Element Fractions And Ecological Risk Assessment Of Soils In Anxin-Qingyuan County In Hebei Province

In recent years,soil pollution,is becoming more and more serious.Heavy metals may enter water body,atmosphere,and the food chain through crops,thereby threatening the health of human beings.The evaluation results would guide the restoration of contaminated soil,improvement of the quality of agricultural products,and protection of human health,which is of great significance.In this paper,37 surface soil samples were collected in Anxin-Qingyuan County in Hebei province.Soil physiochemical properties including soil particle-size,organic matter value,pH and EC,were analyzed.Total contents and binding forms of As,Cd,Cr,Cu,Hg,Ni,Pb,and Zn were also measured.Spatial distributions of total content and forms,possible sources of soil elements,and their influencing factors were discussed.The biological availability,soil environmental quality and the potential ecological risk of the elements were evaluated.The main achievements are shown as follows.（1）Arsenic,Cd,Cu and Zn in some soil samples exceeded the second class of national soil environmental quality standard.Spatial distributions of soils Cd,Cu,Pb and Zn were similar.Factor analysis showed that,the possible sources of Cd was mainly from industrial and agricultural activities and Cu is the main source for industrial activity,Pb mainly came from transportation and industrial activities,the main source of As was from industry and agriculture and the effect of soil parent material;The main source of Cr and Ni was from soil parent materials,while Hg mainly came from industrial coal dust settlement;The possible source of soil Zn was from transportation process in automobile tire wear generated dust.In addition,the soil physicochemical properties affected enrichment of heavy metals Cr,Ni,and had little effect on enrichment of other elements.（2）Arsenic and Cu,Hg mainly existed in the form of residue and humic acid bindingbound-forms.Cd mainly occurred as ions and carbonate bound forms,Cr,and Ni as residual form,and Pb and Zn as residual and Fe Mn oxide bound forms.Binding forms of Cr,Cu,Hg and Ni were greatly influenced by the soil physical and chemical properties.The bioavailability and mobility of Cd was the largest,which was the most harmful to the environment.Pb had high bioavailability,but poor migration ability.C_bio ratio of soil elements followed the order:Cd>Pb>Cu>Zn>Ni>Hg>As>Cr.C_Pbioratio was the highest for Pb,followed by Cu,Hg,Zn,As,Cd,Ni,and Zn,while C_Nbioratio of Cr was the highest,followed by Ni,As,Hg,Zn,Cu,Pb and Cd.（3）Soil pollution in the study area was serious,with Cd,Cu,Pb,and Zn as the main pollutants.Cd was heavy pollution,Cu,Pb,Zn was moderate pollution,As was light pollution,and Cr,Ni,and Hg basically in a clean state.Nemero comprehensive pollution assessment showed heavy pollution of studied soils.（4）A comprehensive potential ecological risk index method based on binding forms of soil elements was established.Evaluation results showed that the average values of potential ecological risk coefficient followed the order:Cd>Hg>Pb>Cu>As>Ni>Zn>Cr,which was consistent with the Hakanson potential ecological risk index method.Therefore,the integrated model is feasible to evaluate the ecological risk of the contaminated soils.