A tunable high-pass filter for simple and inexpensive size-segregation of sub-10-nm nanoparticles

© The Author(s) 2017. Recent advanced in the fields of nanotechnology and atmospheric sciences underline the increasing need for sizing sub-10-nm aerosol particles in a simple yet efficient way. In this article, we develop, experimentally test and model the performance of a High-Pass Electrical Mobility Filter (HP-EMF) that can be used for sizing nanoparticles suspended in gaseous media. Experimental measurements of the penetration of nanoparticles having diameters down to ca 1nm through the HP-EMF are compared with predictions by an analytic, a semi-empirical and a numerical model. The results show that the HPEMF effectively filters nanoparticles below a threshold diameter with an extremely high level of sizing performance, while it is easier to use compared to existing nanoparticle sizing techniques through design simplifications. What is more, the HP-EMF is an inexpensive and compact tool, making it an enabling technology for a variety of applications ranging from nanomaterial synthesis to distributed monitoring of atmospheric nanoparticles

Comparison and complementary use of in situ and remote sensing aerosol measurements in the Athens Metropolitan Area

© 2020 Elsevier Ltd. All rights reserved. This manuscript is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Licence http://creativecommons.org/licenses/by-nc-nd/4.0/.In the summer of 2014 in situ and remote sensing instruments were deployed in Athens, in order to study the concentration, physical properties, and chemical composition of aerosols. In this manuscript we aim to combine the measurements of collocated in situ and remote sensing instruments by comparison and complementary use, in order to increase the accuracy of predictions concerning climate change and human health. We also develop a new method in order to select days when a direct comparison on in situ and remote sensing instruments is possible. On selected days that displayed significant turbulence up to approximately 1000 m above ground level (agl), we acquired the aerosol extinction or scattering coefficient by in situ instruments using three approaches. In the first approach the aerosol extinction coefficient was acquired by adding a Nephelometer scattering coefficient in ambient conditions and an Aethalometer absorption coefficient. The correlation between the in situ and remote sensing instruments was good (coefficient of determination R2 equal to 0.69). In the second approach we acquired the aerosol refractive index by fitting dry Nephelometer and Aethalometer measurements with Mie algorithm calculations of the scattering and absorption coefficients for the size distribution up to a maximum diameter of 1000 nm obtained by in situ instruments. The correlation in this case was relatively good (R2 equal to 0.56). Our next step was to compare the extinction coefficient acquired by remote sensing instruments to the scattering coefficient calculated by Mie algorithm using the size distribution up to a maximum diameter of 1000 nm and the equivalent refractive index (ERICOR), which is acquired by the comparison of the size distributions obtained by a Scanning Mobility Particle Sizer (SMPS) and an Optical Particle Counter (OPC). The agreement between the in situ and remote sensing instruments in this case was not satisfactory (R2 equal to 0.35). The last comparison for the selected days was between the aerosol extinction Ångström exponent acquired by in situ and remote sensing instruments. The correlation was not satisfactory (R2 equal to 0.4), probably due to differences in the number size distributions present in the air volumes measured by in situ and remote sensing instruments. We also present a day that a Saharan dust event occurred in Athens in order to demonstrate the information we obtain through the synergy of in situ and remote sensing instruments on how regional aerosol is added to local aerosol, especially during pollution events due to long range transport.Peer reviewe

Characterizing the Chemical Profile of Incidental Ultrafine Particles for Toxicity Assessment Using an Aerosol Concentrator

Incidental ultrafine particles (UFPs) constitute a key pollutant in industrial workplaces. However, characterizing their chemical properties for exposure and toxicity assessments still remains a challenge. In this work, the performance of an aerosol concentrator (Versatile Aerosol Concentration Enrichment System, VACES) was assessed to simultaneously sample UFPs on filter substrates (for chemical analysis) and as liquid suspensions (for toxicity assessment), in a high UFP concentration scenario. An industrial case study was selected where metal-containing UFPs were emitted during thermal spraying of ceramic coatings. Results evidenced the comparability of the VACES system with online monitors in terms of UFP particle mass (for concentrations up to 95 µg UFP/m3 ) and between filters and liquid suspensions, in terms of particle composition (for concentrations up to 1000 µg/ m3). This supports the applicability of this tool for UFP collection in view of chemical and toxicological characterization for incidental UFPs. In the industrial setting evaluated, results showed that the spraying temperature was a driver of fractionation of metals between UF (<0.2 µm) and fine (0.2– 2.5 µm) particles. Potentially health hazardous metals (Ni, Cr) were enriched in UFPs and depleted in the fine particle fraction. Metals vaporized at high temperatures and concentrated in the UF fraction through nucleation processes. Results evidenced the need to understand incidental particle formation mechanisms due to their direct implications on particle composition and, thus, exposure. It is advisable that personal exposure and subsequent risk assessments in occupational settings should include dedicated metrics to monitor UFPs (especially, incidental).What’s important about this paper: Our work addresses the challenge of characterizing the bulk chemical composition of ultrafine particles in occupational settings, for exposure and toxicity assessments. We tested the performance of an aerosol concentrator (VACES) to simultaneously sample ultrafine particles (UFPs) on filter substrates and as liquid suspensions, in a high UFP concentration scenario. An industrial case study was selected where metal-bearing UFPs were emitted. We report the chemical exposures characterized in the industrial facility, and evidence the comparability of the VACES system with online monitors for UFP particle mass (up to 95 µg UFP/m3) as well as between UFP chemical composition on filters and in suspension. This supports the applicability of this tool for UFP collection in view of chemical and toxicological characterization of exposures to incidental UFPs in workplace settings.Highlights: - The VACES system is a useful tool for UFP sampling in high-concentration settings; - UFP collected simultaneously on filters and in suspension showed good comparability; - UFP chemical profiles were characterized; - Health-hazardous metals Ni and Cr accumulated in UFPs; - Understanding emission mechanisms is key to identifying exposure sources.This work was funded by SIINN ERA-NET (project id: 16), the Spanish MINECO (PCIN-2015-173-C02-01) and the French agency (Region Hauts de France). The Spanish Ministry of Science and Innovation (Project CEX2018-000794-S; Severo Ochoa) and the Generalitat de Catalunya (project number: AGAUR 2017 SGR41) provided support for the indirect costs for the Institute of Environmental Assessment and Water Research (IDAEA-CSIC). We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI).info:eu-repo/semantics/publishedVersio

Temperature and pressure effects on the performance of the portable TSI 3007 condensation particle counter: Implications on ground and aerial observations

One of the most commonly employed instruments in the category of handheld condensation particle counters (CPCs) is the TSI 3007, which employs a simplified system for achieving a temperature difference between its saturator and its condenser in view of increasing portability, energy efficiency and autonomy. As a result, particle growth and consequently the detection efficiency of the instrument can be affected by the measurement conditions. In this work we measure the detection efficiency of the TSI 3007 CPC under temperatures and pressures that differ from standard conditions. Our results show that the performance of the CPC has a strong temperature dependence in the range of 5–30 °C, whereas it is not affected by ambient pressure when this varies between 0.7 and 1.0 atm. The temperature dependent detection efficiency of the instrument becomes significant at sizes below 20 nm. Recording the temperature at which this CPC is operated is therefore strongly advised, especially when required to determine the number concentration of sub-20 nm aerosol particles.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Atmospheric Remote Sensin

Particle size distributions and hygroscopic restructuring of ultrafine particles emitted during thermal spraying

We report measurements of the size, concentration, and hygroscopicity of ultrafine particles (UFPs) emitted during thermal spraying of ceramic coatings in an industrial setting. High concentrations (i.e., higher than 106 cm-3) of fractal-like UFPs were measured inside the spraying booths of the facility. The emitted UFPs were found to take up small amounts of water when exposed to elevated relative humidity (RH = 87%) within a Hygroscopic Tandem Differential Mobility Analyzer (HTDMA) system. The hygroscopicity of the sampled particles was distinguishably lower compared to those of the atmospheric background aerosol particles present in the breathing air. UFPs smaller than 90 nm that are produced by the thermal spraying process, exhibit hygroscopic factors less than unity in a systematic way. This behaviour indicates that the particles were irregularly shaped at dry conditions, and that they underwent a shape change (i.e., restructuring) upon humidification inside the HTDMA. The fractal-like structure of processemitted UFPs was further corroborated by Transmission Electron Microscopy (TEM) conducted on samples collected on site at dry conditions.The authors kindly acknowledge TM COMAS (http://www.tmcomas.com) for their committed cooperation. The current work was carried out in the framework of the CERASAFE project (www.cerasafe.eu), with the support of SIINN ERA-NET (project id: 16), and was funded by the Spanish MINECO (PCIN-2015-173-C02-01) and the respective French agency (Region Hauts de France). Partial funding from the “Generalitat de Catalunya” (project number: AGAUR 2017 SGR41) is also acknowledged.Peer reviewe

Nanoparticle emissions from traditional pottery manufacturing

Traditional pottery manufacturing involves firing of the ceramics in kilns, a process that leads to high concentrations of airborne particles that are harmful to human health. In order to assess the associated exposure levels and the involved risks, here, for the first time, we investigate the size, the concentration and the elemental composition of the particles emitted during the different stages of the ceramic firing process. Number size distributions of the emitted particles, having diameters in the range from 10 nm to 20 [small mu ]m, were measured in a traditional small-sized pottery studio using a Scanning Mobility Particle Sizer (SMPS) and an Optical Particle Counter (OPC). The measurements showed dominance of the nanoparticle mode (i.e., particles smaller than 100 nm) when the kiln reached temperatures above 600 [degree]C. The mean size of the particles ranged from 30 to 70 nm and their peak number concentration was 6.5 [times] 105 cm-3 during the first stage of the firing process where the ceramics were unpainted and unglazed. During the second stage of the firing process, where the ceramics were painted and glazed, the mean particle size ranged from 15 to 40 nm and their number concentration peaked at 1.2 [times] 106 cm-3. Elemental analysis of individual particles collected during the two firing stages and studied by Energy-Dispersive X-ray (EDX) spectroscopy showed that the emitted nanoparticles contain significant amounts of lead. These findings provide new information for understanding the health impacts of traditional pottery manufacturing, and underline the need for adopting adequate measures to control nanoparticle emissions at the source

Performance evaluation of the national air quality testing services V2000 Condensation Particle Counter

The Condensation Particle Counter (CPC) is an effective instrument for measuring the number concentration of aerosol particles in different environments. With only a few exceptions, CPCs are bench instruments with limited portability for use in the field, and have a cost that prevents their use in large numbers for distributed air quality measurements. This has motivated the development of compact and cost-effective CPCs that are already available in the market. Here we test the performance of such a CPC, designed and built by National Air Quality Testing Services Ltd (NAQTS), Lancaster, UK, which is a part of the V2000 compact air quality monitor that also includes gas sensors. The tests were carried out using monodisperse particles produced by atomization and electrical mobility classification. We found that the NAQTS V2000 CPC has a 50% detection efficiency for particles having diameter of ca. 14 nm. Our results also show that the coincidence error of the core CPC occurs at concentrations higher than 1 × 104 #/cm−3. Considering that the standalone CPC employs an ejector pump that provides a nominal dilution factor between 20 and 50 at its inlet, the coincidence error threshold of the system when sampling particles from ambient air is 2–5 × 105 #/cm−3. To extend its range for aerosols with particle concentrations by one order of magnitude higher, and thus expand its capabilities for a wide range of applications, we provide a simple correction equation. Overall, our results demonstrate that the NAQTS V2000 CPC is a highly effective instrument, and considering that it is currently the most cost-effective CPC in the market, to the best of our knowledge, makes it a highly attractive solution for air quality monitoring

Performance evaluation of a 3D-printed sharp-cut cyclone

A sharp-cut cyclone with an aerodynamic cut-off diameter of 1 μm, when operated at a flow rate of 1 L min−1, was built by 3D-printing and tested against a metallic (aluminum) counterpart having the same design and dimensions. The penetration efficiency of both cyclones was experimentally determined using quasi-monodisperse aerosol particles having aerodynamic diameters from ca. 100 nm to 2 μm. The aerodynamic cut-off diameter for both cyclones was very similar and in accordance with the expected design value. The penetration efficiency curve of the 3D-printed cyclone was less steep compared to that of its metallic counterpart. This difference is most likely attributed to the higher surface roughness of the inner parts of the 3D-printed cyclone - as also indicated by the greater pressure drop it exhibits compared to the aluminum cyclone when operated at the same flow rate - and not by higher deviations from its design dimensions resulting from the tolerances of the 3D printer. Despite that, the substantially low cost, speed, and ease of manufacturing, make the 3D-printed cyclone a highly promising solution for applications in aerosol metrology.Atmospheric Remote Sensin

Particle size distributions and hygroscopic restructuring of ultrafine particles emitted during thermal spraying

We report measurements of the size, concentration, and hygroscopicity of ultrafine particles (UFPs) emitted during thermal spraying of ceramic coatings in an industrial setting. High concentrations (i.e., higher than 106 cm−3) of fractal-like UFPs were measured inside the spraying booths of the facility. The emitted UFPs were found to take up small amounts of water when exposed to elevated relative humidity (RH = 87%) within a Hygroscopic Tandem Differential Mobility Analyzer (HTDMA) system. The hygroscopicity of the sampled particles was distinguishably lower compared to those of the atmospheric background aerosol particles present in the breathing air. UFPs smaller than 90 nm that are produced by the thermal spraying process, exhibit hygroscopic factors less than unity in a systematic way. This behavior indicates that the particles were irregularly shaped at dry conditions, and that they underwent a shape change (i.e., restructuring) upon humidification inside the HTDMA. The fractal-like structure of process-emitted UFPs was further corroborated by Transmission Electron Microscopy (TEM) conducted on samples collected at dry conditions on site.Accepted Author ManuscriptAtmospheric Remote Sensin