Comparison of tunable diode laser and long‐path ultraviolet/visible spectroscopic measurements of ambient formaldehyde concentrations during the 1993 OH Photochemistry Experiment

Abstract

Abstract. Two different spectroscopic techniques for measuring atmospheric concentrations of formaldehyde were compared during a 6-week field study in the mountains 17 km west of Boulder, Colorado, in August and September 1993. A long-path ultraviolet/visible (UV/Vis) absorption spectrometer and an IR tunable diode laser absorption spectrometer (TDLAS) were the two instruments employed. The former measured ambient formaldehyde levels over a 10.3 km open path (20.6 km total path) extending between Fritz Peak Observatory and Idaho Hill, while the latter measured in situ levels at the Idaho Hill site. In addition to utilizing different spectral regions, both instruments employed different sampling and calibration approaches. Because of the closer proximity to anthropogenic sources the long-path UV/Vis instrument generally detected higher formaldehyde concentrations than the TDLAS system at all times during the day. Averaged over the entire study for all wind regimes, the former resulted in formaldehyde concentrations 15% higher than the latter. The mean and median formaldehyde concentration measured by both instruments was around 1.5 ppbv and individual 5-min averages varied from a maximum of about 5 ppbv down to levels 0.6 ppbv. However, during periods of strong westerly flow where anthropogenic and meteorological influences are minimized, both techniques were in agreement to within 5%. This regime, which constitutes 19% of the total mutual data set, resulted in a continental background formaldehyde concentration of 0.92 + 0.16 ppbv. The present instrument comparison thus bridges the gap in formaldehyde instrument comparison studies between those in the background free troposphere and those in polluted urban regimes. In addition to providing further confidence in both measurement techniques, the present comparison study also provided a valuable data set necessary for advancing our understanding of tropospheric oxidation mechanisms. A set of guidelines for future comparisons of long-path and in situ measurements of formaldehyde at this site are also discussed.

Ozone production and trace gas correlations during the June 2000 MINATROC intensive measurement campaign at Mt. Cimone

“…The trace gas concentrations at Mt. Cimone are comparable to measurements at two other mountain sites, the Jungfraujoch in the Swiss Alps (Zanis et al, 2000b) and Idaho Hill, Colorado (Cantrell et al, 1997;Harder et al, 1997;, while they are higher than observations at the remote N-Pacific location Mauna Loa (Atlas and Ridley, 1996;Cantrell et al, 1996;Zhou et al, 1997).…”

Formaldehyde over the eastern Mediterranean during MINOS: Comparison of airborne in-situ measurements with 3D-model results

“…The average concentration of HCHO in the marine boundary layer (0-1 km) is at least a factor of three higher than measurements in the remote areas of the Atlantic, Pacific or Indian Ocean (Zafirou et al, 1980;Lowe and Schmidt, 1983;Arlander et al, 1990;Heikes, 1992;Harris et al, 1992;Zhou et al, 1996;Mackay et al, 1996;Jacob et al, 1996;Ayers et al, 1997;Jaeglé et al, 2000;Weller et al, 2000;Wagner et al, 2001) and comparable to continental background conditions (Harder et al, 1997;. This is mainly due to advection of pollution from eastern and western Europe at altitudes below 4 km (Traub et al, 2003).…”

Design and performance of a tunable diode laser absorption spectrometer for airborne formaldehyde measurements

“…[29] Previous versions of the NCAR CH 2 O TDLAS were compared during several field campaigns with other instruments, and in each case good agreement was obtained on average [Harder et al, 1997;Gilpin et al, 1997;. The current TDLAS instrument has been compared with the UCLA DOAS system [Stutz and Platt, 1997] during two separate field campaigns.…”