Phosphorus speciation in the runoff from different land uses in the Liuchahe watershed by Chaohu Lake
六叉河小流域不同景观结构中径流磷形态差异分析

Runoff from the Liuchahe watershed, a typical agricultural watershed characteristic by many Multipond Systems in Southeast China, was evaluated for phosphorus speciation by land use. The runoff from farmland, paddy rice fields and the Liuchahe River was selected for study. Total phosphorus (TP), total dissolved phosphorus (TDP), total particulate phosphorus (TPP), total reactive phosphorus (TRP), particulate reactive phosphorus (PRP) and dissolved reactive phosphorus (DRP) were monitored in the runoff. TP was the highest in the runoff from farmland, while it was the lowest in the river, as was other forms of phosphorus except DRP. Particulate phosphorus was the main form of phosphorus in the farmland runoff, with TPP/TP ratios from 80% to 90%. During the transportation from farmland to paddy rice field and riverway, both the concentration and forms of phosphorus were changed, and particulate phosphorus decreased significantly. As a sink structure of the watershed, the river had better water quality, with TP under 0.4 mg·L-1 and the main component was dissolved phosphorus. The results suggest that the Multipond System in the Liuchahe watershed decreases not only total phosphorus, but also the reactive component, which is important in controlling nonpoint source pollution and protecting the water quality of Chaohu Lake.