Recent Developments in Aerosol Measurement Techniques and the Metrological Issues

A small error in the aerosol measurements can lead to a considerable influence on our understanding towards its impact on climate. To better simulate aerosol effects on the earth's radiation budget, the chemical and physical characterizations of aerosol particles with accurate measurements have been a key interest in the aerosol research for last several decades. Recent advances in the chemical characterization of aerosols at bulk and molecular levels, and their physical characterization, such as size distribution, hygroscopicity, and cloud condensation nuclei (CCN) activity have improved our knowledge to better understand the aerosol sources, concentration distributions, atmospheric processing and their potential climate impacts. Apart from the complexity of atmospheric aerosols, because of the limited availability of aerosol certified reference materials, traceability data and measurement protocols, it is still a challenging task to measure the aerosol properties with reduced uncertainty. The recent developments on aerosol analytical techniques (on-line and off-line), which include gas chromatography/flame ionization detector (GC/FID)/mass spectrometry (MS)/isotope ratio mass spectrometry (irMS), ion chromatography (IC), organic carbon/elemental carbon (OC/EC) and water-soluble organic carbon (WSOC) analyzers, and physical measurements using scanning mobility particle sizer (SMPS), hygroscopicity tandem differential mobility analyzer (HTDMA) and cloud condensation nuclei-counter (CCN-C) are discussed with the metrological issues in the measurements. The importance of aerosol metrology is highlighted giving the data obtained from the laboratory studies and aerosol field campaigns.