Stable Isotope Analysis for Identification of Nitrogen Pollution Sources in Urban Groundwater Systems

Abstract

Nitrogen contamination in urban groundwater systems has become a critical environmental concern due to rapid urbanization, sewage leakage, agricultural runoff, and industrial discharge, leading to deterioration of drinking water quality and ecological imbalance. Accurate identification of nitrogen pollution sources is essential for effective groundwater management and contamination control. The present study investigates the application of stable isotope analysis for identifying nitrogen pollution sources in urban groundwater systems under varying hydrogeological and anthropogenic conditions. The research focuses on evaluating isotopic signatures of nitrogen compounds to distinguish contributions from sewage effluent, fertilizer application, animal waste, and industrial activities. Experimental analysis was conducted using groundwater sampling and isotopic characterization techniques to assess the distribution and transformation of nitrate contamination within urban aquifers. Results demonstrate that stable isotope ratios of nitrogen and oxygen provide reliable indicators for tracing nitrogen origins and understanding biogeochemical processes influencing groundwater contamination. The study further reveals that isotopic fractionation associated with nitrification and denitrification significantly affects nitrate transport and transformation within subsurface environments. Comparative assessment with conventional hydrochemical evaluation methods confirms that stable isotope analysis offers improved source discrimination accuracy and enhanced understanding of contamination pathways. Spatial analysis of isotopic data identified distinct pollution hotspots associated with urban wastewater leakage and intensive anthropogenic activities.