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Evaluation of heavy metal mobilization in creek sediment: Influence of RAC values and ambient environmental factors

Liang, Guannan, Zhang, Bo, Lin, Mao, Wu, Simiao, Hou, Hao, Zhang, Jia, Qian, Guangren, Huang, Xin, Zhou, Jizhi
The Science of the total environment 2017 v.607-608 pp. 1339-1347
acid volatile sulfides, arsenic, cadmium, carbon, chemical speciation, chromium, copper, environmental factors, heavy metals, iron, lead, manganese, mercury, nickel, organic compounds, risk, risk assessment, rivers, sediments, streams, sulfites, zinc, China
The risk assessment code (RAC) is a common method for assessing heavy metal (HM) mobility and their potential health risks, based on HM total concentration and chemical speciation. In this study, both the RAC and the influence of ambient environmental factors were investigated in a river sediment system. Sixty-eight sediment samples were collected from the main river system in Shanghai, China. The total concentration and chemical speciation of Cu, Zn, Ni, Pb, Cd, Cr, As, and Hg were determined in the samples. The influence of sediment environmental factors, such as acid-volatile sulfide (AVS), Fe & Mn, and total organic carbon (TOC), on total metal concentrations and speciation was also investigated. The relationship between the main environmental media and distribution of HMs was discussed using PCA and NMDS. The transfer-transformation behaviors of Pb, Ni, and Cr were mainly controlled by AVS and TOC while Zn, Cu, and Cd were influenced by Fe & Mn and TOC. The relationship between the RAC value of HM and environmental factors revealed that 7% of Cr, 23% of Ni, and 15% of Pb had a high risk of mobility at TOC values below 3.5% and sulfite contents below 10mmol/kg. In comparison, 29%, 10%, and 10% of Zn, Cu, and Cd, respectively, had a high risk of mobility at TOC<3.5% and Fe & Mn content >4×10⁵mg/kg. Evidently, the chemical fractions of HM had a strong dependence on the S, Fe, Mn, and organic compounds in the sediment. This study provides a promising pathway for the rapid evaluation of potential risks from HMs in river sediments.