降雨强度对黄土坡面矿质氮素流失的影响

Impact of rainfall intensity on soil mineral nitrogen loss by runoff on loess slope

利用室内模拟降雨试验,研究了黄土区土壤矿质氮素随地表径流迁移流失和入渗的动态变化,初步探讨了径流与土壤矿质氮素的作用深度EDI,并提出了EDI深度的确定方法。结果表明:土壤矿质氮素流失是降雨、径流与表层土壤矿质氮素作用的结果,随径流流失量显著高于随泥沙流失量,地表产流过程径流养分浓度呈现高—低—较高变化;降雨(降雨强度)和径流是土壤溶质迁移的动力,对土壤矿质氮素随径流流失和入渗有着重要影响。雨强增大,土壤矿质氮素流失量、径流作用深度(EDI)和土壤硝态氮入渗锋值深度均增加;同一坡面不同坡位土壤NO-3-N与径流有效作用深度(EDI)和浓度锋值深度不同,坡中下部最深,坡顶部和坡底部较浅;土壤NO-3-N和土壤NH+4-N入渗和再分布过程截然不同。

According to the result of simulated runoff experiment in laboratory, the dynamic movements of the mineral nitrogen's transport by surface runoff and leaching are studied. Meanwhile, the Effective Depth of Interaction (EDI) of runoff with soil mineral nitrogen is analyzed and confirmed. It is validated that the process of soil nitrogen loss by erosion is restricted by interaction of soil nitrogen with rainfall and runoff. There are much more soil mineral nitrogen loss by runoff than that by sediment. The concentration of soil mineral nitrogen loss in runoff wavelike changes, firstly achieving peak value, then gradually descending and increasing again after the rainfall ceased. Runoff and rainfall intensity are considered as the important drivers for the mineral nitrogen's transport in surface runoff and leaching. The more the rainfall intensity is, the more the amount of soil nitrogen loss by erosion, the depth of peak value of soil NO^-_3-N concentration and the EDI. The observations of the temporal and spatial distribution of mineral nitrogen on the loess slope show, that there are different spatial distribution of the soil NO^-_3-N and the EDI, deepest in the middle and lower parts of the slope land, while shallower in the upper and bottom parts. It is proved that the infiltrating processes between soil NH^+_4-N and NO^-_3-N after the rainfall are distinct different.