Wind Tunnel‐Based Comparison of PM₁₀ Emission Rates for Volcanic Ash and Glaciogenic Aerosol Sources Within Iceland

Abstract

Iceland contributes 30-40 million tons of mineral dust to the atmosphere each year. Emission events are linked to exceedingly high concentrations of PM 10 , poor air quality, and respiratory disease, particularly in Reykjavík. Volcaniclastic aerosols have unique microphysical properties, and usually are porous and highly angular, with large surface areas bearing ultrafine, nanoscale dustcoats. The large internal void space contributes to low particle density, believed to affect emission and deposition rates in the atmospheric boundary layer, as well as the range of transport. However, the aerodynamic and sedimentological factors that govern dust entrainment in these high-latitude settings are not well constrained empirically, providing little guidance for the parameterization of aerosol dispersion models. A series of laboratory wind tunnel simulations were carried out under full climate control to evaluate these effects for Icelandic samples collected from five active dust sources, inclusive of volcanic ash and glaciofluvial sediments. PM 10 emission rates measured in this study are similar in magnitude to those obtained in a small number of field studies within selected high-latitude regions, and for volcanic ash using a PI-SWERL. The scaling with friction velocity is well described by the 1988 dust emission model of Gillette and Passi, while the parameterization appears to be strongly dependent on the median particle size. Sediments from the coarsest Icelandic dust sources were found to be most emissive, owing to the importance of particle impact, while the proportionate amount of PM 10 within the test bed was not found to correlate with the emission rate.

Development of a Mobile Module-Based Wind Tunnel for the Determination of Collection Efficiencies of Particulate Matter on Surface Structures

“…The obtained turbulence intensities were comparable to the measured wind velocity variation levels in urban areas [35]. To reduce this turbulence, a honeycomb structure has been used in other studies in the pre-conditioning zone [21,22]. Thereby, the incoming flows meet the test section with less turbulence, which could easily be realized for our WT.…”

“…Their main characteristics and areas of application are summarized in Table 1. The Trent Environmental Wind Tunnel (TEWT) was used in a study on PM 10 emission rates from ash by Richard-Thomas et al [21]. The WT had an open-loop, straight-line suction design.…”

“…The other technical installations for measurements were a Dantec 2-component Laser Doppler anemometer, a Konica-Minolta Vivid 9i noncontact 3D digitizer, a PCO high-speed digital camera, TSI DustTrak aerosol monitors and Sensit, Wenglor particle counters [29]. In order to create controlled atmospheric conditions, the duct was installed inside a climatic chamber which allowed the regulation of air temperature and air humidity [20][21][22].…”

“…As previous studies have shown, designs often vary depending on the area of application. The construction methods differ primarily regarding closed constructions or open constructions, the size of the test-and cross-sections and the flow speeds achieved [20,21,[23][24][25][26][27][28]. The following requirements were predefined for the design of our WT:…”

“…In addition, a closed construction can achieve higher wind speeds with the same energy [13]. In order to minimize external influences, our WT could be used in a climate chamber due to its modular design and size, in a similar way to the TEWT WT for complete climate control [21]. The technical installations used in our WT were limited to ultrasonic anemometers and temperature and humidity sensors.…”