Atmospheric radicals (such as OH, HO2, RO2, NO3, halogen atoms and halogen oxides) play a central role in the oxidation of trace gases, contributing to the formation of secondary pollutants and influencing Earth’s climate. A thorough understanding of radical sources, including precursor species like HCHO, HONO, organo-halogens, and ClNO2, as well as their chemical fate, such as the conversion of primary pollutants and methane (CH4) oxidation, is essential for addressing regional air quality issues and climate change. Reactive halogen species can have an important influence on the chemistry of the troposphere. For instance, chlorine atoms react faster with most hydrocarbons than OH does and inorganic bromine and iodine can catalytically destroy tropospheric ozone and oxidise mercury. These reactions have been shown to be important in environments as different as the polar troposphere during the springtime ozone depletion events, the boundary layer over salt lakes, and volcanic plumes. Although measuring and modeling radicals is critically important, it remains highly challenging due to their low concentrations, high reactivity, and the complex reaction networks they participate in.
This session welcomes contributions related to the measurement and modeling of radicals, including:
1. Development of novel techniques for detecting radicals, their precursors, and intermediate species;
2. Laboratory studies: determination of gas- and aqueous-phase rate constants, study of complex reaction systems involving halogens, Henry's law and uptake coefficients, UV/VIS spectra, and other properties of reactive species.
3. Adaptation of instruments for various platforms (e.g., ground-based, mobile, shipborne, airborne);
4. Quality assurance and control, such as calibration procedures and intercomparison of different methods;
5. Model development, including new chemical mechanisms, model configurations, and uncertainty analysis;
6. Applications of radical measurements and modeling in field campaigns and satellite-measurements including volcanic plumes as well as chamber studies.