Characterization of a Novel, Mid-Cost Device for Ambient Monitoring of Ultrafine Particles
UNA TRIVANOVIC, Osnan Maragoto Rodriguez, Kevin Auderset, Florian Huewe, Konstantina Vasilatou, Federal Institute of Metrology METAS
Abstract Number: 332
Working Group: Instrumentation and Methods
Abstract
Ultrafine particle (UFP) number concentration is not routinely monitored at air quality monitoring stations despite the potentially significant health impacts relative to larger particles. This is in part due to the relatively high cost and complexity of such measurements compared to mass-based measurements of particulate matter below 2.5 µm (PM2.5). Euro7 regulations for light- and heavy-duty vehicles require measurement of solid particle (sPN) and total particle number concentration (tPN) down to 10 nm. The effectiveness of Euro7 regulations and UFP health effects can only be assessed through ambient monitoring of these quantities. Here, a novel, mid-cost device for monitoring UFPs down to 10 nm is characterized in order to help bridge the gap between ambient air quality and tailpipe emissions.
The AirPN10 uses a diffusion charger (DC), already approved for measuring PN in diesel exhaust, to reliably measure ambient particles with geometric mean mobility diameters (GMDmob) in the range of 10 – 200 nm. Particles either go directly to the detector (tPN) or pass through a high temperature zone to remove volatiles (sPN). The AirPN10 was characterized with polydisperse miniCAST soot with GMDmob of 10, 15, 23, 50, 80, 120 and 200 nm. The two-stage DC sensor provides an estimate of the GMDmob with excellent agreement to that measured by a scanning mobility particle spectrometer (SMPS; TSI 3752, 3082 and 3085). The sPN and tPN concentrations were compared to a traceable reference condensation particle counter (CPC; TSI 3752). Acceptable counting efficiencies (CE) were considered to be the greater of ± 25% or 1500 cm-3. For GMDmob = (15 – 120) nm, the CE was almost entirely within the acceptance bands. At GMDmob = 10 and 200 nm, CE was slightly lower at approximately 0.5 and 0.7, respectively. The AirPN10 also performed well at a range of ambient pressures, temperatures and humidities.