A new submersible probe for the in situ detection of nitrate, nitrite, and chloride in seawater is presented. Inline coupling of a desalination unit, an acidification unit, and a sensing flow cell containing all-solid-state membrane electrodes allows for the potentiometric detection of nitrate and nitrite after removal of the key interfering ions in seawater, chloride and hydroxide. Thus, the electrodes exhibited attractive analytical performances for the potentiometric detection of nitrate and nitrite in desalinated and acidified seawater: fast response time (t₉₅ < 12 s), excellent stability (long-term drifts of <0.5 mV h^–1), good reproducibility (calibration parameter deviation of <3%), and satisfactory accuracy (uncertainties <8%Diff compared to reference technique). The desalination cell, which can be repetitively used for about 30 times, may additionally be used as an exhaustive, and therefore calibration-free, electrochemical sensor for chloride and indirect salinity detection. The detection of these two parameters together with nitrate and nitrite may be useful for the correlation of relative changes in macronutrient levels with salinity cycles, which is of special interest in recessed coastal water bodies. The system is capable of autonomous operation during deployment, with routines for repetitive measurements (every 2 h), data storage and management, and computer visualization of the data in real time. In situ temporal profiles observed in the Arcachon Bay (France) showed valuable environmental information concerning tide-dependent cycles of nitrate and chloride levels in the lagoon, which are here observed for the first time using direct in situ measurements. The submersible probe based on membrane electrodes presented herein may facilitate the study of biogeochemical processes occurring in marine ecosystems by the direct monitoring of nitrate and nitrite levels, which are key chemical targets in coastal waters.

中文翻译：

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潜水式电化学传感器原位检测海水中的大量营养物和氯化物

提出了一种新的潜水探针，用于现场检测海水中的硝酸盐，亚硝酸盐和氯化物。脱盐装置，酸化装置和包含全固态膜电极的传感流通池的在线耦合可在去除海水，氯化物和氢氧化物中的关键干扰离子后，电位滴定法检测硝酸盐和亚硝酸盐。因此，该电极对淡化和酸化海水中硝酸盐和亚硝酸盐的电位测定具有出色的分析性能：响应时间短（t ₉₅ <12 s），出色的稳定性（长期漂移<0.5 mV h ^–1）），良好的重现性（校准参数偏差<3％）和令人满意的精度（与参考技术相比，不确定度<8％Diff）。可以重复使用约30次的脱盐池可以另外用作详尽的，因此无需校准的电化学传感器，用于氯化物和间接盐度检测。这两个参数以及硝酸盐和亚硝酸盐的检测对于将大量营养物含量的相对变化与盐度循环相关联可能是有用的，这在沿海凹陷的水体中尤为重要。该系统能够在部署期间自主运行，并具有用于重复测量（每2小时），数据存储和管理以及对数据进行实时计算机可视化的例程。在阿尔卡雄湾（法国）观察到的原位时间剖面显示出有价值的环境信息，这些信息与泻湖中硝酸盐和氯化物水平的潮汐依赖性循环有关，这是首次使用直接原位测量法进行观察。通过直接监测硝酸盐和亚硝酸盐水平（这是沿海水域中的主要化学目标），基于本文提出的膜电极的潜水探针可以促进对海洋生态系统中发生的生物地球化学过程的研究。