Spatial distribution of gut juice extractable Cu, Pb and Zn in sediments from the Pearl River Estuary, Southern China

In this study, we compared the spatial distribution of total metals (Cu, Pb, and Zn) and bioaccessible metals, which were quantified by incubating sediments with the digestive fluid of sipunculans Sipunculus nudus, in natural sediments of the Pearl River Estuary (PRE). The spatial distribution of bioaccessible metal was not the same as that of total metals in PRE sediments, which were mainly controlled by fine-grained size, total organic carbon (TOC) and Fe. Geochemical factors were important in interpreting this different spatial variation. The similar spatial variations of bioaccessible Cu and total Cu were related to TOC in PRE sediments. Differently from the total Zn, a higher bioaccessible Zn was detected near the West Channel of PRE because of a lower TOC. However, the distribution of bioaccessible Pb was not significantly related to any sediment geochemistry. This study provides a more accurate view of metal pollution in the PRE natural sediments.

► The first quantification of bioaccessible metal in PRE sediment using in vitro method.
► The spatial variation of bioaccessible metal was different from that of total metal.
► The bioaccessible Cu was affected by the total Cu and TOC.
► The higher bioaccessible Zn was detected because of the lower TOC.
► Higher level of Pb in the gut juice led to notable sorption of Pb onto the sediment.