Source-Apportionment of Primary Organic Carbon in the Eastern United States Combining Receptor-Models, Chemical Transport Models, and Laboratory Oxidation ExperimentsEPA Grant Number: R832162
Title: Source-Apportionment of Primary Organic Carbon in the Eastern United States Combining Receptor-Models, Chemical Transport Models, and Laboratory Oxidation Experiments
Investigators: Robinson, Allen , Adams, Peter , Donahue, Neil
Institution: Carnegie Mellon University
EPA Project Officer: Chung, Serena
Project Period: November 1, 2004 through October 31, 2007
Project Amount: $450,000
RFA: Source Apportionment of Particulate Matter (2004) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Particulate Matter , Air
This project is a comprehensive investigation of sources of primary organic carbon in the eastern U.S. using both receptor- and emission-based modeling tools in combination with individual organic compounds that are molecular markers for important source classes (e.g., levoglucosan for wood smoke). An important component of this research is to investigate the chemical stability of molecular markers; this is a critical issue in the Eastern U.S., where regional transport allows for significant time for photochemical processing.
Many PM2.5 non-attainment areas are expected to be in the Eastern U.S., but significant gaps exist in our understanding of sources of organic aerosol in this region. The goal of this research is to quantify the contribution of different source classes and geographic sub-regions to primary organic carbon (OC) in the Eastern U.S.
This project involves integrated application of emission- and receptor based modeling tools to the Eastern U.S. The three-dimensional chemical transport model PMCAMx will be used to predict the contributions of different source classes and the concentrations of individual organic species across the Eastern U.S. A suite of receptor models (CMB, PMF, UNMIX, ME2) will be used to apportion primary organic aerosol using the large datasets of speciated organic carbon data collected by the Pittsburgh Supersite and other EPA sponsored Eastern Supersites. The contribution of long-range transport of OC to PM2.5 will be evaluated using a combination of PMCAMx and receptor-based models. Comparisons of the results from “forward” PMCAMx modeling, the “reverse” receptor modeling, and ambient data from the Supersites will be used to develop a consistent picture of OC source apportionment for the eastern U.S., to improve emission inventories for primary organic carbon, and to evaluate the applicability of existing speciated emission profiles that have been largely developed in Southern California to the Eastern U.S.
Laboratory experiments will be conducted to measure the effects of photochemical aging on the composition of primary organic aerosol by exposing emissions from a diesel engine, woodstove, and meat cooking to ozone and OH radicals in a smog chamber. The proposed experiments will employ a relative rate approach to quantify the oxidation kinetics of the suite of molecular markers used for source apportionment of primary OC across a broad range of atmospheric conditions. Smog chamber experiments will also be used to photochemically age known mixtures of emissions from different sources in order quantify biases caused by photochemical aging in predictions of linear receptor models such as CMB. The oxidation kinetics for the different molecular markers will be implemented into the PMCAMx chemical scheme, and model predictions for individual organic species undergoing aging will be calculated and compared to ambient data. The results from PMCAMx, receptor models, and analyses of ambient data will be combined to assess the importance of photochemical aging on primary organic aerosol composition in the Eastern U.S. and the effects of aging on source apportionment estimates.
This research will determinate the contribution of sources and different geographic regions contribute to primary organic carbon PM2.5 in the eastern U.S. Additionally, the measurement of the oxidation kinetics of molecular markers used in source apportionment under conditions of multi-day, regional transport and quantification of biases due to photochemical aging will reduce uncertainty in source apportionment estimates.