Imprints of anthropogenic air pollution sources on nitrate isotopes in precipitation in a tropical metropolitan area

Identifying the origin of NOx emissions, their transformation into nitrate (NO3−) and its atmospheric deposition is important to better understand impacts air pollution on environment human health, a local regional scale. We measured isotopes (δ15N, δ18O NO3−) in precipitation samples tropical station Brazil 2019–2020 combined them with chemical, geospatial meteorological data trace sources towards wet as NO3−. A total N ∼12 kg N/ha.year showed significant pollution, out which relative contribution NO3−-N was ∼37% (4.6 NO3−-N/ha.year). The δ15N–NO3- values ranged from −8.5 +4.1‰, volume-weighted mean (VWM) value −3.0 ± 2.7‰, whereas δ18O–NO3- +25.9 +63.5‰ VWM +53.3 7.3‰. results mass backward trajectory analysis mapping revealed that emissions Belo Horizonte originated from: vehicles industries urban industrialized areas, biomass burning related wildfires, ship coastal areas. temporal variation δ15N, NO3− attributed source variability processes. use integrated methods evaluate imprints anthropogenic will contribute inform management strategies improve water quality.