Investigators:

Alex Guenther

Chris Geron

Grants:

Description:

Goal: Improve our ability to predict regional air quality (e.g., particulates and ozone) and climate through a quantitative understanding of the processes controlling the exchange of trace gases and aerosols between the atmosphere and vegetation canopies. We also seek to characterize reactive carbon and nitrogen fluxes in both aerosol and gas phase to improve our understanding of the cycling of these elements.

Background: The EPA (Bob Arnts, Chris Geron, Jeff Herrick, John Walker) has collaborated with Duke University (Fred Mowry, Ram Oren, John Sigmon) since 1995 on investigations of leaf to canopy scale emissions of biogenic volatile organic compounds (BVOC). Since the summer of 2000, this has included flux studies using a relaxed eddy accumulation (REA) system and needle level emissions using gas exchange systems at ring 6 of the Duke University FACTS1 experimental site. Recently, data from this study and others (including new ¹⁴C data) have implicated BVOC as important precursors not only of ozone, but also aerosols as well. In addition, nitrogenous trace gases, especially in North Carolina and other agricultural regions, are also increasingly important as a component of the overall nitrogen cycle and in ozone and aerosol chemistry. We seek to conduct an intensive study to characterize and quantify the emission, deposition, and chemical processing of these BVOC and nitrogenous compounds.

Approach: A series of laboratory and field experiments will be used to parameterize and rigorously evaluate the near surface fluxes over vegetated surfaces predicted by chemistry and transport models. A 1-D model will be used to connect the scale at which field measurements will occur with the scale used for 3-D regional air quality models. Laboratory studies will be used to characterize short term (minutes to hours) and long term (days to weeks) variations in biogenic VOC (sesquiterpenes, monoterpenes, isoprene, acetone, methanol, acetaldehyde and other carbonyls) emissions from live foliage and leaf litter. Field enclosure systems will be used to evaluate the observed relationships. Vertical profiling systems (based on towers and tethered balloon) will be used to quantify concentrations and fluxes at multiple heights below, within and above canopies.

Summer 2003 Field Campaign: The initial field campaign will be held at Duke ForestLoblolly Pine Plantation, North Carolina, USA. A 3-4 week intensive has been tentatively scheduled for July. A more limited set of measurements, e.g., a-pinene and sesquiterpene fluxes, will be continue over a longer period. Nitrogen fluxes may also continue if data from the intensive indicates this may be useful. Existing Duke Forest towers will be used to access different measurement heights. The tower in the hardwood stand to the west of the FACTS1 site may also be used during the latter part of July.

Soil, vegetation enclosure, and most importantly, micrometeorological flux measurements of NOx, NOy, VOC and ozone will be conducted. These will be carried out using relaxed eddy accumulation, gradient, and eddy correlation systems using fast online chemical ionization mass spectrometry and spectrometry conventional GC/MS in the EPA and NCAR labs.

Confirmed measurement capabilities that will be deployed include:
Gas: B-carophyllene and other sesquiterpenes, a-pinene and other monoterpenes, isoprene, MVK, MAC, methyl furan, isoprene hydroperoxide, acetone, methanol, acetaldehyde, ozone, NO, NOy, NH₃, CO₂, CO, and H₂O.

Aerosol number and size distribution, chemical analysis (EC/OC, water soluble ions, organic/elemental composition, and radiocarbon ¹⁴C/ ¹²C) will also be conducted.

Other: temperature, humidity, winds, uv-b radiation, PAR, net radiation

Potential measurement capabilities:
Gas: PANs (Huey), organic N (Atlas), oxidation products (pinonic acid, hydroxyacetone, glycoaldehyde, nonanal, decanal) Matsunaga, SO₂ (EPA)

Aerosol: organic analysis (pinonic acid, hydroxyacetone, glycoaldehyde, nonanal, decanal) Matsunaga, fast organic analysis (Smith, Jimenez), other fast chemical analysis (Jimenez)

Confirmed Participants:
NCAR/ACD/BAI: Alex Guenther, Jim Greenberg, Thomas Karl, Peter Harley, Eiko Nemitz, Andrew Turnipseed,
USEPA: Chris Geron, John Walker, Bob Arnts

Other Potential Participants:
NCAR: Elliot Atlas, Jim Smith
Cornell: Jed Sparks
U. Colorado: Jose Jimenez, Detlev Helmig
Georgia Tech: Greg Huey
U Virginia: Jose Fuentes
Hokkaido University: Sou Matsunaga

EPA:
Mike Hays
Dean Smith
Kara Linna
Chuck Lewis

Here are the big items (all are eddy flux systems) that we have for the tower:

1. NO/NOy Ecophysics system. Must be near sonic. Cornell and NCAR. (Dimension 1.5' X 2' x 1.5')
2. NH₃ PTR-MS. Must be near sonic. NCAR and EPA. (1.5' X 2' X 2.5')
3. PAN (speciated) CIMS. Must be near sonic. Georgia Tech (1.5' X 2' X 2.5')
4. VOC PTR-MS. Can be on the ground. NCAR (1.5' X 2' X 2.5')
5. VOC and O₃ disjunct sampler. Near sonic. May have automated GC that could be on the ground. NCAR (Dimension 1.5' X 2' x 1.5')

6. EPA REA (reconfigured to allow better access and mounted to be less obtrusive on tower). Estimate of total power consumption: ~60 amps at 120 VAC.

Total Weight: ~400 Lbs

NCAR will also have a winch at the base of the tower an occasionally operate tethered battery operated systems for vertical profiling to tower top (in other words our tethered balloon stuff but without the balloon):
1. Cartridge samplers for VOC
2. Ozone
3. Particles (numbers and size)
4. CO₂
5. humidity, temperature, winds

Things that we (EPA and NCAR) also measure on the tower top if they are not already being measured (none of which take much space or power):
1. uv-b radiation, PAR, net radiation
2. humidity, temperature, winds
3. CO₂

Also, there is some interest in participation on the part of others:
Elliot Atlas (collect samples for lab. analysis of organics including Nitrogen)
Jim Smith (in-situ aerosol analysis)
Jose Jimenez, Doug Worsnop (AMS for chemical analysis of aerosols)
Michael Webber (TDL for ammonia)
Detlev Helmig (sesquiterpenes)
Sou Matsunaga (gas and aerosol BVOC and oxidation products: pinonic acid, hydroxyacetone, glycoaldehyde, nonanal, decanal).

Status:

Other projects in the Ecosystem group.