Portable Conductometric Sensing Probe for Real-Time Monitoring Ammonia Profile in Coastal Waters

An ability to real-time and continuously monitor ammonium/ammonia profiles of coastal waters over a prolonged period in a simple and maintenance-free fashion would enable economic conducting large-scale assessments, providing the needed scientific insights to better control and mitigate the impact of eutrophication on coastal ecosystems. However, this is a challenging task due to the lack of capable sensors. Here, we demonstrate the use of a membrane-based conductometric ammonia sensing probe (CASP) for real-time monitoring of ammonia levels in coastal waters. A boric acid/glycerol receiving phase is investigated and innovatively utilized to overcome the high salinity of coastal water-induced analytical errors. A calibration-free approach is used to eliminate the need for ongoing calibration, while the issues concerning practical applications, such as salinity variation, ammonia intake capability, and biofouling, are systematically investigated. The field deployment at an estuary confluence water site over a half-moon cycle period confirms that CASP is capable of continuously monitoring the ammonia profile of coastal waters in real-time with high resolution and accuracy to unveil the dynamic ammonia concentration changes over a prolonged period.

Automated summary

The ability to monitor ammonium/ammonia levels in coastal waters in real-time and continuously is crucial for assessing the impact of eutrophication on ecosystems. In this study, a membrane-based conductometric ammonia sensing probe (CASP) was used to monitor ammonia levels in coastal waters. The use of a boric acid/glycerol receiving phase helped overcome the analytical errors caused by high salinity. The findings showed that CASP can accurately monitor the dynamic changes in ammonia concentration in coastal waters over an extended period of time.