Influence of local sources and topography on air quality and rainwater composition in Cubatão and São Paulo, Brazil

•Wet-only deposition was measured from 2009 to 2010 in Cubatão and São Paulo cities.•The rainwater acidity in Cubatão was 5-fold higher than that in MASP, while the sulfur was 3-fold.•S deposition at Cubatão was comparable to others heavily urbanized areas around the world.

Wet deposition was measured in two urban areas of Brazil, Cubatão and São Paulo megacity (MASP), from July 2009 to August 2010. Cubatão is characterized by the large and complex industrial sector and MASP by a large vehicular fleet, and these different sources contributed to 15.5 × 106 and 25.5 × 106 kg year−1 of SO2 air emissions, respectively. The rainwater volume-weighted mean (VWM) pH values and [SO42−] in Cubatão and in MASP were 4.8 and 7.1 μmol L−1, and 5.3 and 24.5 μmol L−1, respectively. Regarding nitrogen content, the difference between reduced and oxidized nitrogen was more pronounced in MASP, where more than 61% of total nitrogen scavenged as NH4+. The wet-only sulfur deposition in Cubatão was 17.0 kg S ha−1 y−1, which was 2.7-fold higher than that in MASP. Although the higher air pollutant emissions occur in MASP, the worst air quality and wet deposition has been observed in Cubatão due to the orographic conditions.