Composition, Sources, and Properties of Airborne Particulate Matter

Abstract

TS7-05 Abstract: Airborne particulate matter is highly diverse in size, morphology, and chemical composition. This lecture reviews knowledge of the size distributions and chemistry of particles sampled from ambient air and highlights the different information, which can be elicited from size distributions expressed in terms of number, surface area, and volume or mass. Particle size distributions are liable to change in the atmosphere and the key determining factors are described. The chemical composition of pollutant particles also varies substantially with location dependent on the contribution of different source types. However, especially within Europe, there are common features among the major components, and it tends to be simply the balance between those components, which varies. Data from Pan-European studies are described. The main subdivisions of airborne particulate matter for regulatory purposes are into the size ranges known as PM10 and PM2.5, with the difference, PM2.5–10, being referred to as coarse particles. There is also a strong interest in ultrafine particles, generally taken to be PM0.1, although the most straightforward means of measuring this fraction is typically through counting the particle number concentration. The dependence of particle size distributions and chemical composition on particle sources is highlighted using road traffic exhaust, secondary particles, and abrasion sources as examples. The role of single particle analysis techniques are discussed. The geographic variation in particle concentrations, size distributions, and chemical composition is generally explicable in terms of local emissions, long-range transport, and atmospheric transformations, and examples are given from typical sampling sites in different parts of the world. In developed countries, much human exposure takes place within buildings, and the effects of penetration into the building on the size and composition of particles are examined.