What Is an Aerosol?
An aerosol consists of fine particles of liquid or solid substances suspended in the air, or in any other gas. It is not, as many people think, merely a spray for use in applying paint easily, or getting rid of unpleasant smells. The germs of diseases, for example, are to be found suspended in the air, and these dangerous aerosols can be dealt with by spraying chemicals to form another aerosol which destroys the germs. Leaves of plants attacked by pests can be treated in the same way.
Chemicals in the container part of an artificial aerosol spray are stored there under very high pressure. When the release trigger is pressed a valve opens, and the chemicals are forced out through a tiny hole in a fine spray. This invention is useful not only in the home, but also to a wide variety of specialist users.
Aerosols can be natural or anthropogenic. Examples of natural aerosols are fog, forest exudates and geyser steam. Examples of artificial aerosols are haze, dust, particulate air pollutants and smoke. The liquid or solid particles have diameter mostly smaller than 1 μm or so; larger particles with a significant settling speed make the mixture a suspension, but the distinction is not clear-cut. In general conversation, aerosol usually refers to an aerosol spray that delivers a consumer product from a can or similar container.
Other technological applications of aerosols include dispersal of pesticides, medical treatment of respiratory illnesses, and combustion technology. Diseases can also spread by means of small droplets in the breath, also called aerosols. Aerosol science covers generation and removal of aerosols, technological application of aerosols, effects of aerosols on the environment and people, and a wide variety of other topics.
For some people, the term “aerosol” refers to the propellant in a spray can — because substances like hairspray and spray paint come out of those cans as a mist of small particles. But, “aerosols are so much more than just what is in your hairspray can.”
Scientists define an aerosol as a suspension of particles in the atmosphere. They have both human-made and natural sources. For example, aerosols can form naturally when pine trees release a chemical called alpha-pinene, an oil that condenses into particles that can be seen suspended as a haze — for example, above the Smoky Mountains (giving them their name). Other types of aerosol particles form during combustion or other industrial processes in factories and car engines, from burning biomass (such as trees and brush) to clear land for agriculture, and even in cooking fires.
“Greenhouse gases like carbon dioxide, methane, and nitrous oxide have a large effect on climate because they trap heat in the atmosphere and warm the planet. However, when we look at our estimates of how much warming we should be seeing based on the amounts of greenhouse gases in the atmosphere, something is off. The warming should be greater, which leads us to assume that something else is mitigating the effect of these gases on warming.”