Wetlands are large expanses of land with a high percentage of water or wet areas, like marshes and swamps. They are extremely important for the health of the environment, because they purify rain and waste water before it enters larger rivers, lakes and oceans. They also provide habitats for wildlife.
Like all water, wetland water has a pH measurement. PH is the acidity of the water, and wetlands can have different levels of acidity that the plants and animals living in them require to thrive. When the pH changes, it can kill these plants and animals as well as prevent the wetlands from functioning. There are three main factors that can affect the pH of water in wetlands.
Waste water is the main factor that can alter the pH of any wetland. Waste water is any water altered by human settlement and can include pool water, sewage water as well as can storm drain water. Waste water can be treated with chemicals to clean out any dangerous compounds as in the case of municipal waste water, or it can be untreated as in the case of storm drain runoff. The removal or addition of chemicals to this water, as well as the existing pH of the water itself can significantly alter the pH of a wetland. For example, water in large cities is often treated to be "soft," or more acidic than in rural areas. This water has a very low pH, or high acid level, raising the pH of a wetland. If the wetland has plants that do not tolerate acidic water, they can die off.
Minerals that exist in the soil surrounding the wetlands, such as salt, can affect the pH of wetlands. While most wetlands are acclimated to the minerals in the surrounding soil, human development, mining, construction and industrial operations can put different minerals into the soil that don't exist there naturally. Rainfall will filter through these minerals, dissolving them and carrying them into the wetlands. Depending on the mineral, the wetland's pH can rise or fall. A mineral like diabase rock for example, which is common in quarries and mines, can increase the pH of a wetland if it is unearthed nearby.
Unlike waste water and dissolved minerals which can cause the pH of a wetland to fluctuate any which way, acid rain will only lower the pH, or make the water in the wetland more acidic. Acid rain is caused by compounds in the atmosphere that react with one another to form acids, which then fall back to the earth as rain. Some of these compounds include sulfur and nitrogen.