A Personal Exposure Aerosol Screen Model (PEASM) for Near-Road Size-Resolved Aerosol and Gas Concentrations: Evalution with Ambient Measurements

Sang-Rin Lee(1), Nicole Riemer(2), JAEMEEN BAEK(1), Matthew West(2), Rahul A Zaveri(3), Katharine Moore(4), Constantinos Sioutas(4), Ralph Delfino(5), Alberto Ayala(6), Todd Sax(6) and Charles O Stanier(1)

(1) University of Iowa, iowa city, (2) University of Illinois, Urbana-Champaign, (3) PNNL, Richland, (4) University Southern California, LA, (5) University of California, Irvine, (6) California Environmental Protection Agency, Sacramento

     Abstract Number: 340
     Last modified: November 9, 2009

Abstract
Ultrafine particles (<0.1 micro-meter) mainly emitted by mobile sources are potentially a key causal pollutant in adverse human health effects. However, due to the well-demonstrated spatial variation in urban environments, and the difficulties in representative sampling of urban air toxics and ultrafine particles, models for exposure of these pollutants are expected to have wide utility. A Personal Exposure Aerosol Screening Model (PEASM) is presented. This is combination of models to allow full simulation of emissions, dilution, particle/gas aerosol dynamics, and thermodynamics for urban scale exposure studies. PEASM uses a two stage calculation approach, first calculating vehicular carbon monoxide at high spatial resolution (but low computational cost), and then in a 2nd pass implementing aerosol dynamics on spatial subdomains upwind of receptors of interest.

At each receptor, the number and mass size distribution can be calculated by PEASM, together with particle chemistry and source (e.g. road) tagged particle loadings. The evaluation of the PEASM against data from the Harbor Communities Monitoring Study will be presented. The measured variables include particle number and particle size distribution measured at over 14 sites. This study was conducted from mid-February to mid-December 2007 to investigate diurnal, seasonal and spatial patterns. Total number concentration varied up to factor of 10 (<10,000 cm-3 up to 90,000 cm-3 for hourly averages).
The road preprocessor program is presented which uses ArcGIS and Matlab, and can successfully duplicate a real road network for simulation in PEASM. Traffic activity model data (from Southern California Association for Governments) and 1x1 km meteorology from the WRF model is also used as input data. Also presented are the results from a vertically resolved Lagrangian model. PEASM implements size resolved aerosol dynamics module using PartMC and gas/particle thermodynamics and photochemistry using MOSAIC.