Wind-blown Transport Research Articles

Aeolian sediment transport on Io from lava\u2013frost interactions

Surface modification on Jupiter’s volcanically active moon, Io, has to date been attributed almost exclusively to lava emplacement and volcanic plume deposits. Here we demonstrate that wind-blown transport of sediment may also be altering the Ionian surface. Specifically, shallow subsurface interactions between lava and Io’s widespread sulfur dioxide (SO2) frost can produce localized sublimation vapor flows with sufficient gas densities to enable particle saltation. We calculate anticipated outgassing velocities from lava–SO2 frost interactions, and compare these to the saltation thresholds predicted when accounting for the tenuous nature of the sublimated vapor. We find that saltation may occur if frost temperatures surpass 155 K. Finally we make the first measurements of the dimensions of linear features in images from the Galileo probe, previously termed “ridges”, which demonstrate certain similarities to dunes on other planetary bodies. Io joins a growing list of bodies with tenuous and transient atmospheres where aeolian sediment transport may be an important control on the landscape.

Foredune morphological changes and beach recovery from the extreme 2013/2014 winter at a high-energy sandy coast

The beach-dune response at Truc Vert, SW France, is analysed using DGPS topographic surveys sampled every 2–4weeks covering an alongshore distance of 1.5km, combined with wave, tide and extreme water level hindcast and beach/dune photographs. During the 2013/2014 winter, which was the most energetic since at least 1948, the beach-dune system at Truc Vert eroded by approximately 180m3 per beach width divided equally between beach and dune erosion. Beach and dune erosion was strongly variable alongshore, with cuspate-type rhythmic dune erosion scarps stripped of vegetation with a cross-shore amplitude of 25m. The alongshore-variable scarps were coupled with an alongshore variability in elevation of the beach, with lower beach levels co-located with the megacusp bays. The following 10months showed modest morphological beach and dune changes with, for instance, destabilisation of the scarped dune by trough blowouts, scarp slumping and filling and seasonal beach berm dynamics. The most profound morphological and vegetation changes occurred during the subsequent 10months. Only 1.5years after that winter, the beach-dune system at Truc Vert almost recovered to its pre-winter volume, but not to its pre-winter foredune profile. Most of the sand volume recovery occurred during spring-summer-autumn 2015 when approximately 120m3/m of sand naturally came back in the system. The beach volume recovery rate was relatively steady and uncorrelated with wave conditions, with rates twice as large across the megacusp bay profile as across the that of the megacusp horns. During that period, the widened and risen dry beach provided large fetch length enhancing onshore windblown transport and a rapid rising of the backshore. The slumped and filled dune scarp, which was providing a high barrier to aeolian transport from the beach to the dune since the 2013/2014 winter, reformed as a dune ramp providing efficient conduit for beach-dune delivery/exchange of sediment by the end of the study. This process favoured both natural revegetation into the scarp and incipient foredune formation. Despite the reinstatement of natural processes between the beach and the dune, the dune foot was still located landward by more than 10m on average with respect to its pre-2013/2014 winter position. This study shows that even after the most severe winter over the last 68years in terms of average wave energy arriving at the coast, beach recovery can be a relatively fast process along high-energy sandy beaches backed by large dunes. In contrast foredune recovery, which timing and magnitude can provide a proxy measure for the resilience of the system to climatic variability and change, is a much slower process that can take years to decades.

Development of a dust deposition forecasting model for mine tailings impoundments using in situ observations and particle transport simulations

Abstract Mine tailings impoundments in arid and semiarid environments are susceptible to wind erosion due to their fine grain silt and sandy composition and lack of vegetative coverage. Aeolian transport of particulate matter from these mine tailings impoundments are potential hazards to human health due to the presence of metal and metalloid contaminants. Predicting windblown transport of mine tailings material can be a useful tool in characterizing the risk and environmental impact on neighboring communities. This work presents a model that can be used to forecast the transport and deposition of windblown dust from mine tailings impoundments. The deposition forecast model uses in situ observations from a tailings field site and theoretical simulations of aerosol transport to parameterize the model. It includes a method for simulating deposition patterns for several different size fractions and can be translated to other regions and applied to different windblown dust sources. The model was developed using data from the Iron King Mine tailings in Dewey-Humboldt, Arizona, a Superfund site that is heavily contaminated with lead and arsenic. A preliminary verification of the model was conducted using topsoil measurements of lead and arsenic as tracers of windblown dust from the tailings impoundment. The tailings tracers support the predicted deposition patterns generated by the deposition forecasting model.

Assessment of chemical and mineralogical characteristics of airborne dust in the Sistan region, Iran

Windblown transport and deposition of dust is widely recognized as an important physical and chemical concern to climate, human health and ecosystems. Sistan is a region located in southeast Iran with extensive wind erosion, severe desertification and intense dust storms, which cause adverse effects in regional air quality and human health. To mitigate the impact of these phenomena, it is vital to ascertain the physical and chemical characteristics of airborne and soil dust. This paper examines for the first time, the mineralogical and chemical properties of dust over Sistan by collecting aerosol samples at two stations established close to a dry-bed lake dust source region, from August 2009 to August 2010. Furthermore, soil samples were collected from topsoil (0–5cm depth) at several locations in the dry-bed Hamoun lakes and downwind areas. These data were analyzed to investigate the chemical and mineralogical characteristics of dust, relevance of inferred sources and contributions to air pollution. X-ray Diffraction (XRD) analysis of airborne and soil dust samples shows that the dust mineralogy is dominated mainly by quartz (30–40%), calcite (18–23%), muscovite (10–17%), plagioclase (9–12%), chlorite (∼6%) and enstatite (∼3%), with minor components of dolomite, microcline, halite and gypsum. X-ray Fluorescence (XRF) analyses of all the samples indicate that the most important oxide compositions of the airborne and soil dust are SiO2, CaO, Al2O3, Na2O, MgO and Fe2O3, exhibiting similar percentages for both stations and soil samples. Estimates of Enrichment Factors (EFs) for all studied elements show that all of them have very low EF values, suggesting natural origin from local materials. The results suggest that a common dust source region can be inferred, which is the eroded sedimentary environment in the extensive Hamoun dry lakes lying to the north of Sistan.

Arid sedimentation in the oceans and atmospheric particulate matter

Recent studies on the continental sources of aerosol production, transport and deposition to the ocean (natural sink) allowed us to recognize the possibility of long-range high-altitude (transoceanic) transport of aerosol dust of specific composition and properties. The dust consists of fine (micro- and nanosized) particles (94%, less than 2 μm) originated in the arid (undrained) tropical and subtropical regions extending into the oceans and are similar in composition to deep-sea (pelagic) red clays. Satellite and aircraft observation data were used to track trajectories of long-range (and transoceanic) transport of dust clouds. These data were coupled with direct shipboard measurements on ice core records and data on nuclear explosions and volcanic eruptions. Several zones of arid sedimentation were identified based on climatic conditions (shortage of water), conditions of dust production, wind-blown transport at different altitudes and deposition onto the ocean surface. The main transport occurs at two altitude scales (from land to the cloud top and above) (5–7 km) where wind speed of 300 km/h will be critical for a long-range transport. Three types of transport are identified based on the particle dynamics, composition and properties: 1—local (0–10 km from the source); 2—regional (100–1000 km); 3—global (over 1000 km). The finer particles are a product of local-scale transport with a total flux of 1.6 billion t/yr, which is almost equal to the net influx of the riverine terrigenous material to the pelagic zones of the oceans (outside the marginal filters). There are four main sources of aerosol dust, which is transported and deposited over arid oceanic regions. The arid oceanic regions account for about 1/3 of the modern ocean surface. During glacial periods, the sea-level drop of 100–120 m caused a significant increase in the size of arid regions due to the exposure of the shelf areas, which is equal to the area of the African continent. This caused 3–5 times higher dust emission, a decrease in the heat flux and in the transparency of the atmosphere. Comparison of ice core records and deep drilling data provide basis for studies on the ancient arid sedimentation.

Electrification of granular systems of identical insulators

Insulating particles can become highly electrified during powder handling, volcanic eruptions, and the wind-blown transport of dust, sand, and snow. Measurements in these granular systems have found that smaller particles generally charge negatively, while larger particles charge positively. These observations are puzzling since particles in these systems are generally chemically identical and thus have no contact potential difference. We show here that simple geometry leads to a net transfer of electrons from larger to smaller particles, in agreement with these observations. We integrate this charging mechanism into the first quantitative charging scheme for a granular system of identical insulators and show that its predictions are in agreement with measurements. Our theory thus seems to provide an explanation for the hitherto puzzling phenomenon of the size-dependent charging of granular systems of identical insulators.

RS-VSP: A New Approach to Support Military Range Sustainability

The Navy, through Range Sustainability and Environmental Program Assessment (RSEPA), is taking the initiative to identify potential off-range transport of munitions constituents. To accomplish this initiative, the Quality Assurance Project Plan (QAPP) for sampling and testing at operational ranges was developed. A key goal of environmental sampling plan design is to specify representative sampling requirements necessary to determine the presence and distribution of environmental constituents. Range Sustainability-Visual Sample Plan (RS-VSP) is a software tool that was developed to achieve the environmental sampling goal of representative sampling for RSEPA QAPP implementation so that data collected provide the data user with the required information for knowledgeable decision making. The VSP-RSM supports a sampling approach designed to bound a “source area” suspected of containing concentrations of munitions constituents above the relevant screening levels. RS-VSP incorporates an innovative approach to selecting data quality objectives, estimate sampling and testing uncertainty, and determining the number and location of samples. Preliminary assessments of off-range migration of explosives particles by windblown transport mechanisms, and the potential environmental impacts to surface water, aquifer recharge zones, and groundwater are planned under RSEPA. Besides windblown transport, infiltration of dissolved explosives residues into groundwater is another important migration pathway being investigated for range sustainability by other DoD agencies.

Seagrass wrack-induced dune formation on a tropical coast (Banc d'Arguin, Mauritania)

The Banc d'Arguin (Mauritania) is a shallow water area with mudflats bordering on the Sahara desert. Mass depositions of seagrass litter were observed on some parts of the shore. Soil profiles of the low dune formations separating the flood debris zone from the desert showed that layers of seagrass detritus, in various stages of decay, extended under the dune formations. The tentative mechanism of dune formation, involving the interacting processes of beaching of seagrass litter and wind-blown transport of desert sediment in a seaward direction, is described. This role in dune formation adds a new element to the significance of seagrass vegetation for the coastal environment.

PREDICTION OF WIND-DRIVEN TRANSPORT RATE

The rate of wind-driven sand movement in a dune field is an important parameter needed to establish management strategies for sand dune fields. Until recently not much attention has been given in engineering circles to the possible effect of wind-blown sand transport. However, there is a wealth of literature on the subject which goes back as far as 1936. A study of literature reveals that there are at least 16 formulae for the prediction of the aeolian transport rates which are readily available. This paper describes a technique which utilizes these 16 formulae in the most effective manner for predicting the best estimate of the potential wind-blown transport rate. Restrictions on the applicability of the method are discussed and fields for further research are recommended.