Partitioning of heavy metals in the surface sediments of Quanzhou Bay wetland and its a availability to Suaeda australis

摘要

In order to investigate distributions of heavy metal pollution in Quanzhou Bay wetland, the total concentration and chemical partitioning of a number of heavy metals (Cu, Zn, Cd, Pb, Cr, Hg) in sediments of three sampling sites of Quanzhou Bay wetland and their availability to Suaeda austrdis were analyzed. The Geoaccumulation Index (I_(geo)) values reveal that the sediments of three sampling sites may all be considered as moderately contaminated for Pb and Zn, and all sediments might be strongly contaminated with cadmium. The partitioning analyses revealed the measured heavy metals in three sites are bound to the exchangeable fraction at lower concentrations. The measured metals in a considerable amount are bound to the reducible and oxidizable fractions, and a high proportion of the measured heavy metals were distributed in the residual fraction in the sediment samples. The concentrations of Cd in each chemical phase extracted from the sediments are above natural global background levels and should be further investigated because of its toxicity. Suaeda austrdis has different accumulation abilities for the measured heavy metals. For the root and stem, the bioaccumulation ability assessed by bioaccumulation factor (BAF) for the measured heavy metals follows the decreasing order as: Cu>Cr> Zn>Cd, Pb, Hg. In the leaf, stronger bioaccumulation ability for Hg is exhibited. The heavy metal concentrations in Suaeda austrdis roots have positive correlations with their available fractions, while the exchangeable fraction of Cu and Cd might have be more important to both mature plant roots and seedling roots uptake than other fractions; as for Cr, the oxidizable fraction might make a greater contribution to the plant root uptake; as for Zn, the reducible fraction might make so contribution ; and for Pb, the oxidizable fraction might make a significant contribution to the mature plant root uptake, however, the exchangeable fraction might have a significant contribution to the seedling root uptake.