Revealing new processes of Urban Climate: An integrated analysis of atmospheric emissions, air pollution and rainwater quality in the city of Rio de Janeiro (Brazil).

The Metropolitan Region of Rio de Janeiro (MRRJ) has the second largest concentration of population, vehicles, industries and pollutant emission sources, according to the state government. In an attempt to broaden the understanding regarding the changes that have occurred in the urban climate as well as the role of rain in cleaning the urban atmosphere, this study aims at establishing a correlation between air quality and physical-chemical parameters of rainwater, including hydrogen potential (pH), electrical conductivity (EC) and ion concentration. The primary data obtained for the research are based upon the comparison between two sampling points: one located in an area of residential use (Maracanã neighborhood) and another located in the industrial district of the city of Rio de Janeiro (Campo Grande neighborhood). In this research, the parameters for determining air quality were selected from the database of the Municipal Secretariat of Environment (SME), whereas the collection of wind data on a regional scale was obtained through ERA5. The preliminary results of the research indicated pH values above 6.0, suggesting a neutralization of the acidic character of the rain due to the concentrations of calcium hardness and ammonia. The presence of Cℓ⁻ and CaCO₃ ions was attributed, respectively, to the effect of maritime activity, given the coastal location of the city, and to the proximity of cement industries. Therefore, it is clear that, despite little scientific attention, the analysis of rainwater is essential to understand the processes inherent to the local climate and the exposure of the population to contamination events. In addition, it is also vital to rediscuss the rainwater quality standards which are almost exclusively associated in the literature with the hydrogen potential classified as acidic.