Spatial and temporal variations in abundant and trace metal concentrations in coastal sediment from near Yim Tin Tsai, Tolo Harbour, Hong Kong

Abstract

Spatial and temporal variations in metal concentrations in near‐coastal surficial marine sediment from Yim Tin Tsai, Tolo Harbour, Hong Kong have been investigated over a two‐year period. The selected metals represented contributions from natural sources (Fe and Mn), biota (Ca), and anthropogenic sources (Cr, Cu, Zn) from three nearby study sites receiving different degrees of pollution. The trace metal concentrations in the sediment samples were consistent with the physical characteristics and activities at these three nearby but very different sites. The levels of Zn and in particular, Cu, were significantly greater than background levels at all sites. Interpretation focused upon the silt‐clay fraction showed that the elevated metal concentrations were found near a landfill, shipyard, industrial estate and urban centre. Metal concentrations within one of the sites, a typhoon shelter remained reasonably constant over a period of 2 years with the notable exception of Cu, presumably due to the use of antifouling paint. The concentrations of Fe found in the silt‐clay fraction of the sediment at the different sites lie within a narrow band so that this element may serve as an internal reference for assessing anthropogenic inputs of other trace metals. The precision of analysis of bulk sediment samples was found to be poor compared with that of the silt‐clay fraction, and more notably, the rank order of metal concentrations was found to differ, due to the predominant sand content of the samples.