Typical urban gully nitrogen migration in Changchun City, China.

In this study, Yitong River, which is located in Changchun, a representative city in northeastern China, was selected as the research area. Using position monitoring and field measurements, we quantitatively investigated the migration path and flux of nitrogen in a gully region in Changchun City undergoing rapid urbanization. The results showed that at the Yitong River subwatershed, the total nitrogen input flux was 188 kg/hm(2), the degree of which can be ranked in descending order as fertilizer input > biological immobilization > feed > atmospheric deposition. The total nitrogen output flux was 102.5 kg/hm(2), ranked in descending degree as products > waste output > denitrification > surface runoff. The net nitrogen storage was 85.5 kg/hm(2). The migration path and flux of nitrogen were markedly impacted by human activities, showing an imbalance between input and output, as well as a tendency toward nitrogen accumulation and pollution. The nitrogen budget for the Yitong River subwatershed suggested that more than 50 % of the net anthropogenic nitrogen input was lost to the environment, and about 14.5 % was discharged in rivers, indicating that agricultural and human activities in the basin substantially impact the river water quality and thus alter the nitrogen environmental geochemistry. Reducing the application and improving the efficiency of nitrogenous fertilizer use as well as reclaiming human life waste are efficient approaches to decreasing the nitrogen input flux and environmental accumulation and to promoting the balance between nitrogen input and output. These practices are also effective approaches to reducing non-point source pollution.