Emerging contaminants in groundwaters and their relation to recharge sources in Bengaluru City, Karnataka, India

(a) Purpose or objectives and status of study or research hypothesis To address the research gap in assessing occurrences of emerging organic contaminants pollutants (EOCs) in Indian groundwater and to investigate and describe potential pollution from different recharge sources. (b) Key issue(s) or problem(s) addressed Groundwaters and surface waters in rapidly developing urban areas are often particularly prone to contamination by EOCs due to system inputs from domestic, and industrial effluents. However, to date water quality assessment in large cities is often biased towards major ion chemistry analysis and surface water sampling. A more comprehensive assessment of occurrences and pathways of EOCs in groundwaters is often lacking, as in the case of the Indian city of Bengaluru (estimated population 8 million). (c) Methodology or approach used A field study was undertaken in Bengaluru city, collecting 25 samples from groundwater, surface water and mains water (imported water from the Cauvery River). The samples were screened (GC-MS and LC-MS) for a total of 1499 EOCs. (d) Results and conclusions derived from the project A total of 63 EOCs were detected in groundwaters at concentrations between 1 and 3200 ng/L. Several of the detected compounds could be linked directly to distinct recharge sources. For example, Perfluoroalkyl and Polyfluoroalkyl substances (PFAS) were detected in concentrations up to 920 ng/L in groundwaters and up 1800 ng/L in surface waters, particularly in rivers receiving treated or untreated sewage. This indicates a connectivity between Vrishabhavathi River and urban lakes with the groundwater system. Conversely, several agricultural products, such as the growth regulator Trinexapac and the herbicide Atrazine were only detected in groundwater and piped mains water, indicating a pollution pathway by recharge from mains water leakage. (e) Policy implications of the project relevant to the selected conference theme, theory and/or practice The study documents the pollutions risks associated to specific recharge sources in Bengaluru which has implications on management options such as implementation of protection measures. High concentrations of PFAS highlight the need for enhanced monitoring and risk assessment.