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Development of a Compact Transportable Instrument for the Measurement of Tropospheric 0H and H02 on remote and Airborne Platforms

Ziel


To develop a compact instrument that can measure the concentrations for OH and HO2 radicals from remote platforms at ground and from aircraft.


Hydroxyl- (OH) radicals are the most important oxidants in the troposphere, because they control the chemical
transformation of most gases released into the atmosphere. Many reactions of atmospheric compounds with OH
form hydroperoxy- (H02) radicals which react with O3 and NO to recycle OH. This HOx cycling is a key
process in the photochemistry of the troposphere, because it increases the oxidation efficiency of OH and
controls the rate of formation of photooxidants (O3, H2O2, PAN, etc.) in the polluted troposphere. Thus, a
thorough understanding of the chemistry of the HOx family is crucial to assess possible changes in the
self-cleansing efficiency of the atmosphere and to understand the photochemical ozone formation in both the
planetary boundary layer and in the free troposphere. Measurements of OH and HO2 are indispensable to test
the existing atmospheric chemistry models; however reliable data are scarce and have only been measured from
locations at ground.
The instrument will be based on the laser induced fluorescence (LIF) technique which has been developed
successfully in a previous EC project (Hofzumahaus and Webb, 1995) for the detection of tropospheric OH.
The specific tasks of the project aim:
1. to expand the measurement capabilities of the OH LIF technique by the development of a measurement
channel for HO2 radicals, in order to allow the true simultaneous measurement of OH, HO2, and of
the ratio of OH/HO2.
2. to develop a compact laser system which can be operated on board on airplane and to downsize the
whole LIF instrument into a compact automatisated package.
3. to improve the LIF detection sensitivity (below 105 molecules per cm3) and to reduce the measurement
time for daytime OH concentrations to a few seconds.
4. to carry out ground-based field measurements to test the new technical developments and to participate
in a field campaign to measure the abundance of OH and HO2, study their natural variability, and their
photochemical response time to rapid variations in atmospheric parameters.
This project aims to improve our understanding of the fast photochemistry playing a role in the regional and
global troposphere. In particular, it is expected that the LIF technique will be sufficiently developed by the end
of the project so that airborne measurements of OH and HO2 can be realised subsequently.

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CSC - Cost-sharing contracts

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Forschungszentrum Jülich GmbH
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Letzte Aktualisierung: 8 Oktober 1998

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Permalink: https://cordis.europa.eu/project/id/ENV4950003/de

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