Nitrogen budget in the Changjiang River drainage area

• Published in: Chinese journal of oceanology and limnology Vol. 30; no. 4; pp. 654 - 667
• Main Author: 江涛 俞志明 宋秀贤 曹西华
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer-Verlag 01.07.2012; SP Science Press; Springer Nature B.V
• Subjects: Agrochemicals; Animal wastes; Basins; Brackish; Chemistry; Crop residues; crops; Deposition; Downstream; Drainage; Drainage area; Drainage basins; Dry deposition; Earth and Environmental Science; Earth Sciences; Estuaries; Estuarine dynamics; Eutrophication; Excreta; Fertilizers; Freshwater; Headwaters; Human impact; Human influences; Human wastes; humans; Industrial wastes; Industrial wastewater; Marine; Nitrogen; nitrogen content; nitrogen fertilizers; Oceanography; Rivers; Rural areas; Sewage; Upstream; Wastes; Wastewater; Watersheds; 上游流域; 人类活动干扰; 弹道跟踪; 氮输入; 流域面积; 长江口; 长江流域; 预算; Changjiang River; China, People's Rep., Jinsha R; INW, China, People's Rep., Changjiang Delta; INW, China, People's Rep., Changjiang Estuary; China, People's Rep., Changjiang R; nitrogen budget; riverine nitrogen transport; eutrophication; Changjiang (Yangtze) River drainage area
• ISSN: 0254-4059; 2096-5508; 1993-5005; 2523-3521
• DOI: 10.1007/s00343-012-1306-5

We established a budget model of nitrogen （N） inputs and outputs between watersheds and waterbodies to determine the sources of riverine N in the Changjiang （Yangtze） River drainage area. Nitrogen inputs in the budget included N from synthetic fertilizer, biological fixation by leguminous and other crops, wet/dry atmospheric deposition, excreta from humans and animals, and crop residues. The total N input was estimated to be 17.6 Tg, of which 20% or 3.5 Tg N was transported into waterbodies. Of the total N transported into waterbodies, the largest proportion was N from animal waste （26%）, followed by N from atmospheric wet/dry deposition （25%）, synthetic fertilizer N （17%）, N in sewage wastes （17%）, N in human waste from rural areas （6%） and industrial wastewater N （9%）. We studied the spatial patterns of N inputs and outputs by dividing the Changjiang River drainage area into four sub-basins, from upstream to downstream： the Tongtian River drainage area （TTD, the headwater drainage area, 138 000 l~n2, less disturbed by human activities）; the Jinsha River drainage area （JSD, 347 000 km2, less disturbed by human activities, approx. 3 500 km upstream of the Changjiang estuary）; the Pingshan-Yichang drainage area （PYD, 520 500 krn2, large-scale human disturbance, about 2 000 km upstream of the Changjiang estuary）; and the Yichang-Datong drainage area （YDD, 699 900 km^2, large-scale httman disturbance, approx. 620 km upstream of the Changjiang estuary）. The average N input into waterbodies was 2.3, 7.3, 24.1, and 28.2 kg N/ha in the TTD, JSD, PYD, and YDD sub-basins, respectively, suggesting an increase of N-components of more than 10 times from upstream to downstream areas.