Spatial distribution and contamination evaluation of heavy metals in the intertidal surface sediments of Eastern Chongming

Using the ArcGIS geostatistical analysis module, this work investigated the spatial distribution pattern of heavy metals (Cu, Pb, Zn, Cr, Cd) and their deposition fluxes in the intertidal surface sediments of Eastern Chongming based on the analysis of grain size, heavy metal concentrations and organic carbon content. The spatial interpolation (Kriging) was performed to estimate the deposition fluxes, and the contamination status of heavy metals was evaluated using geoaccumulation index and potential ecological risk index. The results showed that the average contents of Cu, Pb, Zn, Cr and Cd were 42, 27, 69, 71 and 0.23 μg·g^-1, respectively, all of which exceeded the background value in the Shanghai tidal flat. The contents of heavy metals showed a landward as well as northward increasing trend due to the influences of sediment grain size and organic carbon content. The annual deposition of Cu, Pb, Zn, Cr and Cd in Eastern Chongming were 187, 121, 395, 312 and 1.04 t, respectively; the total deposition flux of these heavy metals was 11 g·(m²·a)^-1. Although the overall contamination level of heavy metals in Eastern Chongming was relatively low, Cd, Pb and Cu had a potential pollution threat to the sediment environment.