Design and Performance of a Cascade Impactor, MAIS-10

概要

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　A new 10-stage low-pressure impactor of MAIS-10 has been developed to sample size-segregated aerosol particles for subsequent chemical analysis by ion or X-ray beam method such as PIXE or XRF and thermo-optical analysis for carbonaceous components. The impactor has reversible impaction plates with the diameters of the aerosol deposition areas smaller than 10 mm for all stages and can employ the collection substrates of two different thicknesses. The collection efficiency curves were experimentally determined for all stages and the 50% cut-off diameters ranging from 30 nm to 8 µm agreed well with the theoretical calculations at each stage. The particle wall losses were experimentally obtained using oleic acid particles labeled with uranine. The performance of MAIS-10 has been tested to collect urban aerosols simultaneously with a commercially available impactor for 24 hrs. The samples were subjected to TXRF, PIXE and thermal optical analysis. MAIS-10 samples showed the reasonable size distributions of typical elements and carbonaceous components, while the levels of the samples collected by the usual impactor in the analytical areas were below the detection limit of each analytical method and the size distributions were not able to be determined.