坡面氮、磷流失特征分析及预测

Analysis and prediction of nitrogen and phosphorous losses from slope surface

利用室内人工降雨系统和大型可变坡土槽,模拟了裸土坡地在不同的初始土壤营养物质量分数、径流量、坡度及植被覆盖率下的产污过程,分析了典型降雨过程中氮、磷质量浓度随时间的变化过程以及径流中营养物质的流失规律.结果表明:径流中氮、磷质量浓度受表层土壤营养物的质量分数影响很大;氮、磷质量浓度在产流初期迅速下降,随后下降速度趋于平稳;在多数情况下,径流中硝酸盐氮的质量浓度高于氨氮质量浓度,亚硝酸盐氮的质量浓度很低.在物理机理研究的基础上提出了氮、磷的污染负荷模型.

By use of artificial precipitation equipment and a large soil tank with changeable slope, the process of nonpoint pollution in uncovered slopes was simulated under different initial soil nutrient contents, runoff, slopes and plant coverage ratios. The dynamic variation of nitrogen and phosphorus concentrations with time in typical precipitation process and the law of nutrient losses in runoff were analyzed. The result shows that the nitrogen and phosphorous concentrations in runoff are greatly affected by mass fraction of nutrients in surface soil, and that the nitrogen and phosphorus concentrations decrease sharply at the initial stage of runoff generation, and then the rate of decrease approaches to a stable state. Under most circumstances, the concentration of nitrate-nitrogen in runoff is higher than that of ammonia- nitrogen, and the concentration of nitrite-nitrogen is relatively low. Finally, a mathematic model for estimating the amounts of nitrogen and phosphorus transfer was developed based on the study of physical mechanism.