缺水地区人类活动净氮输入与河流响应特征——以海河流域为例

人类活动净氮输入(NANI)是影响河流氮输出的重要因素,研究两者的响应关系对制定氮污染的削减策略具有重要意义.基于NANI核算模型,评估了海河流域人为氮输入强度,并采用实测数据估算了同期的河流氮输出,最终得到干旱缺水区河流氮输出对NANI的响应特征.结果表明,海河流域2008—2012年均NANI输入强度为13258 kg·km~(-2)·a~1,化肥施用、食品与饲料输入、大气沉降和农作物固氮分别占76%、17%、5%和2%;在空间分布上,黑龙港运东子流域的NANI负荷最高,达到24238 kg·km~(-2)·a~(-1),最小的是永定河子流域,为5320 kg·km~(-2)·a~(-1);海河流域主要河流的氮通量与子流域NANI输入呈现显著正相关关系(p0.05),NANI变化可解释67%的河流氮通量变化.然而,仅2%的NANI由河流输出,这一比例低于其他地区研究成果,表明缺水地区河流作为氮输出的功能被削弱,河流不是流域氮输出的主要途径.

Net anthropogenic nitrogen inputs (NANI) and riverine response in water shortage region:A case study of Haihe River watershed

Net anthropogenic nitrogen inputs (NANI) is considered a significant factor influencing riverine N export, and exploring their relationship is key to make countermeasures of mitigating N pollution. The relationship between NANI and riverine N export was established for the Haihe River Basin, where the former was calculated using NANI model and the latter was estimated based on monitoring data. Results indicate that i) the NANI in Haihe River watershed reaches 13258 kg·km^-2·a^-1 averaged from 2008 to 2012; ii) synthetic fertilizer, food/feed imports, atmospheric deposition, and agricultural fixation accounts for 76%, 17%, 5% and 2% of NANI, respectively; iii) Heilonggang River-Yundong Canal sub-watershed was ranked as the highest hotspot with NANI of 24238 kg·km^-2·a^-1, whereas Yongding River sub-watershed was the area with the lowest NANI of 5320 kg·km^-2·a^-1; iv) 67% variation of riverine N exports could be explained by the NANI (p<0.05). However, only 2% of NANI was exported by rivers according to the regression, which is much lower than the results from other case studies, indicating that river is not a significant output of watershed N in arid regions.