Photosensitized reduction of nitrogen dioxide on humic acid as a source of nitrous acid

Article

关键词: DIFFERENTIAL OPTICAL-ABSORPTION;    PHOTOCHEMICAL OXIDANT FORMATION;    SIMULATED VERTICAL PROFILES;    HETEROGENEOUS HYDROLYSIS;    SOUTHERN SWITZERLAND;    URBAN ATMOSPHERE;    BOUNDARY-LAYER;    HONO;    CHEMISTRY;    PHOTOLYSIS;   

DOI  :  10.1038/nature04603

来源: SCIE

【 摘 要 】

Nitrous acid is a significant photochemical precursor of the hydroxyl radical(1-13), the key oxidant in the degradation of most air pollutants in the troposphere. The sources of nitrous acid in the troposphere, however, are still poorly understood. Recent atmospheric measurements(7,10-17) revealed a strongly enhanced formation of nitrous acid during daytime via unknown mechanisms. Here we expose humic acid films to nitrogen dioxide in an irradiated tubular gas flow reactor and find that reduction of nitrogen dioxide on light-activated humic acids is an important source of gaseous nitrous acid. Our findings indicate that soil and other surfaces containing humic acid exhibit an organic surface photochemistry that produces reductive surface species, which react selectively with nitrogen dioxide. The observed rate of nitrous acid formation could explain the recently observed high daytime concentrations of nitrous acid in the boundary layer, the photolysis of which accounts for up to 60 per cent of the integrated hydroxyl radical source strengths(3,6-13). We suggest that this photoinduced nitrous acid production on humic acid could have a potentially significant impact on the chemistry of the lowermost troposphere.

【 授权许可】

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