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Atmosphere
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Advancements in the Reduction of Submicron Particle Concentrations
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Advancements in the Reduction of Submicron Particle Concentrations

A special issue of Atmosphere (ISSN 2073-4433). This special issue belongs to the section "Aerosols".

Deadline for manuscript submissions: closed (4 September 2020) | Viewed by 14865

Special Issue Editors

Dr. Christof Asbach

E-Mail Website
Guest Editor
Institute of Energy and Environmental Technology (IUTA) e.V., Duisburg, Germany
Interests: aerosol science; filtration; nanoparticles; aerosol measurements; aerosol technology
Dr. Stefan Schumacher

E-Mail Website
Guest Editor
Institut für Umwelt & Energie, Technik & Analytik e. V. (IUTA), 47229 Duisburg, Germany
Interests: aerosols; filtration; air cleaners; indoor air
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Submicron particles may induce more severe health effects than their larger counterparts. These small particles are ubiquitous in the atmosphere as well as in indoor or workplace air, and may originate from both natural and anthropogenic sources. In light of new insights into the effects of these particles and of new and upcoming legislation (e.g., in the field of traffic emissions), the reduction of submicron-particle concentrations is key to meeting new goals in view of public and occupational health. It is further of paramount importance in clean production. The reduction of submicron-particle concentrations can be achieved by various means, including technical measures (e.g., filtration), mitigation strategies (e.g., low emission zones), or improved process control (e.g., enhancing the stoichiometry in combustion).

Especially the sub-fraction of ultrafine particles (UFPs), that is, particles with a diameter below 0.1 µm, has raised increased attention in recent years, due to the advancements and better availability of aerosol measurement techniques for this size range and the increasing number of studies showing their potential health effects. UFPs can originate from a very wide range of sources, such as aircraft, ship, and street traffic emissions (including tailpipe emissions and brake wear), candle burning, welding fumes, and new particle formation due to the nucleation of natural and/or anthropogenic gaseous precursors. The reduction of UFP concentrations sometimes poses new challenges to the applied technical measures. The experimental proof of their effectiveness can sometimes be rather complex.

Contributions from all applicable fields are welcome, whether they deal with technical reduction measures, short- or long-term observations or simulations of submicron or UFP concentrations in the atmosphere, indoor or workplace air, new measurement techniques or methods for assessing the reduction of the concentration (e.g., filtration efficiency), or studies on the health effects of submicron or UFP concentrations.

Dr. Christof Asbach
Dr. Stefan Schumacher


Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Atmosphere is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • filtration
  • abatement strategies
  • reduction of emissions 
  • traffic emissions
  • industrial emissions
  • agricultural emissions
  • ambient air
  • indoor air
  • workplace exposure
  • health effects

Published Papers (5 papers)

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17 pages, 2279 KiB  
Article
Electret Filters—From the Influence of Discharging Methods to Optimization Potential
by Maximilian Kerner, Kilian Schmidt, Stefan Schumacher, Christof Asbach and Sergiy Antonyuk
Atmosphere 2021, 12(1), 65; https://doi.org/10.3390/atmos12010065 - 04 Jan 2021
Cited by 10 | Viewed by 3380
Abstract
Electret filters are electrostatically charged nonwovens which are commonly used in aerosol filtration to remove fine particles from gases. It is known that the charge and thus also the filtration efficiency can degrade over time. Thus, many testing standards require to remove the [...] Read more.
Electret filters are electrostatically charged nonwovens which are commonly used in aerosol filtration to remove fine particles from gases. It is known that the charge and thus also the filtration efficiency can degrade over time. Thus, many testing standards require to remove the charge by treatment with liquid isopropanol (IPA) or IPA-saturated air. However, the parameters influencing this discharge have not been completely clarified yet. The aim of this work was, on the one hand, to experimentally investigate the influence of the IPA treatment on different electret filters and, on the other hand, to show the optimization potential of electret filters with respect to efficiency and long-term stability by numerical simulations. The experiments revealed that the air permeability is a central influencing parameter. Small pores lead to a reduced discharge efficiency using liquid IPA, while both treatment methods are suitable for larger pores. The simulations showed that a homogeneous charge distribution within the filter depth is advantageous for the initial performance. In contrast, charge penetrating deeper in the filter medium delays the charge decay and thus increases the operating time, with the trade-off of a lower initial performance. Full article
(This article belongs to the Special Issue Advancements in the Reduction of Submicron Particle Concentrations)
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37 pages, 22354 KiB  
Article
A Practicable Measurement Strategy for Compliance Checking Number Concentrations of Airborne Nano- and Microscale Fibers
by Asmus Meyer-Plath, Daphne Bäger, Nico Dziurowitz, Doris Perseke, Barbara Katrin Simonow, Carmen Thim, Daniela Wenzlaff and Sabine Plitzko
Atmosphere 2020, 11(11), 1254; https://doi.org/10.3390/atmos11111254 - 20 Nov 2020
Cited by 8 | Viewed by 2572 | Correction
Abstract
Despite compelling reports on asbestos-like pathogenicity, regulatory bodies have been hesitant to implement fiber number-based exposure limits for biodurable nanoscale fibers. One reason has been the lack of a practicable strategy for assessing airborne fiber number concentrations. Here, a method is proposed, detailed [...] Read more.
Despite compelling reports on asbestos-like pathogenicity, regulatory bodies have been hesitant to implement fiber number-based exposure limits for biodurable nanoscale fibers. One reason has been the lack of a practicable strategy for assessing airborne fiber number concentrations. Here, a method is proposed, detailed and tested for compliance checking concentrations of airborne nano- and microscale fibers. It relies on Poisson statistical significance testing of the observed versus a predicted number of fibers on filters that have sampled a known volume of aerosol. The prediction is based on the exposure concentration to test. Analogous to the established counting rules for WHO-fibers, which use a phase contrast microscopy-related visibility criterion of 200 nm, the new method also introduces a cut-off diameter, now at 20 nm, which is motivated by toxicological findings on multi-walled carbon nanotubes. This cut-off already reduces the workload by a factor of 400 compared to that necessary for imaging, detecting and counting nanofibers down to 1 nm in diameter. Together with waiving any attempt to absolutely quantify fiber concentrations, a compliance check at the limit-of-detection results in an analytical workload that renders our new approach practicable. The proposed method was applied to compliance checking in 14 very different workplaces that handled or machined nanofiber-containing materials. It achieved detecting violations of the German benchmark exposure level of 10,000 nanofibers per cubic meter. Full article
(This article belongs to the Special Issue Advancements in the Reduction of Submicron Particle Concentrations)
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17 pages, 3826 KiB  
Article
Development of a Method to Determine the Fractional Deposition Efficiency of Full-Scale HVAC and HEPA Filter Cassettes for Nanoparticles ≥3.5 nm
by Ana Maria Todea, Frank Schmidt, Tobias Schuldt and Christof Asbach
Atmosphere 2020, 11(11), 1191; https://doi.org/10.3390/atmos11111191 - 03 Nov 2020
Cited by 7 | Viewed by 3726
Abstract
Novel methods have been developed to measure the fractional deposition efficiency for nanoparticles of full-scale HVAC and HEPA filter cassettes down to a particle size of 3.5 nm. The methods use a flame spray nanoparticle generator to produce NaCl test aerosols with narrow [...] Read more.
Novel methods have been developed to measure the fractional deposition efficiency for nanoparticles of full-scale HVAC and HEPA filter cassettes down to a particle size of 3.5 nm. The methods use a flame spray nanoparticle generator to produce NaCl test aerosols with narrow size distributions and very high concentrations. While the efficiency curves of lower efficiency filters of classes F7 and E10 were still able to be determined by measuring the size distributions of the polydisperse test aerosols upstream and downstream of the filter, two new testing procedures were developed for high efficiency filters of class H13. One considers the narrow size distributions of the test aerosols as quasi-monodisperse and follows a similar approach like EN 1822 for flat sheet media. The second one evaluates mobility classified fractions of the quasi-monodisperse test aerosols. A dedicated multiple charge correction scheme was developed to account for the effect of multiply charged particles. While the latter procedure allows to extend the particle size range, the prior significantly reduces the measurement time. All tests delivered meaningful results, which were very comparable with the results from flat sheet media tests. Full article
(This article belongs to the Special Issue Advancements in the Reduction of Submicron Particle Concentrations)
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17 pages, 9001 KiB  
Article
Influence of Disc Temperature on Ultrafine, Fine, and Coarse Particle Emissions of Passenger Car Disc Brakes with Organic and Inorganic Pad Binder Materials
by Hartmut Niemann, Hermann Winner, Christof Asbach, Heinz Kaminski, Georg Frentz and Roman Milczarek
Atmosphere 2020, 11(10), 1060; https://doi.org/10.3390/atmos11101060 - 05 Oct 2020
Cited by 34 | Viewed by 3477
Abstract
Passenger car disc brakes are a source of ultrafine, fine, and coarse particles. It is estimated that 21% of total traffic-related PM10 emissions in urban environments originate from airborne brake wear particles. Particle number emission factors are in the magnitude of 10 [...] Read more.
Passenger car disc brakes are a source of ultrafine, fine, and coarse particles. It is estimated that 21% of total traffic-related PM10 emissions in urban environments originate from airborne brake wear particles. Particle number emission factors are in the magnitude of 1010 km−1 wheel brake during real-world driving conditions. Due to the complexity of the tribological processes and the limited observability of the friction zone between brake disc and pad, the phenomena causing particle emission of disc brakes are only partially understood. To generate a basis for understanding the emission process and, based on this, to clarify which influencing variables have how much potential for reduction measures, one approach consists in the identification and quantification of influencing variables in the form of emission maps. The subject of this publication is the influence of disc brake temperature on ultrafine, fine, and coarse particle emissions, which was investigated with a systematic variation of temperature during single brake events on an enclosed brake dynamometer. The systematic variation of temperature was achieved by increasing or decreasing the disc temperature stepwise which leads to a triangular temperature variation. Two types of brake pads were used with the main distinction in its chemical composition being organic and inorganic binder materials. The critical disc brake temperature for the generation of ultrafine particles based on nucleation is at approximately 180 °C for pads with an organic binder and at approximately 240 °C for pads with inorganic binder materials. Number concentration during those nucleation events decreased for successive events, probably due to aging effects. PM10 emissions increased by factor 2 due to an increase in temperature from 80 °C to 160 °C. The influence of temperature could be only repeatable measured for disc brake temperatures below 180 °C. Above this temperature, the emission behavior was dependent on the temperature history, which indicates also a critical temperature for PM10 relevant emissions but not in an increasing rather than a decreasing manner. Full article
(This article belongs to the Special Issue Advancements in the Reduction of Submicron Particle Concentrations)
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7 pages, 6465 KiB  
Correction
Correction: Meyer-Plath et al. A Practicable Measurement Strategy for Compliance Checking Number Concentrations of Airborne Nano- and Microscale Fibers. Atmosphere 2020, 11, 1254
by Asmus Meyer-Plath, Daphne Bäger, Nico Dziurowitz, Doris Perseke, Barbara Katrin Simonow, Carmen Thim, Daniela Wenzlaff and Sabine Plitzko
Atmosphere 2022, 13(2), 202; https://doi.org/10.3390/atmos13020202 - 27 Jan 2022
Viewed by 1277
Abstract
The authors wish to make the following corrections to this paper [...] Full article
(This article belongs to the Special Issue Advancements in the Reduction of Submicron Particle Concentrations)
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