Volcanic sources of tropospheric ozone‐depleting trace gases

摘要: [1] Recent investigations report mixing ratios of BrO gas reaching 1 ppb in plume 4–7 km downwind the summit Soufriere Hills volcano, Montserrat. The detection volcanic plumes is potentially important evidence halogen-catalyzed tropospheric ozone destruction and suggests that volcanoes either directly emit or bromine species are rapidly converted to reactive plumes. Species distribution models constrained by condensate analytical data for arc, rift, hot spot demonstrate shallow magma degassing generates gases with ppm levels radicals Br, Cl, H, HO but no significant ClO. conversion Br Cl reaction gas-phase catalytic cycles during transport can lead secondary ClO at a ppt higher, possibly approaching especially halogen-rich gases, several kilometers sources. In general, however, probably require near-vent, high-temperature magmatic air and/or in-plume heterogeneous chemical processes involving aerosols transport. These oxidize chlorine HBr HCl, giving rise increased HO, addition NOx. They also produce amounts photochemically active precursors Br2, BrCl, Cl2, which photolyzable Cl. may build up nighttime accelerate production after sunrise. Downwind from sources chains HOBr HOCl trigger processes, essential sustaining Gas-phase reactions HCl might boost downwind. Thus generate halogens contribute significantly Enhanced HOx NOx emissions nonhalogen depleting