Peter Harley

Associate Scientist IV
TIIMES - ACD
BEACHON

Contact Information:
PO Box 3000, Boulder, CO 80307-3000
Office: FL0 - 3170
Telephone: 303-497-1863
Email: harley@ucar.edu
Home Page | BAI Group Page

Project Summary:

Model of Emissions of Gases and Aerosols from Nature ( MEGAN)

My TIIMES research focuses on quantifying trace gas emissions from plants and elucidating short-term and long-term environmental controls over those emissions.  These efforts involve both laboratory and field measurements, and are conducted within the framework of the Model of Emissions of Gases and Aerosols from Nature (MEGAN). Initially, these efforts were focused on the potential impacts of biogenic emissions on tropospheric oxidant chemistry, but now increasingly relate to the involvement of trace gas emissions on formation and growth of secondary organic aerosols.

MEGAN Community Data Portal

MEGAN Interactions Group

Work this fiscal year has included studies of low molecular weight oxygenated compounds (e.g., methanol, acetone, acetaldehyde) and attempts to better quantify emissions of high molecular weight terpenoids such as sesquiterpenes.  Both of these efforts have been facilitated by the development of a laboratory-based FLUXTRON platform for the measurement of emissions under controlled environmental conditions.  To promote sesquiterpene research, I helped organize and coordinate an multi-laboratory intercomparison of analytical techniques for identifying and quantifying sesquiterpenes.

Future plans involve continuing these efforts under the umbrella of BEACHON.  This will involve attempts to better understand and quantify the mid- to long-term effects of global change on biogenic emissions and their potential feedbacks.

Biological & physical controls over emission of potential SOA precursors from vegetation

NCAR PI(s):  Peter Harley, Jim Greenberg, Alex Guenther, Thomas Karl
Collaborators: Russ Monson (CU/CIRES); Ray Fall (CU/CIRES); Chris Geron (USEPA); Mark Potosnak (DRI/Univ. of Nevada, Reno); Detlev Helmig (CU/INSTAAR)

Brief description of the project objectives and approach:
Through a combination of laboratory (including NCAR greenhouse and Fluxtron facilities) and field measurements, we plan to improve our estimation of the magnitude of emissions of BVOC from vegetation and our understanding of the controls over those emissions.  In the context of BEACHON, we will focus on those BVOC implicated in formation and growth of secondary organic aerosol (a list including, but not necessarily restricted to: isoprene, monoterpenes and sesquiterpenes).  Abiotic controls include light and temperature, possibly CO2, and stresses such as drought and elevated O3.  Potential biological controls include plant phenology and stress due to herbivory.  Though emissions of these are incorporated into the current version of MEGAN, realistic parameterizations will require substantially more emissions data from a wide variety of plant species and growth forms.  Elucidation of controls over emissions requires a combination of controlled experiments under laboratory conditions, and field measurements obtained over complete (and ideally multiple) growing seasons.

Measurements will be accomplished using a variety of vegetation enclosure systems, from temperature controlled leaf cuvettes to branch enclosures to whole plant enclosures, and BVOC identification and quantitation will be accomplished using a variety of analytical techniques including GC-FID, GC-MS, and PTR-MS.  Leaf enclosure experiments will also incorporate simultaneous measurements of net photosynthesis, evapotranspiration, and stomatal conductance.

FY2007 accomplishments:

• Data analysis and manuscript preparation arising from July 2006 Fluxtron study of the effects of episodic high O3 concentrations on emissions of isoprene.

• Sesquiterpene measurement technique evaluation study carried out in the NCAR Greenhouse and the laboratory of Detlev Helmig (CU/INSTAAR) involving 13 researchers and 6 institutions.

• Continuing Fluxtron vegetation screening studies for emissions of lightweight oxygenated VOC, mono- and sesquiterpenes.

Relevance to BEACHON:
To the extent that SOA (and ice nuclei from biogenic sources) contribute to cloud formation and determination of cloud radiative properties and precipitation, better understanding of the sources of biogenic SOA precursors is essential.  Understanding of potential feedbacks on BVOC emissions due to alterations in cloud properties and precipitation will require far better understanding of the effects of light and, especially, effects of soil moisture, on these emissions.  Assuming that BEACHON incorporates above-canopy BVOC flux measurements, concomitant measurements at the leaf or branch scale will both constrain above-canopy flux estimates and help explain observed variations in fluxes on diurnal and seasonal (interseasonal) time scales.

Publications:

Harley, P., J. Greenberg, Ulo. Niinemets, A. Guenther, 2007: Environmental controls over methanol emission from leaves. Biogeosciences Discuss., 4, 2593-2640.

Ortega, J., D. Helmig, A. Guenther, P. Harley, S. Pressley, C. Vogel, 2007: Flux estimates and OH reaction potential of reactive biogenic volatile organic compounds (BVOCs) from a mixed northern hardwood forest. Atmos. Environ., Elsevier Ltd., 41, 5479-5495, doi: 10.1016/j.atmosenv.2006.12.033.

Helmig, D., J. Ortega, T. Duhl, D. Tanner, A. Guenther, P. Harley, C. Wiedinmyer, J. Milford, T. Sakulyanontvittaya, 2007: Sesquiterpene emissions from Pine Trees - Identifications, Emission Rates and Flux Estimates for the Contiguous United States. Environ. Sci. Technol., 41, 1545 -1553, doi: 10.1021/es0618907.