06.O.04 Characteristics of vienna aerosols sampled using rotaing cascade impactor

J. Aerosol Sci,,

Pergamon

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Vol. 25, Suppl. 1, pp. $53-$54, 1994 Copyright~)1994 ElsevierScienceLid

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0021-8502/94 $7.00 -¢-0.00

CHARACTERISTICS OF VIENNA AEROSOLS SAMPLED USING RffrAING CASCADE IMPACTOR Mikio K A S A H A R A and Kanji T A K A H A S H I

Institute of Atomic Energy, Kyoto University, U]i, Kyoto 611, JAPAN Axcel Bemer m d O t h m e r P m i n i n g

lnstitute fur Expe~mentolphysik, Universitat Wien Stmdhofgmse 4, A-I090 Wein, AUSTRIA

KEYWORDS PIXE, Elemental concentration, Roatating cascade impactor, Particle size distribution SAMPLING AND ANALYSIS Atmospheric aerosols were collected at two sites of urban (Vienna) and rural (Marchegg: about 50 km east of Vienna) areas using a rotating cascade impactor from February 24 to March 1, 1993. Sampling were conducted every 24 hours. The rotating cascade impactor classifies the aerosol particles into the 10 size fractions from 0.015 to 16 pm (Klaus and Berner, 1985). It was designed such that the aerosol particles are uniformly deposited on a substrate in the form of a ring with mean diameter of 25.5 m m and a width of 5.5 mm (4.41 mm2). Nuclepore film with pores of 0.4 jam was used as the substrate of collected particles. Whether conditions during the sampling period were as follows; Feb. 24, 25 : Snow fall, strong or less strong winds from northern directions, Feb. 26 : Stop snow falling in the morning, Low wind from the northwest, Temp. -3°C, Feb. 27, 28 : No snow fall, Clear skies with clouds, Winds from the south. Five sample sets obtained at each sites have been analyzed by a PIXE method at Kyoto University (Kasahara eta/., 1993). PIXE analysis was performed with 2.0 MeV proton beam from a Tandem accelerator. X-rays with 0.5-15 keV energy induced in the sample were detected by a Si(Li) detector after passing through a 39.3 ~m thick Mylar film absorber. The concentraions of 15 elements (Si, S, CI, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Br, Pb) were determined. RF_SULTS The mass size distributions were obtained each elements and each sample sets. Fig. I shows the average mass size distribution of 8 elements which were averaged concerning five sample sets at

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each sampling sites. Most of the 15 elements could be described by a uni-modal size distn'bution and the peaks of the size distr~utions ranged between 0.25 and 4.0 pm (Stage 5-8) .There is little difference between the shape of the size distribution obtained at two sampling sites. The mass mean diameter, Dm defined by 7.Di.Ci/~Ci were calculated for each distributions. Where Di and Ci mean the representative particle diameter and concentration at i th stage, respectively. The mass mean diameter and the total mass concentration obtained by summing up the concentrations of all stages are summarized in Table 1. The values in the table are averages of five sample sets at each sites. C.V. means the coefficient of variation. The values of both the total mass concentrations and the mass mean diameters determined at two sites are very close for every elements. S, K, V, Zn and Pb skewed to the smaller size ranges and their average mean diameter were smaller than lpm. On the other hand, Ca and Fe skewed contrarily to the larger size ranges and their Dm values were larger than 2pm. The time changes of total concentration of some elements are shown in Fig.2. All elements increased with time due to the wether conditions. Si, S and Pb as well as C1 and Br among the rest changed in the similar way and the changing patterns were exactly same at the two sampling sites. Such a variation of the concentration suggestes the scavenging effect of the atmospheric aerosols by snow fall.

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Table 1

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412 2460 148 324 89 21 11 9.0 13 97 4.7 7.2 52 9. 9 55

Mass mean d i a m e t e r

Vienna Dm(p=) C . V . ( - )

1.23 0.68 1.02 0.75 3.07 1.55 0.99 1.28 1.67 2.21 0.88 1.69 0.85 1.06 0.87

0.20 0.20 0.85 0.12 0.17 0.30 0.10 0.30 0.19 0.16 0.13 0.14 0.22 0.09 0.21

Marehegg P=(p=) C.V. (-)

1.11 0.65 0.78 0.67 2.88 1.28 0.88 1.06 1.43 2.0] 1.18 1.87 0.87 1.03 0.85

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Fig.2 Total concentration change of some elements in atmospheric aerosols: Solid line = Vienna, Dashed line = Marchegg. AC KN OWLED G MEN TS This study was supported by funds from the Grant-in-Aid for Scientific Research from Ministry of Education, Culture and Science, Japan. REFEREN C ES Kasahara, M., K. Yoshida and K. Takahashi, (1993) Sampling and measurement conditions for PIXE analysis of atmospheric aerosols, Nuclear Instruments & Methods, B75, 240-244. Klaus, N. and A. Bemer, (1985) Ein Kaskadcnimpaktor mit Rotierenden Stauplatten, StaubRainkait. Luft, 45, 168-170.