| With the exploitation and utilization of mineral resources,the solid waste generated continues to increase.When piled up,it not only takes up land resources,but also causes harm to the surrounding environment.Under the leaching of rainwater,heavy metals in the waste are dissolved out and enter the surrounding farmland with the rainwater,causing the soil heavy metal content to exceed the standard.The crops grown in this area will also absorb heavy metals in the soil through enrichment,which will have a certain impact on human health through the food chain.In this article,we conducted a more detailed study on the pollution of heavy metals in the tailings of Yangshan,Tongling.Through field investigations,we collected soil and plant samples to discuss the migration law of heavy metals in the farmland soil around the tailings reservoir and the impact of edible plants on human health.The farmland pollution assessment of the reservoir provides theoretical support,so it is of great significance to study the migration law of heavy metals in the soil-plant in the tailings pond in this region.(1)The level of heavy metals in the farmland soil of the tailings pond is mainly Cu,Cr,and Cd pollution,with Cd exceeding the standard in the soil is the most significant,respectively 4.54,3.16,and 2.91 times the background value;from the vertical migration of heavy metals,Mn,Ni and Cr are characterized by a lower surface layer and a higher bottom layer.The content of Mn at 40 cm is higher than that of the surface layer,and there is a tendency to migrate to the subsoil layer.Ni is enriched at 80-100 cm;Cr The change is more obvious,there are two enrichment areas of 0-20 cm and 40-60 cm;Cu and Cd change trend is basically the same,showing the distribution trend of decreasing content from the surface layer to the bottom layer,and the surface layer content is higher than the background value.The activity of Cd is more obvious.(2)The distribution of heavy metal content of crops in the tailings pond farmland.In general,the heavy metal content of the roots is greater than the above-ground part,and the above-ground part of Cr is generally greater than the root content.The content of all plant samples exceeds the general value,and the plants show strong absorption of Cr;Ni,Cd,Cu partially exceed the standard,and the content of Mn in all plant samples is within the general range.(3)Studying the migration characteristics of heavy metals in the soil-plant system,it is found that the enrichment degree of the five heavy metals is generally expressed as: Cd> Cr> Ni> Mn> Cu,where Cd shows a strong enrichment ability in the beans.The strong Mn enrichment ability(BCF> 1)is mainly manifested in the roots of cucumber,eggplant,muskmelon,and pepper;while the enrichment ability of Cu,Ni,and Cr is weak,and the migration ability of the six plants to heavy metals is also different.,The overall performance is: Cd> Ni> Cr> Cu> Mn.Among them,Cd showed a strong migration ability to bean,eggplant and muskmelon,with a TF greater than 1 or close to 1.(4)An evaluation study on the heavy metal content of farmland soil in the horizontal direction,using single factor index and Nemero index evaluation,found that the pollution rates of Cd,Cu,and Cr reached 83%,77%,and 8.3%,respectively,and the pollution degree was in the non-root The inter-soil is significantly larger than the rhizosphere.The evaluation of the field accumulation index leads to the same conclusion.The horizontal soil is mainly polluted by Cu and Cd,while the Mn,Cr and Ni are non-polluted;the same method is used to evaluate the vertical soil,The soil is mainly polluted by Cd and Cu,and the surface soil pollution is the most serious,and the pollution degree gradually decreases with the increase of sampling depth;the evaluation of crops found that the crops were mainly Cd pollution,of which the carob and pepper fruits were severe Contaminated,the carob fruit is 3.3-3.58,the root is 2.22-5.74.The potential ecological index method evaluated the pollution status of heavy metals in farmland soil,and found that Mn,Cr,and Ni are at low risk in the soil,while the ecological risk indexes of Cd and Cu are higher between 21.13-316.90 and 3.48-16.77,respectively.(5)Using the health risk assessment model to carry out risk assessment on residents who eat crops in various areas,the results show that both adults and children HI(risk coefficient)is greater than 10,in which Cd,Cu element HQ(risk coefficient)are greater than 1,edible plants The single element Cd and Cu will also bring certain health risks. |
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