Heavy Metal Pollution Of Intertidal Sediment In Huangpu River And The Influence Of Biological Disturbance

This paper studied the distribution characteristics of intertidal benthic community, heavy metals pollution based on the sampling work in Huangpu River intertidal sediments during July to September in 2014, January to March in 2015. Moreover, this paper also studied the effect of bioturbation on Hg in sediments the most polluted area i.e. estuary. Through intensive sampling, indoor experiment and measurement, main findings are:(1) The contents of heavy metal elements (except for As) in most samples exceeded the background value of Shanghai soil and Shanghai tidal flat, with large disparities in different samples. The content of heavy metal pollution in the upper reaches was relatively low, while the urbanized area, the Wujing district and the estuary were differently polluted. According to the accumulate evaluation method, the heavy metal pollution ranking from high to low with Hg> Zn> Cr> Cu> Cd> Pb> As.(2) The correlation analyses between the heavy metals in sediments and the environment factors showed that, Pb and Zn were significantly positive correlated; Zn and Cu were significantly positive correlated; As was significantly positive correlated with TOC and organic matter.(3) This survey collected 13 species of intertidal benthic community. The species diversity declined from upstream to downstream. The dominant species were with significant difference among the four sections, the dominant species in upper reaches are Diptera, Limnodrilus hoffmeisteri, Neanthes japonica and Dentinephtys; mid-reaches’ were Diptera, Limnodrilus hoffmeisteri, Dentinephtys and Corbicula fluminea; the estuary’s were Branchiura sowerbyi Beddard, Limnodrilus hoffmeisteri. The oligochaete who were stain resistant held the high dominance.(4) Bioturbation could significantly promote the release of TN and TP from sediment to the overlying water. The larger density of limnodrilus, the higher release intensity was. Within a certain range, the increase of temperature could enhance the bioturbation effect on pollutant release; with the passage of time, Hg in sediments would migrate and release to interstitial water and overlying water; through the perturbation of limnodrilus, it would not only enable Hg release to the water, but also enrich the content of Hg in limnodrilus.The correlation analyses between Hg and TN TP showed that, TN in overlying waters and Hg in the sadiments were significantly positive correlated; TN in overlying waters and Hg in interstitial waters were significantly positive correlated.