Abstract:
Aquatic pollution from emerging organic contaminants (EOCs) is of key environmental importance in
India and globally, particularly due to concerns of antimicrobial resistance, ecotoxicity and drinking
water supply vulnerability. Here, using a broad screening approach, we characterize the composition and
distribution of EOCs in groundwater in the Gangetic Plain around Patna (Bihar), as an exemplar of a
rapidly developing urban area in northern India. A total of 73 EOCs were detected in 51 samples, typically
at ng.L 1 to low mg.L 1 concentrations, relating to medical and veterinary, agrochemical, industrial and
lifestyle usage. Concentrations were often dominated by the lifestyle chemical and artificial sweetener
sucralose. Seventeen identified EOCs are flagged as priority compounds by the European Commission,
World Health Organisation and/or World Organisation for Animal Health: namely, herbicides diuron and
atrazine; insecticides imidacloprid, thiamethoxam, clothianidin and acetamiprid; the surfactant perfluorooctane
sulfonate (and related perfluorobutane sulfonate, perfluorohexane sulfonate, perfluorooctanoic
acid and perfluoropentane sulfonate); and medical/veterinary compounds
sulfamethoxazole, sulfanilamide, dapson, sulfathiazole, sulfamethazine and diclofenac. The spatial distribution
of EOCs varies widely, with concentrations declining with depth, consistent with a strong
dominant vertical flow control. Groundwater EOC concentrations in Patna were found to peak within
~10 km distance from the River Ganges, indicating mainly urban inputs with some local pollution hotspots.
A heterogeneous relationship between EOCs and population density likely reflects confounding
factors including varying input types and controls (e.g. spatial, temporal), wastewater treatment infrastructure
and groundwater abstraction. Strong seasonal agreement in EOC concentrations was observed.
Co-existence of limited transformation products with associated parent compounds indicate active microbial
degradation processes. This study characterizes key controls on the distribution of groundwater
EOCs across the urban to rural transition near Patna, as a rapidly developing Indian city, and contributes
to the wider understanding of the vulnerability of shallow groundwater to surface-derived contamination
in similar environments.
