Abstract
Coastal sediments not only contain a majority of trace metals, but they also act as a source of dissolved metal ions to the overlying water column. Distinguishing the level of trace metal enrichment from the natural input in sediments is therefore important to determine the distribution and sources of land-derived detritus and pollutants in the coastal region. This study investigates fine (2) for As, Cd and Pb, suggesting that the sediments were likely enriched by these elements. A comparative study of trace metals concentrations and EF with other coastal regions of China however revealed that the study area is in a pristine environmental condition compared to other coastal regions of eastern China. Factor analysis identified three dominant sedimentological and geochemical associations, accounting for ~70% of total variance recognize terrigenous input, heavy mineral role and anthropogenic input in controlling the distribution of most elements in the study area.
Highlights
Sediments are the major product of chemical and physical weathering that largely exported to the ocean marginal depocenters such as estuaries and coastal regions by rivers roughly on daily to seasonal basis (Milliman and Syvitski, 1992; Meybeck et al, 2003; Syvitski and Milliman, 2007)
Ratios of major elements to Al as well as the calculation of chemical index of alteration (CIA) and chemical index of weathering (CIW) suggest that the surface sediments off northwest coast of Hainan Island were derived mainly from physical erosion and/or chemical weathering of rocks from the surrounding landmasses
Enrichment factors for trace metals with respect to average shale and UCYC reference compositions reveal higher enrichment factor (EF) (>2) for Pb, pointing that the sediments in the study area are slightly contaminated by Pb
Summary
Sediments are the major product of chemical and physical weathering that largely exported to the ocean marginal depocenters such as estuaries and coastal regions by rivers roughly on daily to seasonal basis (Milliman and Syvitski, 1992; Meybeck et al, 2003; Syvitski and Milliman, 2007) These sediments are a mixture of inorganic and organic material, consisting dominantly of solid particulate matter (detritus) or have been incorporated into the sediments from solution (non-detrital) in a number of pathways, but a combination of varying proportions of both in general (Loring, 1991; Loring and Rantala, 1992; Selvaraj et al, 2004, 2010). A critical evaluation of major and trace elemental characteristics of surface and core sediments from the offshore of southwestern Taiwan revealed that sediments were contaminated by few metals due to a non-point source and related biogeochemical changes (Chen and Selvaraj, 2008; Selvaraj et al, 2010)
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