[B._Beckhoff,_et_al.]_Handbook_of_Practical_X-Ray_(b-ok.org).pdf

V 000179 000724 2 cr 000442 00128 15 mn 00113 00455 1

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V 0.00179 0.00724 2 Cr 0.00442 0.0128 1.5 Mn 0.0113 0.0455 1 Fe 0.597 2.14 200 Ni 0.0023 0.00497 1 Cu 0.01 0.0436 2 Zn 0.0384 0.0886 50 Br 0.012 0.0193 10 Rb 0.00271 0.00589 n.a. Sr 0.0058 0.0128 n.a. Pb 0.0371 0.106 0.3
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624 S. Kurunczi et al areas of Hungary [349], and are in accordance with results obtained by wet chemical methods for the time period of 1995—1998 [350]. The average con- centrations are far below the limiting values, and lead is the only element where the maximum concentration is close to the limiting value. There are no large industrial point sources of air pollution near the lake. The nearest power plant, which burns coal, is about 30 km to the northwest. Local sources include motor vehicle emissions and dust suspended by vehicles on paved and unpaved roads or as the result of construction or by wind stress. The time variation of the concentrations did not show characteristic seasonal variations but it was in correlation with the incoming air mass. A temporal resolution of as low as 1 h can be reached using a combination of streaker sampler and EDXRF using capillary optics [346]. The single-stage streaker device draws the air through an 8 × 1 mm 2 rectangular orifice through a polycarbonate membrane filter with an average flow rate of 0.16 L min 1 . The filter is mounted to a circular frame rotating at a speed of 45 /day, result- ing in an 8-mm wide circular deposit of aerosol particles. The pre-impactor with an aerodynamic cut-off diameter of 10 µ m restricted the aerosol collection to PM 10 . The radiation of an X-ray tube was concentrated to a beam diameter of around 1 mm using a glass capillary. A Mo anode X-ray tube was used for measurement of high atomic number elements (19 < Z ), while light elements were determined using a Cr anode tube, in a He purged sample chamber. The analysis was performed using 1-mm steps corresponding to a 1 h of aerosol exposure. Using a 100 s measurement time at each spot, a scan of a complete sample collected during 1 week took about 6 h. The measurement geometry and the filter exposed in the streaker sampler are shown in Fig. 7.119. The detection limits expressed in µ g m 3 compared to that of particle- induced X-ray emission (PIXE) using 2.4 MeV proton excitation, calculated Glass capillary Motor 45 o 45 o Si(Li) detector Incident x-ray beam Deposited air dust R o t a t i o n Fig. 7.119. Geometrical arrangement for the X-ray fluorescence analysis of a fil- ter sample taken with the streaker collection device. Reproduced from Holynska et al. [346] by permission of Elsevier Science B.V.
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Methodological Developments and Applications 625 Table 7.17. Interference-free detection limits (DLs) in capillary optics EDXRF and PIXE analysis of aerosol streaker samples collected on Nuclepore polycarbonate filters DL ( µ g m 3 ) Range of concentrations Element EDXRF PIXE in urban areas ( µ g m 3 ) S 0.8 a 0.23 2–15 Cl 0.5 a 0.2 0.1–10 K 0.2 a 0.14 0.2–4 Ca 0.1 a 0.11 1–20 Fe 0.08 b 0.014 0.5–20 Cu 0.03 b 0.008 0.02–5 Zn 0.03 b 0.008 0.02–10 Br 0.04 b 0.014 0.005–1 Pb 0.07 b 0.028 0.1–10 Comparison with typical ranges of particulate element concentrations in urban areas [345].
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