| As a large agricultural country,the quality of farmland soil environment is crucial.Heavy metal pollution in soil leads to accumulation in plants such as rice and wheat,which are harmful to the human body through the food chain.Cadmium is the most serious heavy metal element in soil pollution with point over-standard rate of 7%.Researchers have never stoped the study of soil heavy metals,but due to objective factors,the research was only carried out in selected small areas.In order to understand the pollution status of cadmium in farmland soils in China in the past 40 years,published domestic and foreign literatures were collected to study the soil cadmium pollution in farmland.Based on 1186 related literature data,this study systematically evaluated the pollution status of cadmium in farmland soils by discussing the concentration level and spatial and temporal distribution characteristics of cadmium,and assessing the ecological risks using geological accumulation index.The health risk assessment model developed by the USEPA were used to evaluate health risk assessment of cadmium in farmland soils.The results showed that:(1)The range of cadmium in farmland soils in China is between0.000013 and 217.23 mg/kg.The concentration of heavy metal cadmium in farmland soils raised in the order of east(0.20 mg/kg)< north(0.21 mg/kg)<northeast(0.25 mg/kg)< west(0.33 mg/kg)< south(0.51 mg/kg).(2)According to the spatial distribution of soil Cd,the distribution of high-concentration Cd contamination spots is relatively more in the south and west than in other regions.From the spatial distribution of soil Cd in various regions,Jiangsu and Anhui in the east are the most polluted provinces in the region;the high concentration of Cd in the west is mainly distributed in Gansu and Yunnan provinces;the pollution in southern Hunan and Guangxi provinces is more prominent;Tianjin is a province with high concentration of Cd;the soil Cd of Jilin and Liaoning in the northeast are more serious.(3)From 1981 to 2016,the medium level of cadmium in farmland soils in China remained stable with no significant fluctuations.The average time trend is divided into two main stages.From 1981 to 2001,the upward trend was obvious,and the growth was relatively fast;from 2002 to 2016,it showed a slow upward trend.This trend of time is consistent with the emergence and increase of cancer villages in China,indicating that there are more and more pollution incidents in polluted areas.(4)Human activity is the main source of Cd in the soil.Atmospheric deposition,sewage irrigation,industrial waste,fertilizer and pesticide application will cause a large amount of input of soil Cd.It is found that there is a linear correlation between the annual application amount of chemical fertilizer and soil cadmium concentration,indicating that chemical fertilizer application is one of the important sources of Cd in farmland soil.(5)The results of ecological risk assessment indicated that the pollution level of heavy metal in farmland soils in China was in the range of 0~6,and soil cadmium caused ecological hazards in some areas.Health risk assessments showed that the proportion of samples that pose non-carcinogenic risks to adult males,adult women,and children were 3.47%,3.65%,and 4.79%,respectively.Children are more susceptible to non-carcinogenic risks in the same environment than adults.Gansu,Hunan,Henan,and Guangxi should be the priority provinces.Different from non-carcinogenic,adults are more susceptible to cancer risks than children.Jilin Changchun Sewage Irrigation District,Huludao Molybdenum Mine,and Yunnan Lead-Zinc Mine should be the priority control areas. |
