Fossil fuel percent of [its] weighted emissions in 1998. Combustion of fossil fuels also produces other air pollutants, such as nitrogen oxides, sulfur dioxide, volatile organic compounds and heavy metals. According to Environment Canada: "The electricity sector is unique among industrial sectors in its very large contribution to emissions associated with nearly all air issues. Electricity generation produces a large share of Canadian nitrogen oxides and sulphur dioxide emissions, which contribute to smog and acid rain and the formation of fine particulate matter. It is the largest uncontrolled industrial source of mercury emissions in Canada. Fossil fuel-fired electric power plants also emit
Sulfur produces the polysulfanes, HS where x = 2, 3, and 4. Ultimately, reduction of sulfur produces sulfide salts: The interconversion of these species is exploited in the sodium-sulfur battery. The radical anion S gives the blue color of the mineral lapis lazuli. The principal sulfur oxides are obtained by burning sulfur: Multiple sulfur oxides are known; the sulfur-rich oxides include sulfur monoxide, disulfur monoxide, disulfur dioxides, and higher oxides containing peroxo groups. Sulfur forms sulfur oxoacids, some of which cannot be isolated and are only known through the salts. Sulfur dioxide and sulfites () are related to the unstable sulfurous