Characteristics of Nitrogen and Phosphorus Losses and Runoff in a Typical Purple Soil Watershed in the Three Gorges Reservoir Area
Cao, R.-X.; Liu, J.; Deng, K.-K.; Xian, Y.; Wang, W.; Fang, F.; Ouyang, W.-J.; Guo, J.-S.
Huan Jing Ke Xue= Huanjing Kexue 40(12): 5330-5339
To understand the runoff pollution characteristics of the typical purple soil small watershed in the Three Gorges Reservoir (TGR), the rainfall-runoff duration under typical land use types of the Xinzheng watershed and the nitrogen (N) and phosphorus (P) concentrations in the outlet runoff of each catchment were dynamically monitored, and the loss rule of N and P in the rainfall runoff in the small watershed in the TGR was investigated and analyzed. The results showed that the losses of runoff N and P were 13.69 kg·(hm2·a)-1 and 1.50 kg·(hm2·a)-1, respectively. N and P in agricultural fertilizers and rainfall scouring were the main causes of runoff pollution in the Xinzheng watershed. The average concentration of total nitrogen (TN) and total phosphorus (TP) reached 10.05 mg·L-1 and 1.10 mg·L-1, far exceeding the occurrence standard of eutrophication, which should be cause for concern. The nitrate nitrogen (NN) and particulate phosphorus (PP) in the rainfall were 69.47 kg and 6.83 kg on August 15, 2010, accounting for 53.91% and 53.78% of TN and TP, respectively. The NN and AN were 6.68 kg and 5.61 kg, respectively, in the rainfall on August 26, 2010, accounting for 37.74% and 31.69% of TN and PP was 1.36 kg, accounting for 57.63% of TP, indicating that nitrogen loss was mainly through the soluble state, while phosphorus migration was dominated by particulate matter. Heavy rainfall in the Xinzheng watershed had a significant impact on the loss of nitrogen and phosphorus. This was related to the properties of purple soil, such as thin soil layer, frequent cultivation and relatively loose soil.