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An aerosol is a colloid of fine solid particles or liquid droplets, in air or another gas.〔Hinds, 1999, p. 3〕 Aerosols can be natural or artificial. 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.〔Hidy, 1984, p. 254.〕 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.〔 == Definitions == An aerosol is defined as a colloidal system of solid or liquid particles in a gas. An aerosol includes both the particles and the suspending gas, which is usually air.〔 Frederick G. Donnan presumably first used the term ''aerosol'' during World War I to describe an aero-solution, clouds of microscopic particles in air. This term developed analogously to the term hydrosol, a colloid system with water as the dispersing medium.〔Hidy, 1984, p. 5〕 ''Primary aerosols'' contain particles introduced directly into the gas; ''secondary aerosols'' form through gas-to-particle conversion.〔Hinds, 1999, p. 8〕 Various types of aerosol, classified according to physical form and how they were generated, include dust, fume, mist, smoke and fog.〔Colbeck, 2014, Ch. 1.1〕 There are several measures of aerosol concentration. Environmental science and health often uses the ''mass concentration'' (''M''), defined as the mass of particulate matter per unit volume with units such as μg/m3. Also commonly used is the ''number concentration'' (''N''), the number of particles per unit volume with units such as number/m3 or number/cm3.〔Hinds, 1999, pp. 10-11.〕 The size of particles has a major influence on their properties, and the aerosol particle radius or diameter (''dp'') is a key property used to characterise aerosols. Aerosols vary in their dispersity. A ''monodisperse'' aerosol, producible in the laboratory, contains particles of uniform size. Most aerosols, however, as ''polydisperse'' colloidal systems, exhibit a range of particle sizes.〔Hinds, 1999, p. 8.〕 Liquid droplets are almost always nearly spherical, but scientists use an ''equivalent diameter'' to characterize the properities of various shapes of solid particles, some very irregular. The equivalent diameter is the diameter of a spherical particle with the same value of some physical property as the irregular particle.〔Hinds, 1999, p. 10.〕 The ''equivalent volume diameter'' (''de'') is defined as the diameter of a sphere of the same volume as that of the irregular particle.〔Hinds, 1999, p. 51.〕 Also commonly used is the aerodynamic diameter. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「aerosol」の詳細全文を読む スポンサード リンク
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