Documenting dissolved inorganic nitrogen (DIN) concentrations and forms at appropriate temporal and spatial scales is key to understanding aquatic ecosystem health, particularly because DIN fuels primary productivity. In addition to point and nonpoint source nutrient inputs, factors such as hydrology, geomorphology, temperature, light, and biogeochemical transformations influence nutrient dynamics in surface waters, allowing for the formation of steep spatial gradients and patchiness. Documenting nutrient variability is also necessary to identify sources, quantify transformation rates, and understand drivers. Because of logistical and cost constraints, it is often unfeasible to measure concentrations of nutrients in surface waters using discrete sampling followed by laboratory analysis at a resolution high enough to identify steep spatial gradients and patchiness. Because of these constraints, data generated from discrete sampling are limited in space and time, often missing key variabilities. Recent advancements of in situ nitrate plus nitrite (${\mathrm{NO}}_3^{-}$ and ${\mathrm{NO}}_2^{-}$) sensor technology have enabled highly temporally and spatially resolved ${\mathrm{NO}}_3^{-}$ concentration measurements in aquatic ecosystems. However, comparable information about ammonium (${\mathrm{NH}}_4^{+}$) concentrations remains unavailable. To address this need, US Geological Survey collaborated with Timberline Instruments to modify their commercially available benchtop TL-2800 ammonia analyzer to operate in flow-through mode, enabling rapid continuous ${\mathrm{NH}}_4^{+}$ concentration measurements at a micromolar (0.5 μM) resolution while receiving water pumped from a moving boat. Although the utility of this method is described for spatial surveys, we anticipate that it would be adaptable to installation at a fixed station for continuous monitoring of ${\mathrm{NH}}_4^{+}$ concentration.

中文翻译：

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高频电导铵分析仪的新型船基现场应用，用于表征水生生态系统的空间变化

在适当的时间和空间尺度记录溶解无机氮 (DIN) 浓度和形式是了解水生生态系统健康的关键，特别是因为 DIN 促进初级生产力。除了点源和非点源养分输入外，水文、地貌、温度、光照和生物地球化学转化等因素也会影响地表水的养分动态，从而形成陡峭的空间梯度和斑块。记录养分变异性对于识别来源、量化转化率和了解驱动因素也是必要的。由于后勤和成本的限制，使用离散采样来测量地表水中营养物的浓度通常是不可行的，然后以足够高的分辨率进行实验室分析，以识别陡峭的空间梯度和斑块。由于这些限制，离散采样生成的数据在空间和时间上受到限制，通常会丢失关键的变量。原位硝酸盐加亚硝酸盐的最新进展（${不}_3^{-}$和${不}_2^{-}$）传感器技术实现了高度时间和空间分辨率${不}_3^{-}$水生生态系统中的浓度测量。然而，有关铵的类似信息（${\mathrm{NH}}_4^{+}$）浓度仍然无法获得。为了满足这一需求，美国地质调查局与 Timberline Instruments 合作，修改其市售台式 TL-2800 氨分析仪，以流通模式运行，从而实现快速连续分析${\mathrm{NH}}_4^{+}$当接收从移动的船上泵送的水时，以微摩尔 (0.5  μM ) 分辨率测量浓度。尽管该方法的实用性是针对空间调查进行描述的，但我们预计它将适用于安装在固定站上以连续监测${\mathrm{NH}}_4^{+}$专注。