沂蒙山区不同强降雨下土壤的氮素流失特征分析

为探讨不同自然强降雨氮素流失特征,实地观测沂蒙山区孟良崮小流域2010年汛期的降雨与径流过程,选取暴雨(汛期首场强降雨)、大雨(土壤水分相对饱和强降雨)和大暴雨(年最大雨强降雨)3场不同典型强降雨,分析降雨径流及氮素流失特征。结果表明,在首场暴雨条件下,除颗粒态氮外,其他形态氮含量在整个降雨过程中均呈现增加趋势;在大雨过程中,总氮含量在径流峰值前达到峰值,溶解态氮和硝态氮含量在径流峰值后达到峰值,并趋于稳定;在大暴雨条件下,总氮和颗粒态氮含量在径流峰值前浓度陡增到最大后迅速降低。总氮与颗粒态氮的流量加权质量浓度表现为大雨<暴雨<大暴雨,溶解态氮流失浓度百分比介于49.9265%～85.292%,且硝态氮在溶解态氮中占主导地位。不同形态氮和泥沙的平均流失率随着降雨强度的增强而增加,均表现为大暴雨>暴雨>大雨。该研究为沂蒙山区小流域水环境保护和非点源污染治理提供依据。

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.