Temporal Variability in Nitrate‐Discharge Relationships in Large Rivers as Revealed by High‐Frequency Data
Temporal Variability in Nitrate‐Discharge Relationships in Large Rivers as Revealed by High‐Frequency Data
复制标题
高频数据揭示大河流硝酸盐排放关系的时间变化
DOI：
10.1029/2018wr023478
复制
发表时间：
2019
影响因子：
5.4
通讯作者：
Gregory Petrochenkov
中科院分区：
文献类型：
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作者：
M. Zimmer;B. Pellerin;D. Burns;Gregory Petrochenkov
人们对大河流年内时间尺度上硝酸盐浓度随流量变化的响应知之甚少。为了调查这一知识差距，我们使用了六年的每日地表水硝酸盐浓度和排放量数据集，这些数据集是美国地质调查局对康涅狄格河、波托马克河和密西西比河测站近乎连续监测的平均值，这三条大河对重要河口造成了大量的营养物污染。年际间，传统离散抓取样本数据集和近连续数据集之间硝酸盐浓度-排放 (c-Q) 关系的比较揭示了不同的 c-Q 斜率，这表明样本频率可以影响我们最终表征水文系统的方式。每年，我们在 30 天的窗口内进行相关性分析，以隔离每月 c-Q 关系的强度和方向。波托马克河的每月 c-Q 斜率在夏季和秋季为正（富集/动员反应），在冬季和春季为负（稀释反应）和弱趋化性（不显着的接近于零的 c-Q 斜率）。康涅狄格州全年都表现出稀释反应，但夏季除外，此时其化学抑制作用较弱。密西西比州的 c-Q 斜率在所有季节都具有弱化学稳定性，并且对流量波动的响应不一致。波托马克河和康涅狄格州的 c-Q 动态与河流温度、流量百分位数和日历日相关（R > 0.3）。密西西比河的最小相关性表明，大盆地面积加上大量土地利用开发造成的时空可变的人为强迫，产生了随机的短期 c-Q 关系。在大型河流网络中使用高频传感器的额外工作可以提高我们对这些自然-人类耦合系统中的空间源输入动态的理解。
Little is known about temporal variability in nitrate concentration responses to changes in discharge on intraannual time scales in large rivers. To investigate this knowledge gap, we used a six‐year data set of daily surface water nitrate concentration and discharge averaged from near‐continuous monitoring at U.S. Geological Survey gaging stations on the Connecticut, Potomac, and Mississippi Rivers, three large rivers that contribute substantial nutrient pollution to important estuaries. Interannually, a comparison of nitrate concentration‐discharge (c‐Q) relationships between a traditional discrete grab sample data set and the near‐continuous data set revealed differing c‐Q slopes, which suggests that sample frequency can impact how we ultimately characterize hydrologic systems. Intraannually, we conducted correlation analyses over 30‐day windows to isolate the strength and direction of monthly c‐Q relationships. Monthly c‐Q slopes in the Potomac were positive (enrichment/mobilization response) in summer and fall and negative (dilution response) and weakly chemostatic (nonsignificant near‐zero c‐Q slope) in winter and spring, respectively. The Connecticut displayed a dilution response year‐round, except summer when it was weakly chemostatic. Mississippi c‐Q slopes were weakly chemostatic in all seasons and showed inconsistent responses to discharge fluctuations. The c‐Q dynamics in the Potomac and Connecticut were correlated (R > 0.3) to river temperature, flow percentile, and calendar day. Minimal correlation in the Mississippi suggests that the large basin area coupled with spatiotemporally variable anthropogenic forcings from substantial land use development created stochastic short‐term c‐Q relationships. Additional work using high‐frequency sensors across large river networks can improve our understanding of spatial source input dynamics in these natural‐human coupled systems.
影响因子：
11.4
作者：
Rode, Michael;Wade, Andrew J.;Jomaa, Seifeddine
通讯作者：
Jomaa, Seifeddine