Grantee Research Project Results
2000 Progress Report: Observation-Based Approaches to VOC Emissions Inventory Reconciliation And Control Strategies for Photochemical Smog
EPA Grant Number: R826238Title: Observation-Based Approaches to VOC Emissions Inventory Reconciliation And Control Strategies for Photochemical Smog
Investigators: Henry, Ronald C.
Current Investigators: Henry, Ronald C. , Chang, Yu-Shuo
Institution: University of Southern California
EPA Project Officer: Hahn, Intaek
Project Period: February 1, 1998 through January 31, 2001 (Extended to August 31, 2003)
Project Period Covered by this Report: February 1, 1999 through January 31, 2000
Project Amount: $441,574
RFA: Ambient Air Quality (1997) RFA Text | Recipients Lists
Research Category: Air , Air Quality and Air Toxics
Objective:
Anthropogenic volatile organic compounds (VOCs) are precursors of ozone in urban atmospheres. Self-reported emission inventories of VOCs are often inaccurate, out-of-date or both (Henry et al., 1996). This project seeks to reconcile emission inventories of VOCs with the results of multivariate receptor modeling applied to ambient measurements from the Photochemical Assessment Monitoring Stations (PAMS) network. Another objective is to estimate the formation rates of ozone in the atmosphere from routine monitoring data with a hybrid source receptor model (Henry et al., 1991). The observed formation rates can then be compared to those predicted by photochemical models and could form the basis of an observational model of ozone formation.Progress Summary:
The emphasis of the project has centered on PAMS VOC data from Houston and Beaumont/Port Arthur, TX, for the years 1994, 1995, 1996, and 1997. The PAMS sites in these cities are located close to major petrochemical industries. Seven major source types were determined from the data by the UNMIX multivariate receptor model. These sources included vehicle tailpipe emissions, refineries, and chemical and plastics manufacturing. Some major sources are yet to be identified (e.g., in Houston 1997 data, a majority of the Total Non-Methane Organic Compound (TNMOC) is from a single species, isobutane). The source of this is not known but may be the manufacture of methyl tertiary butyl ether (MTBE).The emissions inventories for the relevant counties were obtained from the U.S. Environmental Protection Agency's (EPA) Aerometric Information Retrieval System (AIRS) database. An attempt was made to reconcile the VOC emissions inventories with the sources determined from analysis of the PAMS data. In general, the Beaumont/Port Arthur emissions inventory appeared to agree well with the results of the UNMIX analysis of the PAMS data. This was not true for Houston, however. Some sources found in the data did not appear in the inventory and vice versa. Furthermore, the VOC emission inventories for Houston (Harris County) for the years 1995, 1996, and 1997 are similar, except for a general decrease in emission levels. This is in contrast to the receptor modeling results from the PAMS VOC data, which showed great variation in sources and emission levels over the 3-year period.
Rates of ozone formation in the Los Angeles basin were derived for selected months of 1985, 1986, and 1995 from routine ozone monitoring data and wind fields supplied by the South Coast Air Quality Management District. The peak ozone formation rates during August fell from about 30 ppb/hr in 1985 to 7 ppb/hr in 1995, reflecting the progress made in reducing emissions of precursor species in the South Coast Air Basin.
Future Activities:
Our method of reconciliation of sources derived by UNMIX analysis of PAMS data with VOC emissions inventories depends heavily on the use of wind data at the site. The technique has been to average the source contributions to TNMOC over 10 degree windows of wind direction and to compare these to the emissions sources in that 10 degree sector listed in the inventory, after weighting the emissions by the inverse of the distance from the site. Problems with this method are the rather coarse resolution of 10 degrees and the artifacts caused by the arbitrary boundaries of the 10 degree sectors. In the next year, we will apply methods developed for non-parametric regression that overcome both of these problems. We will investigate the use of kernel estimators to find the mean values of source contributions and species concentrations as a function of wind direction in 1-degree increments. Receptor modeling of PAMS data for additional sites and years will be undertaken. Data availability and quality will be the prime criterion in selecting the sites, as always.As a test of the model, an attempt will be made to reconcile the carbon monoxide emissions inventory in Los Angeles with emissions rates estimated by the hybrid receptor model. Empirically derived ozone formation rates will be statistically related to air quality and meteorological parameters.
References:
Henry RC, Spiegelman CH, Collins JF, Park ES. Reported emissions of volatile organic compounds are not consistent with observations. Proceedings of the National Academy of Sciences, USA 1997;94:6596-6599.
Henry RC, Wang YL, Gebhart KA. The relationship between empirical orthogonal functions and sources of air pollution. Atmospheric Environment 1991;25A:503-509.
Journal Articles:
No journal articles submitted with this report: View all 15 publications for this projectSupplemental Keywords:
air, tropospheric, ozone, particulates, VOC, modeling, receptor-based, observational, PAMS, emissions, wind direction, statistical analysis., RFA, Scientific Discipline, Air, particulate matter, Environmental Chemistry, mobile sources, tropospheric ozone, Atmospheric Sciences, Ecological Risk Assessment, Ecology and Ecosystems, photochemical assessment monitoring, phototchemical modeling, multivariate receptor modeling, fine particles, ambient measurement methods, ozone, air quality models, ambient air, VOCs, photochemical smog, air sampling, photochemistry, emissions inventory, atmospheric transport, Volatile Organic Compounds (VOCs), measurement methods , atmospheric chemistry, chemical speciation sampling, particle transportRelevant Websites:
https://www.epa.gov/ttn/amtic/meetings.html
(Workshop on UNMIX and PMF As Applied to PM2.5. Contains links to the
application of UNMIX to two test data sets, one simulated and one real and to the UNMIX user's manual.)
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.