Vehicle emission standardEmission standards are the legal requirements governing air pollutants released into the atmosphere. Emission standards set quantitative limits on the permissible amount of specific air pollutants that may be released from specific sources over specific timeframes. They are generally designed to achieve air quality standards and to protect human life. Different regions and countries have different standards for vehicle emissions. Many emissions standards focus on regulating pollutants released by automobiles (motor cars) and other powered vehicles.
Air quality indexAn air quality index (AQI) is an indicator developed by government agencies to communicate to the public how polluted the air currently is or how polluted it is forecast to become. As air pollution levels rise, so does the AQI, along with the associated public health risk. Children, the elderly, and individuals with respiratory or cardiovascular problems are typically the first groups affected by poor air quality. When the AQI is high, governmental bodies generally encourage people to reduce physical activity outdoors, or even avoid going out altogether.
Peroxyacyl nitratesIn organic chemistry, peroxyacyl nitrates (also known as Acyl peroxy nitrates, APN or PANs) are powerful respiratory and eye irritants present in photochemical smog. They are nitrates produced in the thermal equilibrium between organic peroxy radicals by the gas-phase oxidation of a variety of volatile organic compounds (VOCs), or by aldehydes and other oxygenated VOCs oxidizing in the presence of .
Nitrogen cycleThe nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among atmospheric, terrestrial, and marine ecosystems. The conversion of nitrogen can be carried out through both biological and physical processes. Important processes in the nitrogen cycle include fixation, ammonification, nitrification, and denitrification. The majority of Earth's atmosphere (78%) is atmospheric nitrogen, making it the largest source of nitrogen.
Persistent organic pollutantPersistent organic pollutants (POPs) are organic compounds that are resistant to degradation through chemical, biological, and photolytic processes. They are toxic chemicals that adversely affect human health and the environment around the world. Because they can be transported by wind and water, most POPs generated in one country can and do affect people and wildlife far from where they are used and released.
NitrogenNitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at seventh in total abundance in the Milky Way and the Solar System. At standard temperature and pressure, two atoms of the element bond to form N2, a colorless and odorless diatomic gas. N2 forms about 78% of Earth's atmosphere, making it the most abundant uncombined element in air.
Wood fuelWood fuel (or fuelwood) is a fuel such as firewood, charcoal, chips, sheets, pellets, and sawdust. The particular form used depends upon factors such as source, quantity, quality and application. In many areas, wood is the most easily available form of fuel, requiring no tools in the case of picking up dead wood, or few tools, although as in any industry, specialized tools, such as skidders and hydraulic wood splitters, have been developed to mechanize production.
ParticulatesParticulates or atmospheric particulate matter (see below for other names) are microscopic particles of solid or liquid matter suspended in the air. The term aerosol commonly refers to the particulate/air mixture, as opposed to the particulate matter alone. Sources of particulate matter can be natural or anthropogenic. They have impacts on climate and precipitation that adversely affect human health, in ways additional to direct inhalation.
Radical substitutionIn organic chemistry, a radical-substitution reaction is a substitution reaction involving free radicals as a reactive intermediate. The reaction always involves at least two steps, and possibly a third. In the first step called initiation (2,3), a free radical is created by homolysis. Homolysis can be brought about by heat or ultraviolet light, but also by radical initiators such as organic peroxides or azo compounds. UV Light is used to create two free radicals from one diatomic species.
NitrationIn organic chemistry, nitration is a general class of chemical processes for the introduction of a nitro group () into an organic compound. The term also is applied incorrectly to the different process of forming nitrate esters () between alcohols and nitric acid (as occurs in the synthesis of nitroglycerin). The difference between the resulting molecular structures of nitro compounds and nitrates () is that the nitrogen atom in nitro compounds is directly bonded to a non-oxygen atom (typically carbon or another nitrogen atom), whereas in nitrate esters (also called organic nitrates), the nitrogen is bonded to an oxygen atom that in turn usually is bonded to a carbon atom (nitrito group).
