Comparison of heavy metal accumulation characteristics between dry land and paddy field of volcanic rock area,North of Hainan
To analyze the accumulation characteristics of heavy metals(As,Cd,Cr,Pb,Ni,Hg)in the soil of the volcanic rock area in North of Hainan,surface soil samples were collected from dry land and paddy field,and the physicochemical properties and heavy metal content of the samples were analyzed.The single factor pollution index method and the Nemerow comprehensive index method were used to evaluate the heavy metal pollution status.The results showed that both dry land and paddy field soil in the study area were strongly acidic to acidic,and the cation exchange capacity(CEC)of dry land soil(4.66 cmol/kg)was slightly higher than that of paddy field soil(3.42 cmol/kg),indicating that the nutrient retention ability of dry land soil was better than that of paddy field soil.Compared with the background values of soil in Hainan Province,the study area showed varying degrees of accumulation of four heavy metals,namely Cd,Cr,Pb and Ni,in both dry land and paddy field soil,with Cd being the most heavily accumulated.There was a high positive correlation between Cr and Ni in the soil of dry land and paddy field in the study area,indicating that Cr and Ni might be homologous and greatly influenced by the geological background of basic volcanic rock.The evaluation results of the Nemerow comprehensive pollution index indicated that the heavy metal pollution in the study area's dry land soil was significantly higher than that in paddy field soil.The heavy metal pollution in paddy field soil was mild,while the heavy metal pollution in dry land soil had reached moderate pollution,especially the pollution of Cr and Ni,which should be given sufficient attention.