Single particle characteristics and ice nucleation potential of particles collected during Asian dust storms in 2021

Dust storms have great impacts on air quality and climate. Dust can influence cloud microphysical properties and determine their radiative forcing and precipitation. Asian dust storms (ADS) are important sources of global aerosol. However, the physiochemical characteristics of dust from ADS at a single particle level are less understood, and the exact particles that can serve as ice nucleating particles (INPs) remain unclear. Here, we present the physicochemical properties and ice nucleation ability of dust particles collected in Beijing during two major ADS in March 2021. The particles from two ADS were classified into Illite, Kaolinite, Feldspar, Quartz, Chlorite, Mixed-dust, and Non-dust particles, which contributed 28.6 % ± 3.3 %, 20.0 % ± 3.9 %, 12.3 % ± 2.3 %, 11.1 % ± 2.8 %, 9.8 % ± 0.8 %, 13.7 % ± 1.8 %, and 4.4 % ± 1.7 % in number, respectively. On average, the ADS particles formed ice crystals via deposition ice nucleation from relative humidity with respect to ice (RHice) of 112 % ± 1 % at 250 K to 154 % ± 15 % RHice at 205 K. Part of the samples also formed ice via immersion freezing between 230 K and 250 K. Among the 149 identified INPs, Clay-like particles (Chlorite, Illite, and Kaolinite) contributed 71.1 % ± 6.2 % in number and followed by Mixed-dust-like particles (16.9 % ± 8.7 %) and Feldspar-like particles (10.4 % ± 6.3 %). Enrichment factor of each particle type in INPs is calculated as the ratio of its number fractions in INPs and the aerosol population. It ranges from 0.6 ± 0.7 to 1.3 ± 2.2. The contribution of each particle type to INP was correlated with its fraction in the population. These results imply that each particle type can serve as INP. Clay-like particles are the dominant INPs during the ADS. We conducted ice nucleation kinetic analysis and provided parameterizations of heterogeneous ice nucleation rate coefficient and contact angle for ADS. These parameterizations can be used in the modeling study to evaluate the impact of ADS in atmospheric ice crystal formation in clouds.

New insights into dust emission mechanism in natural environments based on a series of field observations

Most scholars have suggested that dust emission mainly depends on the bombardment of saltation particles based on wind tunnel experiments, because the cohesive forces between finer particles. However, in recent years, researchers have found that dust can be entrained directly in field. To detect the dust emission mechanism in natural environments, two types of field observations were carried out. Long-term observations were implemented on the shore of the Zu Lake, and the results show that the sediments contain large fractions of particulate matter <10 μm (PM10), which indicates that the entrainment of PM10 in sediment cannot solely depend on saltation bombardment. Short-term observations were conducted across the Desert Steppe, the Mu Us Sandy Land, and the shore of the Zu Lake, and a total of 31 plots were observed, which revealed that in most of the plots, the threshold of the friction velocities (TFVs) for PM10 entrainment was lower than for the entrainment of saltation particles, indicating that the PM10 was easier to entrain than the saltation particles. Large fractions of emitted PM10 were directly entrained, especially when the PM10 emission was continuous regardless of whether the PM10 contents of the soils were low or high, because the strong wind environment could renew the surface frequently and provided sufficient PM10 to be emitted. Based on our observations, we concluded that in natural environments, direct dust entrainment is the dominant dust emission mechanism, especially in continuous emission processes. Herein, we developed a parameterization scheme for continuous dust emission in natural environments, and this scheme can accurately simulate dust emission on different surfaces. The results of this study provide robust validation for the fact that direct dust entrainment dominates the dust emission mechanism in natural environments. In addition, the results provide valuable observation data for parameterization of dust emission.

Application of Resuspension Data of Respirable Particles for Early Phase Inhalation Following Deposition Contamination in Radiological Emergencies

In model experiments, wind resuspension rates, Rr, of respirable particles (<10 μm, aerodynamic diameter) and their time dependence after deposition on representatively contaminated urban surfaces were measured under real-life conditions, taking into account different weather conditions (wind velocities, precipitation) as well as countermeasures (fixation). For contamination by dry deposition of particles, short-term resuspension rates averaged over the first half hour, after exposure to wind with a friction velocity, u*, of 0.8 m s−1 ranged between 0.1% h−1 and 2% h−1 depending on the surface material, whereas after wet deposition, resuspension rates were two orders of magnitude lower. The time pattern of the resuspension rates followed a power law decrease, Rr ∝ t −μ , with values of μ close to 1. The measurements revealed a strong dependence on friction velocity, . For a larger area of 200 × 800 m2 contaminated with 106 Bq m−2 of particles in the respirable size range, applying a simple Gaussian dispersion model airborne activity concentration (Bq m−3) was calculated. On this basis, for an initial time of high windspeed, a cautious resuspension factor of Rf = 5 10−6 m−1 is derived for the first day, which diminishes inversely with time. The exposure of persons to external radiation and to inhaled airborne radioactivity is compared with examples for three radionuclides representing strong beta-, gamma- and alpha-radiation.

Similarity study of dust emissions from tracked military vehicles with experimental validation

Accurate prediction of dust emissions from tracked vehicles traveling on unpaved roads is essential for environmental protection and vehicle performance maintenance. However, limited research on dust emissions from tracked vehicles with high precision results from the complex dust emission mechanism and the multitude of influencing factors of tracked vehicles. This paper presents a method for determining the dust emissions from tracked vehicles based on the similarity principle. Specifically, an experimental scheme for the scaling model of T90 tank is designed through the similarity analysis of dust emissions from tracked vehicles, which correlates the mass flow rate of dust emission with seven related variables (soil thickness, dust particle bulk density, dust average particle size, vehicle weight, track width, track landing length, and vehicle speed). The dimensionless empirical equations are obtained by multivariate nonlinear fitting of the experimental results. Furthermore, the applicability of empirical equations is validated experimentally to describe dust emissions from real tracked vehicles. The results show that the similarity principle is a better method to overcome the bottleneck of quantifying dust emissions from tracked vehicles. Meanwhile, the empirical equations derived from the scaling model are also applicable to describe the dust emissions from actual tracked military vehicles.

Morphology and mineralogical composition of sandblasting dust particles from the Taklimakan Desert

The physicochemical characteristics of dust particles from the Taklimakan Desert are the fundamental basis for the assessment of particle variation during their long-distance transport and the subsequent environmental effects. In this study, 43,222 individual sandblasting dust particles, which were mobilised using a chamber with surface soils of sand dunes and Gobi (the two types of surfaces constituting the desert) were analysed to statistically quantify the shape and mineralogical composition of dust particles from the desert. The mode of the number-size distribution of particles from the sand dunes was 0.5-0.7 μm and that of particles from Gobi soils was approximately 1.0 μm. In contrast, the distributions of particle number fractions versus shape factors such as aspect ratio and roundness were similar, despite the irregular shape of the particles. Clay mineral particles were most frequently composed of chlorite and kaolinite, accounting for 66.74 ± 12.08% of the particles from both types of soils. Quartz and feldspar particles accounted for 9.57 ± 4.52% and 2.84 ± 1.28%, respectively. The mineralogical composition of particles smaller than 1.0 μm, in both soil types, was dominated by chlorite (Al-Si-O-Mg), kaolinite (Ai-Si-O), and quartz (SiO). Gypsum (CaS) and halite (NaCl) were the major salt components in particles from both soil types. Gypsum-containing particles existed in a wide size range and occupied 3.42%-8.98% of the particles from Gobi soils and 0.27%-2.18% of the particles from sand dunes. Most gypsum-containing particles were mixed with Si-containing minerals in the form of silicate or aluminosilicate; the remaining gypsum-containing particles were gypsum crystals or mixtures of gypsum and Ca-containing minerals. These results provide a comprehensive statistical profile of dust particles released by the sandblasting process from the Taklimakan Desert to the atmosphere.

The Impact of Salinization and Wind Erosion on the Texture of Surface Soils: An Investigation of Paired Samples from Soils with and without Salt Crust

Wind erosion removes fine soil particles and thus affects surface soil properties, but the existence of a salt crust could prevent wind erosion and protect fine soil particles. Such results referring to wind erosion affecting soil surface textural properties have been reported by many studies. However, it is still not clear whether soil properties differ between salt-crusted soils and adjacent soils without a salt crust in areas experiencing serious wind erosion. Therefore, the objective of this study was to investigate paired samples from salt-crusted and non-crusted surface soils at 23 sites in the Tarim River Basin. The particle size distribution, salt content and composition, and crust thickness and strength were determined. The results of the pooled t-test reveal that, compared with soils without a salt crust, the salt-crusted soils had finer particles (silt + clay), but this difference only occurred in paired soils from the same site, and the silt content showed the largest difference between the paired soils. The salt content and salt crust strength showed great variability, from 88.52 to 603 g·kg−1 and from 0.30 to 5.96 kg·cm−1, respectively, at all sites, but only a weak relationship (R2 = 0.396) between the salt content and crust strength was found, indicating that the salt content was not the only factor affecting crust strength. Our results suggest that wind erosion and salinization cause great soil texture spatial heterogeneity, especially for silt particles in the Tarim River Basin. Variation in salt crust strength can influence dust emissions and must be considered in future management.

Aeolian sediment transport rates in the middle reaches of the Yarlung Zangbo River, Tibet Plateau

Aeolian sediment emission from surfaces and subsequent transport are important geological processes. The Tibet Plateau experiences strong aeolian activity in areas such as the Yarlung Zangbo River basin. The dust storms have caused grounding of aircraft, highway closures, and other consequences for the region's residents. However, few researchers have studied this activity, which means that little knowledge is available on aeolian activity to support efforts to mitigate or prevent aeolian disasters. We measured aeolian sediment transport in the middle reaches of the Yarlung Zangbo River from 2020 to 2021. Field observations showed spatial and temporal variation of the sediment transport rate, with the greatest aeolian sediment transport in spring and winter. The largest total aeolian sediment transport rate occurred over sandy desert, with the smallest emission by a floodplain grassland. The change in sediment transport rate with height followed an exponential function, but the coefficients differed among landscapes. The mean sediment transport rate was greatest above shifting sand near riverbanks (0.21 kg m^-1 d^-1), where the sand is exposed in the winter and spring, followed by shifting floodplain sands (0.13 kg m^-1 d^-1), and was lowest above a floodplain grassland (0.03 kg m^-1 d^-1). Mean grain size also decreased with increasing height above 0.25 m, with a minimum mean grain size (about 52.6 μm) at 3.0 m above a floodplain grassland, and maximum mean grain size (about 100.2 μm) at 3.0 m above a floodplain shifting sand surface. The spatial variation in sediment transport rates and grain size related to the proportion of fine particles in the surface material. By comparing the aeolian sediment transport over different landscapes, we found that river banks and floodplains, which had rich deposits of very fine sand, silt, and clay, were the major sources of dust in this region. Our results indicate that efforts to mitigate or prevent aeolian disasters require a focus on riverbank and floodplain deposits.

On the Spatio-Temporal Characteristics of Aerosol Optical Depth in the Arabian Gulf Zone

The article investigates some of the available measurements (Terra MODIS satellite data) of the aerosol optical depth (AOD) taken in the Arabian Gulf, a zone traditionally affected by intense sand-related (or even sand-driven) meteorological events. The Principal Component Analysis (PCA) reveals the main subspace of the data. Clustering of the series was performed after selecting the optimal number of groups using 30 different methods, such as the silhouette, gap, Duda, Dunn, Hartigan, Hubert, etc. The AOD regional and temporal tendency detection was completed utilizing an original algorithm based on the dominant cluster found at the previous stage, resulting in the regional time series (RTS) and temporal time series (TTS). It was shown that the spatially-indexed time series (SITS) agglomerates along with the first PC. In contrast, six PCs are responsible for 60.5% of the variance in the case of the temporally-indexed time series (TITS). Both RTS and TTS are stationary in trend and fit the studied data series set well.

Analyses of a Lake Dust Source in the Middle East through Models Performance

Drying lakes have become a new source of dust, causing severe problems in surrounding areas. From 2000 to 2017, a statistical study was conducted on Lake Urmia in Iran in the Middle East. The results indicated a significant increase in the annual number of dusty days in stations around the lake and the mean annual aerosol optical depth (AOD) at 550 nm. The sharp decrease in annual snowfall rate over the Lake Urmia area since 2007 has been linked to the lake’s decreasing water level and drying. During a dust storm event from 27 October to 31 October 2017, a local dust storm originated from Lake Urmia before another large-scale dust storm originated from the An-Nafud desert. According to MODIS true-color images, dust particles were lifted from Lake Urmia and transported eastward to the Caspian Sea and the HYSPLIT model. The comparison of the four models under the Sand and Dust Storm Warning Advisory and Assessment System (SDS-WAS) revealed that the models overestimated surface dust concentrations compared to ground-based PM10 measurements. Nevertheless, the NOAA/WRF-Chem and DREAMABOL models simulated higher dust concentrations during the dust period. More emphasis should be placed on the development of dust models for SDS-WAS models in Lake Urmia.

Saltation Activity on Non-Dust Days in the Taklimakan Desert, China

Dust aerosols persistently affect nearly all landscapes worldwide, and the saltation activity caused by dusty weather (e.g., dust days) releases considerable amounts of aerosol into the atmosphere. Nevertheless, dust-induced saltation activity may also occur on non-dust days. To date, few studies have investigated the saltation activity characteristics on non-dust days. Moreover, the contribution of non-dust days to the total saltation activity remains ambiguous. This study comprehensively investigates the characteristics of saltation activity on non-dust days. Specifically, we analyze the influence of the saltation activity of non-dust days on dust aerosols by utilizing saltation, atmospheric, soil, dust aerosol (i.e., PM10 and aerosol optical depth), and weather record data obtained from the Taklimakan Desert, China, between 2008 and 2010. Our results show that lower temperature, vapor pressure, and soil moisture on non-dust days reduces the saltation threshold velocity (5.9 m/s) more compared to on dust days (6.5 m/s). Furthermore, regarding wind speed, relatively strong monthly saltation activity occurs from March to August, and daily saltation activity occurs from 9:00 to 16:00. Although non-dust days only contribute 18.5% and 7.7% to saltation time and saltation count, respectively, both significantly influence the dust aerosols. Therefore, the effect of saltation activity on non-dust days cannot be undervalued, particularly while performing dust aerosol studies.

Limiting Wind-Induced Resuspension of Radioactively Contaminated Particles to Enhance First Responder, Early Phase Worker and Public Safety-Part 1

An accidental radiological release or the operation of a radiological dispersal device (RDD) may lead to the contamination of a large area. Such scenarios may lead to health and safety risks associated with the resuspension of contaminated particles due to aeolian (wind-induced) soil erosion and tracking activities. Stabilization technologies limiting resuspension are therefore needed to avoid spreading contamination and to reduce exposures to first responders and decontamination workers. Resuspension testing was performed on soils from two sites of the Negev Desert following treatment with three different stabilization materials: calcium chloride, magnesium chloride, and saltwater from the Dead Sea in Israel. Two and six weeks post-treatment, resuspension was examined by inducing wind-driven resuspension and quantitatively measuring particle emission from the soils using a boundary-layer wind tunnel system. Experiments were conducted under typical wind velocities of this region. Treating the soils reduced resuspension fluxes of particulate matter < 10 μm (P M 10 ) and saltating (sand-sized) particles to around background levels. Resuspension suppression efficiencies from the treated soils were a minimum of 94% for all three stabilizers, and the Dead Sea salt solution yielded 100% efficiency over all wind velocities tested. The impact of the salt solutions (brine) was directly related to the salt treatment rather than the wetting of the soils. Stabilization was still observed six weeks post-treatment, supporting that this technique can effectively limit resuspension for a prolonged duration, allowing sufficient time for decision making and management of further actions.

Emission of Fine Dust from Open Storage of Industrial Materials Exposed to Wind Erosion

A physical-mathematical model has been designed to estimate the emission of dust from the surface of granular materials exposed to wind erosion. The emission model implements the Monte Carlo probabilistic approach, which for a given wind velocity (i.e., shear stress velocity) ascribes the probability of saltation to the particle aggregates composing the erodible surface and calculates the emission of dust aerosol based on the main laws governing the physics of wind-blown particles. The article discusses the application of the emission code to the surfaces of two metal sulphides (PbS and ZnS), which are typically stored in stockpiles in the open yards of industrial plants that operate in the commodity sector, to be used as raw materials for the production of lead and zinc (non-ferrous metals). The results of the simulation were found to be in agreement with the indication provided by the technical literature about the emission potential of the two metal sulphides. The emission model hereby proposed intends to provide an analytical integration to the experimental and empirical Emission Factors (EF) already suggested by the technical and scientific literature about industrial wind erosion.

Spatial Distribution of Shrubs Impacts Relationships among Saltation, Roughness, and Vegetation Structure in an East Asian Rangeland

Vegetation influences the occurrence of saltation through various mechanisms. Most previous studies have focused on the effects of vegetation on saltation occurrence under spatially homogeneous vegetation, whereas few field studies have examined how spatially heterogeneous cover affects saltation. To examine how spatial heterogeneity of vegetation influences saltation, we surveyed the vegetation and spatial distribution of shrubs and conducted roughness measurements at 11 sites at Tsogt-Ovoo, Gobi steppe of Mongolia, which are dominated by the shrubs Salsola passerina and Anabasis brevifolia. Saltation and meteorological observations were used to calculate the saltation flux, threshold friction velocity, and roughness length. The spatial distribution of shrubs was estimated from the intershrub distance obtained by calculating a semivariogram. Threshold friction velocity was well explained by roughness length. The relationships among roughness, saltation flux, and vegetation cover depended on the spatial distribution of shrubs. When the vegetation was distributed heterogeneously, roughness length increased as the vegetation cover decreased, and the saltation flux increased because the wake interference flow became dominant. When the vegetation was spatially homogeneous, however, the saltation flux was suppressed even when the vegetation cover was small. These field experiments show the importance of considering the spatial distribution of vegetation in evaluating saltation occurrence.

Evaluation of Nine Operational Models in Forecasting Different Types of Synoptic Dust Events in the Middle East

This study investigates four types of synoptic dust events in the Middle East region, including cyclonic, pre-frontal, post-frontal and Shamal dust storms. For each of these types, three intense and pervasive dust events are analyzed from a synoptic meteorological and numerical simulation perspective. The performance of 9 operational dust models in forecasting these dust events in the Middle East is qualitatively and quantitatively evaluated against Terra-MODIS observations and AERONET measurements during the dust events. The comparison of model AOD outputs with Terra-MODIS retrievals reveals that despite the significant discrepancies, all models have a relatively acceptable performance in forecasting the AOD patterns in the Middle East. The models enable to represent the high AODs along the dust plumes, although they underestimate them, especially for cyclonic dust storms. In general, the outputs of the NASA-GEOS and DREAM8-MACC models present greater similarity with the satellite and AERONET observations in most of the cases, also exhibiting the highest correlation coefficient, although it is difficult to introduce a single model as the best for all cases. Model AOD predictions over the AERONET stations showed that DREAM8-MACC exhibited the highest R2 of 0.78, followed by NASA_GEOS model (R2 = 0.74), which both initially use MODIS data assimilation. Although the outputs of all models correspond to valid time more than 24 h after the initial time, the effect of data assimilation on increasing the accuracy is important. The different dust emission schemes, soil and vegetation mapping, initial and boundary meteorological conditions and spatial resolution between the models, are the main factors influencing the differences in forecasting the dust AODs in the Middle East.

Combining Optical and Radar Satellite Imagery to Investigate the Surface Properties and Evolution of the Lordsburg Playa, New Mexico, USA

Driven by erodible soil, hydrological stresses, land use/land cover (LULC) changes, and meteorological parameters, windblown dust events initiated from Lordsburg Playa, New Mexico, United States, threaten public safety and health through low visibility and exposure to dust emissions. Combining optical and radar satellite imagery products can provide invaluable benefits in characterizing surface properties of desert playas—a potent landform for wind erosion. The optical images provide a long-term data record, while radar images can observe land surface irrespective of clouds, darkness, and precipitation. As a home for optical and radar imagery, powerful algorithms, cloud computing infrastructure, and application programming interface applications, Google Earth Engine (GEE) is an invaluable resource facilitating acquisition, processing, and analysis. In this study, the fractional abundance of soil, vegetation, and water endmembers were determined from pixel mixtures using the linear spectral unmixing model in GEE for Lordsburg Playa. For this approach, Landsat 5 and 8 images at 30 m spatial resolution and Sentinel-2 images at 10–20 m spatial resolution were used. Employing the Interferometric Synthetic Aperture Radar (InSAR) techniques, the playa’s land surface changes and possible sinks for sediment loading from the surrounding catchment area were identified. In this data recipe, a pair of Sentinel-1 images bracketing a monsoon day with high rainfall and a pair of images representing spring (dry, windy) and monsoon seasons were used. The combination of optical and radar images significantly improved the effort to identify long-term changes in the playa and locations within the playa susceptible to hydrological stresses and LULC changes. The linear spectral unmixing algorithm addressed the limitation of Landsat and Sentinel-2 images related to their moderate spatial resolutions. The application of GEE facilitated the study by minimizing the time required for acquisition, processing, and analysis of images, and storage required for the big satellite data.

Analysis of Mineral Aerosol in the Surface Layer over the Caspian Lowland Desert by the Data of 12 Summer Field Campaigns in 2002–2020

In-situ knowledge on characteristics of mineral aerosols is important for weather and climate prediction models, particularly for modeling such processes as the entrainment, transport and deposition of aerosols. However, field measurements of the dust emission flux, dust size distribution and its chemical composition under realistic wind conditions remain rare. In this study, we present experimental data over annual expeditions in the arid and semi-arid zones of the Caspian Lowland Desert (Kalmykia, south of Russia); we evaluate characteristics of mineral aerosol concentration and fluxes, estimate its chemical composition and calculate its long-distance transport characteristics. The mass concentration in different years ranges from several tens to several hundred of μg m−3. The significant influence of wind velocity on the value of mass and counting concentration and on the proposed entrainment mechanisms is confirmed. An increased content of anthropogenic elements (S, Sn, Pb, Bi, Mo, Ag, Cd, Hg, etc.), which is characteristic for all observation points in the south of the European Russia, is found. The trajectory analysis show that long-range air particles transport from the Caspian Lowland Desert to the central regions of European Russia tends to increase in the recent decades.

Application of a High-Precision Aeolian Sand Collector in Field Wind and Sand Surveys

Sand collectors are important for quantitatively monitoring aeolian sand activities. In this paper, an automatic high-precision sand collector was designed. Based on the measured data of aeolian transport performed with a piezoelectric saltation sensor (H11-Sensit) and a 10 m high meteorological tower, the sampling efficiency of the automatic sand sampler and the horizontal dust flux of the near surface were analyzed based on observed data. The results were as follows: the best-fitting function between the number of impacting sand particles and the amount of collected sand was a linear relationship. The average value of R² was 0.7702, and the average sand collection efficiency of the sand collector at a height of 5 cm was 94.3%, indicating good sand collection performance. From all field tests conducted so far, it appeared that a high-precision sand sampler was a useful device for making field measurements of horizontal dust fluxes and ascertaining the relationship between transition particles and wind speed. In the future, the equipment costs and wind drive will continue to be optimized.

Improved representation of the global dust cycle using observational constraints on dust properties and abundance

Even though desert dust is the most abundant aerosol by mass in Earth's atmosphere, atmospheric models struggle to accurately represent its spatial and temporal distribution. These model errors are partially caused by fundamental difficulties in simulating dust emission in coarse-resolution models and in accurately representing dust microphysical properties. Here we mitigate these problems by developing a new methodology that yields an improved representation of the global dust cycle. We present an analytical framework that uses inverse modeling to integrate an ensemble of global model simulations with observational constraints on the dust size distribution, extinction efficiency, and regional dust aerosol optical depth. We then compare the inverse model results against independent measurements of dust surface concentration and deposition flux and find that errors are reduced by approximately a factor of two relative to current model simulations of the Northern Hemisphere dust cycle. The inverse model results show smaller improvements in the less dusty Southern Hemisphere, most likely because both the model simulations and the observational constraints used in the inverse model are less accurate. On a global basis, we find that the emission flux of dust with geometric diameter up to 20 μm (PM20) is approximately 5,000 Tg/year, which is greater than most models account for. This larger PM20 dust flux is needed to match observational constraints showing a large atmospheric loading of coarse dust. We obtain gridded data sets of dust emission, vertically integrated loading, dust aerosol optical depth, (surface) concentration, and wet and dry deposition fluxes that are resolved by season and particle size. As our results indicate that this data set is more accurate than current model simulations and the MERRA-2 dust reanalysis product, it can be used to improve quantifications of dust impacts on the Earth system.

The Road Map to Classify the Potential Risk of Wind Erosion

Environmental degradation, for example, by wind erosion, is a serious global problem. Despite the enormous research on this topic, complex methods considering all relevant factors remain unpublished. The main intent of our paper is to develop a methodological road map to identify key soil–climatic conditions that make soil vulnerable to wind and demonstrate the road map in a case study using a relevant data source. Potential wind erosion (PWE) results from soil erosivity and climate erosivity. Soil erosivity directly reflects the wind-erodible fraction and indirectly reflects the soil-crust factor, vegetation-cover factor and surface-roughness factor. The climatic erosivity directly reflects the drought in the surface layer, erosive wind occurrence and clay soil-specific winter regime, making these soils vulnerable to wind erosion. The novelty of our method lies in the following: (1) all relevant soil–climatic data of wind erosion are combined; (2) different soil types “sand” and “clay” are evaluated simultaneously with respect to the different mechanisms of wind erosion; and (3) a methodological road map enables its application for various conditions. Based on our method, it is possible to set threshold values that, when exceeded, trigger landscape adjustments, more detailed in situ measurements or indicate the need for specific management.

Experimental Evaluation of PM Emission from Red Mud Basins Exposed to Wind Erosion

The disposal of industrial and mineral processing residues represents a major concern for human health and the environment as a whole. In order to reduce the impact on soil and groundwater due to the waste leachability, the implementation of environmental regulations worldwide has favored the conversion of the disposal techniques from wet to dry (i.e., dry stacking or dry disposal). Such a change in the storage practice may cause the increase of particulate matter (PM) emission from the dry surfaces of the tailings exposed to wind erosion. Considering the significance of the environmental issue on a global scale and the increasingly stricter orientation of environmental policies, the need for modeling tools capable of estimating the contribution of tailing basins to air pollution becomes apparent. The paper deals with the disposal of red mud resulting from the bauxite processing in the alumina industry. An experimental research was carried with an environmental wind tunnel to estimate the Emission Factor (EF) of the basin surfaces as a function of the main affecting variables (i.e., residue water content and wind velocity). The article reports the results of the experimental test carried out on the red mud from a major basin located in Sardinia (Italy).

Distribution of microplastics in soil and freshwater environments: Global analysis and framework for transport modeling

Microplastics are continuously released into the terrestrial environment from sources where they are used and produced. These microplastics accumulate in soils, sediments, and freshwater bodies, and some are conveyed via wind and water to the oceans. The concentration gradient between terrestrial inland and coastal regions, the factors that influence the concentration, and the fundamental transport processes that could dynamically affect the distribution of microplastics are unclear. We analyzed microplastic concentration reported in 196 studies from 49 countries or territories from all continents and found that microplastic concentrations in soils or sediments and surface water could vary by up to eight orders of magnitude. Mean microplastic concentrations in inland locations such as glacier (191 n L^-1) and urban stormwater (55 n L^-1) were up to two orders of magnitude greater than the concentrations in rivers (0.63 n L^-1) that convey microplastics from inland locations to water bodies in terrestrial boundary such as estuaries (0.15 n L^-1). However, only 20% of studies reported microplastics below 20 μm, indicating the concentration in these systems can change with the improvement of microplastic detection technology. Analysis of data from laboratory studies reveals that biodegradation can also reduce the concentration and size of deposited microplastics in the terrestrial environment. Fiber percentage was higher in the sediments in the coastal areas than the sediments in inland water bodies, indicating fibers are preferentially transported to the terrestrial boundary. Finally, we provide theoretical frameworks to predict microplastics transport and identify potential hotspots where microplastics may accumulate.

Evaluation of Groundwater Salinization Risk Following Application of Anti-Dust Emission Solutions on Unpaved Roads in Arid and Semiarid Regions

Unpaved roads could be a significant source of dust emission. A common and effective practice to suppress this emission is the application of brine solution on these roads. However, this application could increase the risk of water source salinization in arid and semiarid regions, such as Israel. The general objective of the present study was to investigate the potential effects of treated wastewater (TWW), fresh water (FW), and brine applications as anti-dust emission solutions on water source salinization in these regions. A rainfall simulator experiment and a mass balance model were used for this goal. The TWW loaded the highest amounts of Cl, Na, and Ca+Mg on the unpaved roads, while the brine loaded higher amounts of Cl and Ca+Mg than the FW, and ~0 Na. In the rainfall experiment, runoff was not formed, and ~100% of the loaded amounts were leached downwards by rain, indicating a negligible salinization risk to surface water. We estimated that the average increases in the Cl concentrations in the modeled aquifer, following TWW, brine, and FW applications, were low: 1.2–1.6, 0.58–0.8, and 0.32–0.4 mg L−1, respectively. Thus, the solution selection for preventing dust emission should be based on the total cost of the solution application.

Physical Crust Formation on Sandy Soils and Their Potential to Reduce Dust Emissions from Croplands

The sandy croplands in the Free State have been identified as one of the main dust sources in South Africa. The aim of this study was to investigate the occurrence and strength of physical soil crusts on cropland soils in the Free State, to identify the rainfall required to form a stable crust, and to test their impact on dust emissions. Crust strength was measured using a fall cone penetrometer and a torvane, while laboratory rainfall simulations were used to form experimental crusts. Dust emissions were measured with a Portable In-Situ Wind Erosion Laboratory (PI-SWERL). The laboratory rainfall simulations showed that stable crusts could be formed by 15 mm of rainfall. The PI-SWERL experiments illustrated that the PM10 emission flux of such crusts is between 0.14% and 0.26% of that of a non-crusted Luvisol and Arenosol, respectively. The presence of abraders on the crust can increase the emissions up to 4% and 8% of the non-crusted dust flux. Overall, our study shows that crusts in the field are potentially strong enough to protect the soil surfaces against wind erosion during a phase of the cropping cycle when the soil surface is not protected by plants.

Generation, Resuspension, and Transport of Particulate Matter From Biochar-Amended Soils: A Potential Health Risk

Large-scale soil application of biochar is one of the terrestrial carbon sequestration strategies for future climate change mitigation pathways, which can also help remove and sequester pollutants from contaminated soil and water. However, black carbon emissions from biochar-amended soils can deteriorate air quality and affect human health, as the biochar particles often contain a higher amount of sorbed toxic pollutants than the soil. Yet, the extent and mechanism of inhalable particulate matter (PM10) emission from biochar-amended soils at different wind regimes have not been evaluated. Using wind tunnel experiments to simulate different wind regimes, we quantified particulate emission from sand amended with 1-4% (by weight) biochar at two size fractions: with and without <2-mm biochar. At wind speeds below the threshold speed for soil erosion, biochar application significantly increased PM10 emission by up to 400% due to the direct resuspension of inhalable biochar particles. At wind speeds above the threshold speed, emission increased by up to 300% even from biochar without inhalable fractions due to collisions of fast-moving sand particles with large biochar particles. Using a theoretical framework, we show that particulate matter emissions from biochar-amended soils could be higher than that previously expected at wind speeds below the erosion threshold wind speed for background soil. Our results indicate that current models for fugitive dust emissions may underestimate the particulate matter emission potential of biochar-amended soils and will help improve the assessment of biochar emission from amended soils.

Volcanic Ash Resuspension in Patagonia: Numerical Simulations and Observations

Resuspension of pyroclastic deposits occurs under specific atmospheric and environmental conditions and typically prolongs and exacerbates the impact associated with the primary emplacement of tephra fallout and pyroclastic density current deposits. An accurate forecasting of the phenomenon, to support Volcanic Ash Advisory Centers (VAACs) and civil aviation management, depends on adapting volcanic ash transport and dispersion models to include specific ash emission schemes. Few studies have attempted to model the mechanisms of emission and transport of windblown volcanic ash, and a systematic study of observed cases has not been carried out yet. This manuscript combines numerical simulations along with a variety of observational data to examine the general features of ash resuspension events in northern Patagonia following the 2011 Cordón Caulle eruption (Chile). The associated outcomes provide new insights into the spatial distribution of sources, frequency of events, transport patterns, seasonal and diurnal variability, and spatio-temporal distribution of airborne ash. A novel modelling approach based on the coupling between Advanced Research core of the Weather Research and Forecasting (WRF-ARW) and FALL3D models is presented, with various model improvements that allow overcoming some limitations in previous ash resuspension studies. Outcomes show the importance of integrating source information based on field measurements (e.g., deposit grain size distribution and particle density). We provide evidence of a strong diurnal and seasonal variability associated with the ash resuspension activity in Patagonia. According to the modelled emission fluxes, ash resuspension activity was found to be significantly more intense during daytime hours. Satellite observations and numerical simulations strongly suggest that major emission sources of resuspended ash were distributed across distal areas (>100 km from the vent) of the Patagonian steppe, covered by a thin layer of fine ash. The importance of realistic soil moisture data to properly model the spatial distribution of emission sources is also highlighted.

Mass flux decay timescales of volcanic particles due to aeolian processes in the Argentinian Patagonia steppe

We investigate the timescales of the horizontal mass flux decay of wind remobilised volcanic particles in Argentina, associated with the tephra-fallout deposit produced by the 2011–2012 Cordón Caulle (Chile) eruption. Particle removal processes are controlled by complex interactions of meteorological conditions, surface properties and particle depletion with time. We find that ash remobilisation follows a two-phase exponential decay with specific timescales for the initial input of fresh ash (1–74 days) and the following soil stabilisation processes (3–52 months). The characteristic timescales as a function of particle size shows two minimum values, identified for sizes around 2 and 19–37 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\upmu$$\end{document}μm, suggesting that these size-range particles are remobilised more easily, due to the interaction between saltation and suspension-induced processes. We find that in volcanic regions, characterised by a sudden release and a subsequent depletion of particles, the availability of wind-erodible particles plays a major role due to compaction and removal of fine particles. We propose, therefore, a simple and reproducible empirical model to describe the mass flux decay of remobilised ash in a supply-limited environment. This methodology represents an innovative approach to link field measurements of multi-sized and supply-limited deposits with saltation erosion theory.

Dust Emission Thresholds in Loess Soil Under Different Saltation Fluxes

Soil-derived dust particles produced by aeolian (wind) processes have significant impacts on humans and the Earth’s systems. The soil particle size distribution is a major soil characteristic in dust emission models. Yet empirical information on the dependence of dust emission thresholds on soil particle size distribution is still lacking. The main goal of this study was to explore the dust emission threshold from semi-arid loess soil samples by a targeted wind-tunnel experiment. The results clearly show that the dust emission threshold is associated with the saltation threshold with no distinct direct aerodynamic lifting of the loose dust particle. The dust flux depends on the amount of the clay-silt fraction in the soil, the shear velocity, and the saltation flux under certain shear velocity. The study aimed to advance our understating of the dust emission processes, and to provide empirical information for parametrization in dust emission models and for management strategy of soils in preventing dust emission.

Dependence of the Dust Emission on the Aggregate Sizes in Loess Soils

Dust emission resulted from soil erosion by wind with significant impacts of soil (nutrient) loss and air pollution of particulate matter (PM). The ejection of dust from soil aggregates due to saltation has been hypothesized to play a major role in dust emission. Yet empirical information on the role of different aggregate sizes in dust emission is still lacking. The main goal of this study was to explore the dust emission threshold in different aggregate sizes of a semiarid loess soil. To this end, we conducted targeted wind-tunnel experiment on dust emission. The results show that dust emission from aggregate at size of 63–250 µm, 250–500 µm, and 500–1000 µm is enabled only under the conditions of saltation. The dust-PM threshold at shear velocities of 0.24–0.52 m/s depends on the aggregates size. Aggregates at the size of saltators (125–500 µm) were the most productive in dust generation by the mechanism of aggregate disintegration. In our bulk sample, the aggregate group of 63–250 µm has the highest contribution to the total dust emission. The study aimed to advance our capability in soil resources management and for model parameterization in dust emission schemes.

A wind-albedo-wind feedback driven by landscape evolution

The accurate characterization of near-surface winds is critical to our understanding of past and modern climate. Dust lofted by these winds has the potential to modify surface and atmospheric conditions as well as ocean biogeochemistry. Stony deserts, low dust emitting regions today, represent expansive areas where variations in surficial geology through time may drastically impact near-surface conditions. Here we use the Weather Research and Forecasting (WRF) model over the western Gobi Desert to demonstrate a previously undocumented process between wind-driven landscape evolution and boundary layer conditions. Our results show that altered surficial thermal properties through winnowing of fine-grained sediments and formation of low-albedo gravel-mantled surfaces leads to an increase in near-surface winds by up to 25%; paradoxically, wind erosion results in faster winds regionally. This wind-albedo-wind feedback also leads to an increase in the frequency of hours spent at higher wind speeds, which has implications for dust emission potential.

Stepwise Assessment of Different Saltation Theories in Comparison with Field Observation Data

Wind-blown dust models use input data, including soil conditions and meteorology, to interpret the multi-step wind erosion process and predict the quantity of dust emission. Therefore, the accuracy of the wind-blown dust models is dependent on the accuracy of each input condition and the robustness of the model schemes for each elemental step of wind erosion. A thorough evaluation of a wind-blown model thus requires validation of the input conditions and the elemental model schemes. However, most model evaluations and intercomparisons have focused on the final output of the models, i.e., the vertical dust emission. Recently, a delicate set of measurement data for saltation flux and friction velocity was reported from the Japan-Australia Dust Experiment (JADE) Project, which enabled the step-by-step evaluation of wind-blown dust models up to the saltation step. When all the input parameters were provided from the observations, both the two widely used saltation schemes showed very good agreement with measurements, with the correlation coefficient and the agreement of index both being larger than 0.9, which demonstrated the strong robustness of the physical schemes for saltation. However, using the meteorology model to estimate the input conditions such as weather and soil conditions, considerably degraded the models’ performance. The critical reason for the model failure was determined to be the inaccuracy in the estimation of the threshold friction velocity (representing soil condition), followed by inaccurate estimation of surface wind speed. It was not possible to determine which of the two saltation schemes was superior, based on the present study results. Such differentiation will require further evaluation studies using more measurements of saltation flux and vertical dust emissions.

Identification of Dust Sources in a Saharan Dust Hot-Spot and Their Implementation in a Dust-Emission Model

Although mineral dust plays a key role in the Earth’s climate system and in climate and weather prediction, models still have difficulties in predicting the amount and distribution of mineral dust in the atmosphere. One reason for this is the limited understanding of the distribution of dust sources and their behavior with respect to their spatiotemporal variability in activity. For a better estimation of the atmospheric dust load, this paper presents an approach to localize dust sources and thereby estimate the sediment supply for a study area centered on the Aïr Massif in Niger with a north–south extent of 16 ∘ –22 ∘ N and an east–west extent of 4 ∘ –12 ∘ E. This approach uses optical Sentinel-2 data at visible and near infrared wavelengths together with HydroSHEDS flow accumulation data to localize ephemeral riverbeds. Visible channels from Sentinel-2 data are used to detect sand sheets and dunes. The identified sediment supply map was compared to the dust source activation frequency derived from the analysis of Desert-Dust-RGB imagery from the Meteosat Second Generation series of satellites. This comparison reveals the strong connection between dust activity, prevailing meteorology and sediment supply. In a second step, the sediment supply information was implemented in a dust-emission model. The simulated emission flux shows how much the model results benefit from the updated sediment supply information in localizing the main dust sources and in retrieving the seasonality of dust activity from these sources. The described approach to characterize dust sources can be implemented in other regional model studies, or even globally, and can thereby help to get a more accurate picture of dust source distribution and a more realistic estimation of the atmospheric dust load.

Fluid flow lifting a body from a solid surface

If a body is at rest on horizontal ground and a sudden horizontal flow of fluid is applied, the body either remains on the ground (rocking, rolling, sliding or spinning) or is lifted off impulsively. This lift-off is followed by a return to the ground or by a fly-away in the sense of continued departure from the ground. Related phenomena arise in the lift-off of an air vehicle from, effectively, moving ground. The present investigation seeks fairly precise mechanistic conditions under which lift-off and subsequent return or fly-away occur for a thin body or more generally for any thin gap of fluid between a body and the ground. Nonlinear fluid–solid interaction takes place in which the motion of the body and the surrounding fluid affect each other. Small-time analysis on lift-off and a numerical study are presented, followed by large-time analysis showing a critical flow speed for fly-away for any shape of the body. The changes in ground effect, from being dominant during lift-off to diminishing in fly-away, are explored together with relevant applications.

Global development and trend of wind tunnel research from 1991 to 2014: a bibliometric analysis

Development and trend of global wind tunnel research from 1991 to 2014 were evaluated by bibliometric analysis. Based on the statistical data from Science Citation Index Expanded from Web of Science, publication performance of wind tunnel research was analyzed from various aspects, including publication output, category distributions, journals, countries, institutions, leading articles, and words analysis. The results show that scientific articles associated with wind tunnel increased dramatically, with Journal of Wind Engineering and Industrial Aerodynamics as the most productive journal. The USA has been leading in publication output since 1991, while China has become a new-rising force of wind tunnel research. NASA was the dominant institution in wind tunnel field which published most single institution articles and nationally and internationally collaborative articles. The citation lifecycles of the leading articles exhibited different patterns of their trends, but all reached a plateau in certain years. Based on synthesized analysis of title words, abstract words, author keywords, and KeyWords Plus, computational fluid dynamic (CFD) was found to be a hot issue, which needs experimental validation by wind tunnels. Wind loads and wind turbine also caused increasing attentions while lepidoptera and sex pheromone were less studied. In the wind tunnel articles, numerical simulation of CFD was increasingly mentioned while field measurement showed minor change, suggesting the rapid developments of CFD.

Statistical analysis and estimation of the regional trend of aerosol size over the Arabian Gulf Region during 2002-2016

In this article, we present the results of the regional estimation of the evolution of monthly mean aerosol size over the Arabian Gulf Region, based on the data collected during the period July 2002 – September 2016. The dataset used is complete, without missing values. Two methods are introduced for this purpose. The first one is based on the partition of the regional series in sub-series and the selection of the most representative one for fitting the regional trend. The second one is a version of the first method, combined with the k-means clustering algorithm. Comparison of their performances is also provided. The study proves that both methods give a very good estimation of the evolution of the aerosol size in the Arabian Gulf Region in the study period.

Highly cited articles in wind tunnel-related research: a bibliometric analysis

Wind tunnels have been widely employed in aerodynamic research. To characterize the high impact research, a bibliometric analysis was conducted on highly cited articles related to wind tunnel based on the Science Citation Index Expanded (SCI-EXPANDED) database from 1900 to 2014. Articles with at least 100 citations from the Web of Science Core Collection were selected and analyzed in terms of publication years, authors, institutions, countries/territories, journals, Web of Science categories, and citation life cycles. The results show that a total of 77 highly cited articles in 37 journals were published between 1959 and 2008. Journal of Fluid Mechanics published the most of highly cited articles. The USA was the most productive country and most frequent partner of internationally collaboration. The prolific institutions were mainly located in the USA and UK. The authors who were both first author and corresponding author published 88% of the articles. The Y index was also deployed to evaluate the publication characteristics of authors. Moreover, the articles with high citations in both history and the latest year with their citation life cycles were examined to provide insights for high impact research. The highly cited articles were almost earliest wind tunnel experimental data and reports on their own research specialty, and thus attracted high citations. It was revealed that classic works of wind tunnel research was frequently occurred in 1990s but much less in 2000s, probably due to the development of numerical models of computational fluid dynamic (CFD) in recent decades.

Numerical simulation of wind-sand movement in the reversed flow region of a sand dune with a bridge built downstream

A bridge built inside the reversed flow region of a sand dune will change the characteristics of wind-sand movement in this region. The Reynolds-averaged Navier-Stokes simulation and discrete particle tracing are used to simulate the wind-sand movement around a sand dune with a bridge built inside the reversed region. Three cases with different bridge positions are studied. The results show that 1) compared with the isolated dune case, a tall bridge built at the leeward toe leads to an increase in the deposition rate on the leeward slope and a longer reversed flow region downstream of the sand dune; meanwhile, the high speed of crosswind on the bridge indicates that some measures should be taken to protect trains from strong crosswind; 2) a low bridge at the leeward toe has little effect on the sand deposition and reversed flow region of the dune; however, low sand transport rate and crosswind speed on the bridge show that anti-crosswind/sand measures should be taken according to the actual situation and 3) a low bridge on the leeward slope has little effect on the length of reversed flow region, however, high crosswind speed and sand flux on the bridge reveal the need of anti-crosswind/sand measures on the bridge. Moreover, the bridges in the reversed flow region increase the sand flux near the leeward crest; as a result, the moving patterns of the sand dune are changed.

Development and evaluation of a physics-based windblown dust emission scheme implemented in the CMAQ modeling system

A new windblown dust emission treatment was incorporated in the Community Multiscale Air Quality (CMAQ) modeling system. This new model treatment has been built upon previously developed physics-based parameterization schemes from the literature. A distinct and novel feature of this scheme, however, is the incorporation of a newly developed dynamic relation for the surface roughness length relevant to small-scale dust generation processes. Through this implementation, the effect of nonerodible elements on the local flow acceleration, drag partitioning, and surface coverage protection is modeled in a physically based and consistent manner. Careful attention is paid in integrating the new windblown dust treatment in the CMAQ model to ensure that the required input parameters are correctly configured. To test the performance of the new dust module in CMAQ, the entire year 2011 is simulated for the continental United States, with particular emphasis on the southwestern United States (SWUS) where windblown dust concentrations are relatively large. Overall, the model shows good performance with the daily mean bias of soil concentrations fluctuating in the range of ±1 μg m-3 for the entire year. Springtime soil concentrations are in quite good agreement (normalized mean bias of 8.3%) with observations, while moderate to high underestimation of soil concentration is seen in the summertime. The latter is attributed to the issue of representing the convective dust storms in summertime. Evaluations against observations for seven elevated dust events in the SWUS indicate that the new windblown dust treatment is capable of capturing spatial and temporal characteristics of dust outbreaks.

Use of a size-resolved 1-D resuspension scheme to evaluate resuspended radioactive material associated with mineral dust particles from the ground surface

A size-resolved, one-dimensional resuspension scheme for soil particles from the ground surface is proposed to evaluate the concentration of radioactivity in the atmosphere due to the secondary emission of radioactive material. The particle size distributions of radioactive particles at a sampling point were measured and compared with the results evaluated by the scheme using four different soil textures: sand, loamy sand, sandy loam, and silty loam. For sandy loam and silty loam, the results were in good agreement with the size-resolved atmospheric radioactivity concentrations observed at a school ground in Tsushima District, Namie Town, Fukushima, which was heavily contaminated after the Fukushima Dai-ichi Nuclear Power Plant accident in March 2011. Though various assumptions were incorporated into both the scheme and evaluation conditions, this study shows that the proposed scheme can be applied to evaluate secondary emissions caused by aeolian resuspension of radioactive materials associated with mineral dust particles from the ground surface. The results underscore the importance of taking soil texture into account when evaluating the concentrations of resuspended, size-resolved atmospheric radioactivity.

Quantitative 3D shape description of dust particles from treated seeds by means of X-ray micro-CT

Crop seeds are often treated with pesticides before planting. Pesticide-laden dust particles can be abraded from the seed coating during planting and expelled into the environment, damaging nontarget organisms. Drift of these dust particles depends on their size, shape and density. In this work, we used X-ray micro-CT to examine the size, shape (sphericity) and porosity of dust particles from treated seeds of various crops. The dust properties quantified in this work were very variable in different crops. This variability may be a result of seed morphology, seed batch, treatment composition, treatment technology, seed cleaning or an interaction of these factors. The intraparticle porosity of seed treatment dust particles varied from 0.02 to 0.51 according to the crop and generally increased with particle size. Calculated settling velocities demonstrated that accounting for particle shape and porosity is important in drift studies. For example, the settling velocity of dust particles with an equivalent diameter of 200 μm may vary between 0.1 and 1.2 m s(-1), depending on their shape and density. Our analysis shows that in a wind velocity of 5 m s(-1), such particles ejected at 1 m height may travel between 4 and 50 m from the source before settling. Although micro-CT is a valuable tool to characterize dust particles, the current image processing methodology limits the number of particles that can be analyzed.

Spontaneous vegetation encroachment upon bauxite residue (red mud) as an indicator and facilitator of in situ remediation processes

The spontaneous colonization of a bauxite residue (alumina refining tailings) deposit by local vegetation in Linden, Guyana, over 30 years, indicates that natural weathering processes can ameliorate tailings to the extent that it can support vegetation. Samples were collected from vegetated and unvegetated areas to investigate the relationships between bauxite residue properties and vegetation cover. Compared to unvegetated areas, bauxite residue in vegetated areas had lower pH (mean pH 7.9 vs 10.9), lower alkalinity (mean titratable alkalinity 0.4 vs 1.4 mol H(+) kg(-1)), lower electrical conductivity (mean EC 0.3 vs 2.1 mS cm(-1)), lower total Al (mean Al2O3 19.8 vs 25.8% wt) and Na (mean Na2O 0.9 vs 3.7% wt), and less sodalite and calcite. Accumulation of N, NH4(+), and organic C occurred under vegetation, demonstrating the capacity for plants to modify residue to suit their requirements as a soil-like growth medium. Aeolian redistribution of coarse grained tailings appeared to support vegetation establishment by providing a thin zone of enhanced drainage at the surface. Natural pedogenic processes may be supplemented by irrigation, enhanced drainage, and incorporation of sand and organic matter at other tailings deposits to accelerate the remediation process and achieve similar results in a shorter time frame.