Impact/Purpose:

The objective of this project is to investigate two major revisions to our current conceptual model for organic aerosols: (i) gas-particle partitioning of primary organic aerosol (POA) emissions and significant evaporation of POA at ambient conditions; (ii) photochemical aging of low-volatility organic vapors as an important source of secondary organic aerosols (SOA).

Description:

The proposed research integrates emissions testing, smog chamber experiments, and regional chemical transport models (CTMs) to investigate the sources of organic aerosol in urban and regional environments.

URLs/Downloads:

2009 Progress Report

Record Details:

Record Type:PROJECT( ABSTRACT )

Start Date:09/01/2007

Completion Date:08/31/2010

Record ID: 187706

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Related Organizations:

Role :OWNER

Organization Name :CARNEGIE MELLON UNIVERSITY

Mailing Address :5000 Forbes Ave

Citation :Pittsburgh

State :PA

Zip Code :15213

Project Information:

Approach :

Our approach relies heavily on the “basis set” framework developed at Carnegie Mellon University. The basis set lumps low-volatility organics into a set of “volatility bins” according to their vapor pressures, thereby representing the volatility distribution of the mixture. The volatility basis set, in conjunction with absorptive partitioning theory, is an efficient means for tracking gas-particle partitioning of all organics in CTMs. It also allows for multiple generations of SOA chemistry. Using dilution samplers and a smog chamber, we propose experiments to measure the effects of dilution and temperature on the gas-particle partitioning of organic aerosol from three key source classes: diesel exhaust, gasoline exhaust (with and without a catalytic converter), and wood smoke. These data will be fit using partitioning theory to determine the volatility distribution of the emissions from each source. Smog chamber experiments will be conducted to measure the SOA produced from photo-oxidation of diluted exhaust from each source across a range of atmospheric conditions. In the basis-set framework, the effects of photochemical aging are represented using a transformation matrix that maps more volatile reactant species into lower volatility bins as they undergo oxidation. This matrix will be derived from the chamber data, providing an empirical description of how the initial volatility distribution of the emissions evolves in order to match the SOA produced in the experiments. Finally, results from the experiments will be use to develop a module for CTMs such as PMCAMx and CMAQ to represent gas-particle partitioning and photochemical aging of primary emissions. This module will be implemented in PMCAMx and simulations will be performed to investigate the effects of our proposed revisions on urban and regional air quality and to evaluate model performance.

Cost :$600,000.00

Project IDs:

ID Code :R833748

Project type :EPA Grant