AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Wintertime Indoor and Outdoor PM2.5 Northern Utah’s Cache Valley
Randy Martin, KORI MOORE, Utah State University
Abstract Number: 611 Working Group: Indoor Aerosols
Abstract The Cache Valley in northern Utah, with a resident population of around 125,000 and no significant air pollutant point sources, has been well documented as having some of the nation’s highest PM2.5 levels during wintertime inversion events. Since 2000, the air shed has exceeded the current EPA 24-hr standard (35 micrograms per cubic meter) an average of 19 times per year (range: 2 – 40). The area was officially promulgated as non-attainment in December 2009. Past research has shown that during elevated PM2.5 episodes, the bulk of the PM2.5 consists of ammonium nitrate. It is well established that the thermal equilibrium drives the particle back into the gaseous precursors at warmer temperatures and drier humidities and, as such, one of the protective measures recommended by state and local agencies has been for the susceptible populations to remain inside during poor air quality days. As a measure of the efficacy of this recommendation, indoor PM2.5 concentrations were measured at numerous residential and public buildings across several winter episodes and compared to local outdoor concentrations. Indoor PM2.5 concentrations were determined using AirMetrics MiniVol portable, filter-based samplers. While the ambient concentrations were found to vary from <5 to >80 micrograms per cubic meter, the indoor concentrations never exceeded 30 micrograms per cubic meter. Although there was some variability, the filter-based data produced a rough linear PM2.5 relationship of INDOOR = (0.19 * OUTDOOR) + 1.64, with an overall correlation coefficient of 0.49. Additionally, a subset of studies was conducted using MetOne Aerosol Profilers, a type of optical particle counter, which showed indoor particle counts for diameters ≤ 2.5 micrometers were ≤ 15% of outdoor particle counts. These data indicate that, in reference to the PM2.5 experienced in the Cache Valley, remaining indoors does serve as an effective protective measure.