On The Distribution, Speciation And Bioavailability Of Heavy Metals In The Soils At Xiang'an, Xiamen, China

Heavy metals in soils have been received increasing attention due primarily to their potential environmental and ecological consequences. This is particularly true in China and issues related to soil metals have been emerging along with the rapid social and economic development during the past 30 years. Xiang'an, a district of Xiamen is a primary base of agricultural production with protected farmlands. This study is sought to assess the current status of heavy metals in this important region by investigations of their contents, speciation and potential risk assessment.Based on the bulk concentrations of heavy metals in soils at Xiang'an measured in 2005 and their comparison with the national census data of soils monitored in 1990, we observed an increase in soil metal concentrations during the past 15 years. Overall, the quality of soils in terms of heavy metals is relatively good, at second-level by the national standard of environmental quality.Data from soil columns reveal that heavy metals assemble in the top layers of the soil. The concentration gradually declines with depth. Taking into account the key indexes of socio-economic development in Xiamen, we reason that three major multi-dimensional factors such as human lives, secondary industry, automobile circulation and agricultural production have affected the distribution of heavy metals in soils at Xiang'an. At the same time, we examined the spatial variation and the controls of five species of heavy metals in the soils at Xiang'an.We also evaluated the latent ecological hazard and health risk of heavy metals in soils at Xiang'an, which appears that Xiang'an is at the medium level ecological hazard. The reference value of health risk of heavy metals in surface soils at Xiang'an is in the fist-level of national request, but the measured value is higher than the reference value, which has certain latent health risk. Moreover, through regression equation fitting of the concentrations of heavy metals in 3 typical crops (carrot, cauliflower and pachyrhizus) and the concentrations of different species of heavy metals in soils at Xiang'an, we obtained the correlation of 5 different species of heavy metals in the soils and the concentrations of heavy metals in 3 typical crops.