Aerosol samples were collected at Catania (Italy), from 16 March to 13 June 2005. The sampling was performed using a low pressure five-stage Berner cascade impactor. The samples were analysed for ...total aerosol mass, Water Soluble Organic Carbon (WSOC), Total Carbon (TC) and main inorganic ionic species. The Water-Insoluble Carbon (WINC) was derived by the difference: TC-WSOC. The samples share some common features: ammonium sulphate and carbon-containing species (both soluble and insoluble) are the largest contributors of fine particle mass, while coarse particles essentially consist of sea-salt, sodium nitrate and unaccounted PM (probably crustal material). The WINC/WSOC ratio decreases from the smallest size range to the large accumulation mode range (0.42-1.2 μm), while the graphic removed and graphic removed contribution rises. The water-insoluble carbonaceous matter is the dominant component in the smallest particles (0.05-0.14 μm). We identified four different aerosol types, corresponding to different sources, contributing to the total particles load of the investigated urban environment: vehicular traffic, producing primary carbonaceous insoluble particles, secondary aerosols, dominating the composition of accumulation mode particles, and marine particles and mineral dust (both important components of the coarse aerosol fraction).
Characterizations of urban and regional sources of particulate matter (PM) were performed in the Milan area (North of Italy) during Föhn and stagnant (non-Föhn) conditions. The measurements were ...performed at two different places: in an urban area North of Milan (Bresso) and in a regional area at the EMEP-GAW station in Ispra (about 65 km NW from Milan) during the winter periods of the years 2002–2007. Particle size distributions and chemical bulk analysis of aerosols are combined with single particle mass spectrometry to obtain information about the chemical content of the particles and their mixing state. Föhn conditions are characterized by extremely clean background air from which background aerosol is scavenged, and consequently local sources (here defined as sources between the sampling sites and the mountain range top about 100–150 km away depending on the wind direction) determine the aerosol properties.
It was observed that during Föhn events the accumulation mode in the size range 50 nm
<
d
<
300 nm practically disappears and that the size fraction below 50 nm dominates the total number distribution. The significant change in the number size distribution and the large decrease in PM10 mass during Föhn events are accompanied by a significant change in the chemical composition of the particles. Results from bulk chemical analysis showed high amounts of carbonaceous compounds and very low concentrations of ammonium nitrate (as indicator for secondary chemistry) during Föhn episodes, in contrast to stagnant conditions, when secondary components are dominating the aerosol composition. Single particle measurements confirm the high contribution of carbonaceous compounds in locally emitted particles.
It was concluded that particles that originated in the urban area come mainly from combustion processes, especially direct traffic emissions, domestic heating and industrial activities, whereas the regionally emitted particles are different with much less traffic contribution.
We estimate that under prevailing (non-Föhn) winter conditions, about 50–65% of the aerosol mass load in the city of Milan are caused by local emissions, and about 35–50% come from regional background. This finding suggests that in order to improve air quality in a big city like Milan, it is important to combine local traffic restriction interventions with other long-term regional scale air-quality-measures.
The synthesis of silicon quantum dots is performed in the 3–5 nm range using CO2 laser pyrolysis of SiH4. This size range is particularly relevant for potential applications in photovoltaic devices ...and biomedical imaging. The laser pyrolysis technique offers convenient control of the synthesis parameters in the case of nanoparticle production. However, controlling the size of small silicon objects remains difficult. The original approach consists here in a time-control of the energy injected into the reaction by gating the laser. The laser gate-on duration is adjusted in the range of 10 to 80 μs while keeping the average power constant. In parallel, supersonic expansion and on-line time-of-flight mass spectrometry are performed for on-line size characterization. A monotonic increase of the size as a function of the gate-on duration is observed for several SiH4 volume concentrations. The results are discussed qualitatively.
A novel method for analyzing electromechanical properties (e.g., size, electrostatic charge, polarity) of therapeutic aerosols produced by four different commercially available pressurized metered ...dose inhalers (pMDIs), including Albuterol™, Atrovent™, Qvar™, and Ventolin™, is presented. Respiratory drug particles aerosolized from pulmonary drug delivery devices may not only have different aerodynamic particle size distributions but also electrostatic charge distributions. The interactive effects of these two electromechanical properties on regional deposition of inhaled aerosols in the lung airway have been acknowledged by the investigators of aerosol medicine research, which requires precise quantification for analytical perspective. Experimental studies using a multi-stage electrical low pressure impactor (ELPI) reported the net charge (q(+) or q(-)) and aerodynamic diameter (d(a)) of the pMDIs. However, the ELPI has a limitation of providing the net charge of all particles deposited on its impaction stage, not for each particle in real time. To resolve this issue, this study reports the application of an electronic single-particle aerodynamic relaxation time (ESPART) analyzer, which operates on the principle of laser Doppler velocimetry to measure simultaneously d(a), q(+), and q(-) (charge magnitude and polarity) on a single particle basis and in real time. Aerosol particles from all drug delivery devices were found to not only have different size and charge distributions but they also varied in their polarities. The drug aerosols cloud emitted by Albuterol™ and Ventolin™ were determined to be electropositive, while Atrovent™ and Qvar™ were electronegative. Count and mass distributions were reproducible for all pMDIs. In conclusion, the ESPART provided more detailed charge information about the pMDI aerosol particles.
The proposed noninvasive method of measurement of the charge level on a population of particles employs the phase Doppler anemometry (PDA) technique in conjunction with a high-resolution ...computer-controlled traversing system. The PDA system was used to track the motion of charged particles in the presence of a DC electric field. By solving the equation of particle motion in a viscous medium combined with the simultaneous measurement of its size and velocity, the magnitude as well as the polarity of the particle charge can be obtained. In order to detect particles with high electrical mobility and to cover the wide range of electrostatic charges the probe volume was moved mapping the velocity of the particles within the space between the parallel-plate electrodes. The preliminary experimental tests were carried out on dioctyl-phthalate aerosol droplets produced by nebulizing isopropanolic solutions using a Medic-Aid Sidestream nebulizer. The narrow size distribution, in the range from 0.5 to 3 /spl mu/m, was achieved using this method of aerosolization. The experimental results show that inherent electrostatic charge on dioctyl-phthalate droplets ranged from -250 to 250 electrons with an average charge-to-mass ratio of 0.24 /spl mu/C/g. After charging the aerosol using corona source the average charge-to-mass ratio increased to 20 /spl mu/C/g. The results demonstrate the capability of the technique to allow real-time determination of particle size and charge with a high-particle-count rate on the order of several thousands particles per second.
This paper describes a novel automatic method for measurement of bipolar charge on aerosols. The developed system is dedicated to measuring aerosols existing in the form of short duration, high ...velocity plumes with a wide angle of particle dispersion. The system incorporates a front-end cylindrical arrangement consisting of two “D” shaped precipitation sections followed by a series of charge sensing electrodes. Apart from theoretical and construction details, the results of the experimental tests carried out with unipolarly and bipolarly charged aerosols are presented.
In collaboration with major Pacific Rim countries monitoring transported yellow dust (YD) from East Asia Aerosol Characterization Experiment in Asia (ACE-Asia), we made measurements of PM2.5 and PM10 ...at the Shi-Men site located on Taiwan's northern tip from March to May 2001. Herein we report the results from those measurements.
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