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 (NO). We present measurementsusing a MARGA wet annular denuder device alongside measurements ofNO with a discussion of evidence from the laboratory and thefield which suggests that alkali- and aqueous-denuder measurements aresensitive to the sum of HNO + 2NO. Nocturnal data fromthese denuder devices should be treated with care before using HNOconcentrations 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 NO is significantproportion of NO. It is also likely that deposition estimates ofHNO via data obtained with these methods is compromised to greater andlesser extents depending on the season and environment of the samplinglocation.