Transfer Mechanism, Uptake Kinetic Process, and Bioavailability of P, Cu, Cd, Pb, and Zn in Macrophyte Rhizosphere Using Diffusive Gradients in Thin Films

The transfer-uptake-bioavailability of phosphorus (P), Cu, Cd, Zn, and Pb in rhizosphere of Zizania latifolia (ZL) and Myriophyllum verticiilaturn (MV) cultivated in rhizoboxes in Lake Erhai (China) is evaluated by DGT (diffusive gradients in thin films) technique. DGT induced fluxes in sediments (DIPS) model reveals that resupply ability (r), liable pool size in sediment solid (kd), kinetic parameter (k(-1)), or response time (T-c) control the diffusion-resupply characters of P and Cu (standing for four metals) in rhizosphere interface. The linear fitting curves of element content in ZL or MV roots(C-root) against DGT (C-DGT), porewater (C-o), or sediment concentration demonstrate that coo, for five elements can be predicted by C-DGT more effectively than the other methods. (I) DOC (dissolved organic carbon) in porewater controlled by OM (organic matter) in solid plus pH for Cu and Cd or (II) DOP/DTP ratio in porewater (between dissolved organic P and dissolved total P) for P controlled by Fe bound P and OM in solid, can affect phytoavailability in rhizosphere. They lead to (I) the larger slope (s) and the linear regression coefficient (122) in the first part than those for the complete fitting curve (ZL or MV root against C-DGT(Cu) or Co(Cu) and MV root against C-DGT(Cd)) or (II) the outliers above or below the fitting curve (ZL root (P) against C-0(P) or C-DGT(P)) and the larger R-2 without outliers. DGT rhizobox DIFS should be a reliable tool to research phytoremediation mechanism of macrophytes.