北运河下游灌区不同土地利用方式非点源氮素输出规律

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3...

Dissolved nitrogen runoff from different land use types in the downstream irrigation area of the Beiyunhe River Basin

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 of 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, NH4+-N and NO3--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 was organic N in forest land, NH4+-N in farmland, and organic N and NO3--N in 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 village>forestland>farmland. Overall the dissolved N runoff losses varied among farmland, forestland and village, and the export concentration from village was the highest.