Some one mentioned carbonaceous oxides. Most of us would say carbon dioxide but the way you said it sounded more erudite. Industry, vehicles, and power plants put out a lot of these oxides which form carbonic acid when it combines with water. It's a weak acid when compared to sulfuric acid but it is produced in huge quantities so it is an important part of the picture.
What do you think?
A solution of carbon dioxide in water in equilibrium with the atmosphere has a pH of 5.6. Rain water is normally not quite saturated in CO2, and has a pH of around 6 in the absence of atmospheric pollutants. Even though sulphurous oxides which ...