Design and calibration of a multi-channel aerosol sampler for tropopause region studies from the CARIBIC platform

• An aircraft-based, multi-channel aerosol sampler for studies of the upper troposphere and lowermost stratosphere from the CARIBIC ( Civil Aircraft for Regular Investigation of the Atmosphere Based on an Instrument Container) platform was designed and calibrated. The sampler operates with an impaction technique at a flow rate of 10.4 lpm and consists of sixteen sampling channels. Samples are collected in a time sequence. Each channel contains two sample types that are used for quantitative measurement of concentrations, using particle-induced X-ray emission ( PIXE), and single particle analysis with electron microscopy. The minimum detection limits for PIXE analysis after 1.5 h sampling are, for example, 2.0, 0.14, and 0.02 ng/m(3) STP ( standard temperature and pressure) for sulfur, potassium, and nickel. Calibration included penetration studies of a cyclone arrangement used to define the upper size limit in the sampling to 2.0 mu m diameter and the collection efficiency of the impactor. Both components of the sampling system showed penetration and collection efficiency close to 100%, respectively, in the particle size range of interest. The impactor cut-off was found to be dependent on the ratio of the impactor upstream-to-downstream pressure for ratios well below the critical pressure drop (i.e., the pressure where the jet reaches sonic velocity) being 0.15 mu m and 0.08 mu m for ratios 0.41 and 0.2.

Ämnesord

NATURVETENSKAP  -- Kemi -- Fysikalisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Physical Chemistry (hsv//eng)

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