How relevant is halogen chemistry for the sulfur cycle from a global, quantitative viewpoint?
Additional halogen-related projects that are ongoing or in the final stage of proposal writing are i) NOVAC, an EU-funded global network of volcano observatories, which are mainly for the monitoring of SO2 emissions but which is also envisioned to be used to study halogen oxide emissions (project started in 2006); ii) HALOPROC, a German project involving 8 institutions focusing on halogenation processes in soils, salt lakes, and aerosols (preproposal accepted, final proposal submitted); iii) as part of CARIBIC II, a measurement container on commercial aircraft, a MAX-DOAS system is installed, which is being used for the investigation of free tropospheric BrO. Pilot studies that would be very well suited for Phase 1 and that can be easily added to other projects include the investigation of halogen chemistry in dust and biomass burning plumes. Several large campaigns for each of these topics are being planned (e.g., as part of UK-SOLAS) and it would be easy to add a small, exploratory h
