Analysing physical and chemical properties of airborne particles
NPL is actively researching measurement techniques for airborne particles. We provide services and also can give advice and consultancy to help companies and researchers understand how to make measurements and understand the results.
Airborne particles in ambient air are a serious human health issue and are deemed responsible for 500,000 premature deaths per year within the EU. They have traditionally been regulated for human health purposes by the mass concentration of the size fractions such as PM10 and PM2.5. However, legislation requires other metrics to be measured, such as elemental and organic carbon, total carbon, anions and cations and major metals (lead, arsenic, cadmium, mercury, nickel).
In parallel with regulations aimed at improving human health, aerosol particles also have an impact on atmospheric science. They have a direct effect on the optical properties of the atmosphere via scattering and absorption of radiation, and an indirect optical effect via cloud formation and their chemical interactions. Aerosol properties are one of the Essential Climate Variables identified by the GCOS of the World Meteorological Organisation (WMO) and many of the relevant metrics in the GCOS (such as aerosol particle number concentration, size distribution and composition) are largely in common with those in the EU Air Quality Directive. Metrology is bringing a common basis to these two different fields with benefit to both.
Specific issues associated with measuring ambient aerosol particles, as opposed to industrial or vehicle emissions, are the temporal and spatial variability of their concentrations and composition, the large range of particle sources (from the directly-emitted to those formed by gaseous precursors), the high proportion of semi-volatile particles, their hygroscopicity and the possible losses of target analyte during sampling and extraction.
NPL is actively involved in research and standardisation activities for all these physical and chemical measurements of airborne particles, including a wide range of metals (arsenic, cadmium, mercury, nickel, lead, platinum, chromium, copper, cobalt, iron, thallium, manganese, vanadium, antimony and zinc), plus number concentration (Condensation Particle Counters), size distribution (Scanning Particle Mobility Sizers) and black carbon.