Grantee Research Project Results
2000 Progress Report: Development of Lightweight Instrumentation for Measurement of Long-Lived Trace Gases
EPA Grant Number: R825222Title: Development of Lightweight Instrumentation for Measurement of Long-Lived Trace Gases
Investigators: Avallone, Linnea M.
Institution: University of Colorado at Boulder
EPA Project Officer: Hahn, Intaek
Project Period: December 1, 1996 through November 30, 2001
Project Period Covered by this Report: December 1, 1999 through November 30, 2000
Project Amount: $466,074
RFA: Exploratory Research - Early Career Awards (1996) RFA Text | Recipients Lists
Research Category: Early Career Awards
Objective:
The primary goal of the research supported under this grant is the development, testing, and deployment of a prototype, lightweight gas chromatograph system, based on micro-GC technology. As originally conceived, this GC system would be integrated into a suite of sensors (the rest of which are funded through a grant from the NASA Atmospheric Effects of Aviation Program) to be flown on a commercial airliner. The aim of this larger project is to obtain extensive measurements of several key trace species (O3, CO2, H2O, and C2Cl4) in the upper troposphere (8-12 km). This dataset can be used for a variety of purposes, including testing of global three-dimensional chemical transport models and models of ozone precursor emissions and ambient air quality, and the assessment of the effects of subsonic aviation on upper tropospheric and lower stratospheric ozone distributions.Progress Summary:
At the time of last year's report, we had just finished building the suite of instruments proposed?sensors to measure ozone, water vapor, carbon dioxide, and halocarbons. In November 1999, these instruments, along with a pump/flow system, computer, power supply, and gas-handling system (bottles for standards and carrier gas) were installed on the NASA DC-8 "Flying Laboratory." Over the course of the winter, we participated in NASA's SAGE III Ozone Loss and Validation Experiment (SOLVE), carried out from a base in Kiruna, Sweden. We obtained approximately 200 hours of flight data throughout the high latitude upper troposphere and lower stratosphere. Although we are still analyzing data, preliminary results are described below.
Funding from this project was largely directed toward the development of an automated gas chromatograph. This dual-channel instrument consists of custom ovens for the pre- and analytical columns, a compact gas-handling system, incorporating commercial Valco multi-port switching valves, and Hewlett-Packard micro-ECDs and control electronics. The pressure of the sample loops and of the ECD exhaust manifold are controlled to better than 1 percent using custom-designed pressure controller electronics and MKS orifice valves. The instrument has turned out somewhat larger and heavier than we had originally planned, largely due to a failure of the planned ECD control electronics. This necessitated use of the Hewlett-Packard motherboard and AC transformer, which added approximately 8 kg to the original mass of 22 kg. Nonetheless, the instrument performed nearly flawlessly, with the exception of an (easily replaced) ECD electrometer failure in March.
We are able to measure six halocarbons (CFCs -11, -12, -113, Halon 1211, CH3CCl3, and CCl4) every four minutes, rather than just a single species (C2Cl4) as originally proposed. A sample chromatogram from each instrument channel is shown below. As a result, we have measured approximately 80 percent of total organic chlorine (CCly) present in the air masses sampled. This quantity will be used to determine the extent of chlorine activation following exposure of air to polar stratospheric clouds; active chlorine (ClO) was measured simultaneously on the DC-8. Once data processing is complete, the observations will be used in a variety of studies to assess not only chlorine chemistry in the tropopause region, but also to estimate the stratospheric lifetimes of these halocarbons. From the slope of a correlation plot of two species, one with known lifetime (such as nitrous oxide), the lifetime of the gas of interest can be estimated. This technique has been used in prior studies (Plumb and Ko, 1992; Avallone and Prather, 1997) and shown to be quite powerful. This type of analysis will help us to refine our understanding of the lifetimes of significant ozone-depleting gases, which will be important as the CFC reductions mandated by the Montreal Protocol take effect.
Sample chromatogram from GC Channel 2, showing peaks from air, CFC-11, CFC-13, CH3CCI3, and CCI4 (left to right).
Some chromatogram from GC Channel 1, showing peaks from air,
CFC-12, Halon 1211, and CFC-11 (left to right). Halocarbon measurements from one
flight during the SOLVE campaign (January 27, 2000).
Future Activities:
With continued funding from this EPA grant, we plan to further minimize the size and weight of the GC, and to explore the measurement of additional halocarbons. We are collaborating with colleagues at the University of Cambridge to develop control circuitry for the electron capture detectors which will eliminate the need for the HP electronics used this past year.We will participate in a trace-gas intercomparison based on data obtained during the SOLVE mission. This intercomparison will involve colleagues from several institutions and nearly simultaneous observations made from multiple aircraft and balloons. It is planned that the results of the intercomparison will be published in the next year.
Although we maintain an interest in flying this suite of sensors on commercial aircraft as originally proposed, this has continued to be a difficult goal to achieve. The NASA AEAP program, which funded much of the instrument development, no longer supports this project financially. However, there is considerable enthusiasm for such a program of measurements among the scientific community, so we will continue to pursue this goal. Meanwhile, flight opportunities on research aircraft will be sought, so the instruments will most certainly be used to gather meaningful observations for analysis of tropospheric chemistry and transport.
Journal Articles:
No journal articles submitted with this report: View all 17 publications for this projectSupplemental Keywords:
atmosphere, ozone, stratospheric ozone, chemical transport, CFCs., RFA, Scientific Discipline, Air, Environmental Chemistry, air toxics, climate change, Ecology and Ecosystems, tropospheric ozone, Atmospheric Sciences, monitoring, ambient ozone data, ozone occurrence, chemical composition, chemical transport model, gas chromatography, atmospheric chemical cycles, chemical kinetics, carbon dioxide, diode laser spectrometer, atmospheric monitoring, field measurements, lightweight instrumentation, measurement methods , three dimensional model, convective boundary layer, trace gas measurementRelevant Websites:
http://cloud1.arc.nasa.gov/solve/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.