LAUSR

Abstract This work investigates the effect of public policies related to vehicle emissions on the lower tropospheric concentrations of H2O2 in a typical midsized city in tropical Brazil. The concentrations of H2O2, SO42−, and NO3− in rainwater samples were determined from 2014 to 2017 in the municipality of Ribeirao Preto in Sao Paulo State. A fluorometric method, based on the formation of a highly fluorescent product (2′,7′-dichlorofluorescein, DCF), was adapted and optimized for the measurement of H2O2 in natural water samples including seawater. The method was highly specific, accurate and sensitive (LOD = 2 nmol L−1). Its main advantage compared to others, was that the fluorophore remained stable for at least 48 h, offering a longer time interval in which to perform the analysis and therefore facilitating fieldwork. Concentrations of H2O2 in rainwater ranged from 5.8 to 96 μmol L−1, with VWM of 28.6 ± 1.4 μmol L−1 (n = 77). Solar radiation appeared to have a greater impact on production than on consumption of H2O2. The annual VWM concentrations of H2O2 in rainwater were negatively correlated with sulfate (at pH