Environmental Engineering Reference
In-Depth Information
Source: Environmental Protection Agency
Particulate matter (PM) includes solid or liquid particles in the atmosphere and can be either a primary pol-
lutant from direct emissions, or a secondary pollutant formed from the chemical reactions of substances such
as SO 2 and NO x . Dust, soot, smoke, dirt, metals, and liquid particles are all examples of particulate matter.
Particle size tends to vary depending on the source. As a primary pollutant, PM can come from wood burning,
trucks, factories, buses, stone crushing, construction sites, unpaved roads, and bare fields. Secondary or indir-
ect forms of PM can come from vehicle, factory, or power plant emissions.
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