Acid Rain - In the air carbon dioxide and water react to produce carbonic acid, making normal rain slightly acidic, a pH of 5.6. However the rain becomes more acidic due to air pollutants, such as sulfur oxides and nitrous oxides from vehicles,factories, and combustion-based power stations , which combine with water thus forming sulfuric acids and nitric acids. Acid rain has completely damaged the biodiversity of mountains and lakes, and even buildings and historic sculptures.

To learn more go to: https://www.epa.gov/acidrain/effects-acid-rain

Emissions of nitrogen and sulfur compounds that lead to acid rain have dropped a lot over the decades. Take a look at the maps on this page: https://www.epa.gov/acidrain/acid-rain-program-results