Correlation analysis between concentrations of soil heavy metal species and organic carbon in different land use types

【Objective】 In order to evaluate the correlation between soil heavy metal forms and organic carbon content(SOC)under different land use types,and to understand the environmental geochemical behavior of soil SOC and heavy metals,it had important theoretical value and practical significance for the risk assessment of soil environment and human health.【Method】 The contents of arsenic(As),chromium(Cr),copper(Cu),zinc(Zn)and lead(Pb),SOC and mineral bound organic carbon(MAOC)in soils of three different land use types(paddy field,dry land,abandoned land)in Qionghai City and Ding'an County of Hainan were determined. The morphological content,enrichment,bioeffectiveness and the association between heavy metals and SOC and MAOC were also analyzed.【Result】 The results showed that,the contents of heavy metals in soil of different land use types were as follows:paddy field:Cr>Zn>Pb>Cu>As;dry land:Cr>Zn>Pb>As>Cu;abandoned land:Cr>Zn>Cu>Pb>As. The forms of heavy metals in soil were mainly residual;the enrichment degree of heavy metals under different land use types was quite different.The enrichment index showed that,paddy field:Cr>As>Cu>Zn>Pb,dry land:As>Cr>Cu>Zn>Pb,abandoned land:As>Cu>Cr>Zn>Pb. The bioavailability coefficients of Cr,Cu,Zn and Pb were small in the soil,which was in a relatively stable presence,and had less ecological potential risk,while As had large potential threat to human health. The contents of SOC and MAOC in soil showed the following order:paddy field>abandoned land>dry land. The content of SOC and MAOC in soil was significantly(P<0.05)or extremely significantly(P<0.01)correlated with some forms of Cr,Cu,Zn and Pb.【Conclusion】 The change of land use types not only affects the physical and chemical properties of soil,but also affects the sources and properties of heavy metals and the content of organic matter in soil. The contents of some heavy metals in soils under different land use typesare significantly or extremely correlated with SOC and MAOC(except As). It has important theoretical significance for the indepth understanding of Hainan's soil pollution status,ecological and environmental benefits,and its soil self-purification capabilities and mechanisms,in order to provide theoretical support for Hainan's soil quality improvement and sustainable use.