal Cr and Cd ranged from 0.03mg/kg to 2.91mg/kg,0.004mg/kg to 0.38mg/kg,1.99mg/kg to 198.76mg/kg and 0.01mg/kg to 1.28mg/kg,respectively.The combined risk values of crop heavy metal As for children and adults were 0.35mg/kg and 0.55mg/,respectively.The comprehensive risk values of As children and adults were 0.35 mg/kg and 0.55 mg/kg,respectively;those of Cr children and adults were 1.56 mg/kg and 2.43 mg/kg,respectively;and those of Cd children and adults were 2.52 mg/kg and 3.92 mg/kg,respectively.The risk control measures of heavy metal pollution in the region were put forward,including scientific planning,regional management of cultivated land,strengthening the scientific control of heavy metal pollution prevention and control,strengthening the construction of laws and regulations and policy research of agricultural products pollution prevention and control.Focus on the cultivation of heavy metal pollution prevention and control industry;formation of a heavy metal control system construction.