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
Oil sands pyrene, and benzo(a)pyrene) and that these emissions had been previously unreported. The Alberta government computes an Air Quality Health Index (AQHI) from sensors in five communities in the oil sands region, operated by a "partner" called the Wood Buffalo Environmental Association (WBEA). Each of their 17 continuously monitoring stations measure 3 to 10 air quality parameters among carbon monoxide (CO), hydrogen sulfide (), total reduced sulfur (TRS), Ammonia (), nitric oxide (NO), nitrogen dioxide (), nitrogen oxides (NO), ozone (), particulate matter (PM2.5), sulfur dioxide (), total hydrocarbons (THC), and methane/non-methane hydrocarbons (/NMHC). These AQHI are said to indicate 'low