Speciation of heavy metals in marine sediments from the East China Sea by ICP-MS with sequential extraction Chun-gang Yuan, Jian-bo Shi, Bin He, Jing-fu Liu, Li-na Liang, Gui-bin Jiang * Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, 100085 Beijing, China Received 12 September 2003; accepted 12 January 2004 Abstract Twelve elements (V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Sn, Cd and Pb) in 24 sediment samples at eight sites (S1–S8) from the East China Sea were analyzed with the BCR sequential extraction (SE) protocol to obtain the metal distribution patterns in this region. The results showed that the heavy metal pollutions in S4 and S8 were more severe than in other sampling sites, especially Cd and Pb pollution. In the top sediments at S4 and S8, both the total contents and the most dangerous non-residual fractions of Cd and Pb were extremely high. More than 90% of the total concentrations of V, Cr, Mo and Sn existed in the residual fraction. Fe, Co, Ni, Cu and Zn mainly (more than 60%) occurred in the residual fraction. While Mn, Pb and Cd dominantly presented in the non-residual fractions in the top sediments. The metal distribution patterns with depth and the correlations between total organic carbon (TOC) and the total Fe – Mn content were also investigated. The results showed that, for most of the elements except Fe, the concentration of elements in fraction A in the top sediments was higher than that in other depth. The similar rule was also found in fraction B but not in fraction C. Besides, the distributions of V, Cd in fraction B and Pb, Cd, Cu in fraction C might be affected by TOC. D 2004 Elsevier Ltd. All rights reserved. Keywords: Speciation; Heavy metals; Sequential extraction; Marine sediments 1. Introduction Many negative effects have been done on human health by the environmental pollution of heavy metals. The remedia- tion of heavy metal pollution is often problematic due to their persistence and not degradability in the environment. As a sink and source, sediments constitute a reservoir of bioavail- able trace elements and play an important role in geochemical cycles. Much concern has been focused on the investigation of the total metal contents in sediments. However, it cannot provide sufficient information about mobility, bioavailability and toxicity of metals. Their properties depend not only on their total concentration but also on the physicochemical form they occur (Davidson et al., 1994), which has been described as ‘‘speciation’’ (Ure et al., 1993). Metals are distributed throughout sediment components and associated with them in various ways including ion exchange, adsorption, precipitation, and complexation. They are not permanently fixed by sediment. Changes in environ- ment conditions, such as acidification, redox potential or organic ligand concentrations, can cause mobilization of element from solid to liquid phase and cause contamination of surrounding waters. Sequential extraction (SE) (Tessier et al., 1979) can provide information about the identification of the main binding sites, the strength of metal binding to the partic- ulates and the phase associations of trace elements in sediment. This could help us to understand the geochemical processes governing heavy metal mobilization and potential risks induced. Among the sequential extraction schemes proposed to investigate the distribution of heavy metals in soil and sediment, the five-step and six-step extraction schemes developed by Tessier et al. (1979) and Kersten and Forstner (1986), respectively, were used most widely. Following these two basic schemes, some modified procedures with different sequences of reagents or operational conditions have been developed (Borovec et al., 1993; Campanella et al., 1995; Zdenek, 1996; Gomez Ariza et al., 2000). Considering the diversity of procedures and lack of uniformity in different 0160-4120/$ - see front matter D 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.envint.2004.01.001 * Corresponding author. Fax: +86-10-62849179. E-mail address: gbjiang@mail.rcees.ac.cn (G. Jiang). www.elsevier.com/locate/envint Environment International 30 (2004) 769 – 783