Traceability and Biogeochemical Process of Nitrate in the Jinan Karst Spring Catchment, North China

Accurate identification of nitrate (NO3−) sources is critical to addressing groundwater pollution, especially in highly vulnerable karst aquifers. The hydrochemistry and δ15NNO3 δ18ONO3 isotopes were analyzed samples taken from the Jinan Spring Catchment, which has been affected by urbanization agricultural activities. study highlighted use hydrochemistry, environmental isotopes, a multisource linear mixed model for NO3− source apportionment. results showed that, controlled carbonate rocks, hydrochemical types both rainy dry seasons consistent, HCO3·SO4−Ca was dominant type, accounting 60%. Except Ca2+, Mg2+ HCO3−, coefficients variation other ions all greater than 0.5 seasons. chemical composition mainly water–rock interaction. Ca2+ HCO3− derived rock dissolution; K+, Na+, SO42−, Cl− partially atmospheric precipitation. IsoSource quantitatively revealed that majority surface water influenced manure sewage (M&S) contributing 39.3% 52.3% season, 37.1% 56.9% respectively. fraction rates order M&S > SON AF CF AD. In addition, pollution control measures suggestions different areas are put forward. rural residential areas, free discharge livestock should be strictly controlled. planting fertilizers pesticides used rationally prevent non-point pollution. urban centralized treatment industrial strengthened point