Acid rain is caused by the release of sulfur dioxide SO2 and nitrogen oxides NOx into the atmosphere, primarily from burning fossil fuels. These gases react with water, oxygen, and other substances to form sulfuric acid H2SO4 and nitric acid HNO3 , which then fall to the ground as rain, snow, or fog. Acid rain has a pH value lower than the normal pH of rainwater, which is around 5.6 due to the presence of dissolved carbon dioxide.The pH value of water bodies affected by acid rain can change over time depending on several factors, such as the frequency and intensity of acid rain, the buffering capacity of the water body, and the surrounding environment. When acid rain falls into a water body, it can lower the pH, making the water more acidic. Over time, if the input of acidic substances exceeds the water body's ability to neutralize them, the pH will continue to decrease.The buffering capacity of a water body is its ability to resist changes in pH. This is mainly determined by the presence of alkaline substances, such as calcium carbonate CaCO3 , which can neutralize acids. Water bodies with a high buffering capacity, such as those surrounded by limestone bedrock, can better withstand the effects of acid rain. However, water bodies with low buffering capacity, such as those in granite or sandstone regions, are more susceptible to pH changes.The impact of acid rain on aquatic life depends on the sensitivity of the organisms and the extent of the pH change. Many aquatic organisms, such as fish, invertebrates, and plants, have a preferred pH range in which they can thrive. When the pH of a water body becomes too acidic, it can have several negative effects on aquatic life:1. Direct toxicity: Some organisms, particularly fish and invertebrates, are sensitive to low pH levels and may die or experience reduced growth and reproduction.2. Disruption of physiological processes: Changes in pH can affect the uptake and balance of essential ions, such as calcium, which is crucial for the proper functioning of nerves and muscles in fish.3. Release of toxic metals: Acidic conditions can cause the release of toxic metals, such as aluminum, from the sediments into the water. These metals can be harmful to aquatic organisms, causing damage to gills, impairing reproduction, and even leading to death.4. Alteration of food webs: The decline or loss of certain species due to acidification can have cascading effects on the entire food web, potentially leading to a reduction in biodiversity and overall ecosystem health.To mitigate the effects of acid rain, it is essential to reduce the emissions of SO2 and NOx by implementing cleaner energy sources, improving industrial processes, and using technologies that capture and reduce these pollutants. Additionally, monitoring and managing the health of water bodies, as well as implementing strategies to increase their buffering capacity, can help protect aquatic life from the harmful effects of acid rain.