Characteristics of soil nitrogen loss under different intense rainfalls in Yimeng mountainous area

In order to analyze the loss characteristics of different forms of nitrogen under different natural rainfall intensities,a fixed-point experiment was conducted in Meng Lianggu basin, a typical watershed in the area of YiHe upstream located in Yimeng Mountainous area. The processes of rainfall and runoff in 2010 were observed and three typical rainfall events including the first rainstorm, a heavy rain and a heavy rainstorm were selected. Results showed that different forms of nitrogen contents presented the same increasing tend except for particulate nitrogen during the first rainstorm event of the flood season. In the heavy rain process,total nitrogen content reached the maximum before the runoff peak and dissolved nitrogen and then dissolved nitrate nitrogen contents reached the maximum. During the heavy rainstorm, total nitrogen and particulate nitrogen contents reached rapidly the maximum before the runoff peak and then declined quickly. The discharge weighted concentration of total nitrogen and particulate nitrogen increased with the rainfall intensity in the order of heavy rainrainstorm>heavy rain. The research could provide a basis for the protection of water environment and the control of non-point pollution of typical watersheds in Yimeng Mountainous area.