What term refers to rain with a pH lower than 5.6?

The term that refers to rain with a pH lower than 5.6 is acid precipitation. This type of precipitation occurs when rainwater mixes with pollutants in the atmosphere, such as sulfur dioxide and nitrogen oxides, which can be emitted by industrial processes and vehicles. These pollutants react with water vapor to form sulfuric and nitric acids, leading to a decrease in pH.

Rain is typically considered neutral at a pH of 7, and since pH is on a logarithmic scale, a pH lower than 5.6 indicates a significantly higher concentration of hydrogen ions compared to neutral water. Acid precipitation can have harmful effects on ecosystems, including soil degradation, damage to aquatic environments, and harm to vegetation. Therefore, the identification of rain with a pH below 5.6 as acid precipitation is important in understanding and addressing the impacts of environmental pollution.