Host: Abstracts of Annual Meeting of the Geochemical Society of Japan
Pages 113-
Baiyin district was well-known for its non-ferrous metals mining and smelting and has caused serious heavy metals (HMs) contamination to surrounding soil and sediment for a long-term range. In this study, the concentrations (Zn, Cu, Pb, Ni, Co, Cd, and Cr) and chemical fractions (main Zn and Cd) were analyzed in soil and sediments collected from Bainyin district.For soil, the mean concentrations of Zn, Cu, Pb, Ni, Co, Cd and Cr were 134.28, 62.88, 72.59, 23.5, 12.7, 4.99, and 60.8 mg kg-1, respectively. For Zn, Cu, Pb and Cd, an obvious decline was exhibited versus the results in 2012. However, Zn, Cu, and Pb still exceeded the background values and Cd was extremely contaminated. The contaminated area mainly focused on the mining and smelting regions and the sewage irrigation regions. As is well known, HMs mobility strongly depends on their chemical speciation in the environment. Zn was mainly present in soil samples as residue fraction. While for the farmland soil samples from sewage irrigation region, the percentages of unstable fractions increased. As for Cd, the bioavailable fractions were extremely high (over 90%) and have much higher ecological risk compared to other HMs. The sequential experiments showed that the chemical fractions were affected by environmental conditions, especially pH values, soil mineralogy, and TOC contents. From the present study, the concentrations of HMs in sediments along the Dongdagou stream were extremely high. But there were few researches on investigating the HMs contamination in sediments of the study area. The mean concentrations of the sewage stream sediments were the highest, versus about 30-200 times to the concentrations of the Yellow River sediment samples. Once the environment conditions and climate change, HMs in sediments will easily release and influence the groundwater and the irrigation water. Furthermore, as shown in the sequential extraction, one can see that both the available parts of Zn and Cd were over 80%, which suggesting high bioavailability and mobility in sediments. The HMs pollutions in sediments should be paid more attentions.
