Groundwater nitrogen pollution index in an urbanized area, Bandung Regency, Indonesia

Despite previous reports of contamination from domestic waste, agricultural runoff, and fertilizers, shallow groundwater (GW) within Bandung Regency remains a clean water source. Nitrogen is one of the most common contaminants identified in the region. This study aims to assess nitrogen concentrations and determine the groundwater pollution index (GWPI) caused by nitrogen. The GWPI categorizes water as excellent water (GWPI <0.5), good (0.5< GWPI <0.75), moderately polluted (0.75< GWPI <1), and highly polluted (GWPI >1). Twenty-seven GW samples were collected during the wet season in October 2022, and physicochemical parameters were analyzed, including pH, dissolved oxygen, GW temperature, electrical conductivity, total dissolved solids, oxidation-reduction potential, dissolved iron and manganese, ammonium, nitrate, and nitrite. According to the analysis, there was a significant variation in the dissolved inorganic nitrogen (DIN), with 12 samples dominated by ammonium and 15 samples dominated by nitrate. The GWPI calculation ranges from 0.96 to 3.52, indicating that 33% of the samples exhibit excellent water quality, 19% show good water quality, 22% demonstrate moderately polluted water, and 26% demonstrate highly polluted water. Based on the spatial distribution analysis, it was found that the settlement exhibited the most substantial levels of GW pollution due to DIN.