Low-pressure impactor

The electrical Itw-pressure impactor (ELPl) has been developed, using the Berner-type multijet low-pressure impactor stages. The cut sizes of the seven channel system range from 0.030 to 1.0 pm. Real-time measurements can be achieved due to the instrument s fast time response. The schematic representation of the impactor construction is shown in Fig 13.44. 

The electrical low-pressure impactor was used to measure the number concentrations of diesel exhaust particles. The particle size distribution ranges from 30 nm upward were then determined using the aerodynamic diameter as the characteristic dimension. ... 

The deposits on the stainless-steel collection plates of the low-pressure impactor (LPI) were leached with a solution of 1 H HNO3 and the leachate rapidly evaporated on 5.08-cm stainless steel plates (using a hot plate). The concentrations of Pb-212 and Pb-214 in the impactor plate leachates were measured using seven ZnS(Ag) alpha scintillation counters. 

Figure 1. Representative plots from 46 low-pressure impactor measurements, illustrating aerodynamic size (Dp) distributions of Pb-212 and Pb-214 (R = radioactivity), (a) type results occurred 46% of the time, (b) 39% of the time, (c) 8.7% of the time, and (d) 6.5% of the time. Lower Dp limits are arbitrary.

Figure 3. A comparison of mean Pb-212 activity (R), and SO4" mass (M) aerodynamic size (Dp) distributions from low-pressure impactor measurements made between Feb. and Sept. 1985. Lower Dp limits are arbitrary.

Figure 5. Results of an empirical model that calculated, for each low-pressure impactor size range, the percentage recoil losses of Pb-214 [subplot (a)] necessary to produce a calculated Pb-214 distribution is best agreement with the observed distribution [subplot (b)]. Lower Dp limits are arbitrary.

The aerodynamic size distributions of Pb-214, Pb-212, Pb-210, Be-7, P-32, S-35-SoJ , and stable SO4 were measured using cascade impactors. Pb-212 and Pb-214, measured by alpha spectroscopy, were largely associated with aerosols small than 0.52 11m. Based on over 46 low-pressure impactor measurements, the mean activity median aerodynamic diameter (AMAD) of Pb-212 was found to be 0.13 11m, while for Pb-214 the AMAD was larger—0.16 lim. The slightly larger size of Pb-214, confirmed with operationally different impactors, was attributed to a-recoil-driven redistribution of Pb-214 following decay of aerosol-associated Po-218. A recoil model was presented that explained this redistribution. Low-pressure impactor measurements indicated that the mass median aerodynamic diameter of SoJ ... 

Aerosol was occasionally sampled with low pressure impactors (LPI s) to obtain sulfur and elemental mass distributions using the techniques described by Ouimette (13). 

Aerosol samples for composition measurements were collected using the Caltech low pressure impactor (LPI) (21,22). This fully calibrated instrument classified particles into eight size fractions between 0.05 and 4 ym aerodynamic diameter. Collection of particles smaller than 0.3 ym is achieved by reducing the pressure and increasing the velocity of the jets. 

In this work, we use a University of Washington low pressure impactor (LPI) and instrumental neutron activation analysis (INAA) to determine the elemental composition of aerosols from a two 430 MWe coal-utility boilers, ranging in diameter from less than 0.07 to about 10 )Jm, and to investigate the modification of the aerosol by a modern flue-gas desulfurization system. A preliminary account of the work is presented here. 

Low-Pressure Impactor Data. Table I lists the count medians and geometric standard deviations from log-normal fits of the distributions obtained by SEM analyses of sample MKV-1, Listed also are the corresponding mass medians calculated from the count distributions. 

We have operated the University of Washington MKV impactor as a low-pressure impactor to provide for chemical analysis, four discretely sized fly-ash fractions in the sub-half-micrometer- diameter aerosol accumulation region. Instrumental neutron activation analysis provided the sensitivity to determine accurately the concentrations of 28 major, minor, and trace elements with sufficient precision to reveal fine structure in the elemental distributions that might be missed by techniques of lesser accuracy and precision. 

Some examples of ambient air impactors include the low-pressure impactor (LPI) (10), the Battelle (II, 12), the Multi-Day (MD) (13), the Davis Rotating Unit for Monitoring (DRUM) (14, 15), the Berner Low-Pressure Impactor (BLPI) (16), and the Micro-Orifice Uniform Deposit Impactor (MOUDI) (17). Each has a different way of collecting particulate matter. Because of the small mass of aerosols, certain parameters of the design of the impactor are adjusted so that the aerosol can be analyzed with a maximum degree of sensitivity. Some of the parameters involve the flow rate at which the impactor operates the material is concentrated to a smaller area or the... 

Note DMS differential mobility spectrometer, SMPS scanning mobility particle sizer, CPC condensation particle counter, TDMPS twin differential mobility particle sizer, DMPS differential mobility particle sizer, OPC optical particle counter, APS aerodynamic particle sizer, MAS mass aerosol spectrometer, LAS-X optical laser aerosol spectrometer, ELPI electrical low pressure impactor... 

Los Angeles smog, 241 Low-pressure impactors, 103 Lowan, A. N., 283 Lower explosive limit (LEL), 336 Ludlum, F. H., 255 Lumergs, 265 Lumination, 264 Luminators, 264 Lungs ... 

Low-pressure impactors utilize the fact that Cc is a function of not only particle diameter but also, through the gas mean free path, pressure. Therefore at low pressures Cc can be substantially larger than for the same size particle at atmospheric pressure. 

Kwok, P.C.L. Chan, H.-K. Measurement of electrostatic charge of nebulised aqueous droplets with the electrical 79. low pressure impactor. In Respiratory Drug Delivery IX ... 

Very favorable calibration results in the size range of 0.06 to 10 pm AD have been obtained for a low-pressure impactor designed by Berner (1978) (Wang and John... 

Some new developments in impactor design include a parallel stage impactor a micro-orifice impactor for sub-micron aerosol size classification and an eight stage, low pressure impactor... 

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