Review of Measurement Methods and Compositions for Ultrafine Particles

Abstract

Impactor, virtual impactor/aerosol concentrator, and aerodynamic lenses are used to separate the ultrafine particle (UP) fraction from other particle sizes for chemical analysis. Cascade impactors, such as the Micro-Orifice Uniform Deposit Impactor (MOUDI), are most commonly used in field studies, with sampling onto substrates amenable to different chemical analyses.Impactors need sufficient sampling flow rates and homogeneous deposits on the impaction surfaces for multiple chemical analyses. Mass, elements, ions, and carbon fractions can be measured on these substrates by several analytical methods. Specific organic compounds measured by solvent extraction require substantial mass loadings that can only be obtained by compositing samples from several measurement periods unless aerosol concentrators or highvolume sampling devices are used. Thermal desorption-gas chromatographic/mass spectrometry has potential to obtain organic speciation with small sample sizes. Studies of UP composition began in the late 1990s, with 25 ambient studies surveyed here. These are mostly from urban areas. Organic material, including polycyclic aromatic hydrocarbons (PAHs), usually constituted the most abundant portion of UP, with high elemental concentrations found near industrial sites.Much of the UP < 50 nm appears to be semi-volatile, consistent with it being composed by organic materials such as hopanes from engine oils or condensed secondary organic aerosol such as organic acids.

Size Resolved Particle Number Emission Factors of Motorway Traffic Differentiated between Heavy and Light Duty Vehicles

“…between gasoline and diesel cars (on road tailpipe measurement), Leipzig * # * kg / fuel total vehicle fleet. (Biswas et al, 2009) and different PAHs can easily condense on other particles (Chow and Watson, 2007). In diesel exhaust emissions of HDV around 560-760 µg/m 3 PAH were detected (Tsai et al, 2011).…”

“…The nucleation mode (< 50 nm) is mainly dominated by volatile organic and sulphur compounds, which are formed during exhaust dilution and cooling, as well as solid carbon and metal compounds (Kittelson, 1998;Chow and Watson, 2007). The nucleation mode shows the highest particle number concentration, whereas the accumulation mode (50-300 nm), dominated by carbonaceous agglomerates, contributes most significantly to the mass concentration.…”

Air Quality Measurements from the Southern Particulate Matter Supersite in Taiwan

“…Single particle mass spectrometers (SPMS) (Carson et al, 1995;Johnston and Wexler, 1995;Nordmeyer and Prather, 1994;Jayne et al, 2000;Thomson et al, 2000;Middlebrook et al, 2003) provide information on particle size (down to ~ 50 nm) and compositions (Wexler and Johnston, 2008). The micro-orifice uniform deposit impactor (MOUDI) (Marple et al, 1991) and Nano-MOUDI (MSP, USA) are alternative devices that collect PM substrates for different size bins that can be analyzed in the laboratory (Lin et al, 2005b;Tsai, et al, 2005;Fang et al, 2006;Chow and Watson, 2007).…”

Field Application of a Newly Developed Personal Nanoparticle Sampler to Selected Metalworking Operations

“…Although largely in common, exposure assessment techniques and strategies for incidental nanoparticles have been summarized by Brouwer et al (2004) and Chow and Watson (2007), whereas those for engineered nanoparticle by Maynard and Aitken (2007) and Kuhlbusch et al (2011). As shown in those reviews, exposure assessment of nanoparticles thus far has focused mostly on the particle number and mass/composition, whereas measurements of particle surface area are still sparse (Brouwer et al, 2004;Brouwer, 2010).…”