AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Modeling Secondary Particulate Matter Concentrations and Sources for Health Effects Research in California
JIANLIN HU, Hongliang Zhang, Michael Kleeman, UC Davis
Abstract Number: 231 Working Group: Health Related Aerosols
Abstract Particulate matter (PM) mass is associated with adverse health effects but routine PM measurement data does not provide the exposure information needed to test the detailed relationships between health effects and PM trace chemical components, size fractions smaller than 2.5 µm, or sources other than the top six contributors to PM mass. In previous work we have developed a chemical transport model (UCD_Primary model) to predict exposure fields for ~20 primary PM trace components from ~900 sources in multiple size fractions (including PM$_(0.1)) over a 7-year period (2000-2006). This study has provided useful information for epidemiological studies to examine the associations between primary PM and health effects. In the present study, we develop and apply the UCD/CIT air quality model to predict the secondary PM concentrations and sources in the same time period to improve our understanding of the relationships between health and secondary PM.
The UCD/CIT model is applied to estimate hourly population weighted concentrations of primary and secondary PM. Source apportionment calculations are included for secondary organic aerosol from 9 sources: onroad gasoline, offroad gasoline, onroad diesel, offroad diesel, wood smoke, food cooking, high sulfur-content fuel, biogenic, and other sources. Gas-phase reactions are simulated using the SAPRC11 chemical mechanism.
The model predictions for gaseous and secondary PM composition are compared to ambient measurements. The current results demonstrate that O$_3, NO$_2, PM$_(2.5), EC agree well with measurements, with monthly mean fractional bias within ±0.2. NO$_3$^-, NH$_4$^+ and OC are currently under-predicted in all months. The underlying causes for this discrepancy will be discussed. The model results are used to estimate regional concentration fields and population-weighted exposure for gaseous pollutants and size/chemistry/source resolved secondary PM broken down by source types. Relationships between health effects and secondary PM are explored using the same epidemiological framework employed previously for primary PM health effects.