Distribution and contamination status of heavy metals in estuarine sediments near Cua Ong Harbor, Ha Long Bay, Vietnam
Vietnam Institute of Geosciences and Mineral Resources (VIGMR), Thanhxuan, Hanoi, Vietnam. E-mail: hohuuhieu@yahoo.com [Corresponding author]
Department of Earth and Environmental Sciences, Catholic University of Leuven (K.U. Leuven), Celestijnenlaan 200E, B-3001 Leuven-Heverlee, Belgium. E-mail: Rudy.Swennen@ees.kuleuven.be
Department of Earth and Environmental Sciences, Catholic University of Leuven (K.U. Leuven), Celestijnenlaan 200E, B-3001 Leuven-Heverlee, Belgium. E-mail: An.VanDamme@ees.kuleuven.be
Abstract
The distribution, controlling geochemical factors and contamination status of heavy metals in estuarine sediments near Cua Ong Habor, Ha Long Bay (Vietnam) were investigated. 36 surface sediment samples were collected and analyzed for major elements (Al, Ca, Fe, K, Mg, S), heavy metals (As, Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn), organic matter, loss on ignition (LOI), grain size composition and pH. Spatial distribution patterns of heavy metals as well as their controlling factors were elucidated based on geochemical mapping and statistical methods such as the Pearson Product-Moment linear correlation and Factor Analysis. The results illustrated that the distribution patterns of As, Cd, Cr, Cu, Ni, Pb and Zn are mainly controlled by organic matter and clay minerals and determined by the distribution of the fine-grained fraction (Φ < 63 µm) in the sediments. In contrast, Fe and Mn compounds seem to exert some control on the distribution of Co. Carbonates partly control the distribution of Mn, but are not important with respect to the other studied heavy metals. The contamination status by heavy metals was assessed based on comparison with Canadian, Wisconsin- United States and Flemish numerical Sediment Quality Guidelines, and calculation of Geo-accumulation Index (Igeo) and Enrichment Factor (EF). The results indicated that natural processes such as weathering and erosion of bedrock are the main supply sources of heavy metals in sediments near Cua Ong Harbor. Among the studied heavy metals, only As is of concern whereas Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn seem to reflect their background concentrations in sediments of Ha Long Bay.