Airborne aerosol inlet passing efficiency measurement

Abstract

We have evaluated the aerosol passing efficiency of a variety of inlet systems during three experiments on the National Center for Atmospheric Research Electra. During the Dynamics and Chemistry of the Marine Stratocumulus (DYCOMS) program, we found discrepancies between concentrations in cloud water and the air below cloud, which we attribute to curved-inlet aerosol losses. In the First ISCCP Regional Experiment (FIRE) program, the same curved inlet passed significantly less material than a straight one. In the Particulate Matter Airborne Sampling Inlet Experiment (PASIN), we analyzed the material deposited within one inlet tube to establish an efficiency reference. Six different inlets were used simultaneously with six filter samplers to evaluate the effects of tube diameter, radius of curvature, and surface coating. The PASIN filters collected different amounts of material when they should have been sampling the same aerosol. Extraction of the 1-inch metal reference tube routinely found that 50--90% of the aerosol material had been deposited in the tube. None of the inlets had an average bulk efficiency greater than about 50% for the aerosol species we measured. In the commonly used 1-inch ID curved tube inlet, only 10-20% of marine sodium made it to the filter. High turbulence in the diffuser cone may be responsible for much of the observed loss. It is possible that many of the existing aircraftderived aerosol data in the literature are serious underestimates of actual ambient concentrations. We suggest some changes in strategy to improve the collection of aerosols from aircraft.

PELTI: Measuring the Passing Efficiency of an Airborne Low Turbulence Aerosol Inlet

“…It did much better in the FT than the MBL. Its performance in sea salt was similar to that reported by Huebert et al ( 1990) for a similar large-diameter, gradually curved (but unshrouded) inlet: half or less of the sea salt was able to penetrate the SD, and ten or more percent of submicron particles were also removed in its turbulent diffuser.…”

Urban/industrial aerosol: Ground‐based Sun/sky radiometer and airborne in situ measurements

“…Larger particles are more susceptable to impaction and sedimentation than smaller particles. This creates errors in particle concentration of the larger particles and errors in size distribution [Huebert et al, 1990]. Furthermore, the aircraft must be airborne in order to make measurements, and therefore observations are a relatively rare event.…”

Characterization of atmospheric aerosols across Canada from a ground‐based sunphotometer network: AEROCAN

“…These high fitted scaleheight values can be linked to an underestimation of the real volume size distribution by the PCASP measurements which are not necessarily representive of those at ambiant conditions, taking into account the fact that the aerosols may have dried before the measurements were taken. In addition particles may not have been captured at the airflow inlet or by the detection circuit (Huebert et al, 1990). More simultaneous field measurements with the sunphotometer, the PCASP or preferably the FSSP-300 (forward scattering spectrometer probe of PMS Inc., Boulder, Colorado) instrument, which do not dry the aerosols in various seasonal conditions, are necessary to assess better the difference in the magnitude of volume size distributions.…”