Diameter Of Aerosol Particles Research Articles

In situ measurements of total reactive nitrogen, total water, and aerosol in a polar stratospheric cloud in the Antarctic

Measurements of total reactive nitrogen (NOy), total water, and aerosol were made as part of the Airborne Antarctic Ozone Experiment during August and September 1987. The measurements were made using instruments located on board the NASA ER‐2 aircraft, which conducted 12 flights over the Antarctic continent, reaching pressure altitudes of 20 km at 72°S latitude. The data presented here focus on a flight during which a polar stratospheric cloud (PSC) was encountered, containing concentrations of 0.8‐ to 2.6‐μm diameter aerosol particles greater than 1 cm−3. The temperatures in the cloud ranged as low as 184 K near 65‐mbar pressure, but they remained above the frost point of water ice, except for short intervals. From knowledge of the vapor pressures over nitric acid condensates, the appearance of aerosol above the background level is consistent with the formation of the trihydrate phase, HNO3·3H2O. The anisokinetic feature of the NOy sample probe enhances the concentration of large aerosol particles in the inlet by a factor of ∼9. NOy levels above 20 parts per billion by volume (ppbv) observed in the PSC indicate that aerosol NOy species contribute substantially to the NOy signal. The amount of aerosol HNO3·3H2O necessary to enhance the NOy signal to observed levels is calculated from aerosol impaction theory and is found to be in satisfactory agreement with the observed aerosol volume. In addition, using the saturation vapor pressures and an estimate of available HNO3 in the cloud, the predicted volume of HNO3·3H2O also shows satisfactory agreement with the directly measured aerosol volume. These results indicate that substantial aerosol volume containing HNO3 and H2O is formed at temperatures above the frost point in the Antarctic stratosphere in the winter and spring months. Such aerosol formation is thought to be the prerequisite for the production of active chlorine in heterogeneous reactions and for the large‐scale removal of NOy through aerosol sedimentation.

Experimental Assessment and Calibration of an Inertial Spectrometer

An experimental assessment has been made of the performance of an inertial spectrometer to measure the aerodynamic diameter of aerosol particles. These studies have included a determination of the optimum operating conditions for good size resolution, and the calibration of the instrument with monodisperse aerosol particles. Sampling conditions had to be chosen with care in order to ensure that the instrument operated correctly and separated particles on the basis of their aerodynamic size. When the instrument was upright, the calibration curves agreed closely with those of the manufacturer. However, when the spectrometer was inverted, the calibration curves were slightly displaced due to the change in direction of the gravitational force with respect to the other forces acting on the particles as they passed through the spectrometer.

Sterilization efficacy of ultraviolet irradiation on microbial aerosols under dynamic airflow by experimental air conditioning systems.

In order to know the sterilization efficacy of ultraviolet irradiation on microbial aerosols, the size and the weight of the aerosol particles were evaluated, and these were irradiated under dynamic air flow created by an experimental air conditioning system. The experimental apparatus consisted of a high efficiency particulate air (HEPA) filter, an aerosol generator, spiral UV lamps placed around a quart glass tube, an Andersen air sampler and a vacuum pump. They were connected serially by stainless steel ducts (85 mm in diameter, 8m in length). Six types of microbial aerosols generated from an ultrasonic nebulizer were irradiated by UV rays (wavelength 254nm, mean density 9400 microW/cm2). Their irradiation time ranged from 1.0 to 0.0625 seconds. The microbial aerosols were collected onto the trypticase soy agar (TSA) medium in the Andersen air sampler. After incubation, the number of colony forming units (CFU) were counted, and converted to particle counts. The diameter of microbial aerosol particles calculated by their log normal distribution were found to match the diameter of a single bacteria cell measured by a microscope. The sterilization efficacy of UV in standard airflow conditions (0.5 sec. irradiation) were found to be over 99.5% in Staphylococcus aureus, Staphylococcus epidermidis, Serratia marcescens, Bacillus subtilis (vegetative cell) and Bacillus subtilis (spore) and 67% in Aspergillus niger (conidium). In A. niger, which was the most resistant microbe to UV irradiation, the efficacy rose up to 79% when irradiated for 1.0 sec., and it was observed that the growth speed of the colonies was slower than that of the controls. It was thought that UV rays caused some damage to the proliferation of A. niger cells.

The optimum rate of drum rotation for aerosol aging

Rotating chambers (drums) are used to age aerosols. This analysis derives the rate of drum rotation that optimizes the quantity of aerosol retained during the aging period. This optimum rotation rate is much slower than what is used in general practice. The optimum rotation rate is dependent upon the suspension fluid (typically air) density and viscosity, the drum radius, the aging period, and the suspended aerosol particle density and diameter. However, the optimum rotation rate is essentially independent of the particle size for an aerosol particle diameter of 10 μm or less. For these particles, the optimum rotation rate is dependent only upon the drum radius and the aging period. The air motion within the drum is assumed to be isothermal, isobaric, and fully developed to a uniform angular velocity before the aerosol particles are introduced (injected).

Long-range transport of continentally-derived particulate carbon in the marine atmosphere: evidence from stable carbon isotope studies

Since 1979, we have investigated marine and non-marine sources of particulate carbon in the marine atmosphere from measurements of carbon concentration and isotopic composition 13 C/ 12 C). Aerosol samples were collected, mostly during the Sea/Air Exchange (SEAREX) Program experiments, in the northern and southern hemispheres (Sargasso Sea, Enewetak Atoll, Peru upwelling, American Samoa, New Zealand, Amsterdam Island). The concentration and the isotopic composition of particulate carbon of marine origin are about the same in both hemispheres (C mean =O.O7 μgC m -3 , δ 13 C mean C = -21‰) This component is primarily associated with large sea-salt particles (diameter > 3 μm). Particulate carbon of continental origin displays a variable isotopic composition (δ 13 C range: - 23 to - 28‰,) and is primarily found attached to the smallest aerosol particles (diameter < 1 μm). This continental component shows little temporal variability, but its concentration is much lower in the southern hemisphere (0.06 μgC m -3 ) than in the northern hemisphere (0.45 μgC m -3 ). Also, the northern hemisphere samples appear strongly depleted in 13 C compared to those from the southern hemisphere. This can be explained on the basis of our isotopic data over various continental areas (Paris region, Ivory Coast, Congo) as due to the predominance in the northern hemisphere of carbonaceous aerosols of anthropogenic origin derived either from industrial combustion processes or from biomass burning. On the other hand, our data set from the southern hemisphere appears to reflect primarily natural land-derived biogenic emissions. DOI: 10.1111/j.1600-0889.1986.tb00184.x

Characterization of aerosols generated by thermospray nebulization for atomic spectroscopy

The performance of an inductively coupled plasma (ICP) for atomic emission spectroscopy (AES) is strongly dependent upon the sample introduction system. The Thermospray Vaporizer has recently been shown to yield enhanced sensitivity compared to conventional pneumatic nebulizers when used as a sample introduction source for the ICP. This report is a study of the properties of the aerosols produced by the thermospray. Aerosol particle diameter distributions have been related to droplet size distribution and nebulization efficiencies as a function of the relevant variables of the nebulization system. The results help explain high emission intensities and lower detection limits achieved using the thermospray. The higher efficiencies with thermospray, compared to conventional pneumatic nebulization, also makes the thermospray a prime candidate for sample introduction into molecular gas ICPs.

A new diffusion battery design for the measurement of sub- 20 nm aerosol particles: The diffusion carrousel

A new design of a screen type diffusion battery is presented. Tests and calibration of the device prove that it is suited for the determination of the diameter of aerosol particles below 20 nm.

A non-selective preconcentration technique for water analysis by pixe

A non-selective preconcentration technique for water (such as rain water) with an especially low concentration of dissolved constituents is proposed. By means of a nebulizer the water is sprayed to a droplet aerosol, which is dried with clean dry air. The dry aerosol particles (diameter about 1 μm) are deposited on a thin polystyrene foil in a multijet impactor. The setup is thoroughly described. The best detection limits achieved for the present setup are approximately 0.1 ppb ( ppb = μg l for a 10 ml sample. A recovery test is shown and discussed. Comparisons with other non-selective preconcentration methods for X-ray analysis are also made.

Some acute cardiopulmonary effects of mainstream and sidestream cigarette smoke in man

Acute physiological effects of alkaline and acid nicotine following transient inhalation of mainstream or sidestream cigarette smoke and nicotine aerosol have been compared. Two groups of seven healthy male students, one group smokers and the other nonsmokers, were passively exposed for 2 sec to each preparation. Heart rate, blood pressure, finger pulse wave, forehead electromyogram, and respiratory movement were monitored. After inhalation of the preparations, decreases in the amplitude of finger pulse wave and increases in the amplitude of electromyogram were observed in both groups. The results showed that the irritation by sidestream smoke provokes the nasopharyngeal reflex more strongly and for longer periods than by mainstream smoke in an equivalent dose of nicotine for them and that this difference was mainly attributable to the percentage of nicotine presented as uncharged molecules according to pH. Although the equivalent dose of nicotine was applied, nicotine aerosols induced stronger and/or longer changes than cigarette smoke did. These differences may be partly ascribed to the rather large diameter of nicotine aerosol particles. In addition, more irritant effects of smoke were observed on nonsmokers than on smokers.

The influence of phloroglucinol aerosol dispersity on its ice-forming activity

The dependence of phloroglucinol ice-forming characteristics on the mean-cubed diameter of aerosol particles ( d 3), over a wide range of d 3 (200—10 4Å), has been studied. These experimental dependences have been compared with theoretical ones calculated on the basis of the Fletcher model of ice formation by particles with uniform surface. This model has been shown to disagree with experimental results.

Aerodynamic particle size measurement by laser-doppler velocimetry

A method of measuring the aerodynamic diameter of aerosol particles is presented. Particles are accelerated in a converging nozzle and their velocity is measured near the exit with a laser-Doppler velocimeter. Nozzle parameters and flow conditions are chosen so that the particle velocity depends primarily on aerodynamic diameter. Experimental studies utilizing a test nozzle are reported. Particles of a known diameter in the range from 0.5 to 11.3 μm were accelerated under various flow conditions. Particle velocities were measured near the nozzle exit. The measurements demonstrated the feasibility of determining particle size from particle velocity. Theoretical studies of the test nozzle showed that it was possible to accurately calculate the particle velocities. Additional theoretical investigations showed that aerodynamic diameter can be determined from particle velocity if the particle motion is not too ultra-Stokesian. A nozzle configuration and flow rate are proposed for the measurement of the aerodynamic diameter of atmospheric aerosol in the range from 0.5 to 10 μm.

Experimental results on the counting efficiency of condensation nuclei counters for aerosol particle diameters between 0.03 and 0.003 μm

Experimental results on the counting efficiency of condensation nuclei counters for aerosol particle diameters between 0.03 and 0.003 μm

A standard crustal aerosol as a reference for elemental enrichment factors

Elemental composition measurements of > 4μ m aerodynamic diameter aerosol particles have been made with cascade impactors at remote continental locations in Argentina, Bolivia, and Brazil during the winter 1976 and summer 1977 seasons. The aerosol samples have been analyzed by proton induced X-ray emission (PIXE) for the crustal elements Al, Si, K, Ca, Ti, and Fe. Experimental results show that a high degree of homogeneity is exhibited by the crustal elements in the remote continental aerosol. Although the crustal element concentrations in air vary by two orders of magnitude, the data suggest that a standard crustal aerosol (SCA) having the following geometric means of ratios to Fe can be used as the reference material in aerosol enrichment factor calculations: Ti = 0.10(1.2); Al = 2.0(1.4); Si = 4.5(1.5); Ca = 0.41 (1.9); K = 0.20 (2.0), where the numbers in parentheses are standard deviations over 8 locations weighted equally. The elements Al, Si, Ti, and Fe, which show constancy in relative proportions to a factor of 1.5 or better, are shown to be suitable reference elements in the enrichment factor calculations. The SCA is used to examine enrichments from different continental locations. SCA enrichment factor calculations for the South American cities of La Paz, Bolivia, Buenos Aires, Argentina, and Brasília and São Paulo, Brazil show that the proportions of crustal elements in these cities are similar to those found in remote continental locations, although concentration variations of at least two orders of magnitude are present. The inclusion of additional elements in the SCA obtained by other analytical techniques is suggested.

Aerosol particles: remarks on the optical properties

The comparison of light scattering diameter determined by forward scattering measurements in the airborne state and the geometrical size (projected area diameter) of atmospheric aerosol particles at the earth surface and of NaCl nuclei shows that the particles can approximately be described as spheres with an equivalent projected diameter and a refractive index of 1.54 +/- 2%. The investigation refers to particles ranging between 0.3 microm and 2 microm and relative humidities less than 60%.

Comparison of “light scattering diameter” based on forward scattering measurements and aerodynamic diameter of aerosol particles

The influence of the physical properties of aerosol particles on the “light scattering diameter” determined with a Royco particle monitor, Model 225, was investigated. This dia. was compared with the aerodynamic dia. determined with a Stöber aerosol spectrometer. Particles of NaF, NaCl, CuSO 4 ·5H 2 O, NiSO 4 ·7H 2 O, malachite green, particulate carbon, and atmospheric aerosol were used as test aerosols. The median of the aerodynamic dia. was approx. 0.5 μm. It turned out that the light scattering dia. is larger than the aerodynamic dia. by a factor ranging from 1.2 to 2.4, and larger than the equiv. dia. by a factor ranging from 1.3 to 3.2.

A new centrifuge to measure the aerodynamic diameter of aerosol particles in the submicron range

A new centrifuge to measure the aerodynamic diameter of aerosol particles in the submicron range

Die Anlagerung von radioaktiven Atomen und Ionen an Aerosolteilchen

The attachment of radioactive atoms and ions to spherical aerosol particles has been studied theoretically. For uncharged atoms the deposition is considered to be solely governed by thermal diffusion. With calculations based on the “limiting-sphere”-method ofArendt-Kallman it is found, that the attached activity is proportional toΦ 2 for aerosol particle diametersΦ smaller than 0.1 μm, and proportional toΦ forΦ greater than 1 μm. For charged ions the diffusion process is modified by the influence of electrostatic forces between the diffusing ions and the aerosol particles. In the frequently occurring case of a symmetrically bipolar charged aerosol this influence can be expressed by a functionG p(Φ), which depends on the diameterΦ and the effective numberp of elementary charges on the aerosol particle. For an aerosol particle diameterΦ greater than 0.1 μm the attached activity is proportional toΦ 1.1, and forΦ smaller than 0.01 μm it is proportional toΦ 1.55. The effects of neglecting various terms in the calculation are considered. The distribution of natural radioactivity on atmospheric aerosols has been calculated for various particle size distributions according toJunge. The calculation shows that about 90% of the total natural activity should be attached to particles smaller thanΦ=0.5 μm, and about 35% to particles smaller thanΦ=0.1 μm. The time T1/2, in which the concentration of the radioactive particles decreases to half the initial value, depends on the concentration of the aerosol particles and on their size distribution. For 104 aerosol particles per cm3 and the size distributions mentioned,T 1/2 varies between 15 and 30 seconds for radioactive ions. For radioactive atomsT 1/2 is greater than it is for ions in the range of aerosol particle diameters belowΦ=0.25 μm, and smaller ifΦ greater than 0.25 μm.