Where does partiulate matter originate from?
Particulate matter consists of primary and secondary particles. The distinction between both is made based on their origin.
Primary particles are emitted directly into the atmosphere and can be solid or fluid.They can for example be mineral particles originating from soil erosion, desert sand, volcanic ashes etc. Also black carbon, originating from domestic heating or particles emitted by traffic, either directly from the exhaust or by wear of tyres or brakes, are included. Also particles that are resuspended by traffic (i.e. dust on the road which is blown up again ) belong in this primary fraction.
Secondary particles originate in the atmosphere, through chemical reaction of gaseous precursor compounds such as ammoniac (NH3), sulphur dioxide (SO2), nitrogen oxides (NOx) or organic compounds. From these gases or the reaction products thereof, aerosols can be formed through the formation of new particles (nucleation) or by adhesion to already existing particles (coagulation). From research carried out by VMM, it turns out the secondary anorganic fraction contributes for about 40% to the total mass of PM10 in Vlaanderen. This secondary anorganic fraction is formed out of NH3, SO2 and NOx.