Environmental Geochemical Characteristics And Risk Assessment Of Heavy Metals In Jiapigou Mining Area,Jilin Province

In order to study the geochemical characteristics and ecological risks of heavy metals in Jiapigou mining area in the upper reaches of the second Songhua River and better maintain the mine environment,taking Jiapigou mining area as the research object,collected samples of corn,wild Artemisia,soil,water,surface sediment and tailings mud in the area,and analyzed the content characteristics and spatialed distribution characteristics of heavy metals.The pollution characteristics of soil and surface sediments were analyzed by Nemero comprehensive pollution index method and ground accumulation index method,and the ecological risk of soil and surface sediments was evaluated by potential ecological risk assessment method.The target hazard coefficient method,water environment human health risk assessment model and human health risk assessment model under three exposure routes were used for corn to evaluate the human health risk of river water and soil.BCR continuous extraction method was used to study the distribution characteristics of four forms of heavy metals(including weak acid extraction state,oxidizable state,reducible state and residue state)in sediments and tailings mud.Finally,factor analysis was used to analyze the source of surface sediments.The main research results are as follows:(1)The average values of Cu,Pb,Zn,Cd,As and Hg in the river water in the study area are lower than the grade III standard of GB3838-2002.The average values of Cd and As are lower than the background value of the second Songhua River,and the average values of Cu,Pb,Zn and Hg are 4.2,18.0,1.7 and 6.9 times higher than the background value of the second Songhua River.Among the eight elements of Cu,Pb,Zn,Ni,Cd,Cr,As and Hg in the surface sediments of Weisha River,except that the content of Zn is less than the background value of the second Songhua River,the average content of the other seven elements is higher than the background value of the second Songhua river.The morphological analysis results of surface sediments show that Cu,Ni and Cr mainly exist in residual state,which is less likely to cause harm to the environment;Pb and Cd mainly exist in the bound state of iron manganese oxide,which has strong release under certain conditions and is easy to form secondary pollution.Zn mainly exists in strong organic binding state,which is potentially harmful to organisms.Factor analysis divides the eight elements into three categories: factor 1:Cu,Pb,Cd and Hg.The pollution sources are mainly tailings accumulation and tail gas emission;factor 2: Zn,Ni and Cr,and the pollution sources are transportation,pesticides and fertilizers;factor 3: As,the pollution source mainly comes from gold mining and tailings stacking.(2)The contents of Cu,Zn,Cr,As and Hg in corn don't exceed the industrial standard limit stipulated by the Ministry of agriculture,but the contents of Pb and Cd exceed the standard;The content of heavy metals in the root of Artemisia annua is about1.4 ? 3.8 times that in the stem.On the whole,the closer to the tailings,the higher the content of heavy metals.Taking the soil background value of the second Songhua River as the standard,the average contents of eight heavy metals in the corn root soil around the tailings don't exceed the class II standard limit of edible agricultural products land,but the average contents of Zn,Cr,Cu,Ni,Pb,Cd and Hg exceed the soil background value of the second Songhua River Basin;Except for As,the average content of other elements in the root soil of Artemisia annua near the tailings exceeds the background value of soil elements in the second Songhua River Basin,but Cu and Cd exceed the level II standard limit.(3)The results of water pollution assessment show that the overall pollution degree of Weisha River in Jiapigou mining area is relatively light,and only Pb and Hg elements in individual samples are light pollution.The surface sediments of Weisha River are at light to medium pollution level,Zn is non pollution,Ni,Cd and As are slightly polluted,Cu and Hg are moderately polluted,and Pb is medium to strong pollution.Crop root soil is slightly to moderately polluted.(4)The human health risk assessment results of river water show that the carcinogenic risk level of carcinogenic elements is low,and the health risk of non carcinogenic elements is negligible.The results of human health risk assessment of corn show that corn around tailings has no health risk to adults,but it is likely to have a negative impact on children's health.The results of human health risk assessment of corn root soil showed that the carcinogenic and non carcinogenic risks of each element through three exposure routes were oral intake > skin contact > respiratory intake,and the non carcinogenic risk HQ and total non carcinogenic risk hi were less than 1,which would not cause harm to human health.Cr is the main source of carcinogenic risk.Adults have a certain carcinogenic risk through oral intake and skin contact.The carcinogenic risk caused by respiratory route to children is not obvious,but the other two routes will cause carcinogenic risk to children.