Nitrate in Streams During Winter Low‐Flow Conditions as an Indicator of Legacy Nitrate
Nitrate in Streams During Winter Low‐Flow Conditions as an Indicator of Legacy Nitrate
复制标题
冬季低流量条件下溪流中的硝酸盐作为遗留硝酸盐的指标
作者：
Henry M. Johnson;E. Stets
冬季低流量（LF）条件下的流提供了一个潜在的机会，以评估传统的硝酸盐在集水区的重要性，由于缓慢流动的运输途径和降低生物活性的主导地位。在这项研究中，在美国接壤的320个地点分析了冬季低流量条件下溪流中硝酸盐的浓度、通量和趋势。LF流量标准化的硝酸盐浓度从<0.1 to >20 mg-N L−1变化，LF条件贡献了冬季硝酸盐通量的2%至98%。在中中西部地区北部，LF硝酸盐浓度通常超过2.5 mg-N L-1，德克萨斯州东部和大西洋中北方沿着的LF硝酸盐浓度较高。地下水被推断为主要或唯一的贡献者硝酸盐的流在冬季LF条件在我们的320个站点的140。在这140个站点中，来自地下水的硝酸盐占冬季硝酸盐通量的45%或更多。在同样的140个站点中，在2002年至2012年期间，在冬季LF条件下，40%或更多的冬季通量来自地下水的站点，溪流中硝酸盐的浓度普遍增加，这表明贡献地下水系统中的硝酸盐浓度正在增加。使用本文开发的指标，我们的特点在本研究中的网站传统硝酸盐的潜在重要性，并讨论方法来表征网站的样本比我们的模型所需的或在网站没有连续流放电测量。
Winter low‐flow (LF) conditions in streams provide a potential opportunity to evaluate the importance of legacy nitrate in catchments due to the dominance of slow‐flow transport pathways and lowered biotic activity. In this study, the concentration, flux, and trend of nitrate in streams during winter low‐flow conditions were analyzed at 320 sites in the conterminous United States. LF flow‐normalized nitrate concentrations varied from <0.1 to >20 mg‐N L−1 and LF conditions contributed between 2% and 98% of the winter nitrate flux. LF nitrate concentrations generally exceeded 2.5 mg‐N L−1 in the upper Midwest, with smaller regions of high LF nitrate concentrations in eastern Texas and along the northern mid‐Atlantic coast. Groundwater was inferred to be the primary or sole contributor of nitrate to streams during winter LF conditions at 140 of our 320 sites. Among these 140 sites, nitrate from groundwater comprised 45% or more of the winter nitrate flux at a quarter of the sites. Among the same 140 sites, concentrations of nitrate in streams during winter LF conditions generally increased between 2002 and 2012 at sites where 40% or more of the winter flux was from groundwater, suggesting that concentrations of nitrate in the contributing groundwater system were increasing. Using metrics developed herein, we characterize the potential importance of legacy nitrate at sites in this study and discuss methods to characterize sites with fewer samples than required by our models or at sites without continuous stream discharge measurements.
河流内过程、排放和土地覆盖对阿巴拉契亚山脉南部流域氮输出的影响
影响因子：
3.2
作者：
Webster, Jackson R.;Stewart, Rebecca M.;Knoepp, Jennifer D.;Jackson, C. Rhett
通讯作者：
Jackson, C. Rhett