Anthropogenic point-source and non-point-source nitrogen inputs intoHuai River basin and their impacts on riverine ammonia–nitrogen flux

[摘要] This study provides a new approach to estimate both anthropogenic non-point-source and point-source nitrogen (N) inputs to the landscape, and determinestheir impacts on riverine ammonia–nitrogen (AN) flux, providing a foundationfor further exploration of anthropogenic effects on N pollution. Our studysite is Huai River basin of China, a water–shed with one of the highest levelsof N input in the world. Multi-year average (2003–2010) inputs of N to thewatershed are 27 200 ± 1100 kg N km⁻² yr⁻¹. Non-pointsources comprised about 98 % of total N input, and only 2 % of inputsare directly added to the aquatic ecosystem as point sources. Fertilizerapplication was the largest non-point source of new N to the Huai River basin(69 % of net anthropogenic N inputs), followed by atmospheric deposition(20 %), N fixation in croplands (7 %), and N content of imported foodand feed (2 %). High N inputs showed impacts on riverine AN flux:fertilizer application, point-source N input, and atmospheric N depositionwere proved as more direct sources to riverine AN flux. Modes of N deliveryand losses associated with biological denitrification in rivers, waterconsumption, interception by dams may influence the extent of export ofriverine AN flux from N sources. Our findings highlight the importance ofanthropogenic N inputs from both point sources and non-point sources inheavily polluted watersheds, and provide some implications for AN predictionand management.

[学科分类] 地球化学与岩石