Windblown Sediment Research Articles

The hidden oases: unveiling trophic dynamics in Namib's fog plant ecosystem

The Namib Desert is a hyperarid coastal desert where fog is a major moisture source. We hypothesized that the fog-harvesting grass Stipagrostis sabulicola establishes an important ecological niche, termed the "Fog-Plant-Oases" (FPOs), and serves as the primary carbon source for the invertebrate community. To determine this, we measured the natural variations of the stable carbon and nitrogen isotopes (δ13C and δ15N) of invertebrates as well as that of plant biomass and belowground detritus and estimated the contributions of the fog plants in their diets. Our findings revealed a complex trophic structure and demonstrated that S. sabulicola fuels carbon flow from lower to higher trophic levels in the aboveground food web. The distinct δ13C values of bacterial- and fungal-feeding nematodes indicated however the separation of the aboveground niche, which is primarily sustained by S. sabulicola, from the belowground niche, where wind-blown sediments may serve as the main energy source for the soil biota. Our findings further accentuate the critical role of S. sabulicola FPOs in establishing complex trophic dynamics and a distinctive food web within the hyperarid Namib dunes.

The effect of short-term plants cultivation on soil organic/inorganic carbon storage in newly formed soils

Studying total soil carbon (STC), which encompasses organic (SOC) and inorganic carbon (SIC), as well as investigating the influence of soil carbon on other soil properties, is crucial for effective global soil carbon management. This knowledge is invaluable for evaluating carbon sequestration, although its scope is currently limited. Boosting soil carbon sequestration, particularly in arid regions, has direct and indirect implications for achieving over four Sustainable Development Goals: mitigating hunger, extreme poverty, enhancing environmental preservation, and addressing global climate concerns. Research into changes within SOC and SIC across surface and subsurface soils was conducted on aeolian deposits. In this specific case study, two sites sharing similar climates and conditions were chosen as sources of wind-blown sediment parent material. The aim was to discern variations in SOC, SIC, and STC storage in surface and subsurface soils between Sistan and Baluchistan Province (with rapeseed and date orchard cultivation) and Kerman Province (with maize cultivation) in southeastern Iran. The findings highlighted an opposing pattern in SOC and storage concerning soil depth, unlike SIC. The average SOC content was higher in maize cultivation (0.2%) compared to date orchard and rapeseed cultivation (0.11%), attributed to the greater evolution of these arid soils (aridisols) in comparison to the other region (entisols). Conversely, SIC content in the three soil uses demonstrated minimal variation. The mean STC storage was greater in maize cultivation (60.35 Mg ha−1) than in date orchard (54.67 Mg ha−1) and rapeseed cultivation (53.42 Mg ha−1). Within the examined drylands, SIC, originating from aeolian deposits and soil processes, assumes a more prominent role in total carbon storage than SOC, particularly within subsurface soils. Notably, over 90% of total carbon storage exists in the form of inorganic carbon in soils.

Amount and characteristics of microplastic and organic matter in wind-blown sediment at different heights within the aeolian sand saltation layer

Soils of croplands especially where plastic film mulch is commonly applied, are normally contaminated by Microplastics (MPs). Microplastics can threaten air quality, food and water health, as well as human health by wind erosion processes. In this research, we investigated MPs collected in four wind erosion events at sampling heights between 0 and 60 cm in typical semiarid farmlands in northern China that employ plastic film mulch. Height distribution and enrichment heights of the MPs were measured. The results revealed that the average amounts of MPs for 0–20 cm, 20–40 cm and 40–60 cm sampling heights were 868.71 ± 249.21, 799.87 ± 271.25, 1102.54 ± 317.44 particles kg−1. The average enrichment ratios of MPs for the different heights were 0.89 ± 0.54, 0.85 ± 0.56, 1.15 ± 0.73. Height distribution of MPs was combined affected by shape (fiber and non-fiber) and size of MPs, wind speed and soil aggregate stability. The amount of fibers approximately <4 mm in size and non-fibers <2 mm in size increased with sampling height, while both shapes of larger MPs than these two sizes was almost independent of the sampling height. Enrichment ratios of microfibers were positively related to wind speed but negatively related to soil aggregate stability at each sampling height. The results revealed that although MPs have similar density to organic matter (OM), the MPs’ amount and enrichment were independent of height but the OM content and enrichment ratios increased with height. These results suggested that more attention should be paid to the exploration of the influence of higher sampling heights (>60 cm) on the distribution of MPs in the future and the MPs characteristics for different sampling heights require carefully parameterization in detailed models of atmospheric MPs transport by wind erosion.

Abrigo 1, Cerro El Sombrero: An Early Site in Eastern Argentina

ABSTRACT Late Pleistocene human occupations are well represented in the Tandilia Range, Argentine Pampas. Abrigo 1 is a small shelter in close relation to the main and better-known site on the hilltop of Cerro El Sombrero, with both sites including Fishtail points. The oldest levels at the shelter dated to 13,000–12,000 calendar years ago and yielded two Fishtail points. This paper deals with the analysis of the sedimentary context, stratigraphy, artifact distribution, and site formation processes at Abrigo 1. The sedimentary record is dominantly composed of geogenic sediments with a minor participation of anthropogenic material, mainly lithic artifacts. The geogenic input includes sediments coming from the physical and chemical weathering of the rockshelter’s quartzites and windblown sediments. Pedogenesis is the prevailing site formation process. Artifact distribution, the homogeneity of the assemblage, and refitting are considered relevant to assess site integrity. The results are compared to other early cultural contexts of the immediate vicinity.

Accumulation of windblown sand in impact craters on Mars

Abstract Loose sand, blown away from source regions by winds, is transported across Mars's surface into sand sheets and dunes and accumulates within topographic sinks. In the absence of plate tectonics, impact craters constitute a dominant sink for windblown sediments on Mars today. We analyzed the volume of all mapped eolian sands in martian craters &amp;gt;1 km in diameter to reveal spatiotemporal patterns of sediment accumulation on the planet's surface. We combined our results with global climate simulations, maps of depth to the ice table and dust cover, as well as lithologic and age information of the underlying geologic units, to better understand the controls on intracrater sand accumulation rates. We find that crater age, latitude, and lithology influence the accumulation rate of windblown sand and, notably, that it is enhanced in mechanically weaker substrates, high-latitude craters (suggesting that modern cryogenic processes may enhance sand production), and in Late Noachian and Early Hesperian craters (possibly hinting at increased erosion rates at that time).

Transport preferences of P forms in wind-blown sediments of two susceptible soils

• P forms concentrations of aeolian sediments of different textured soils was assessed. • Mineral and organic P were transported in particulate matter of both soils. • Labile mineral P was transported in saltating sediments of both soils. • Labile P showed a secondary accumulation in particulate matter of the sandy loam soil. • The total P reflected the vertical distribution of the major form, the mineral one. • P forms vertical distribution depended greatly on the bulk soil characteristics. Wind erosion of agricultural soils affects their stock of essential elements for plants, like phosphorus (P). It is known that the composition of the eroded sediments varies with height, according to the size and density of the transported substances. Aim of this study was to analyze the concentration and enrichment ratios of P forms in sediments transported by the wind. A wind-tunnel study was performed on a sandy- and a sandy loam soil in order to measure P forms concentrations in the saltating sediments. P concentrations were also measured in the particulate matter (PM) of each soil, gained with the Easy Dust Generator. In both soils, inorganic- (P i ) and organic P (P o ) were preferentially transported in PM, with enrichment ratios of 1.8 and 5.5, respectively. Nevertheless, a P i /P o of 0.9 indicated that the accumulation of the minor P o in PM was more pronounced than P i . This agrees with P-rich light and easily erodible organic compounds, almost exclusively accumulated in PM, and in relatively heavy and less erodible minerals, like apatites, in lower height sediments. Labile P (P l ) was preferentially transported in saltating sediments of both soils. This was attributed to the selective Bray & Kurtz I’s extraction of the abundant inorganic P forms of these sediments. Total P (P t ) copied the transport trends of P i , the major form. According to the transporting trends, P i and P o would be re-sedimented at longer distances from the source than P l . Outcomes become useful for modeling the influence of wind erosion on P cycling.

Opposite dust grain-size patterns in the Pacific and Atlantic sectors of the Southern Ocean during the last 260,000 years

Downcore sediment grain-size records of mineral dust (2–10 μm) can provide key insights into changes in wind strength and source-area characteristics over glacial-interglacial timescales. However, so far, little is known about glacial-interglacial changes of dust grain size in the open Southern Ocean, which are potentially associated with changes in the strength and position of the southern westerly winds. Here, we analyzed the grain-size distributions of subantarctic deep-sea sediments from the Pacific (PS75/056–1) and Atlantic (ODP Site 1090) sectors of the Southern Ocean, downwind of the major Southern Hemisphere dust source regions. Dust mean grain sizes show opposite trends in the two Southern Ocean sectors. Larger glacial grain sizes are observed in the Pacific sector, while finer glacial grain sizes are observed in the Atlantic sector. In the South Pacific, larger mean dust grain sizes parallel higher Fe fluxes during glacials. In contrast, in the South Atlantic record increased glacial Fe fluxes coincide with a decrease in glacial mean dust grain sizes consistent with some Antarctic ice core records. Our results suggest that the opposing grain-size trends are the result of different responses to glacial conditions in the sources and of changing wind and transport patterns. For the South Pacific, a possible explanation of our results could be an intensification of wind strength over Australia enabling emission of larger dust particles. This strengthening would imply a northward shift of the westerlies which facilitated the transport of dust from enhanced and/or more Australian and New Zealand sources. For the Atlantic, the decreased glacial dust grain size could be the consequence of increased glacial activity in the Patagonian Andes, generating and supplying more and finer-grained dust from the exposed continental shelf to the South Atlantic. These findings indicate that more extensive studies of wind-blown sediment properties in the Southern Ocean can provide important insights on the timing and latitudinal extent of climatic changes in the sources and variations of transport to the Southern Ocean by the westerly winds.

Differences in the Efficiency of the Vertical Transfer of Windblown Sediment over Different Ploughed Surfaces during Wind Erosion Events

Airborne sediment fluxes were measured in southern Tunisia on two experimental plots tilled with a moldboard and a tiller plough, respectively, during five wind erosion events of different intensities. The sediment fluxes were sampled on both plots using a mast equipped with seven sand traps positioned between ≈10 and 120 cm height. The windblown sediment fluxes in the 0–100 cm layer were about eight times higher on the plot tilled using the tiller plough compared to the plot tilled using the moldboard plough due to different efficiencies in the trapping of the saltating particles in the furrow, depending on the ridges characteristics. On both plots, sediment fluxes of larger particles were depleted in the sediment samplers compared to the proportions measured in the soil from which they were derived. When examining the sediment flux in the 30–100 cm layer, we observed that the efficiency of the vertical transfer was about twice higher on the moldboard plot than on the tiller one. This implies that a higher fraction of the sediment mobilized by wind can be transported over long distances in the case of a surface ploughed with a moldboard. This result could reduce in part the benefit of using the moldboard instead of the tiller plough regarding soil loss by wind erosion.

The imprint of windblown dust from the North American Southwest on the California Channel Islands and Pacific Ocean sediments

Climate projections for the North American Southwest (NASW) predict an increasing frequency and duration of droughts over the 21st century in response to human-induced warming, with potentially severe economic and social consequences. The geological record provides a way to contextualise this prediction because of the past occurrence of abrupt hemispheric warming events and sustained intervals of atmospheric carbon dioxide loading equivalent to those projected for AD 2100 (between ∼500 and 900 ppmv). Yet, terrestrial climate archives are typically too short and incomplete to provide a full record of these events. In principle, drill cores from deep sea sediments in the eastern Pacific Ocean can be used to overcome this problem because they contain long records of continental dust and distal riverine-supplied sediments from North America. Yet our limited understanding of the provenance and transport pathways of these sediments impedes use of these marine archives for this purpose. Here we present radiogenic isotope data (Sr, Nd and Pb) from known NASW dust-producing hot spots – playa lakes in the Mojave Desert, Quaternary silts mantling the California Channel Islands and the terrigenous fraction from marine sediments of the eastern Pacific Ocean, supported by new maps of bedrock isotopic composition in the NASW. We use these and published data sets to infer the origin of playa lake silts in the Mojave Desert and the source of windblown sediments to the California Channel Islands and nearby ocean basins. Our Results rule out a significant contribution from the distal tails of either the Pacific Asian dust plume or the North African dust plume to the Quaternary Channel Island silt mantles, corroborating the suggestion that they are aeolian in origin and sourced from the NASW on the Santa Ana winds. We identify the Outer California Borderland basins as an attractive proposition for studying past dust flux and palaeoaridity in the North American Southwest.

Windblown Hadean zircons derived by erosion of impact-generated 3.3 Ga uplifts, Barberton Greenstone Belt, South Africa

In the absence of a rock record older than about 4.03 Ga, Hadean (>4.0 billion-years-old) zircons provide a unique window into crustal development and surface conditions on the Earth within a few hundred million years of its formation. Recently discovered Hadean detrital zircons, 4.0–4.2 Ga, in the Barberton Greenstone Belt, South Africa, occur in a 3 to 5 m thick layer termed the Green Sandstone Bed (GSB) that is composed largely of mafic to komatiitic volcaniclastic debris and trace amounts of sand-sized quartz, chromite, and zircon. The youngest concordant zircons in the GSB and ages of zircons in immediately underlying strata suggest a depositional age of about 3.306 ± 6 Ga. Hadean zircons are concentrated in the lower 200 cm of the unit: higher parts of the GSB lack Hadean zircons and the uppermost 150 cm contain zircons 3.312 ± 5 Ga. The quartz and heavy minerals in the lowest 200 cm of the GSB appear to have been transported as windblown sediments in a subaerial environment. They were subsequently incorporated into mass flows represented locally by the lowest 200 cm of the GSB. The bulk of the overlying GSB sediments were worked and deposited in wave- and current-active, shallow-marine to intertidal settings. Cathodoluminescence studies suggest that a high proportion of the detrital GSB quartz is of plutonic origin although the GSB is underlain by 10–12 km of volcanic and volcaniclastic silicified sedimentary rocks with no evidence of uplift or terrigenous sediment sources. The GSB lies <2 m above impact layer S6 and we infer that much of the windblown sediment was derived by erosion of crustal rocks that were uplifted and emplaced at the surface during the S6 impact and of komatiites exposed subaerially between the impact and depositional sites.

Morphology, properties, and source of windblown sediments of the coastal dune field in the Gioia Tauro Plain, Calabria, southern Italy

Geomorphological investigations coupled with sedimentological, petrographical, and SEM analyses allowed to identify, for the first time, a paleo-fixed and inland aeolian dune field in the Gioia Tauro Plain, on the Tyrrhenian side of southern Calabria (southern Italy). The aeolian landforms, extended over an area of 43 km2, are characterized by smoothed and elongated NW-SE trending vegetation-fixed linear dunes, varying in height from a few meters up to 20 m.Forty sand samples were collected from dunes to perform laboratory analyses. Grain size analyses showed that samples are composed of unimodal coarse-grained sands (Mz = 0.820 φ), moderately sorted (σ = 0.862), positively skewed (Sk1 = 0.173) and mesokurtic (KG = 1.115). Petrographic analyses highlighted a composition dominated by quartz and minor feldspars. Modal data, and especially the high F/Q ratio and the Rg:Rs:Rm triangular plot, suggest a plutoniclastic supply from the Aspromonte Massif crystalline source rocks. SEM analyses of sand grains clearly displayed the presence of typical wind-generated features mainly represented by rounded form with low relief, bulbous edges, and dish-shaped depressions. These results combined with morphological analyses showed that these aeolian deposits fall into the category of sand sheets. Furthermore, geological and geoarchaeological data evidenced that dune field was formed in the time interval between ~28 ka and the VI - IV century B.C. The dune filed formation has been interrupted presumably by the combined effect of Holocene tectonics, along the Gioia Tauro-San Ferdinando normal fault, and the lowering of sea level, during the Last Glacial period, originating a natural barrier to windblown sand particles.The findings of the paper will help in understanding both inland aeolian products in southern Europe associated to the second colder phase of the Last Glacial period in the Mediterranean area and the complex patterns of spatial and temporal distribution, as well as the control factors determining preservation of the aeolian sediments throughout the rock record.

Elemental composition of wind-blown sediments from contrasting textured soils

• Element composition of aeolian sediments of two different textured soils was studied. • Ca and Mg were transported at low heights in both soils. • Organic C and N were transported at great heights in both soils. • S was transported at low and high heights, possibly in its organic and mineral forms. • The transport along height was less segregated in sandy loam- than in sandy soil. Wind eroded sediment is sorted by height by both size and density. Less information is available about the elemental composition and enrichment ratios of these sediments. Because of that, the concentration of elements in wind-blown sediments of a sandy- and a sandy loam soil of the semiarid Argentinean Pampas were analyzed. With this purpose, a wind tunnel study was performed for obtaining the saltating sediments transported at different heights, and a sorption-based laboratory procedure was used to separate the particulate matter. Results showed that Ca and Mg were transported at low- and C and N at high heights. These tendencies were attributed to the accumulation of Ca and Mg in coarse minerals, probably apatite and Ca-feldspars, which are heavily transported by the wind, and to the accumulation of C and N in low-dense organic substances, fresh debris and polysaccharides, easily transported by the wind. Total S did not show a preference to be transported at any height, possibly due to its accumulation in organic and mineral substances. The transport of C and N was more segregated in the sandy- than in the sandy loam soil, in agreement with the better aggregation of the latter, in which some of its organic substances (carboxylic acids, amides and aromatics), form coarse and heavily transportable aggregates. From the obtained results it can be deduced that C and N would be widespread larger than Ca and Mg. Assembling of data obtained to mass fluxes, becomes relevant for modeling the biogeochemical cycles.

Late Cretaceous plateau deserts in the South China Block, and Quaternary analogues; sedimentology, dune reconstruction and wind-water interactions

Plateau deserts are among those continental systems with the most significant examples of clastic deposits associated with the complex combination of the action of ice, wind and water. The Late Cretaceous rocks of China contain the record of desert systems migration and partial destruction in a palaeoplateau desert. The evolution of the South China Block during Late Cretaceous was characterized by widespread destructive plate margin activity, this favoured orogenic uplift and high-altitude mountain ranges of which a direct consequence was a widespread rain shadow effect, triggering desertification and erg expansion similar to that of Quaternary counterparts in the Tibetan Plateau. This work presents a detailed analysis of the sedimentology, stratigraphic architecture, palaeogeography and palaeocurrent reconstruction of aeolian and associated alluvial depositional systems. The reconstruction of aeolian bedforms based on field-data analysis indicates that, during Late Cretaceous, draas and crescentic dunes accumulated and migrated in extensive intermontane desert systems. Heavy rains led to partial destruction of aeolian dunes and the reworking of aeolian sands in interdraa corridors. The fault-controlled subsidence and an increasing input of windblown sediments favoured the long-lasting accumulation of the erg system. Possible monsoonal rains recharged the groundwater system causing the rise of the regional phreatic level that favoured the ulterior long-lasting preservation of the aeolian system in the Xinjiang Basin. The dimensions and processes inferred from this Cretaceous desert system are similar to those observed today in the linking zone of the Taklamakan-Gobi Deserts, where meltwater flows from alpine glaciers in surrounding mountain ranges recharge the alluvial and fluvial network of the erg margin. The occurrence of striated cobbles in the alluvial facies suggests glacial activity in the catchment areas of the Cretaceous plateau.

Assessing geomorphological and pedological processes in the genesis of pre-desert soils from southern Tunisia

Arid environments are fragile and the associated soils are subject to serious threats like water deficiency, erosion, salt accumulation, and loss of fertility. In this context, understanding the processes involved in soil genesis may contribute toward protecting land from degradation. This study highlights the interconnection between geomorphic and pedogenetic processes in soil formation of the Jeffara Plain, a pre-Saharan area of southern Tunisia. To reach this goal, one coastal oasis (Chenini Nahel) and two inland environments (Matmata Nouvelle and Menzel Habib) were studied. After geomorphological and pedological surveys, the soils were sampled by genetic horizons and characterized by physical, mineralogical, and chemical analyses, and by microscope observation. Field observations and laboratory data suggest that soil formation in the Jeffara Plain was a combination of additions and losses controlled by climate changes. At Chenini Nahel, the soils developed by accumulation of wind-blown sediments coming from a close area dominated by gypsum-bearing rocks. At Matmata Nouvelle, the soils mainly formed from sedimentation of repeated mudflows during a rainy period between 9000 and 5000 years before present, followed by drought periods. Finally, the soils of Menzel Habib developed from an early gypsum formation in the presence of a salt-rich water table and repeated cycles of sedimentation/deflation of wind-blown materials. The different genesis of these pre-desert soils produced characteristic B horizons: Byy horizons with poorly developed soil structure at Chenini Nahel, Bw horizons with a hard rupture-resistance at Matmata Nouvelle, and Bk horizons at depth due to intense sedimentation with CA + BC horizons at the surface due to the accretion of wind-blown materials at Menzel Habib.

Induced biological soil crust controls on wind erodibility and dust (PM10) emissions

ABSTRACTInducing biological soil crust (biocrust) development is an appealing approach for dust mitigation in drylands due to the resistance biocrusts can provide against erosion. Using a portable device, we evaluated dust emissions from surfaces either inoculated with biocrust, amended with a plant‐based soil stabilizer, or both at varying wind friction velocities. Four months after application, emissions from all treatments were either indistinguishable from or greater than controls, despite evidence of biocrust establishment. All treatments had greater surface roughness and showed more evidence of entrapment of windblown sediment than controls, factors which may have been partially responsible for elevated emissions. There was a synergistic effect of inoculation and stabilizer addition, resulting in a nearly two‐fold reduction in estimated emissions compared to either treatment alone. Stepwise regression analysis indicated that variables associated with surface crust strength (aggregate stability, penetration resistance) were negatively associated with emissions and variables associated with sediment supply (sand content, loose sediment cover) were positively associated with emissions. With more time to develop, the soil‐trapping activity and surface integrity of biocrust inoculum and soil stabilizer mixtures is expected to increase with the accumulation of surface biomass and enhancement of roughness through freeze–thaw cycles. © 2019 John Wiley &amp; Sons, Ltd.

45,610–52,160 years of site and landscape occupation at Nawarla Gabarnmang, Arnhem Land plateau (northern Australia)

We present Bayesian modelling on a long sequence of radiocarbon ages from the archaeological site of Nawarla Gabarnmang, central Arnhem Land plateau, northern Australia. A horizon of wind-borne sediments containing flaked stone artefacts and charcoal commencing >45,610 cal BP (the young end of the modelled boundary age range, which extends beyond the limit of the calibration curve), with a median modelled age of 48,500 cal BP, signals the onset of aeolian mobilisation of fine sands and silts across the landscape, and re-deposition within the site at a time synchronous with the first evidence of people. This earliest cultural horizon (Stratigraphic Unit 4) contains 509 stone artefacts, and is marked by a contemporaneous sedimentary break, from underlying culturally sterile sediments consisting of disintegrating roof-fall and in situ sandstone and quartzite to overlying culturally-rich wind-blown sand. The new radiocarbon ages and wind-blown sediments together provide evidence for the commencement of noticeable landscape burning on the Arnhem Land plateau c. 48,500 cal BP, suggesting an intensification of landscape management practices at the summit of the Arnhem Land plateau some 10,000–15,000 years after the lowest dense band of artefacts (Phase 2) at Madjedbebe on the floodplains 90 km to the north. These results have ramifications for the structure and timing of the spread of people across Australia, and the extinction of megafauna in Sahul.

Anemochory of diapausing stages of microinvertebrates in North American drylands.

1. Dry, ephemeral, desert wetlands are major sources of windblown sediment, as well as repositories for diapausing stages (propagules) of aquatic invertebrates. Zooplankton propagules are of the same size range as sand and dust grains. They can be deflated and transported in windstorm events. This study provides the evidence that dust storms aid in dispersal of microinvertebrate propagules via anemochory (aeolian transport). 2. We monitored 91 windstorms at six sites in the southwestern U.S. over a 17-year period. The primary study site was located in El Paso, Texas in the northern Chihuahuan Desert. Additional samples were collected from the Southern High Plains region. Dust carried by these events was collected and rehydrated to hatch viable propagules transported with it. 3. Using samples collected over a six-year period, 21 m above the ground which included 59 storm events, we tested the hypothesis that transport of propagules is correlated with storm intensity by monitoring meteorological conditions such as storm duration, wind direction, wind speed, and PM10 (fine dust concentration). An air quality monitoring site located adjacent to the dust samplers provided quantitative hourly measurements. 4. Rehydration results from all events showed that ciliates were found in 92% of the samples, rotifers in 81%, branchiopods in 29%, ostracods in 4%, nematodes in 13%, gastrotrichs in 16%, and tardigrades in 3%. Overall, four bdelloid and 11 monogonont rotifer species were identified from rehydrated windblown dust samples. 5. PCA results indicated gastrotrichs, branchiopods, nematodes, tardigrades, and monogonont rotifer occurrence positively correlated with PM10 and dust event duration. Bdelloid rotifers were correlated with amount of sediment deposited. NMDS showed a significant relationship between PM10 and occurrence of some taxa. Zero-inflated, general linear models with mixed-effects indicated significant relationships with bdelloid and nematode transport and PM10. 6. Thus, windstorms with high particulate matter concentration and long duration are more likely to transport microinvertebrate diapausing stages in drylands.

Hydrochemical processes, variability and natural background levels of Arsenic in groundwater of northeastern Mendoza, Argentina

Northeastern Mendoza is an arid area dominated by stabilized dunes and paleochannels. Groundwater is the main source of water for domestic and subsistence economy. Two types of wells are used for groundwater withdrawal. Wells operated by conventional windmills or pumps (Ws) and local traditional bucket wells operated manually (BWs). These wells are drugged a few cm below the water table, normally with a diameter of 1 m, remain always open and are located near corrals. The aim of this study was to evaluate the processes that control As in groundwater used As drinking water by rural communities. The study approach included an assessment of the natural as background levels and the use of environmental isotopes (δ18O and δ2H) to determine the origin of groundwater and improve the conceptual model for groundwater flow. Significant statistical differences were found between the chemical features of groundwater from Ws and BWs. The conceptual hydrogeologic model supported by isotopic data indicated that groundwater recharge was from the main Mendoza/Tunuyan Rivers in remote areas and that local rainwater recharge is negligible. The isotopic data suggests that a faster groundwater flow recharge could occur without any influence of a previous evaporation process. The natural As background level was 104 µg/L, with a range of between 8.6 and 394 µg/L. The average As concentration in Ws was 114 µg/L. Water from BWs showed higher average As concentration of 235 µg/L with a higher dispersion, high HCO3−, NO3− PO 4 −3 and Cl− concentrations, and the lowest concentrations of O2 with greater turbidity than groundwater from Ws. The increase in As concentrations in groundwater of NE Mendoza is not related to evaporation processes despite arid climatic conditions. According to the oxidizing environment in the aquifer, high pH and very fine sediments, adsorption–desorption processes from solid surfaces were the determining factors for the availability and spatial variability of As in groundwater. Spatial variability was related to type of well rather than to geomorphologic units or to flow direction. The design of bucket wells, near corrals, allows the input of windblown sediments and leachate from livestock units creating point sources of As contamination in water used for human consumption.

Effect of wind speed on aggregate size distribution of windblown sediment

Abstract Wind speed is critical in wind erosion and dust emission processes; however, previous studies, especially field measurements, have been unable to verify the effect of wind speed on particle size distribution of windblown sediment. The aim of this study was to elucidate changes in the aggregate size distribution of windblown sediment in relation to friction wind velocity based on field observations conducted during 2012–2018 in Bashang District (North China). The results showed that for loamy, sandy, and sandy loam soils, the geometric mean diameter of sediment increased exponentially with increasing friction wind velocity. The mass percentages of particles with diameters of 0.1). Correlations in the aggregate size distribution between windblown sediment and in-situ soil were enhanced with increasing friction wind velocity. The results indicate the influence of wind speed on particle size distribution of windblown sediment should be considered when determining dust emission efficiency, or when analyzing the influence of the particle size distribution of soil on that of windblown sediment.

Difference in wind erosion characteristics between loamy and sandy farmlands and the implications for soil dust emission potential

AbstractDust emission depends directly and indirectly on soil particle distribution, but little information is available that examines dust emission potential and its relationship with wind erosion for different soils. This study aimed to elucidate the difference in wind erosion characteristics between loamy farmland (LF) and sandy farmland (SF) and discuss the influence of this difference on dust emission potential. Field observations were conducted during 2012–2016 in Bashang district, North China. With increasing friction wind speed, the horizontal mass flux increased exponentially in LF but obeyed the power function in SF. The horizontal mass flux was higher in SF than in LF, but the gap narrowed from 766 times at friction wind speed of 0.3 m s−1 to 50 times at 0.6 m s−1. The dry aggregate size distribution of sediment in LF was finer than in SF. Fine particle content (diameter &lt; 0.05 mm) in windblown sediment was much higher in LF (31.39%) than in SF (5.92%), which was influenced by parent soils. With height increasing, the mass percentage of sediment decreased more rapidly in SF than in LF, with 86% and 66% of sediment clustering at height 0–20 cm, respectively. Because the horizontal mass flux and dust content in sediment both increased more quickly in LF than in SF with increasing friction wind speed, the dust emission potential was larger in LF than in SF under strong winds. The adverse effect of dust emission in loamy soils on atmospheric pollution should receive more attention in strong wind erosion events.