【摘要】 通过研究长江流域 1 968～ 1 997年氮的输入、输出、平衡的生物地球化学循环 ,表明长江流域 1 997年氮的输入量、输出量和储存量分别为 1 0 .0× 1 0 9、 6.7× 1 0 9、和 3.5× 1 0 9kg,分别是 1 968年氮输入量、输出量和储存量的 4、 5和 3倍。在氮的输入中 ,1 977年以前 ,长江流域氮输入主要是生物固氮 ,年均固氮量约 1 .0× 1 0 9kg;而在 1 985年后 ,化学氮肥年均输入量约5 .0× 1 0 9kg,占总氮输入的 5 0 %以上。在氮的输出中 ,1 997年通过长江大通站水体中溶解态无机氮 ( DIN)的浓度和通量分别是 1 .60 mg/ L和 1 .40× 1 0 9kg,从 1 968年到 1 997年约增加了1 0倍 ;大约 2 5 %的氮输入通过长江输送到东海 ,约 33%的氮输入通过反硝化和氨挥发进入大气中 ,剩余 42 %的氮输入储存在流域内。研究发现 ,长江流域的氮输入量 ,特别是化肥氮的输入量 ,是造成长江输送无机氮通量上升的主要因素更多还原

【Abstract】 In this paper, we present estimates of nitrogen (N) biogeochemical cycling in the Changjiang drainage basin, including N inputs, outputs and internal transfer for the period 1968 1997. The total N input, output and internal storage are approximately 10.0×10 9 , 6.7×10 9, and 3.5×10 9 kg, respectively, in 1997, which is about fourfold, fivefold, and threefold of these in 1968, respectively. In terms of N inputs, N fixation was often a dominant input before 1977, providing about 1.0×10 9 kg year 1 ; while N fertilizer dominated N input after 1983, supplying an additional input of some 5.0×10 9 kg year 1 . In terms of N output, we estimate that the river dissolved inorganic nitrogen (DIN) concentration and flux have increased by about 10 fold from 1968 to 1997, reaching 1.60 mg L 1 and 1.40×10 9 kg, respectively, in 1997. Our study shows that about 25.0% of the total N input is transported through the river, while some 33% of the input is emitted by denitrification and volatilization, and the remaining 42% of the input is stored within the basin. The integrated N input, budget and storage have been linked to the increasing temporal trends of Changjiang River DIN. It is demonstrated that integrated N input, especially N fertilizer application, rather than human population density in the basin is the preferable predictor of the river DIN concentration and flux. Therefore, how N fertilizer is effectively applied is of crucial importance to the sustainable development of agriculture in the basin.更多还原