Improving chemical transport model predictions of organic aerosol: Measurement and simulation of semivolatile organic emissions from mobile and non-mobile sourcesEPA Grant Number: RD834554
Title: Improving chemical transport model predictions of organic aerosol: Measurement and simulation of semivolatile organic emissions from mobile and non-mobile sources
Investigators: Robinson, Allen
Current Investigators: Robinson, Allen , Donahue, Neil
Institution: Carnegie Mellon University
EPA Project Officer: Chung, Serena
Project Period: April 1, 2010 through March 31, 2013
Project Amount: $500,000
RFA: Novel Approaches to Improving Air Pollution Emissions Information (2009) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Air
Organic material contributes a significant fraction of PM2.5 mass across all regions of the United States, but state-of-the-art chemical transport models often substantially underpredict measured organic aerosol concentrations. Recent revisions to these models that account for gas-particle partitioning of primary emissions and secondary organic aerosol production from all low-volatility organics improve model performance, but full implementation of these ideas is hampered by critical data gaps. This proposal addresses one of those gaps, namely volatility-based emissions data that are needed to develop inventories for the next generation of chemical transport models.
The core hypothesis underlying this project is that volatility based representations of primary organic aerosol emissions data will improve predictions of chemical transport models. Specific project objectives include: to investigate methodologies for routine measurement of the volatility distribution of emissions of low-volatility organics from combustion systems; to measure emission factors for, and volatility distributions of, low-volatility organics emitted by on-road and non-road mobile sources; to develop techniques to efficiently update emission inventories for use with the volatility basis set approach using the emissions data collected by this project and other studies; and to conduct chemical transport model simulations with the updated inventories for the Eastern United States and California and to compare model predictions with ambient organic aerosol data.
The proposed research integrates emissions testing, ambient measurements, a tunnel study, emission inventory development, and regional chemical transport modeling to quantify and fix suspected errors involving the representation of low-volatility organics in existing emission inventories. The plan is to update inventories by representing primary organic aerosol emissions using a volatility distribution and by quantifying the amount of missing intermediate volatility vapors. The source testing will be performed in collaboration with the California Air Resources Board using chassis dynamometers and gasoline, diesel and non-road sources recruited from the in-use fleet.
The source test data will be compared to measurements made in a highway tunnel to assess the applicability of the chassis dynamometer data to in-use vehicle emissions. The experiments will feature advanced instrumentation coupled with dilution sampler and thermodenduer volatility measurements. Gas-chromatography mass-spectrometry of filter and sorbent samples will be used to quantify the emissions of all low volatility organics. The new data will be used to update emission inventories used by chemical transport models. Predictions of these models for the Eastern United States and California will be compared to ambient organic aerosol data to evaluate the impact of the proposed revisions on model performance.
Expected results and outputs from this research include: an extensive database of the effects of dilution and temperature on gas-particle partitioning of organic aerosols emitted by mobile sources; fuel-based emission factors of all low-volatility organic mass emitted by different classes of mobile sources including gasoline powered vehicles, diesel vehicles, and non-road sources; updated emission inventories of low-volatility organics from mobile sources and biomass burning for the next generation of chemical transport models; assessment of the effects of the updated inventories on chemical transport model predictions on urban and regional organic aerosol levels in different seasons; and a detailed evaluation of model predictions using ambient data.