中文摘要：

通过对北运河下游灌区3种土地利用方式（农田、林地和村庄）进行降雨径流水质监测,分析了不同土地利用方式地表径流溶解态氮素的流失情况.结果表明,林地总氮浓度最低,为3.14mg·L^-1;农田较高,为12.68mg·L^-1;村庄最高,为17.81mg·L^-1.氮主要以有机氮、铵氮、硝态氮这3种形态流失,流失比例分别为33.6%、28.9%、35.0%.其中,林地氮流失方式以有机氮和铵氮为主,农田和村庄以有机氮和硝态氮为主;不同土地利用方式的含氮化合物流失浓度随产流时间变化规律基本一致,均为双峰型.对村庄而言,产流前期氮素流失以无机态氮为主,后期有机态氮流失比重上升,农田和林地由于受植被吸收、拦截等的影响,其规律表征不明显;此外,3种土地利用方式均存在初期冲刷效应,村庄最为显著,林地次之,农田不明显.该监测区3种土地利用方式氮素输出规律差异大,村庄输出浓度最高.

英文摘要：

Runoff is the most important path way of the non-point source nitrogen（N） pollution.In this study,we investigated runoff characteristics of different dissolved nitrogen species from three land use types,farmland,forest and village,in the downstream irrigation area of the Beiyunhe River Basin.The results showed significant variation in dissolved N export from different land use types.The event mean concentrations（EMC） of total dissolved N in forestland,farmland and village were 3.14 mg · L^-1,12.68 mg · L^-1 and 17.81 mg · L^-1,respectively.Organic N,NH＋4-N and NO-3-N were the dominant species of dissolved N,accounting for 33.6%,28.9% and 35.0% of the total dissolved N,respectively.The N species with high proportion in the total dissolved N were organic N and NH＋4-N in forest land,organic N and NO-3-N in both farmland and village.The temporal variations of dissolved N concentrations in runoff water were similar in the three land use types.In the village,inorganic N was the dominant species of the dissolved N in the earlier stage of runoff and then the proportion of organic N was increasing.The dissolved N loss from farmland and forestland did not show a clear corresponding pattern with that of runoff due to the buffer of runoff and possible impacts of the N absorption and retention of vegetation.First-flush of dissolved N was obvious in all three land use types with the rank of villageforestlandfarmland.Overall the dissolved N runoff losses varied among farmland,forestland and village,and the export concentration from village was the highest.