Evaluation of Aeris mid-infrared absorption (MIRA), Picarro CRDS (cavity ring-down spectroscopy) G2307, and dinitrophenylhydrazine (DNPH)-based sampling for long-term formaldehyde monitoring efforts

Abstract

Abstract. Current formaldehyde (HCHO) measurement networks rely on the TO-11A offline chemical derivatization technique, which can be resource intensive and limited in temporal resolution. In this work, we evaluate the field performance of three new commercial instruments for continuous in situ formaldehyde monitoring: the Picarro cavity ring-down spectroscopy G2307 gas concentration analyzer and Aeris Technologies' mid-infrared absorption Pico and Ultra gas analyzers. All instruments require regular drift correction, which is accomplished through instrument zeroing using dinitrophenylhydrazine (DNPH)-coated cartridges, Drierite, or molecular sieves, while heated Hopcalite failed to remove all incoming HCHO. We show that a modified precision estimate accounting for regular instrument zeroing results in values of 0.09, 0.20, and 0.22 ppb at a 20 min integration time for the G2307, Ultra, and Pico, respectively. After applying standard addition and dynamic dilution calibrations, all instruments agreed within 13 % and were well correlated with each other (all r ≥ 0.90). TO-11A HCHO observations resulted in a normalized mean bias of −58 % compared to co-located Picarro G2307 measurements (r=0.62, slope = 0.38, int = 0.07 ppb HCHO). Using a 6-month deployment period in the Atlanta metropolitan area, we determined that the Picarro G2307 and Aeris units have sufficient accuracy and precision to capture the Atlanta spatial HCHO gradient. We find that midday HCHO concentrations have decreased by 22.3 % since 1999 in the city's urban core, and DNPH measurements at a nearby Photochemical Assessment Monitoring Station (PAMS) site show a greater decrease of 53 %.

Role of chemical production and depositional losses on formaldehyde in the Community Regional Atmospheric Chemistry Multiphase Mechanism (CRACMM)

“…The lack of hourly data for evaluation of the HCHO diurnal variability in CMAQ is a limitation of the AQS HCHO observations. In addition, previous work indicates offline network measurements of HCHO can be biased high or low (Zhu et al, 2017;Mouat et al, 2024), and we find AQS measurements show a summer, regional maximum in HCHO in the Carolinas (Fig. S17-S18) rather than in the northern Georgia region, in contrast to CMAQ and TROPOMI (Fig.…”

“…For the several locations in the northeastern US (Westport, New Brunswick, and Flax Pond) The error in the HCHO diurnal profile during summer in CMAQ is pronounced for two sites in Atlanta, GA, where data has been collected as part of a longer-term HCHO sampling effort (Mouat et al, 2024). One site is co-located with a Photochemical Assessment Monitoring Stations (PAMS) network site, known as the South DeKalb (SDK) monitoring site, located in a suburban part of the Atlanta metro area.…”

Supplementary material to "Role of chemical production and depositional losses on formaldehyde in the Community Regional Atmospheric Chemistry Multiphase Mechanism (CRACMM)"

“…PAMS and NATTS sites typically have sample collection schedules of three 8-h samples or one 24-h sample which limits the usefulness for evaluation of the diurnal variability of HCHO. The DNPH measurement technique has also recently been found to measure lower HCHO values compared to other instruments in Atlanta, GA, (Mouat et al, 2024) and in Salt Lake City, UT, (Jaffe et al, 2024). While there is some uncertainty in these measurements, we report a comparison between the daily average HCHO observations available in AQS and daily averages from CMAQ using CRACMM1 and CRACMM2 (Figure S14).…”