Weathering release occurs of Ca and other ions into surface waters. Rainfall is acidic because atmospheric carbon dioxide dissolves in the rainwater producing weak carbonic acid. In unpolluted environments, the rainfall pH is around 5.6. Acid rain occurs when gases such as sulfur dioxide and nitrogen oxides are present in the atmosphere. These oxides react in the rain water to produce stronger acids and can lower the pH to 4.5 or even 3.0. Sulfur dioxide, SO, comes from volcanic eruptions or from fossil fuels, can become sulfuric acid within rainwater, which can cause solution weathering to the rocks on which it
Nitrogen dioxide poisoning The standards also based on the concentration of nitrogen dioxide that show a significant and profound effects on the function of the pulmonary of asthmatic patients. Historically, some cities in the United States including Chicago and Los Angeles have high levels of nitrogen dioxide but the EPA set a standard values less than 100 ppb for a one-hour exposure and less than 53 ppb for chronic exposure. Nitrogen dioxide poisoning is not harmful to all forms of life just like "chlorine gas poisoning" and carbon monoxide poisoning. It is easily absorbed through the lungs and its inhalation result in heart