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A New Diffusion Denuder System for Long-Term,Regional Monitoring of Atmospheric Ammonia and Ammonium
Sutton M. A. Tang Y. S. Miners B. Fowler D. 《Water, Air, & Soil Pollution: Focus》2001,1(5-6):145-156
Estimating regional patterns in concentrations of atmosphericammonia (NH3) gas and ammonium (NH4 +) in aerosolis essential to assess dry deposition, as well as to test theperformance of long-range transport models. Until now, methods for monitoring NH3 and NH4 + (collectively NHx) have focused on either passive sampling, which does not sample aerosol NH4 +, or active sampling techniquessuitable for sampling over several minutes to 24 hr. The classicalactive sampling approach is the diffusion denuder, which typically involves either a complex annular denuder or a long(0.5 m) and fragile glass tube. A new denuder implementationis reported here that has been designed for long-term samplingof NH3 and NH4 +. By sampling at just 0.35 L min-1, the method is suitable for monthly measurementsand uses 0.1 m long glass denuders, which may be sent safelyby the normal postal service to monitoring sites. Two denudersare applied in series to test for adequate NH3 captureefficiency in each sample, while a subsequent acidified paperfilter collects NH4 +. The method has been implementedat over 50 sites across the U.K. as part of a new national monitoring network. The detection limit is <0.01 μg m-3 and the sampling is sufficiently accurate to show theseasonal patterns at different sites. This low-cost method willbe useful to address future trends in NH3 and NH4 +, especially in relation to compliance with international agreements to reduce NH3 emissions. 相似文献
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