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We present a study characterizing aerosol particles resulting from a skyscraper blasting. High PM 10 mass concentrations with a maximum of 844.9 μg m -3 were present for a short time period of approximately 15 minutes. They result in a day mean of 32.6 μg m -3 compared to a 27.6 μg m -3 background not exceeding the 50 μg m -3 EU maximum permissive value. The increase in particle number concentration was less pronounced with a maximum concentration of 6.9 ⋅ 10 4 cm -3 compared to the local background value of 1.8 ⋅ 10 4 cm -3 . The size-resolved number concentration shows a single mode of ultrafine particles at approximately 93 nm. The spatial distribution of deposited dust was investigated with Bergerhoff glass collection vessels, showing a decrease with distance. In the deposited dust samples the concentrations of twelve metals was determined, non of them exceeded the regional background concentrations significantly. The chemical composition of individual particles emitted by the demolition was studied by Scanning Electron Microscopy. They were mainly concrete and steel particles, with 60% calcium carbonates, 19% calcium sulfates, 19% silicates and 2% steel. In energy-dispersive X-Ray Spectroscopy, no fibers like asbestos were observed. Using a broad spectrum of instruments and methods, we obtain comprehensive characterization of the particles emitted by the demolition. [ABSTRACT FROM AUTHOR]

We measured physical properties and optical properties of the black carbon (BC) generated in a spark discharger which did not produce soluble organic fractions. Effective densities and absorption cross-sections of the fresh BC were estimated using the electrical mobility diameter, the number concentration and the mass concentration. Size distribution measurements using a differential mobility analyzer (DMA) and a condensation particle counter (CPC) showed that the mode diameter and the number concentration increased with increasing spark frequency of the spark discharger. The primary particle size was also measured through the analysis of images observed using a field emission scanning electron microscope (FESEM), decreasing from 36.3 to 15.1 nm with increasing a spark frequency. The effective densities were estimated from 0.054 to 1.392 g/cm 3 and compared to be lower than those of atmospheric aerosols which might be aged. The absorption cross-sections were estimated as 1.0×10 –15 to 1.7×10 –15 m 2 depending on spark frequency. For the BC generated at a fixed constant spark frequency, the absorption cross-section was estimated to be larger as the BC became bigger in electrical mobility diameter. For the BC having the same electrical mobility diameter generated at different spark frequencies, however, the absorption cross-section generated at a faster spark frequency was smaller. Fractal dimension for the BC larger than 160 nm was measured to be 1.79, which is very similar to that for the spark-generated BC studied by other research group. In conclusion, the effective density allowed us to distinguish the core BC from aged BC. [ABSTRACT FROM AUTHOR]

Recently, inexpensive (<$300) consumer aerosol monitors (CAMs) targeted for use in homes have become available. We evaluated the accuracy, bias, and precision of three CAMs (Foobot from Airoxlab, Speck from Carnegie Mellon University, and AirBeam from HabitatMap) for measuring mass concentrations in occupational settings. In a laboratory study, PM 2.5 measured with the CAMs and a medium-cost aerosol photometer (personal DataRAM 1500, Thermo Scientific) were compared to that from reference instruments for three aerosols (salt, welding fume, and Arizona road dust, ARD) at concentrations up to 8500 µg/m 3 . Three of each type of CAM were included to estimate precision. Compared to reference instruments, mass concentrations measured with the Foobot (r-value = 0.99) and medium-cost photometer (r-value=0.99) show strong correlation, whereas those from the Speck (r-value range 0.91-0.99) and AirBeam (0.7–0.96) were less correlated. The Foobot bias was (−12%) for ARD and measurements were similar to the medium-cost instrument. Foobot bias was (<−46%) for salt and welding fume aerosols. Speck bias was at 18% for ARD and −86% for welding fume. AirBeam bias was (−36%) for salt and (−83%) for welding fume. All three photometers had a bias (<−82%) for welding fume. Precision was excellent for the Foobot (coefficient of variation range: 5–8%) and AirBeam (2–9%), but poorer for the Speck (8–25%). These findings suggest that the Foobot, with a linear response to different aerosol types and good precision, can provide reasonable estimates of PM 2.5 in the workplace after site-specific calibration to account for particle size and composition. [ABSTRACT FROM AUTHOR]

This paper experimentally investigates the particle concentration distribution and deposition in three-dimensional 90° bends considering three potential influencing factors: inlet mass concentration C m , Reynolds number Re and wall material. Particle penetrations were found to decrease moderately within 11% with the increase of C m under current conditions, but deposition velocity would increase by 1.29–2.87 times. The inlet particle concentration will not affect the outlet concentration distribution and particle penetration for the particles of St=5.15×10−4. For larger particles, however, higher C m , St and Re cause higher concentration near the outer wall of bend outlet, lower concentration near the inner wall and even ‘particle free zone’. For the outlet concentration distribution, apexes and concave points are observed, which may be formed by the rebounding particles. Furthermore, concentration polarization factor is introduced to analyze the outlet nonuniformity. Accordingly, Re is found to be a higher weighting factor compared with C m . Compared to penetration, deposition velocity is more sensitive to wall materials, for example, with an increase factor up to 1.45. Furthermore, a rough estimation method and an empirical model are suggested to establish the correlation among dimensionless outlet concentration, St and ‘particle free zone’. [ABSTRACT FROM AUTHOR]