Origin of the Sinai-Negev erg, Egypt and Israel: mineralogical and geochemical evidence for the importance of the Nile and sea level history

The Sinai-Negev erg occupies an area of 13,000 km2 in the deserts of Egypt and Israel. Aeolian sand of this erg has been proposed to be derived from the Nile Delta, but empirical data supporting this view are lacking. An alternative source sediment is sand from the large Wadi El Arish drainage system in central and northern Sinai. Mineralogy of the Negev and Sinai dunes shows that they are high in quartz, with much smaller amounts of K-feldspar and plagioclase. Both Nile Delta sands and Sinai wadi sands, upstream of the dunes, also have high amounts of quartz relative to K-feldspar and plagioclase. However, Sinai wadi sands have abundant calcite, whereas Nile Delta sands have little or no calcite. Overall, the mineralogical data suggest that the dunes are derived dominantly from the Nile Delta, with Sinai wadi sands being a minor contributor. Geochemical data that proxy for both the light mineral fraction (SiO2/10-Al2O3 + Na2O + K2O-CaO) and heavy mineral fraction (Fe2O3-MgO-TiO2) also indicate a dominant Nile Delta source for the dunes. Thus, we report here the first empirical evidence that the Sinai-Negev dunes are derived dominantly from the Nile Delta. Linkage of the Sinai-Negev erg to the Nile Delta as a source is consistent with the distribution of OSL ages of Negev dunes in recent studies. Stratigraphic studies show that during the Last Glacial period, when dune incursions in the Sinai-Negev erg began, what is now the Nile Delta area was characterized by a broad, sandy, minimally vegetated plain, with seasonally dry anastomosing channels. Such conditions were ideal for providing a ready source of sand for aeolian transport under what were probably much stronger glacial-age winds. With the post-glacial rise in sea level, the Nile River began to aggrade. Post-glacial sedimentation has been dominated by fine-grained silts and clays. Thus, sea level, along with favorable climatic conditions, emerges as a major influence on the timing of dune activity in the Sinai-Negev erg, through its control on the supply of sand from the Nile Delta. The mineralogy of the Sinai-Negev dunes is also consistent with a proposed hypothesis that these sediments are an important source of loess in Israel

Soil Erosion by Wind and Dust Emission in Semi-Arid Soils Due to Agricultural Activities

Many soils throughout the world are currently associated with soil erosion by wind and dust emissions. Dust emission processes have major implications for loss of soil resources (such as clays and nutrients) and human exposure to air pollution. This work provides a review on field experiments of dust emission based on previous studies, with new insight into the role of soil aggregation. The work focuses on dust processes in semi-arid soils that are subjected to increased agricultural land use. A boundary-layer wind tunnel has been used to study dust emission and soil loss by simulation and quantification of high-resolution wind processes. Field experiments were conducted in soil plots representing long-term and short-term influences of land uses such as agriculture, grazing, and natural preserves. The results show the impacts of soil disturbances by human activities on the soil aggregation and dust fluxes and provide quantitative estimates of soil loss over time. Substantial loss of PM10 (particulate matter [PM] that is less than 10 micrometers in diameter) was recorded in most experimental conditions. The measured PM10 fluxes highlight the significant implications for soil nutrient resources in annual balance and management strategies, as well as for PM loading to the atmosphere and the risk of air pollution

Special Issue on Soil Erosion: Dust Control and Sand Stabilization (Volume II)

This is the second volume of the Special Issue on Soil Erosion: Dust Control and Sand Stabilization, following the first volume published in 2020 [...

Comparison of Diverse Dust Control Products in Wind-Induced Dust Emission from Unpaved Roads

Surfaces of unpaved roads are subjected to dust PM10 (particulate matter < 10 µm) emission by wind process regardless of vehicles (wheels) transport. However, there is little quantitative information on wind-induced dust emission from unpaved roads and the efficiency of diverse dust control products. The study aimed to fill this clear applied scientific gap using wind-tunnel experiments under laboratory and field conditions. The wind-tunnel complies with aerodynamics requirements and is adjusted to dynamic similitude by appropriately scaling all variables that affect dust transport. The results of the control sample (no-treatment) clearly show that dust emission by wind from unpaved road could be a substantial contribution to mass transfer and air pollution, and thus should be considered. Diverse dust control products of synthetic and organic polymers (Lignin, Resin, Bitumen, PVA, Brine) were tested. In the first stage, the products were tested under controlled-laboratory conditions. The results enabled quantitative assessment of the product efficacy in wind erosion without the impact of vehicle transport. In the second stage, the products were tested in field experiment in an active quarry, in which the products were applied on plots along the road. The field experiment was conducted after transportation of the quarry-haul trucks in two time points: several days after the application, and several weeks after the application. The results show that in most of the plots the dust emission increases with the wind velocity. PM10 fluxes from the road surface in each plot were calculated to determine the effectiveness of the dust control products. Some products significantly reduced dust emission from quarry roads, especially when using the Hydrous magnesium chloride (Brine). Additional experiments revealed that such Brine can be applied with reduced amounts and still keeping on low 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

Exposure Assessment of Indoor PM Levels During Extreme Dust Episodes

Millions of people live in areas that are subject to frequent dust events; however gaps remain in our knowledge about the association between dust, air quality and corresponding particulate matter (PM) exposure levels inside buildings. This case study demonstrates how the PM2.5 and PM10 levels in an urban environment respond to strong natural dust episodes. Real-time measurements were recorded simultaneously in indoor and outdoor environments in households in the city of Beer-Sheva, Israel during several strong dust events. A typical strong event was used for a detailed analysis of PM10 and PM2.5. Outdoor daily concentrations were above 1000 µg m−3 for PM10, the maximum hourly value of which was 1320 µg m−3. The indoor PM10 peaked at about 700 µg m−3 and fluctuated in parallel with the outdoor level but with a time lag of about 15 min. Indoor air tended to remain for several hours after the dust event had subsided. Analyses of multiple events revealed that the dependence of indoor PM2.5 and PM10 on natural dust varies but is not directly linked to the level of atmospheric dust concentration. From a health perspective, the exposure risk posed by extreme indoor PM2.5 and PM10 levels generated by natural dust episodes should be considered

Insights into Indoor/Outdoor PM Concentration Ratios due to Dust Storms in an Arid Region

Dust storms have impacts on both human and physical environments, associated with an increase in atmospheric particulate matter (PM) concentrations. Most studies on exposure to PM have focused on the outdoor air, while information on indoor pollution, is still lacking. The aim of this study was to examine the impact of desert dust events on PM concentrations in indoor environments. A total of over 200 real time measurements of PM were conducted in houses in the Negev Desert during dust storms. Indoor and outdoor PM concentrations were characterized, as well as the relationships between the two datasets. The findings indicated that atmospheric PM10 concentrations can increase from 20–120 μg·m−3 on non-dust days to more than 1500 μg·m−3 during dust events. Indoor concentrations can reach as high as 1000 μg·m−3. The calculated indoor/outdoor (I/O) PM ratio ranged from 0.79 for low-level storms to 0.58 during stronger events. Indoor PM concentrations were found to be dependent on the dust storm intensity (low, medium, high) and duration with a time lag. The information obtained in this study is critical for assessment of policy interventions to reduce exposure risk and health effects due dust storms

Dust Particles as a Pesticide’s Carrier in Agro-Ecosystems; Qualitative and Quantitative Analysis

The agricultural landscape constitutes a mosaic of various crop plots intertwined with non-disturbed natural areas. Extensive use of pesticide spraying can pollute the natural areas, causing damage to the natural food webs. The damages to the natural systems can be temporary and cumulative. Although many studies have dealt with the results of pesticide spraying drift to the natural environment, we lack knowledge on the role of dust particle transfer of pesticides. The study aims to investigate the dust particles as pesticide carriers. It examines the presence and accumulation of pesticides in vegetation and soils of the farmlands and natural areas nearby in two different climatic zones, Mediterranean and semiarid. It was hypothesized that seasonal agricultural activities affect the transport of dust particles with pesticides. The research methods included qualitative and quantitative analyses of pesticides in a hierarchy of distances from agriculture fields into natural and nearby. The renewal of the results indicated that seasonal agricultural activity leading to the transport of dust particles was a major contribution to the spatial distribution of pesticides, in both climate zones. Here we reveal results that must be an essential principle in the use of pesticides in agricultural fields, especially in nearby uninhabited areas

Tree Belts for Decreasing Aeolian Dust-Carried Pesticides from Cultivated Areas

The aim of this study was to investigate the function of tree belts in reducing the aeolian transport of dust particles carrying pesticides. The study examined the importance of the buffer zones created by commonly planted trees (Eucalyptus camaldulensis, Pinus halepensis (pine) and Ceratonia siliqua (carob)). The methods include analyzing the quantity and the chemical composition of pesticides carried by aeolian dust particles from the intensively cultivated fields and orchards, where pesticides were applied, towards the tree belts nearby. Eighteen different chemicals used as insecticides, fungicides and herbicides, were found both in the agricultural fields and in the adjacent tree belts, suggesting an important function of the trees. This ecological service has rarely been taken into consideration by management policies of tree plantings in farmland areas. To integrate this service into agriculture, especially in the case of agricultural fields and orchards, which are adjacent to populated areas, planting tree belts should be positively considered as a means for reducing aeolian dust and air pollution, mainly in order to reduce leakage of pesticides, which are a cause for significant health concerns

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