Acid rain typically has a pH of less than 5.6, which is significantly lower than the pH of normal rain (around 5.6). While normal rain is slightly acidic due to dissolved carbon dioxide, acid rain is more acidic because of pollutants like sulfur dioxide and nitrogen oxides.
Understanding the pH Scale
The pH scale measures how acidic or alkaline a substance is. It ranges from 0 to 14, with 7 being neutral. Numbers below 7 indicate acidity, while numbers above 7 indicate alkalinity. The lower the pH number, the more acidic the substance.
- Pure water: pH 7 (neutral)
- Normal rain: pH 5.6 (slightly acidic due to naturally occurring carbon dioxide)
- Acid rain: pH less than 5.6 (significantly more acidic due to air pollution)
Factors Affecting Acid Rain pH
The exact pH of acid rain varies depending on several factors, including:
- The concentration of polluting gases (sulfur dioxide and nitrogen oxides) in the atmosphere.
- The distance the rain travels before falling.
- The presence of other substances in the atmosphere that can affect the pH.
Examples of Acid Rain pH Levels
Various sources report slightly different pH ranges for acid rain:
- Some sources state that acid rain can have a pH of around 4.3 (as indicated in one of the provided references).
- Other sources mention a pH range of 5.0-5.5 for acid rain.
- It's important to note that the pH of acid rain is highly variable and not a fixed value.
The EPA and other agencies regularly monitor the pH of rainfall to assess the impact of acid rain.
Conclusion
Acid rain, characterized by a pH lower than 5.6, represents a significant environmental concern due to its impact on ecosystems and infrastructure. While the exact pH value varies, it's consistently below that of normal rainfall, indicating increased acidity caused by pollution.
