中文摘要：

以浙江某典型流域为研究对象,基于1980～2010年的水质水量和氮源数据及LOADEST模型,估算了逐年河流NO3^--N通量和净人类活动氮输入（NANI）,分析了河流NO^-3-N通量和NANI的年际演化特征及其动态响应关系,探讨了每年NANI、滞留氮库、自然背景源对河流NO3^--N通量的贡献.结果表明,1980～2010年,河流NO^-3-N通量和NANI总体上都呈现出先增后减的抛物线型变化趋势,均在1998年左右分别达到峰值5.74 kg·（hm^2·a）^-1和77.5 kg·（hm^2·a）^-1;过去31 a,河流NO^-3-N通量和NANI分别净增加了～42%和～77%.化肥氮和大气氮沉降是NANI的主要来源,分别占了NANI的～48%和～40%.河流NO^-3-N通量的年际变化不仅与NAIN（R^2=0.27＊＊）和化肥氮输入量（R^2=0.32＊＊）显著相关,而且与河流年均流量（R^2=0.79＊＊）或降雨量（R^2=0.63^＊＊）具有更强的相关性,意味着河流NO^-3-N的来源除了当年的NAIN,还受滞留氮库的影响.所建立的以NANI和流量为自变量的回归模型能很好地模拟河流NO^-3-N通量变化（R^2=0.94^＊＊）.该模型预测结果显示,在NANI和流量分别降低30%的情况下,河流年均NO^-3-N通量将分别减少～21%和～30%;每年的NANI、滞留氮库、自然背景源对河流当年NO3^--N通量的贡献率分别为～53%、～24%、～23%.河流NO3^--N通量长期的年际变化是NANI和水文要素共同作用的结果;但是,由于滞留氮库的影响,与源控制方式相比,增加＂汇＂景观应该能更加快速地削减河流NO3^--N通量.

英文摘要：

Based on long-term records of river water quality and discharge and nitrogen sources as well as the LOADEST model,annual riverine NO^-3-N flux and net anthropogenic nitrogen input（NANI） were both estimated for a typical river catchment（2 474 km2） in Zhejiang Province over the 1980-2010 period. Historical trends in both riverine NO^-3-N flux and NANI and their dynamic relationships were then fully addressed. Finally,the contributions of annual NANI,retained nitrogen pools,and natural background sources to riverine NO^-3-N flux were indentified. Results indicated that both riverine NO^-3-N flux and NANI showed parabolic changing trends with peak value of 5. 74 kg·（hm^2·a）^- 1for flux and 77. 5 kg·（hm^2·a）^- 1for NANI both occurring around 1998. In 1980-2010,net increase of riverine NO^-3-N flux and NANI was ～ 42% and ～ 77%,respectively. Chemical nitrogen fertilizer application and atmospheric nitrogen deposition,which accounted for ～ 48% and ～ 40% of NANI,respectively,were the major sources of NANI. Although interannual change of riverine NO^-3-N flux was significantly related to NANI（R^2= 0. 27＊＊） as well as the chemical nitrogen fertilizer application amount（R^2= 0. 32＊＊）,it showed higher dependence on the river water discharge（R^2= 0. 79＊＊） or precipitation（R^2= 0. 63＊＊）,implying that annual riverine NO^-3-N was not only originated from current year＇s NANI,but also derived from retained N pools that were ultimately derived from NANI in previous years. A regression model developed by incorporating both NANI and water discharge could account for 94% of the variability of annual NO^-3-N flux. This model predicted that NO^-3-N flux could have been reduced by ～ 21% and～ 30% if the annual NANI and water discharge had been cut by 30%,respectively. Annual NANI,retained nitrogen pools,and natural background sources contributed to ～ 53%,～ 24%,and ～ 23% of the riverine NO^-3-N flux,respectively,suggesting that ～ 77% of flux was derived from anthropog