Soil Heavy Metal Enrichment Characteristics And Ecological Risk Assessment In Carbonate Background Area Of Qingyang,Anhui Province

The soil developed from carbonate rock have significantly higher Cd concentrations than those from non-carbonate rock in south China.The parent material of soil formation has a great influence on the content and characteristics of heavy metals in soil.Heavy metals are regularly enriched from carbonate rocks to developed soils.We carried out relevant research in Qingyang,Anhui province.We systematically collected soil,bedrock,rice and root soil samples,and compared the similarities and differences of heavy metal elements in various samples in carbonate rock area and non-carbonate rock area,and obtained the following results and conclusions:In surface soil samples,the content of heavy metal elements in the soil developed by carbonate rocks is significantly higher than that of sand shale and granite,especially Cd,Ni and As.Similar rules also exist in the deep soil samples,the heavy metal content in the developed soil of carbonate rock is higher than that in the sand shale area,and the heavy metal content in the granite area is the lowest.We used the method of geoaccumulation index for risk assessment and found that Cd and As in carbonate rock area have great ecological risks.According to the evaluation results of potential ecological risk index method,the potential ecological risk of the soil with carbonate rock development is greater.37.76% of the soil is of grade 1 slight ecological hazard,59.82% is of grade 2 moderate ecological hazard,and 2.42% is of grade 3 strong ecological hazard.However,most of the samples in the sand-shale area and granite area are of grade 1 slight ecological hazard.Heavy metals were enriched to varying degrees from carbonate rock to soil,and the enrichment degree of Pb,Cd and As was greater,among which the enrichment coefficient of Cd reached 11.38.The heavy metal enrichment coefficient in carbonate rock area is higher because more primary rock is consumed in carbonate rock weathering.The morphology of different kinds of heavy metals in the soil profile is significantly different,and the potential risk of Pb and Cd may be greater,because the proportion of residue state is smaller,and there will be more effective heavy metals in the soil environment when the soil environment is changed.The distribution characteristics of elements in soil profiles of different provenances are different,and the potential risk of heavy metals in soils in carbonate rock areas may be higher than that in non-carbonate rock areas.The contents of Cd in some rice samples exceeded the standard.In particular,the excess rate of Cd in rice seed in carbonate rock region reached 41.67%,higher than that in non-carbonate rock region.The Cd absorption prediction model of rice seed was established based on the influence factors of heavy metal migration and transformation.And the model fits well.In summary,although the heavy metal content in carbonate rocks is not high,it is relatively high in the soil with carbonate material sources.Moreover,the morphological distribution of heavy metals leads to a greater potential ecological risk in soils developed by carbonate rocks.Therefore,it is of great significance to pay attention to heavy metal accumulation in geological background to improve soil environmental quality and guarantee human health and safety.