Quantitative detection of aerial suspension of particles with a full-frame visual camera for atmospheric wind tunnel studies

Esders, Eike; Georgi, Christoph; Babel, Wolfgang; Thomas, Christoph K.

doi:10.1080/02786826.2022.2048789

Cited by 6 publications

(7 citation statements)

References 41 publications

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“…Detachment of microspheres was measured as the decreasing number of microspheres in the field of observation. The algorithm used to quantitatively determine the number of microspheres in each individual image is described in Esders et al (2022). In a single experiment, up to approximately 1500 microspheres were placed on a substrate as described above, positioned in the wind tunnel on the substrate mount, and subsequently exposed to airflows with increasing friction velocities.…”

Section: Determining Detachment From Measurementsmentioning

confidence: 99%

Is transport of microplastics different from that of mineral dust? Results from idealized wind tunnel studies

Esders

Sittl

Krammel

et al. 2023

Preprint

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Abstract. Atmospheric transport disperses microplastic particulate matter to virtually every environment on the planet. Despite the well-known long-range transport, only few studies have examined the fundamental transport mechanisms for microplastics and contrasted it with the existing body of knowledge accumulated for mineral dust over the past decades. Our study addresses this research gap and presents results from wind tunnel experiments, which examine the detachment behavior of microplastics ranging from 38 to 125 µm in diameter from idealized substrates. We here define 'detachment' as microspheres detaching from a substrate and leaving the field of observation, which includes several transport modes including creeping, rolling, directly lifting off. The detachment behavior of polyethylene microspheres (PE69) and borosilicate microspheres (GL69) of nominally the same physical diameter (63–75 µm) are contrasted across hydrophilic to hydrophobic substrates. We further examine the effect of microsphere-microsphere collisions on the detachment behavior of both polyethylene and borosilicate microspheres. Differentiating between collision independent microspheres and collisions dependent microspheres revealed that collisions impact detachment from enhancing to mitigating. Further, results indicate that GL69, as a hydrophilic particle, is highly dependent on substrate hydrophobicity and PE69 is less affected by it. A more detailed comparison between GL69 and PE69 regarding surface and substrate hydrophobicity is masked by the influence of capillary forces. Moreover, the smallest polyethylene microspheres behave similar to mineral microspheres. Results demonstrate that PE69 and GL69 as proxy for plastic and mineral dust, respectively, detach at u* between 0.1 to 0.3 ms-1 fitting to the prediction of the simple wind erosion model by Shao et al. (2000). In the observed range of rH, capillary forces can increase the median detachment by about 0.2 ms-1 for PE69 and GL69. Polyethylene microspheres, smaller than 70 µm in diameter, behave like borosilicate microspheres of the same size. For bigger microspheres, the lesser density of polyethylene drives their higher erodibility. We conclude that it is no surprise, that like mineral dust, plastic dust is found all around the globe, transported via the atmosphere.

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Section: Determining Detachment From Measurementsmentioning

confidence: 99%

Is transport of microplastics different from that of mineral dust? Results from idealized wind tunnel studies

Esders

Sittl

Krammel

et al. 2023

Preprint

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show abstract

“…For the "Windtunnel" evaluation, one SoPhaB containing a section of approximately 5 m length toward the end of the described fiber-optic cable was placed in the wind tunnel of about 21 • C with the CPU heat sink element attached, but electric fan detached. The ventilation speed of the CPU heat sink was set through the wind tunnel controls (for details of the tunnel see [21,22]). The setpoint for the two Peltier elements was initially set to cool to 19.0 • C for the first 30 min, then adjusted to 7.2 • C for the remainder of the experiment.…”

Section: Field and Laboratory Evaluationsmentioning

confidence: 99%

Solid-Phase Reference Baths for Fiber-Optic Distributed Sensing

Thomas

Huss

Abdoli

et al. 2022

Sensors

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Observations from Raman backscatter-based Fiber-Optic Distributed Sensing (FODS) require reference sections of the fiber-optic cable sensor of known temperature to translate the primary measured intensities of Stokes and anti-Stokes photons to the secondary desired temperature signal, which also commonly forms the basis for other derived quantities. Here, we present the design and the results from laboratory and field evaluations of a novel Solid-Phase Bath (SoPhaB) using ultrafine copper instead of the traditional mechanically stirred liquid-phase water bath. This novel type is suitable for all FODS applications in geosciences and industry when high accuracy and precision are needed. The SoPhaB fully encloses the fiber-optic cable which is coiled around the inner core and surrounded by tightly interlocking parts with a total weight of 22 kg. The SoPhaB is thermoelectrically heated and/or cooled using Peltier elements to control the copper body temperature within ±0.04 K using commercially available electronic components. It features two built-in reference platinum wire thermometers which can be connected to the distributed temperature sensing instrument and/or external measurement and logging devices. The SoPhaB is enclosed in an insulated carrying case, which limits the heat loss to or gains from the outside environment and allows for mobile applications. For thermally stationary outside conditions the measured spatial temperature differences across SoPhaB parts touching the fiber-optic cable are <0.05 K even for stark contrasting temperatures of ΔT> 40 K between the SoPhaB’s setpoint and outside conditions. The uniform, stationary known temperature of the SoPhaB allows for substantially shorter sections of the fiber-optic cable sensors of less than <5 bins at spatial measurement resolution to achieve an even much reduced calibration bias and spatiotemporal uncertainty compared to traditional water baths. Field evaluations include deployments in contrasting environments including the Arctic polar night as well as peak summertime conditions to showcase the wide range of the SoPhaB’s applicability.

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“…While many studies have measured microplastics in agricultural soils, ,− limited field studies have examined the wind transport of microplastics from biosolid-applied agricultural lands, − and far fewer studies have examined the conditions that affect the resuspension potential of microplastics using wind tunnel experiments in agricultural fields. − Some of these studies added microplastics created in the laboratory at a concentration much higher than that expected in agricultural fields, thereby affecting interactions between soil grains and microplastic particles . Additionally, microplastics created in the laboratory by abrading plastic materials could differ significantly in shape, size, and surface properties compared to microplastics present in biosolids.…”

Section: Introductionmentioning

confidence: 99%

Preferential Emission of Microplastics from Biosolid-Applied Agricultural Soils: Field Evidence and Theoretical Framework

Leonard,

Ravi,

Mohanty

2024

Environ. Sci. Technol. Lett.

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Land application of wastewater biosolids on agricultural soils is suggested as a sustainable pathway to support the circular economy; however, this practice often enriches microplastics and associated contaminants in topsoil. Wind could transport these contaminated microplastics, thereby increasing their inhalation health risks. Analyzing wind-borne sediments collected from wind tunnel experiments on biosolid-applied agricultural fields, we show enrichment of microplastics in wind-blown sediments. We explain this preferential transport and enrichment of microplastics by using a theoretical framework. This framework reveals how the combined effects of the low density of microplastics and weakened wet-bonding interparticle forces between microplastics and soil particles lower their threshold velocity, the minimum wind velocity necessary for wind erosion to occur. Our calculations indicate that microplastics could be emitted at wind speeds lower than the characteristic threshold of background soil. Analyzing the windspeed distribution for 3 months of wind events over a bare soil surface, we showed that more than 84% of the wind events exceed the threshold velocity of microplastics of size 150 μm, while only 23% of the wind events exceed the threshold velocity of the background soil. Thus, current models for fugitive dust emissions may underestimate the microplastic emission potential of biosolid-amended soils.

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Quantitative detection of aerial suspension of particles with a full-frame visual camera for atmospheric wind tunnel studies

Cited by 6 publications

References 41 publications

Is transport of microplastics different from that of mineral dust? Results from idealized wind tunnel studies

Is transport of microplastics different from that of mineral dust? Results from idealized wind tunnel studies

Solid-Phase Reference Baths for Fiber-Optic Distributed Sensing

Preferential Emission of Microplastics from Biosolid-Applied Agricultural Soils: Field Evidence and Theoretical Framework

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