Integrated sensor platform for real-time monitoring of nitrate, ammonium, temperature, and pH in aquatic environments

This study reports the development and characterization of an integrated electrochemical sensor platform for real-time, simultaneous detection of nitrate, ammonium, temperature, and pH in aquatic environments. The nitrate and ammonium sensors utilized customized copper (Cu) and polyaniline (PANI) electrodes, respectively, which exhibited high sensitivity within a detection range from 1 to 100 mg/L for nitrate and 0.05-10 mg/L for ammonium. Calibration plots revealed excellent linear response for both sensors (R² = 0.98), with detection limits of 0.84 mg/L for nitrate and 0.02 mg/L for ammonium. This platform is distinguished by its multi-parameter detection capability, where real-time measurements of temperature and pH offer contextual accuracy in ion measurements by compensating for environmental changes that affect ion detection. The results indicate robust selectivity and stability against common interferents in water, demonstrating this platform's reliability for on-site environmental monitoring. The integration of all sensor elements onto a single flexible substrate, combined with encapsulation in a waterproof 3D-printed housing, enables field applications and continuous data collection, with real-time transmission to a remote server for monitoring. This integrated system was deployed in a recirculating aquaculture system to monitor nitrate and ammonium levels over a 24-h period. The sensors demonstrated high accuracy when compared to commercial test kits, with a root mean square error of 2.64 mg/L NO₃^--N (R² = 0.83) for the nitrate sensor and 0.41 mg/L NH₃-N (R² = 0.84) for the ammonium sensor. Hence, this multi-parametric platform represents an innovative step forward for sustainable, accurate, and precise water quality assessment for aquacultural and environmental management applications.