[Comparision of Ecological Risk Assessment Based on the Total Amount and Speciation Distribution of Heavy Metals in Soil:A Case Study for Longyan City, Fujian Province].

A total of 110 topsoil samples and 61 crop samples along the Lantian-Yangdong Villages were collected in Shizhong, Longyan City. The total amount and speciation of heavy metals(Pb, Cd, As) in soil and crops were determined. The characteristics of the absorption of heavy metals by specific crops in the study area were analyzed, and a new method of risk assessment based on the heavy metal speciation and its bioavailability was established by statistical analysis. This new method was used to evaluate the soil ecological risk and to compare it with the traditional method of potential ecological risk index (RI). The results indicated that the Lantian-Yangdong Villages were located in an area where Pb, Cd, and As mainly originate from the natural soil parent material with weak human disturbance. There was no significant Pb or As pollution in the whole region. Cd was the main pollutant with low pollution intensity. Four types of biological components except for the residual form followed the order of Cd(53.28%) > Pb(43.28%) > As(30.71%). Correlation and regression analyses of total metal concentrations, heavy metal speciation, and crop uptake in the study area showed that the correlations between the total amount of heavy metals and the ion exchange state, carbonate state, and other active forms were low; the results even showed nonlinear relationships between those variables.The ion exchange state had the greatest effect on the absorption of Pb, Cd, and As by coix seed and rice. From the perspective of bioavailability, the new method based on the heavy metal speciation was more accurate than the traditional method based on the total amount of heavy metals.