Abstract
It is well known that electric fields occur in wind-blown dust, due to the triboelectric charging of particles as they collide. Triboelectric charging, or contact electrification, is a poorly understood and complex phenomenon. It is especially important in granular systems, as the high surface-to-volume ratio can lead to the build-up of large amounts of charge. A particularly surprising effect, which is important in dust systems, is that charge transfer occurs in systems of a single composition, such that there is a particle-size dependent polarity of the particles. Here, we use a combined experimental and theoretical approach to elucidate the electrostatic charging that occurs during dust storms, and the effects of this electrostatic charging on dust transport. We create laboratory-scale wind-blown dust systems, and study the electrostatic charging. We find that larger particles tend to charge positive and to stay at or near the sand bed, while smaller particles tend to charge negative and get lofted to higher elevations. This self-segregating of charged particles would lead to electric fields within a dust storm. Our results show that electric fields then increase the dust transport by more easily lofting charged particles.
Highlights
For over a century, scientists have known that large electric fields develop in dust storms [1]
We address the effect of an electric field, such as that which is found to occur in dust storms by looking at the difference of the large particle fraction between the bottom and top cups
At an applied potential of -10 kV, the difference in large particle fraction was 0.27 ± 0.7. This result aligns with the idea that large particles charge more positively, and small particles charge more negatively; the result is corroborated by the charge data collected
Summary
Scientists have known that large electric fields develop in dust storms [1]. The electric fields come about from the electrostatic charging of the dust particles. The electrostatic charging effects can be very dramatic, as described in a book about America’s “Dust Bowl” in the 1930’s, when catastrophic dust storms ravaged parts of the country [2]:. Ignitions shorted out...Every car dragged a metal chain to ground the static...Men avoided shaking hands with each other because the static electricity was so great it could knock a person down.”. Electrostatic charge on the dust particles is believed to significantly increase the magnitude of wind-blown dust [3,4]. Of particular relevance is the role of wind-blown dust in desertification, a serious problem in Asia and Africa
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