Element remobilization, "internal P-loading," and sediment-P reactivity researched by DGT (diffusive gradients in thin films) technique

Abstract

Labile P, Fe, and sulfide with the high spatial resolution in sediment porewater of five sites (A-E) of Dianchi Lake (China) were measured at same locations using AgI/Chelex-100, Chelex-100, and ferrihydrite DGT (diffusive gradients in thin films) probes. DGT derived P/Fe/S concentrations in sediment porewater on millimeter or sub-millimeter scale in order to reveal the element remobilization process and the mechanism of "internal P-loading" of sediments in Dianchi Lake. Decomposition of alga biomass in the uppermost sediment layer and the reductive dissolution of Fe-bound P in the anoxic sediment were the two main processes causing P release. A dynamic numerical model-DIFS (DGT-induced flux in sediments) was used to assess sediment-P reactivity (capacity of solid pool and rate of transfer) and P release risk by kinetic parameter-T C (1089∼20,450 s), distribution coefficient-K d (167.09∼502.0 cm(3) g(-1)), resupply parameter-R (from 0.242 to 0.518), and changes of dissolved/sorbed concentration, R and M at the microzone of DGT/porewater/sediment.

Keywords: DGT (diffusive gradients in thin films); DIFS (DGT-induced fluxes in sediments); Sediment-P reactivity; “Internal P-loading”.