Measuring pH in low ionic strength glacial meltwaters using ion selective field effect transistor (ISFET) technology
Measuring pH in low ionic strength glacial meltwaters using ion selective field effect transistor (ISFET) technology
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DOI：
10.1002/lom3.10416
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发表时间：
2021-01-27
影响因子：
2.7
通讯作者：
Mowlem, Matthew C.
中科院分区：
文献类型：
--
作者：
Bagshaw, Elizabeth A.;Wadham, Jemma L.;Mowlem, Matthew C.
测量冰川融水的pH值具有挑战性，因为它们寒冷，偏远，易受冻融循环的影响，并且离子强度低。传统的方法往往表现不佳;玻璃电极具有高漂移和长的响应时间，分光光度技术在寒冷，偏远的环境中是不实用的。离子选择性场效应晶体管（ISFET）传感器是一种很有前途的替代品，在海洋和工业应用中得到了证实。我们通过一系列的实验室和现场实验，评估了两种型号的ISFET，霍尼韦尔Durafet和坎贝尔科学Sentron，用于冰川融化的适用性。传感器具有出色的冻融耐受性和最小的长期漂移，Durafet的漂移比Sentron模型要小。尽管Durafet外壳在快速循环过程中会导致一些滞后，但它们对温度的响应是可预测的，并且搅拌的影响比玻璃电极小一个数量级。在低离子强度（< 1 mmol L-1）下，存在可测量的误差，但这是可量化的，并且小于玻璃电极。实地测试表明，电池消耗低，寿命长，耐极端条件，并揭示了不太可能用标准方法记录的地球化学过程。格陵兰两个冰川集水区的融水pH值保持在7以上，从第一次融水流动开始就具有一致的昼夜周期。我们建议使用ISFET传感器来评估冰川融水的pH值，因为它们的耐受性明显优于替代方法：当沃茨的离子强度> 1 mmol L-1时，Durafet的pH值精确到+/- 0.2，当水的离子强度< 1 mmol L-1时，pH值精确到+/- 0.3。
Measuring pH in glacial meltwaters is challenging, because they are cold, remote, subject to freeze-thaw cycles and have low ionic strength. Traditional methods often perform poorly there; glass electrodes have high drift and long response times, and spectrophotometric techniques are unpractical in cold, remote environments. Ion selective field effect transistor (ISFET) sensors are a promising alternative, proven in marine and industrial applications. We assess the suitability of two models of ISFET, the Honeywell Durafet and Campbell Scientific Sentron, for use in glacial melt through a series of lab and field experiments. The sensors have excellent tolerance of freeze-thaw and minimal long-term drift, with the Durafet experiencing less drift than the Sentron model. They have predictable response to temperature, although the Durafet housing causes some lag during rapid cycling, and the impact of stirring is an order of magnitude less than that of glass electrodes. At low ionic strength (< 1 mmol L-1), there is measurable error, but this is quantifiable, and less than glass electrodes. Field tests demonstrated low battery consumption, excellent longevity and resistance to extreme conditions, and revealed biogeochemical processes that were unlikely to be recorded by standard methods. Meltwater pH in two glacial catchments in Greenland remained > 7 with consistent diurnal cycles from the very first meltwater flows. We recommend that ISFET sensors are used to assess the pH of glacial meltwater, since their tolerance is significantly better than alternative methods: the Durafet is accurate to +/- 0.2 pH when waters are > 1 mmol L-1 ionic strength, and +/- 0.3 pH at < 1 mmol L-1.