High‐frequency in situ sensors have enabled researchers to measure solute concentrations at a time scale that captures the variability in stream discharge. We analyzed discrete samples and high‐frequency time series of solutes to characterize how nitrate (NO₃⁻) and fluorescent dissolved organic matter (fDOM; a proxy for dissolved organic carbon) respond to changes in discharge at annual and intra‐annual timescales across a stream network in New Hampshire, USA. NO₃⁻ and fDOM exhibited highly variable concentration‐discharge (c‐Q) behavior at intra‐annual scales. Transport limitation, source limitation, and chemostatic behavior were observed to occur within and among years in all our study watersheds. Annual assessment of c‐Q misclassified streams 31% of the time, as the annual time step missed seasonal and event‐induced shifts in c‐Q dynamics. In some instances, anomalous events lasting less than 5% of the year determine the annual c‐Q behavior for a site. Catchment land use appeared to drive some of the variability among watersheds in c‐Q relationships and their temporal variability. Forested streams had highly variable NO₃⁻ c‐Q behavior and streams draining watersheds with more development had greater variability in fDOM c‐Q behavior. Sample frequency impacts how hydrologic systems are characterized and extrapolating c‐Q behavior from discrete samples alone can bias interpretations of c‐Q dynamics and our understanding of solute transport.

中文翻译：

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各种规模的溶解有机碳和硝酸盐浓度-排放行为：土地利用，远足和分类错误

高频原位传感器使研究人员能够在一定的时间范围内测量溶质浓度，以捕获水流排放的变化。我们分析了离散样本和高频的时间序列的溶质的表征如何硝酸盐（NO ₃ ^- ）和荧光溶解的有机物质（FDOM;用于溶解的有机碳的代理）在跨年度内和年度时间尺度来响应变化的放电美国新罕布什尔州的流网络。NO ₃ ^-fDOM在年内尺度上表现出高度可变的浓度-放电（c-Q）行为。在我们所有的研究流域中，几年之内和之间都发生了运输限制，源限制和趋化行为。每年对c-Q错误分类的流进行年度评估，因为年度时间步长错过了c-Q动态的季节性和事件引起的变化。在某些情况下，持续不到一年的5％的异常事件决定了站点的年度c-Q行为。流域土地利用似乎推动了流域之间的c-Q关系及其时间变异性的某些变化。森林溪流的NO ₃变化很大^-c-Q行为和流域分水岭随着更多的开发而变化，其fDOM c-Q行为的变异性更大。样品频率会影响水文系统的特征，仅从离散样品中推断c-Q行为就可能会影响c-Q动力学的解释和对溶质运移的理解。