The detection of nocturnal N2O5 as HNO3 by alkali- and aqueous-denuder techniques

[摘要] The almost total anthropogenic control of the nitrogen cycle has led to wideranging trans-national and national efforts to quantify the effects ofreactive nitrogen on the environment. A number of monitoring techniques havebeen developed for the measurement of nitric acid and subsequent estimationof nitrogen deposition within large networks and for process studies onshorter measurement campaigns. We discuss the likelihood that many of thesetechniques are sensitive to another important gas-phase component of oxidizednitrogen: dinitrogen pentoxide (N₂O₅). We present measurementsusing a MARGA wet annular denuder device alongside measurements ofN₂O₅ with a discussion of evidence from the laboratory and thefield which suggests that alkali- and aqueous-denuder measurements aresensitive to the sum of HNO₃ + 2N₂O₅. Nocturnal data fromthese denuder devices should be treated with care before using HNO₃concentrations derived from these data. This is a systematic error which ishighly dependent on ambient conditions and is likely to cause systematicmisinterpretation of datasets in periods where N₂O₅ is significantproportion of NO_y. It is also likely that deposition estimates ofHNO₃ via data obtained with these methods is compromised to greater andlesser extents depending on the season and environment of the samplinglocation.

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