![]() ![]() They correspond to a lower visibility disorder than fogs, except in exceptional cases of haze in desert or semi-desert regions. Mists (mist or haze), are made up of smaller droplets or solid particles.When visibility is reduced to less than 1 kilometer,particles often have a size greater than 5 µm.In the atmosphere near the ground, the term fog is used when visibility is reduced to less than 1 kilometre. ![]() Fogs ( fog and smog) are formed by a suspension of liquid droplets resulting from the condensation of a vapour, or from a spray.In English, fume also refers to very fine particles resulting from the condensation of a vapour. The term smoke refers to generally finer particles resulting from combustion.Dust is a solid particle, usually greater than 1 µm, suspended by mechanical processes such as wind erosion (examples: sandstorm, ash, road dust, pollen).1.2 Terminologies used to differentiate between particlesĭifferent terms are used to describe particular types of aerosols, often incorrectly. It is generally accepted that the (spherical) particles of an aerosol have a dimension (their diameter) approximately less than 100 µm or 0.1 mm. For them to remain suspended in the gas, their falling rate must be low. Particulate matter is therefore one of the components of an aerosol. In reality, the word aerosol refers to the mixture of a gas, usually air, and fine solid or liquid suspended particles (see Figure 1). A particle is often and incorrectly called an aerosol. Aeolian aerosol from the Sahara photographed over the northeast Atlantic Ocean. ![]() This article aims to provide a better understanding of what particulate matter in the atmosphere means and the problems it raises, particularly in terms of quantifying its effects on health. Their finely divided state covers designations as well as physical and mechanical properties that are often poorly understood. They are considered to be one of the main causes of pollution-related mortality. Particulate matter is a major component of air pollutants. ![]()
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