Wet annular denuder measurements of nitrous acid: laboratory study of the artefact reaction of NO2 with S(IV) in aqueous solution and comparison with field measurements

Real-time measurements of ammonia, acidic trace gases and water-soluble inorganic aerosol species at a rural site in the Amazon Basin

“…This has not been considered in our study for the following reasons: (a) artifact HONO formation is only significant for alkaline aqueous solutions, whereas the pH of the absorption solution in our study was nearly neutral, (b) the observed SO 2 mixing ratios were at least 10 times lower (mostly <0.3 ppb, see Fig. 4) than those relevant for artifact HONO formation according to Spindler et al (2003), and (c) since the absorber liquid was continuously pumped through the denuder, the contact time of the gas with the liquid was limited to 2 or 3 minutes. Figure 7 shows diel patterns of HONO measured from 17 to 20 September 2002 (biomass burning season) and from 17 to 20 October 2002 (transition period).…”

“…The main reasons for this behavior are: (a) intensive turbulent mixing from the free troposphere into the boundary layer dur- ing daytime, (b) deposition processes at night promoted by a stable thermal stratification of the nocturnal surface layer (limiting HNO 3 supply from residual layer), (c) higher temperature and lower relative humidity during daytime which enables evaporation of HNO 3 from the aerosol phase, and (d) daytime photochemistry (reaction of NO 2 with OH radical). Spindler et al (2003) have proposed a correction algorithm for artifact aqueous formation of HONO from dissolved NO 2 and SO 2 at wetted denuder walls. This has not been considered in our study for the following reasons: (a) artifact HONO formation is only significant for alkaline aqueous solutions, whereas the pH of the absorption solution in our study was nearly neutral, (b) the observed SO 2 mixing ratios were at least 10 times lower (mostly <0.3 ppb, see Fig.…”

“…NH 4 NO 3 is believed to form via reversible phase equilibrium with gaseous NH 3 and HNO 3 (Stelson & Seinfeld, 1982). Comparably, gaseous NH 3 and HCl are precursors for the reversible formation of NH 4 Cl (Pio and Harrison, 1987).…”

Measurements of nitrous acid (HONO) in urban area of Shanghai, China

“…Taking into consideration the important role of the HONO photodissociation in the atmosphere, various techniques have been developed and deployed for its atmospheric measurements, such as long path differential optical absorption spectroscopy (LP-DOAS) and chemical techniques (Febo et al 1996;Spindler et al 2003), long path absorption photometry (LOPAP) (Heland et al 2001;Kleffmann et al 2006) and ion-drift chemical ionization mass spectrometry (ID-CIMS) (Hirokawa et al 2009;Levy et al 2014). Time resolution, sensitivity, the absence of any artefact and the capability to perform measurements under diverse environmental conditions are paramount of importance in the performance of analytical instruments.…”

Measurement Techniques

“…While all methods have been extensively tested in the laboratory, the performance of these systems in the open atmosphere is difficult to assess (Appel et al, 1990;Febo et al, 1996;Kleffmann et al, 2006;Liao et al, 2006;Spindler et al, 2003). Typically chemical and spectroscopic methods agree well during the night but chemical techniques generally overestimate HONO during daytime.…”