In situ and combined variations of phosphorus, iron and sulfur across the sediment-water interface of Lake Luoma

This study firstly obtained 8 typical profiles of labile phosphorus (P), iron (Fe), and sulfur (S) in the sediments of Lake Luoma using the in situ, diffusive gradients in thin films (DGT) technology, and then quantitatively calculated the combined fluxes of P, Fe and S across the sediment-water interfaces (SWI). Our results demonstrated that highly heterogeneous distributions of DGT-measured labile P, Fe and S in the sediment profiles, with the concentration ranges from 0 to 2.05mg/L, 0 to 11.10mg/L and 0.01 to 0.63mg/L, respectively. Generally, the concentrations of labile P and Fe in the northwest lake area were higher than those in the southeast lake area, while the variations of labile S showed no significant regularity. For all the profiles collected, the variations of labile P, Fe, and S exhibited a similar shape reflected by downward increases in concentration with sediment depth, and appear concentration peaks were observed within 60mm depth. Moreover, there was a significant positive correlation(r>0.65, P2•d), 1.671~5.592mg/(m2•d) and 0.007~0.071mg/(m2•d), respectively, indicating that P, Fe and S of Lake Luoma were released from sediments to water. It may increase the risk of water pollution during the South-to-North Water Diversion and accordingly should be taken seriously. The above results supported the coupled release mechanism of P and Fe, and clarified the migration characteristics of active P, Fe and S in SWI of Lake Luoma, providing reference and theoretical basis for water quality control of Luoma Lake. © 2021, Editorial Board of China Environmental Science. All right reserved.