Atmospheric & Environmental Chemistry Seminar
Dwayne Heard, University of Leeds, will give a talk on "Field Measurements of OH and Other Small Radicals/Intermediates in the Atmosphere and Comparison with Models."
The OH radical removes the majority of trace gases in the atmosphere emitted either naturally or via human activities, initiating the formation of a wide range of secondary products, many of which are implicated in poor air quality, for example ozone and organic aerosols. However, in situ measurements of OH and other radical species in the atmosphere are extremely challenging, and laser-induced fluorescence (LIF) spectroscopy offers a very sensitive method for their quantitative detection. The talk will describe LIF detection of atmospheric OH, HO2, RO2 and IO radicals at low pressure using the so called FAGE (fluorescence assay by gas expansion) technique from ground and airborne platforms. My group has also made measurements of OH reactivity, which is a kinetic parameter representing the total removal rate of OH via reaction with its atmospheric sinks. More recently we have developed instruments for field measurements of formaldehyde and glyoxal, and also a new method to detect CH3O2. Comparison of field measurements of radicals and other short-lived species with numerical model calculations constitutes one of the best ways to evaluate chemical mechanisms within models. Our focus has been using the Leeds Master Chemical Mechanism which contains up to ca. 6,700 chemical species and 17,000 reactions. I will show a flavour of measurements and model comparisons from field campaigns in a range of environments.