Humans have altered the nitrogen cycle by emitting excess reactive nitrogen into the atmosphere causing ammonia (NH₃) and nitrogen oxide (NO_x) concentrations in the atmosphere to increase exponentially over the last century. This excess nitrogen causes negative environmental and health effects by contributing to acid rain, decreased air quality, soil acidification, eutrophication, and a change in biodiversity. In order to better understand the nitrogen cycle, emission sources, and mitigation strategies, regional emissions of NH₃ and NO_x should be quantified. This study will measure the stable isotopic composition of nitrate (NO₃^-) and ammonium (NH₄⁺) in wet deposition in order to estimate NH₃ and NO_x emission sources in the Ribeirao Preto region of Sao Paulo, Brazil. Wet deposition in the form of rain samples were collected after every rain event in Ribeirao Preto from October 2018 through October 2019. Preliminary δ¹⁵N-NO₃^- and δ¹⁵N-NH₄⁺ data from October 2018 to June 2019 ranged from -6.4 to 14.4‰ (n = 25) and -19.8 to 11.3‰ (n = 17) with an average of -0.9 ± 4.4‰ and -8.6 ± 7.4‰ respectively. The δ¹⁵N-NO₃^- and δ¹⁵N-NH₄⁺ values in rainwater will be corrected for fractionation processes and along with δ¹⁵N values of NO_x and NH₃ emission sources will be applied to the Stable Isotope Analysis in R (SIAR) mixing model program to estimate source contributions. This project will help understand the emission sources affecting air quality in Sao Paulo, Brazil and provide information on the emission and transportation of NO_x and NH₃ in the environment.