Potential Ecological Risk Assessment of Heavy Metals in Soil for Reclamation of Coal Mining Collapsed Land in Tangkou Mining Area in Shandong Province
In this paper,through collecting 39 soil samples from a coal mining subsidence area in Shandong province,the content and pH value of As,Hg,Cr,Pb,Zn,Cd,Cu,Ni in the tested samples have been analyzed.Different reference ratios have been selected and the potential ecological risk index method has been used to evaluate the heavy metal pollution status and potential ecological risk in reclaimed soil.It is showed that heavy metal content in reclaimed soil in the study area can not exceed the soil pollution risk screening value specified in the"Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard(Trial)(GB15618-2018)"except for Cd.The average contents of Hg,Pb,and Zn are higher than geochemical background values of the surface soil in Ji'ning city.The correlation analysis of heavy metals in reclaimed soil shows that Cr Ni element has high homology.As-Cu-Pb-Zn elements may have similar sources,accompanied by the possibility of composite sources.The sources of Hg and Cd elements are different from other heavy metals.When using the national risk screening value as a reference,the o-verall ecological risk level of the reclaimed soil in the study area is light as showed by the evaluation re-sults.There is a moderate pollution risk of single heavy metal Cd which needs to be focused on.When u-sing soil background value as a reference,As,Pb,Ni,Cu,Cr and Zn in the reclaimed soil in the study ar-ea are at a mild ecological risk level as showed by the evaluation results.Hg is at a strong ecological risk level,and some samples have very strong or extremely strong ecological risk levels.Although Cd is at a mild ecological risk level,some samples have moderate to strong ecological risk levels.The comprehensive potential ecological risks of heavy metals in the reclaimed soil in the study area are mainly mild and moder-ate with Hg and Cd being the main contributing factors.
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