Design and initial characterization of an inlet for gas‐phase NO_y measurements from aircraft

Abstract

Abstract. An understanding of gas-phase HNO3 transmission through an inlet is necessary to evaluate the quality of NOy measurements from an aircraft platform. A simple, inexpensive, low-volume Teflon inlet is described and its suitability as an aircraft inlet for gas-phase NOy is assessed. Aerosol transmission is not characterized, but inlet design and orientation probably discriminates against the majority of aerosol by mass. Laboratory data, in-flight HNO3 standard addition calibrations, and ambient NOy measurements from the 1997 North Atlantic Regional Experiment aircraft mission are used to characterize inlet transmission efficiencies and time constants. Laboratory tests show high transmission efficiencies for HNO3 which are relatively independent of ambient temperature and humidity. In-flight standard addition calibrations were carried out at ambient temperatures ranging from -20 ø to +8øC and relative humidities from 3% to 71%. These data suggest that nearly all the sampled air contacts an inlet surface, with 90% of added HNO3 being transmitted in -1.5 s. Ambient data are presented to demonstrate negligible hysteresis in 1-Hz NOy measurements, relative to variability observed in ozone data, from an air mass where HNO3 is expected to be a large fraction of the total NOy. Power spectra of ambient NOy (at temperatures from -35 ø to +35øC and relative humidities from 3% to 100%) and ozone measurements suggest an effective NOy instrument time constant of-2 s.

Chemistry of the Antarctic Boundary Layer and the Interface with Snow: an overview of the CHABLIS campaign

“…These data and issues of CO calibration and standardisation are discussed by Bauguitte et al (2008) Nitric acid is notoriously difficult to collect and measure because of its tendency to stick to any available surface (see e.g. Ryerson et al, 1999). Apart from the more expensive routes (such as Chemical Ionisation Mass Spectrometry), three main methods have been used to sample HNO 3 in the past: nylon filters, annular denuders, and mist chambers.…”

Atmospheric measurements of gas-phase HNO<sub>3</sub> and SO<sub>2</sub> using chemical ionization mass spectrometry during the MINATROC field campaign 2000 on Monte Cimone

“…By contrast to HNO 3 our lab studies have shown that SO 2 is not affected by adsorption on and/or desorption from sampling-line surfaces (Teflon and stainless steel). Unfortunately, in contrast to inlet systems for aircraftborne measurements of HNO 3 (Kondo et al, 1996;Ryerson et al, 1999), attention has only recently been directed to the development of a proper sampling system for groundbased and long-term continuous measurements of HNO 3 in the boundary layer where the air is usually characterized by high relative humidities and heavy aerosol loading Furutani et al, 2002;Mauldin et al, 1998;Neuman et al, 1999).…”

Total Peroxy Nitrates (ΣPNs) in the atmosphere: the Thermal Dissociation-Laser Induced Fluorescence (TD-LIF) technique and comparisons to speciated PAN measurements

“…Total weight was approximately 270 kg and power consumption was about 2 kW. The inlet was machined from PFA Teflon following the design of Ryerson, et al (1999). Pinholes just prior to each LIF cell gave pressures of 1-5 hPa over the 0-8 km altitude range, with a flow rate of 2 liters per minute per channel at sea level.…”