Development of Techniques for Eddy-Correlation Measurements of Non-Methane Volatile Organic Compound Fluxed in the AtmosphereEPA Grant Number: R825221
Title: Development of Techniques for Eddy-Correlation Measurements of Non-Methane Volatile Organic Compound Fluxed in the Atmosphere
Investigators: Helmig, Detlev
Institution: University of Colorado at Boulder
EPA Project Officer: Hahn, Intaek
Project Period: December 1, 1996 through November 30, 2001
Project Amount: $499,926
RFA: Exploratory Research - Early Career Awards (1996) RFA Text | Recipients Lists
Research Category: Early Career Awards
Description:An analytical technique for the measurement of the exchange (flux) of trace gases between the earth's surface and the atmosphere will be developed. Measurements will rely on the eddy correlation method (ECM). Target compounds are biogenically and anthropogenically emitted volatile organic compounds (VOCs). A Finnigan MAT quadrupole ion trap mass spectrometer will be modified to allow the in situ monitoring of individual atmospheric trace gases by multidimensional mass spectrometry/mass spectrometry (MS/MS) analysis at the required time resolution of 2 to 10 Hz. Besides the primary target compound group of VOCs, other compounds that will be investigated during the method development phase with this technique include: carbon dioxide (CO2), ozone (O3), nitrous oxide (N2O), methyl bromide (CH3Br) and chlorofluorocarbons (CFCs).
Different inlet options will be investigated for their suitability in this application. A restricted flow into the quadrupole ion trap mass spectrometer will be achieved by sampling air through a temperature controlled uncoated fused silica capillary column. Methods that will be tested for their usefulness in enhancing the instrument sensitivity include jet separators and nafion dryers. Other analytical parameters that will be investigated include different ionization modes, such as electron impact (EI) ionization, chemical ionization (CI), electron capture ionization (ECD) and positive and negative ion analysis.
A substantial improvement of this instrumental approach over other ECM techniques is the capability to measure different atmospheric trace gases with the same instrument. It will be attempted to develop a system that will allow simultaneous flux measurement of several chemical species. The ultimate goal is the development of an instrument that can be used for the ambient monitoring of VOC fluxes of compounds that have been recognized as being of importance in the photochemical formation of ozone in the troposphere. Field testing of this method will be performed in close collaboration with EPA and NOAA coordinated field campaigns on tropospheric ozone formation and transport.