Assessment of phosphorus pollution and phosphorus release mechanisms of sediment in the Tuojiang River, Southwest China

Abstract

Study regionThe study region was the Tuojiang River, a tributary of the upper Yangtze River. Study focusSediment phosphorus (P) release remains unclear in the Tuojiang River in Southwest China. The sediments were collected from the upper, middle, and lower reaches of the Tuojiang River in this study. The potential of sediment P release (percentage saturation of zero equilibrium P concentration, EPCsat) was determined by isotherm experiments. The influential factors and mechanisms on sediment P release were explored. New hydrological insights for the regionThe sediment mainly acted as a source to release P. Phosphorus bound by Fe oxides (Fe-P), organic matter (OM), water temperature (T), and the P content originally adsorbed on sediment (Q0) were the most influential factors on the EPCsat. The pH, T, or disturbance had the greatest effect on the content of exchangeable P (Ex-P), organic P (Org-P), and Fe-P. FeCl3 has an inhibitory effect on sediment P release. Fe-P mainly participates in the sediment P release process. The release kinetics were well fitted to the pseudo-second-order model. These results obtained could help to understanding the P pollution status of sediment, improve our knowledge of the sediment P release mechanisms and provide significant information for further management of P pollution in sediment.