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What are the causes of particulate matter?

Particulate matter particles can either originate from antropogenic (caused by humans) or from natural sources. Volcanic eruptions, soil erosion, sea salt or the import of desert sand are all examples of possible sources of particulate matter. Also pollen (from vegetal origin) can be a component of particulate matter.

A distinction needs to be made between the emissions and the atmospheric concentrations (also called immissions) of particulate matter. With emissions (expressed as f.e. tons per year), solely the emission of particulate matter by sources (traffic, agriculture, industry) is meant. The concentrations (most often expressed as micrograms per cubic meter) in open air are determined by those emissions and the meteorological conditions. There is, however, no linear relation between the emissions and the concentrations of particulate matter.

The primary and secondary emissions in Europe (EU27), Belgium, Flanders, Brussels and Wallonia are shown in the numbers below. The secondary emissions are expressed as an Aerosol Formation Potential (AFP), which takes into account the extent to which gaseous emissions of the precursors NOx, SO2 and NH3 contribute to the formation of secondary particulate matter (De Leeuw, 2002).

The most important antropogenic primary emissions of PM10 in Europe (EU27) of 2008 were the emissions of combustion processes in commercial, institutional and domestic energy use (35%), industrial processes (17%), road transport (14%) and agriculture (12%). These are also the most important sectors for Belgium, although industrial processes (30%) and road transport (21%) do carry some more weight. The most important antropogenic secondary emossions of PM10 in Europe are energy production and distribution (26%), road transport (25%), agriculture (17%) and industrial energy use. In Belgium, we see road transport (32%) representing an important share of these secondary emissions. The proportions of emissions per sector can vary depending on the region considered, the activities taking place, the population density, the amount of traffic, etc.