Anthropogenic Fingerprint in Beibu Gulf (South China Sea) Sediments

Abstract

Xia, Z.; Waniek, J.J., and Leipe, T., 2013. Anthropogenic fingerprint in Beibu Gulf (South China Sea) sediments. In: Harff, J., Leipe, T., Waniek, J.J., and Zhou, D. (eds.), Depositional Environments and Multiple Forcing Factors at the South China Sea's Northern Shelf, Journal of Coastal Research, Special Issue, No. 66, pp. 72–90. Coconut Creek (Florida), ISSN 0749-0208.Surface sediments and five cores were chosen to determine grain size, geochemical elements, heavy metals concentrations and age using 14C dating to study sedimentary environment and anthropogenic impact in the Beibu Gulf (South China Sea). The grain size analysis shows differences in the depositional environment amongst the subareas of the gulf. In the north of the gulf, the depositional environment is strong and unstable with complicated hydrodynamics because of the combined influence of rivers, tide, littoral current and the monsoon. In the central part, the depositional environment is weaker and stable, whereas in the south of the gulf (at the entrance), the deposition is higher and influenced mainly by tide. The deposition rate is around 0.3 mm/yr based on 14C dating. The geochemical element analysis indicates different sediment sources in different subareas of the gulf and possible influence of a biogenic source. The terrigenous elements (Al, Fe, Li, Ti, K and Zr) have high positive correlation coefficients, and originate from the northern coast and Hainan Island. The trace elements are mostly enriched within the fine sediments. The enrichment factors (EF) and cultural enrichment factors (CEF) based on aluminum and titanium show that total organic carbon (TOC), As and Hg have high concentrations in the surficial sediments in the north (9.92 mg/kg and 34 μg/kg) and the south (15.5 mg/kg and 22 μg/kg) of the gulf, and are enriched below the surface. Despite the regional differences in heavy metal concentrations in surface sediments, no anthropogenic impact was observed in the center of the gulf according to the results of EF and CEF using the core data. Measured concentrations of the anthropogenic elements were below the evaluation criterion values of the National Standards of GB18668-2002, P. R. China indicating low anthropogenic impact in the entire gulf.