An Ion Generator for Neutralizing Concentrated Aerosols

Hinds, William C.; Kennedy, Nola

doi:10.1080/027868200303740

Cited by 79 publications

(126 citation statements)

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“…The sampling efficiency of quartz filters used in TOM is not well 17 characterized for small particles (Lim et al, 2014). However, smaller particles normally contribute little 18 to total particulate mass (Hinds 1999). Thus, each method for measuring BC in snow has both 19 advantages and disadvantages.…”

Section: Methods (Tom) Provides An Actual Measurement Of Elemental Carmentioning

confidence: 99%

Contribution of dust and elemental carbon to the reduction of snow albedo in the Indian Himalaya and the Finnish Arctic

Svensson

Ström

Kivekäs

et al. 2017

Preprint

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1Light-absorbing impurities (LAI) have the potential to substantially affect snow albedo, with 2 subsequent changes on snow melt and impact on climate. To more accurately quantify the snow albedo, 3 the contribution from different LAI needs to be assessed. Here we estimate the main LAI components, 4 elemental carbon (EC) (as a proxy for black carbon) and mineral dust in snow from Indian Himalaya 5 and compared it to snow samples from Arctic Finland. The impurities are collected onto quartz filters 6 and are analyzed thermal-optically for EC, as well as with an additional optical measurement to estimate 7 the light-absorption of dust separately on the filters. Laboratory tests were conducted using substrates 8 containing soot and mineral particles specially prepared to test the experimental setup. Analyzed 9 ambient snow samples show EC concentrations that are in the same range as presented by previous 10 research, for each respective region. In terms of the mass absorption cross section (MAC) our ambient 11EC had surprisingly about half of the MAC value compared to our laboratory standard EC (chimney 12 soot), suggesting a less light absorptive EC in the snow, which has consequences for the snow albedo 13 reduction caused by EC. In the Himalayan samples, larger contributions by dust (in the range of 50 % 14 or greater for the light absorption caused by the LAI) highlighted the importance of dust acting as a 15 light absorber in the snow. Moreover, EC concentrations in the Indian samples, acquired from a 120 cm 16 deep snow pit (covering possibly the last five years of snow fall), suggest an increase in both EC and 17 dust, while at the same time there is a tendency for a reduction in the MAC value with snow depth. This 18 work emphasizes the complexity in determining the snow albedo, showing that LAI concentrations 19 alone might not be sufficient, but additional transient effects on the light-absorbing properties of the EC 20 need to be considered and studied in the snow. Equally imperative is to confirm the spatial and temporal 21 representativeness of these data by comparing data from several and longer pits explored at the same 22 time. 23Atmos. Meas. Tech. Discuss., https://doi

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Section: Methods (Tom) Provides An Actual Measurement Of Elemental Carmentioning

confidence: 99%

Contribution of dust and elemental carbon to the reduction of snow albedo in the Indian Himalaya and the Finnish Arctic

Svensson

Ström

Kivekäs

et al. 2017

Preprint

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“…Other factors, such as the grease coating thickness, particle hardness, and shape, can also affect bouncing behavior. 11,15,17 Another important design parameter that can significantly affect the overall impactor performance is the S/W ratio, where S is the distance between the nozzle exit and the impaction plate and W is the nozzle diameter. According to the numerical analysis of conventional impactors by Marple et al, 18 the S/W ratio should be greater than 1 for round nozzles and 1.5 for rectangular impactors.…”

Section: Methodsmentioning

confidence: 99%

Development and Evaluation of an Impactor for a PM_2.5Speciation Sampler

Demokritou

Kavouras

Harrison

et al. 2001

Journal of the Air & Waste Management Association

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A conventional impactor for a particle speciation sampler was developed and validated through laboratory and field tests. The speciation sampler consists of the following components: a PM 2.5 conventional impactor that removes particles larger than 2.5 µm, an all-glass, coated honeycomb diffusion denuder, and a 47-mm filter pack. The speciation sampler can operate at two different sampling rates: 10 and 16.7 L/min. An experimental characterization of the impactor's performance was conducted. The impactor's collection efficiency was examined as a function of critical design parameters such as Reynolds number, the distance from the nozzle exit to the impaction plate, and the impaction substrate coating method. The bounce of particles larger than the cut point was successfully minimized by using a greased surface as the impaction substrate. Additionally, a series of field intercomparison experiments were conducted at both 10 and 16.7 L/min airflow. PM 2.5 mass and SO 4 2-concentrations were measured and compared with the Federal Reference Method (FRM) and found to be in good agreement. Results of the laboratory chamber tests also indicated that the impactor's performance was in good agreement with the FRM.

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“…The median number diameter in the "ESP on" case is ϳ25-30 nm, a size range where it is difficult to get very high charging efficiency. 12,13 These particles contribute less than 2% to the aerosol mass for the aerosol distributions used in these experiments. Because ambient aerosol distributions nearly always have median diameters much larger than the 60 -80 nm measured in these tests, 14 one expects the ESP to remove an even greater fraction of the mass under ambient conditions.…”

Section: Self-referencing Differential Teom Monitormentioning

confidence: 99%

Laboratory Characterization of Modified Tapered Element Oscillating Microbalance Samplers

Schwab

Hogrefe

Demerjian

et al. 2004

Journal of the Air & Waste Management Association

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Laboratory tests with generated aerosols were conducted to test the efficacy of two recent design modifications to the well-established tapered element oscillating microbalance (TEOM) continuous particulate matter (PM) mass monitor. The two systems tested were the sample equilibration system-equipped TEOM monitor operating at 30°C, which uses a Nafion dryer as part of the sample inlet, and the differential TEOM monitor, which adds a switched electrostatic precipitator and uses a self-referencing algorithm to determine "true PM mass." Test aerosols included ammonium sulfate, ammonium nitrate, sodium chloride, copper (II) sulfate, and mixed aerosols. Aerosols were generated with an atomizer or a vibrating orifice generator and were equilibrated in a 450-L slow flow chamber before being sampled. Relative humidity in the chamber was varied between 10 and 90%, and step changes in humidity were executed while generating aerosol to test the response of the instruments. The sample equilibration system-equipped TEOM monitor does reduce, but not totally eliminate, the sensitivity of the TEOM mass monitor to changes in humidity. The differential TEOM monitor gives every indication of being a very robust technique for the continuous real-time measurement of ambient aerosol mass, even in the presence of semi-volatile particles and condensable gases. INTRODUCTIONThe tapered element oscillating microbalance (TEOM) mass monitor uses a hollow oscillating microbalance to detect and report changes in mass caused by the passage of ambient air through a replaceable filter. 1 The monitor provides a continuous measure of collected mass. The purpose of this work is to understand how to better measure the atmospheric particulate matter (PM) to which people are exposed in the ambient environment. Continuous measurements of PM are desirable for a number of reasons, including (1) the capture of short, but intense, pollution events; (2) hourly mass concentration data are required for use in PM with an aerodynamic diameter less than or equal to 2.5 m (PM 2.5 ) mapping projects; and (3) more highly time resolved data are required for model evaluation. While data with higher time resolution answer some of the objections to the 24-hr integrated filters collected in the U.S. Environmental Protection Agency (EPA) Federal Reference Method (FRM) network, the TEOM monitor still uses a filter for particle collection and is subject to the same artifact and interference problems of other filter-based PM collection methods. These limitations as they relate to the FRM for PM 2.5 2 are discussed and evaluated by Eatough et al. 3 The research described here consists of a thorough laboratory evaluation of modifications to the TEOM monitor. The modifications were made to address the limitations of the basic method and primarily involve treatment of the sample before it reaches the oscillating microbalance. The sample equilibration system (SES)-equipped TEOM monitor 4 was developed to mitigate interferences from water vapor, so extensive laboratory te...

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An Ion Generator for Neutralizing Concentrated Aerosols

Cited by 79 publications

References 1 publication

Contribution of dust and elemental carbon to the reduction of snow albedo in the Indian Himalaya and the Finnish Arctic

Contribution of dust and elemental carbon to the reduction of snow albedo in the Indian Himalaya and the Finnish Arctic

Development and Evaluation of an Impactor for a PM_2.5Speciation Sampler

Laboratory Characterization of Modified Tapered Element Oscillating Microbalance Samplers

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An Ion Generator for Neutralizing Concentrated Aerosols

Cited by 79 publications

References 1 publication

Contribution of dust and elemental carbon to the reduction of snow albedo in the Indian Himalaya and the Finnish Arctic

Contribution of dust and elemental carbon to the reduction of snow albedo in the Indian Himalaya and the Finnish Arctic

Development and Evaluation of an Impactor for a PM2.5Speciation Sampler

Laboratory Characterization of Modified Tapered Element Oscillating Microbalance Samplers

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Development and Evaluation of an Impactor for a PM_2.5Speciation Sampler