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2005 Progress Report: Atmospheric Aerosols from Biogenic Hydrocarbon Oxidation
EPA Grant Number: R831079Title: Atmospheric Aerosols from Biogenic Hydrocarbon Oxidation
Investigators: Milford, Jana B. , Guenther, Alex , Helmig, Detlev , Wiedinmyer, Christine
Institution: University of Colorado at Boulder , National Center for Atmospheric Research
EPA Project Officer: Winner, Darrell
Project Period: October 1, 2003 through September 30, 2006 (Extended to September 30, 2007)
Project Period Covered by this Report: October 1, 2004 through September 30, 2005
Project Amount: $440,000
RFA: Measurement, Modeling, and Analysis Methods for Airborne Carbonaceous Fine Particulate Matter (PM2.5) (2003)
Research Category: Air Quality and Air Toxics , Particulate Matter
Description:
Objective:The objective of this research project is to estimate contributions of biogenic volatile organic compounds (BVOC), especially monoterpenes and sesquiterpenes, to secondary aerosol production in the eastern United States.
Progress Summary:The research project includes studies of sesquiterpene emissions; incorporation of biogenic emissions into the Model of Emissions of Gases and Aerosol from Nature (MEGAN); development of BVOC emission inventories for base case and future land-use scenarios; and regional-scale air quality modeling using these inventories in the Community Multiscale Air Quality Model (CMAQ). During Year 2 of the project our work focused on emissions measurements, further development of MEGAN and associated land-use databases, and preliminary modeling and performance evaluation with CMAQ.
During the past year, procedures have been developed to calculate biogenic emissions using a preliminary MEGAN framework and produce CMAQ-ready emissions files. These procedures include GIS processing of MEGAN input files and FORTRAN90 modules developed to create IO/API hourly emissions files. Sesquiterpene emissions have been included in this processing.
The CMAQ model was modified to include secondary organic aerosol formation from sesquiterpene emissions. Preliminary BVOC emissions estimates, including sesquiterpenes, were produced for the 36 km resolution CMAQ model domain used for this project. These emissions have been input to model simulations for July 2001 and January 2002.
The model performance with and without sesquiterpene emissions was investigated using an evaluation tool developed at the University of California at Riverside (UCR MPE Tools Air Quality Model Evaluation Software v2.0.1). Using this evaluation tool, the CMAQ model output was directly compared to measurements made at the IMPROVE, SEARCH, AIRS, and STN sites. Inclusion of sesquiterpene emissions generally improved the performance of the model for aerosol organic carbon (OC) concentrations during the July 2001 episode. In comparison to OC measurements at IMPROVE sites, the base case model without sesquiterpene emissions underestimated organic carbon by 48 percent in the northwestern United States, 93 percent in the Southwest, 49 percent in the Northeast, and 84 percent in the Southeast. With preliminary estimates of sesquiterpene emissions included, the model underestimated organic carbon aerosol concentrations by 62 percent in the Southwest, and overestimated organic carbon aerosol concentrations by 22 percent in the Northwest, 58 percent in the Northeast, and 12 percent in the Southeast.
Several experimental improvements in our vegetation enclosure technique and in the sample analysis procedures were achieved during the reporting period. The field GC was finalized and all previously observed problems were resolved. This instrument was used extensively at three field sites during the 2005 summer and more than 500 emission samples were analyzed on this system. We also have constructed a second, analogous instrument that was provided to colleagues at the U.S. Environmental Protection Agency National Risk Management Research Laboratory, where it is similarly being used for in-field measurements of BVOC emissions. We completed an extensive study on analytical interferences in SQT analysis that result from atmospheric ozone. A research manuscript on this work was published in the journal Environmental Science & Technology (Pollmann, et al., 2005).
Emission studies were conducted continuously during February to October 2005. Both our established adsorbent cartridge sampling technique with subsequent sample analysis on our laboratory GC/FID/MS system and the new field-GC/FID/MS instrument were used for these studies. Experiments were performed first in the National Center for Atmospheric Research greenhouse (spring) and subsequently at various locations in Boulder, Colorado. During June to August 2005, BVOC emission rates on the most important local tree species were determined at the University of Michigan Biological Station. Two 12-day experiments were conducted at the Duke Forest site in North Carolina and in the Pacific Northwest in Northern California. All together, 60 enclosure experiments on 43 different vegetation species were performed. Each experiment typically lasted 2 to 3 days to capture diurnally occurring changes in emission rates. All data have been analyzed and currently are undergoing final quality control procedures.
Future Activities:The CMAQ model is being updated to version 4.5. Additional modifications are being made to the gas-phase chemistry and secondary organic aerosol modules in CMAQ to account for reactive gas-phase products of sesquiterpene oxidation and to consider the polymerization of secondary organic aerosol. Testing of these modifications is underway. In the coming year, the biogenic isoprene emissions estimates used in CMAQ will be updated following the most recent version of MEGAN and biogenic sesquiterpene emissions in MEGAN and CMAQ will be refined based on greenhouse and field data. If available from EPA colleagues, the CMAQ model will be set up at 12 km horizontal resolution and increased vertical resolution. Quantitative evaluation of CMAQ will be performed with the new BVOC emission estimates from the updated MEGAN outputs. Supersite measurements will be included in future evaluations.
More enclosure experiments are planned during the 2006 growing season. We have established a highly beneficial partnership with a local tree nursery and are planning to continue experiments at this facility. Experiments will be started in early spring with the intent to specifically investigate BVOC emissions during the flowering phase of many local tree species in the early season. So far, most of our experiments have been on important shrubs and tree species, and we have investigated only a few crops. More thorough studies on important U.S. crops will be an emphasis of our planned 2006 experiments.
Journal Articles on this Report: 1 Displayed | Download in RIS Format
| Other project views: | All 16 publications | 5 publications in selected types | All 5 journal articles |
| Type | Citation | ||
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Pollmann J, Ortega J, Helmig D. Analysis of atmospheric sesquiterpenes: sampling losses and mitigation of ozone interferences. Environmental Science & Technology 2005;39(24):9620-9629. |
R831079 (2005) |
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biogenic hydrocarbons, secondary organic aerosols, sesquiterpenes, air quality, analytical chemistry, atmospheric sciences, environmental monitoring,
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Ecosystem Protection/Environmental Exposure & Risk, Air, Scientific Discipline, RFA, Analytical Chemistry, Air Pollution Effects, air toxics, Atmospheric Sciences, Environmental Engineering, particulate matter, Environmental Chemistry, Monitoring/Modeling, Environmental Monitoring, mass spectrometry, aerosol analyzers, health effects, Volatile Organic Compounds (VOCs), carbon particles, particulate matter mass, measurement methods, aerosol particles, air sampling, emissions, biogenic hydrocarbon oxidation, air quality models, atmospheric particulate matter, thermal desorption
Relevant Websites:
http://bai.acd.ucar.edu/Megan/index.shtml
Progress and Final Reports:
2004 Progress Report
Original Abstract
2006 Progress Report
Final Report