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Geogene Versus Anthropogene Origin of Trace Metals in Sediments in Cua Luc Estuary and Ha Long Bay, Vietnam |
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| Authors: | Huu Hieu Ho Rudy Swennen Valérie Cappuyns Elvira Vassilieva Gerda Neyens Mustafa Rajabali Tan Van Tran |
| Institution: | 1. Geology, Department of Earth and Environmental Sciences, KU Leuven, Heverlee-Leuven, Belgium 4. Vietnam Institute of Geosciences and Mineral Resources (VIGMR), Hanoi, Vietnam 3. Center for Economics and Corporate Sustainability, Hogeschool-Universiteit Brussel, Brussels, Belgium 2. Instituut voor Kern-en Stralingsfysica, KU Leuven, Heverlee-Leuven, Belgium |
| Abstract: | In the present study, the geochemistry of 49 surficial-bed and 101 core sediment samples is investigated to clarify the origin of trace metals in the Cua Luc Estuary and Ha Long Bay, which is a famous World Natural Heritage Site in Vietnam. Moreover, the potential mobility of trace metals is also assessed and their relationship with reference elements (Al, Fe, and Ca) and organic matter is established in order to make recommendations for sediment management and monitor future pollution. Generally, trace metals display higher concentrations in Ha Long Bay compared to the Cua Luc Estuary. However, this is controlled by the distribution of the fine (clay?+?silt) fraction, and hence the concentrations of Al, Fe, Ca, and organic matter (OM). The comparison of concentrations of trace metals (normalized towards Al) between the surficial sediments and the subsurface core sediments based on 137Cs datings indicates that almost all surficial-sediment data fall inside or deviate slightly from the 95 % prediction interval of a background regression line. In addition, as determined by a Community Bureau of Reference three-step extraction, trace metals mainly dominate in the residual fraction (assumed to relate to crystal lattice of primary and secondary minerals), and this fraction does not change much in recent sediment layers. Therefore, trace metals are supposed to be derived from natural bio/geochemical processes and are characterized by a low potential mobility. Consequently, the established linear regression relationships of trace metal vs. Al or multiple regression relationships of trace metal vs. multi-elements (Al, Fe, Ca, and OM) are useful for the prediction of background levels of trace metals in sediments in future pollution monitoring and assessment programs. |
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