Pollution Characteristics And Health Risk Assessment Of Heavy Metals In Cultivated Soil Of Haigou River Watershed

Soil resources are one of the most important resources in human production and life.With the rapid development of the social economy,the speed of urbanization and industrialization has gradually accelerated.Humans have discharged a large amount of toxic and harmful substances into the surrounding environment,far exceeding the environmental capacity,and the ecological environment has been severely damaged.Heavy metal pollutants have the characteristics of being difficult to degrade and easy to accumulate,and are easy to collect in the soil,which leads to a decline in the quality of the cultivated land and threatens the sustainable use of cultivated land.In addition,heavy metal elements in the soil will enter the plant through the plant root system,resulting in plant disease,decreased yield,and even enter the human body through the food chain,seriously harming human health.According to the "National Soil Pollution Survey Bulletin",China’s soil environment,especially the heavy metal pollution of cultivated land and industrial and mining waste land,is serious.Among them,the heavy metal sample points of the cultivated land exceed 80% of the total sample points of the cultivated land.attention.The Haigou River small watershed is located on the edge of the black soil belt at the southern end of the Songnen Plain,16 km away from the provincial capital Harbin.The excellent soil topography and location conditions have made the agricultural development and urban-rural construction activities in the small watershed vigorous.Representativeness and typicality.Collect 136 surface soil samples in the watershed and determine the contents of 8 heavy metals Cu,Pb,Zn,Hg,As,Cd,Ni,Cr in the soil samples.Based on this,the single-factor pollution index and Nemero comprehensive pollution were used.Index,land accumulation index,Hankson potential ecological risk model,human health risk assessment model under the US＿EPA framework,and GIS spatial analysis and other model methods to analyze the accumulation characteristics,pollution risk and spatial distribution of soil heavy metals in small watersheds,with a view to the subsequent improvement of cultivated land productivity,Provide scientific basis for agricultural production and sustainable use of cultivated land.The main conclusions of the study are as follows:(1)Based on the background value of each element in the soil of Heilongjiang Province as a reference object,the heavy metal pollution and accumulation characteristics of cultivated soil in the watershed are analyzed.The results show that: 8 heavy metals Zn,Ni,Hg,Pb,and Cd in the watershed soil all exceed the soil background value of Heilongjiang Province;8 heavy metals all belong to moderate variation;ordinary Kriging interpolation results show that samples with high heavy metal content Most of them are concentrated in the low-lying watershed outlets on the northwestern part of the study area,on both sides of highways and around the formed towns,indicating that the hydrogeological conditions and human activities in the small watershed greatly affect the accumulation of heavy metals in the soil.(2)The single-factor pollution index shows that the order of the pollution of the eight heavy metals is Cu-0.829,Zn-1.033,Hg-1.923,As-0.009,Pb-1.016,Cd-2.628,Ni-1.008,Cr-0.849;Nemero ’s comprehensive pollution index reveals that the study area is at a light pollution-moderate pollution level;the geoaccumulation index indicates that the order of the pollution levels of the eight heavy metal elements from high to low is Cd(0.748)> Hg(0.244)> Pb(-0.572)> Ni(-0.621)> Cr(-0.857)> Zn(-0.894)> Cu(-0.926)> As(-7.620);it can be seen that light-moderate heavy metal pollution has occurred in the study area,among which Cd and Hg are more polluted.(3)The results of potential ecological risk assessment indicate that the comprehensive risk index RI of the heavy metals in the watershed soil is 172.829,which presents a moderate degree of ecological threat to the environment.Among them,Hg and Cd are the most threatening to the environment,and the proportion of samples at a stronger level 47.06% and 39.71% respectively;the interpolation results of the comprehensive ecological risk index show that the northwest corner of the watershed poses a great threat to the surrounding ecological environment,which is closely related to the topography of the northwestern area of the study area.The heavy metals in the soil around the forest land affect the ecological environment.The threat is relatively small.(4)The results of health risk assessment show that the exposure route of oral intake of soil is the most harmful to human health;there is no non-carcinogenic risk to the surrounding population of heavy metals in the watershed soil;only As,Cr,Cd and Ni in the evaluated heavy metals have The carcinogenic slope has a carcinogenic effect on the human body,and the carcinogenic risk for adults and children is Cr> Ni> Cd> As,where Cr and Ni are beyond the maximum range acceptable to the human body,causing serious human health Threats,and children are more sensitive to heavy metals,with higher risk values than adults.