Development of rugged ozone instrumentation and its application to Antarctic tropospheric ozone depletion events.

摘要

Ozone Depletion Events (ODEs) are naturally occurring phenomena which episodically deplete tropospheric ozone in the polar regions each spring. These events are thought to be caused by catalytic halogen chemistry; however, the exact mechanism and site of these reactions are uncertain. Measurements taken during the 2004-2007 Antarctic spring seasons examined both the activation and transport of halogens and the depletion of ozone.;Frost flowers were previously thought to be a site for the activation of bromine; however, the elevated pH of frost flowers sampled in McMurdo Sound indicate that bromine activation is unlikely to occur. Yet the composition of frost flowers makes them a likely source of particulate bromine. Analysis of the chemical composition of surface snow from the Ross Island areas shows substantial and variable halogen content that suggests aerosol deposition of halogens, as well as gas-phase emission of bromine. Snow also provides an acidic environment that is much more conducive to the activation of bromine than frost flowers. Furthermore, measurements of ozone fluxes over the Ross Ice Shelf indicate that ozone is destroyed on or near the snow pack. It is expected that this depletion is related to the emission of reactive bromine from the snow pack.;Simultaneous measurements of aerosol size distributions, bulk composition, and ozone mixing ratios were made in the spring of 2007. These measurements show a clear correlation between depleted ozone and enhanced fine particulates (diameter 500 nm) rich in sulfate and chloride. Meteorology points to ozone-depleted air and aerosols having a common source in areas closer to the ice edge. It is also possible that the oxidation of biogenic sulfates may be responsible for the activation of bromine and the nucleation and growth of fine sulfate aerosols.;The lack of instrumentation suited for use in the Antarctic has been one of the limiting factors in this research. A newly developed ultraviolet ozone analyzer based on solid-state optoelectronics with applications to Antarctic ozone monitoring is described. This novel instrument should allow future field studies at remote locations much closer to the suspected site of halogen activation and ozone depletion than previous measurements.