Nitrate photolysis on ice surfaces
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Introduction Conclusions References Tables Figures Back Close Full Screen / Esc Abstract Introduction Conclusions References Tables Figures Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion EGU Abstract Nitrate photolysis in the wavelength range 250–1200 nm was studied on ice in a controlled laboratory experiment. Monolayer coverage of nitrate was achieved by dosing well-known amounts of HNO 3 from the gas phase onto a frozen water surface. Fluxes of HONO and NO 2 into the gas phase with time were quantified at temperatures be-5 tween 193 K and 258 K and as a function of illumination wavelength in the range: 250– 345 nm. Whereas HONO release showed a strong temperature dependence at colder temperatures, attributed to reversible adsorption processes, NO 2 fluxes were independent of temperature. The observed fluxes of HONO and NO 2 at high temperature were not affected by diffusion or adsorption processes, and could be used to estimate 10 a quantum yield for HONO formation of (3.8±0.6)×10 −4. A different wavelength dependence for HONO and NO 2 fluxes indicates that additional reactions besides nitrate photolysis and subsequent release of the products contribute to the emission of nitrogen oxides.
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تاریخ انتشار 2006