Search for a command to run...
The majority of the worldwide demand for electricity and transportation is currently met through the combustion of fossil fuels such as natural gas, petroleum-based liquid fuels, coal, and biomass. As a result, combustion remains one of the major anthropogenic sources of pollutant emissions. Key pollutants generated by combustion of hydrocarbon fuels include nitrogen oxides (NyOx), carbon monoxide (CO), sulfur oxides (SOx), unburned hydrocarbons (UHC), and particulate matter (PM). The primary nitrogen oxides generated from combustion systems are nitric oxide (NO), nitrogen dioxide (NO2), and nitrous oxide (N2O). The sum of NO and NO2 is generally referred to as NOx. Nitrogen oxides are a primary air pollutant linked to photochemical smog, acid rain, tropospheric ozone, ozone layer depletion, and global warming (Prather and Sausen, 1999; Skalska et al., 2010). When released in the atmosphere, NOx can react photochemically with organic compounds to generate O atoms, which combine with O2 to form ozone (Brasseur et al., 1998). Ground-level ozone formed in this way is one of the major components, along with particulate matter, of photochemical smog (Grewe et al., 2002). NOx can also eventually form N2O5, which reacts with water to form HNO3 (nitric acid), one of the components of acid rain (Brasseur et al., 1998).