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.