• • GPMCS achieved real-time in-situ monitoring of ammonia nitrogen in surface river water and landscape aquaculture water, with mean concentrations of 4.67 mg/L (river inlet) and 7.04 mg/L (lake site 2), demonstrating field applicability across diverse water matrices.
• • The sensor exhibited high accuracy, with correlation coefficients of r1=0.8132 and r2=0.7483 against national standard methods, validating its reliability for regulatory compliance monitoring.
• • Biofouling from microbial attachment over 4 days caused less than 3% error in measured ammonia concentrations, indicating robust long-term stability without frequent maintenance.
• • GPMCS detected concentration ranges from 0.28 to 11.16 mg/L across sites, capturing dynamic fluctuations linked to operational and environmental factors, enabling early warning of pollution events.