Diameter, aerodynamic operational

Impactors utilize aerodynamic forces to separate the various particle size classes. This is consistent with the particles aerodynamic diameter. The operation... 

The particles most likely to cause adverse health effects are the fine particulates, in particular, particles smaller than 10 p and 2.5 mm in aerodynamic diameter, respectively. They are sampled using (a) a high-volume sampler with a size-selective inlet using a quartz filter or (b) a dichotomous sampler that operates at a slower flow rate, separating on a Teflon filter particles smaller than 2.5 mm and sizes between 2.5 mm and 10 mm. No generally accepted conversion method exists between TSP and PM,o, which may constitute between 40% and 70% of TSP. In 1987, the USEPA switched its air quality standards from TSP to PMk,. PM,q standards have also been adopted in, for example, Brazil, Japan, and the Philippines. In light of the emerging evidence on the health impacts of fine particulates, the USEPA has proposed that U.S. ambient standards for airborne particulates be defined in terms of fine particulate matter. 

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 ... 

In general, dry ESPs operate most efficiently with dust resistivities between 5 x 103 and 2 x 1010 ohm-cm. In general, the most difficult particles to collect are those with aerodynamic diameters between 0.1 and 1.0 pm. Particles between 0.2 and 0.4 pm usually show the most penetration. This is most likely a result of the transition region between field and diffusion charging. 

The size distribution of the particulate matter in the 0.01-5 ym size range is analyzed on line using an electrical mobility analyzer and an optical particle counter. Samples of particles having aerodynamic diameters between 0.05 and 4 ym are classified according to size using the Caltech low pressure cascade impactor. A number of analytical procedures have been used to determine the composition distribution in these particles. A discrete mode of particles is observed between 0.03 and 0.1 ym. The major components of these particles are volatile elements and soot. The composition of the fine particles varies substantially with combustor operating conditions. 

St. Louis Sample Collection. Ambient aerosols were collected in St. Louis in 6-h Intervals with a TWOMASS automated sequential tape sampler. This sampler fractionated the aerosol into two size classes, fine particles having aerodynamic diameters less than 3pm, and coarse particles with diameters greater than 3pm. It was equipped with a beta-attenuation mass monitor to determine fine-particle mass (11). Only the fine particle filter was examined in this study. Pallflex E70 glass-fiber filter tape with a detachable cellulose backing (Pallflex Inc. Putnam, CT) was used with this sampler. An aerosol sampler operating from the same inlet manifold as the... 

The experiments were carried out in a 1 MWth atmospheric fluidised bed combustion pilot plant, at different operation conditions. Emitted fly ash was collected with an Andersen cyclone cascade system from the stack. The higest concentration of the dangerous PAHs were found on particles having aerodynamic diameter <2.0 pm. The objective of this study, is to expand our knowledge of PAH formation and characterization, emitted in the combustion of a determinate biomass (poplar tree)... 

The Malvern API Aerosizer (Malvern Instruments Ltd., Southborough, MA) operates on the principle of supersonic flow in a jet, followed by laser Doppler velocimetry to measure the aerodynamic diameter of particles in the size range from 0.5 to 200 pm using 50 channels. The operating flowrate is 6 L/min. The Atcor Net-2000 is a similar device for determining aerodynamic diameter, except that it is capable of sizing particles up to only 5.0 pm in diameter at a flowrate of 0.1 ft3/min (2.83 L/min). 

The FisoNeb and Pulmosonic nebulizers both operate at a frequency of 1.3 MHz that generates a mass median aerodynamic diameter (MMDA) of 4-6 pm [9,10]. The Pulmosonic nebulizer has been reported not to deliver many particles smaller than 2 pm and, therefore, is unsuitable for pentamidine administration [10]. The Portosonic (DeVilbiss) device is a 2.3-MHz ultrasonic nebulizer and may offer the combination of less than 2-pm MMAD and a high output. In any study using ultrasonic nebulizers, the output and particle size of each device need to be periodically sampled, because the frequency of the piezoelectric crystal may alter with age [10]. Any MMADs between 0.5 and 2 pm are available. The Respirgard nebulizer II has one-way valves that control a drug reservoir, allow entrainment of room air in patients whose minute ventilation is... 

The calculation of average, volume-equivalent, diameters was based upon total suspended particulate mass and the total number of particles, the latter determined by a condensation particle counter. Aerodynamic size distributions were determined via sedimentation. The operational assumption in this technique is that an insignificant... 

Analyses of such radioactive aerosols were performed by Yu et al. (1993) at Chin-Shan Nuclear Power Plant, NPP in Taiwan, comprising a 636-MWe boiling water reactor (BWR) that has been in operation since 1977. They used Andersen ambient cascade impactors (1 ACFM normal cascade impactors at an airflow rate of 28.3 1 min ) with a preseparator to discriminate large particles with an aerodynamic diameter greater than 10 pm. For the segregation of smaller size aerosol particles in the accumulation mode, they applied a low-pressure adaptor to the Andersen cascade impactor. At an airflow rate of 3 lmin the effective cutoff aerodynamic diameter of sampled aerosols by the low-pressure Andersen cascade impactor (LPI) was between 0.08 and 35 pm. Fission products including and " La and the ac-... 

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