Effects of temperature on phosphorus release in sediments of Hongfeng Lake, southwest China: an experimental study using diffusive gradients in thin-films (DGT) technique

Abstract

The effects of temperature on phosphorus (P) release in sediments of Hongfeng Lake, southwest China, were investigated under simulation condition. The distributions of labile P in sediments were measured in situ using a diffusive gradients in thin-films (DGT) technique (Zr-oxide DGT) at a two-dimensional, sub-millimeter spatial resolution. The changes of P fractions in sediments at different temperatures were also investigated using a chemical fractionation technique which divided sediment P into NH4Cl–P, BD–P, NaOH–P, HCl–P, and Residual P. The results showed that the concentrations of labile P in sediments increased rapidly as the simulating temperature increased, reflecting a rapid P release from sediments. The NaOH–P concentrations in sediments showed the greatest decrease (accounting for 79.3 % of total decrease) during the experiment, suggesting that the increase of labile P in sediments was mainly due to the transformation of NaOH–P. The release of HCl–P also occurred in sediments, increasing the labile P concentration in pore waters. The seasonal variation of temperature and its induced biological–chemical changes at the sediment–water interface (such as organic matter degradation, and respiration) might be an important factor affecting the P release in sediments of Hongfeng Lake. Our results provide new information for illuminating P biogeochemical cycling processes at the interface in eutrophic lakes.