Geochemical behavior of metals–sulfide–phosphorus at SWI (sediment/water interface) assessed by DGT (Diffusive gradients in thin films) probes

Abstract

Element profiles/images in sediment porewater at five sites of Dianchi Lake (China) were measured by AgI/Chelex-100, ferrihydrite and Chelex-100 DGT (Diffusive gradients in thin films) probes for labile sulfide, metals and P. Based on DGT profiles, remobilization character and geochemical behavior of multi-elements at fine scale were assessed. Fe remobilization characters at five sites indicated the distinct Fe-reduction process. The correspondence of Fe and Cu/Al/Zn, and good linear correlation in profiles verified the co-release of them by Fe-redox process in some sites. The reduction of Fe (III) hydroxyoxide caused P-release from Fe-bound P in anoxic sediment and “internal P loading” character, which has been verified by the linear correlation (R=0.77) in the whole DGT-profiles of Fe/P and the co-existence of Fe/P peaks at same depths. The peak flux (1.13×10−6–1.10×10−5μgcm−2s−1), niche area (3.6×10−5–6.0×10−2cm2), circularity (0.204–1.0) and RJM (4.02–6.62%) derived by CID (computer image densitometry) have revealed the existence of sulfide microniche in sediments.