Atmospheric Dust Research Articles

The Sandwich Mode for Vertical Shear Instability in Protoplanetary Disks

Abstract Turbulence has a profound impact on the evolution of gas and dust in protoplanetary disks (PPDs), from driving the collisions and the diffusion of dust grains, to the concentration of pebbles in giant vortices, thus, facilitating planetesimal formation. The vertical shear instability (VSI) is a hydrodynamic mechanism, operating in PPDs if the local rate of thermal relaxation is high enough. Previous studies of the VSI have, however, relied on the assumption of constant cooling rates, or neglected the finite coupling time between the gas particles and the dust grains. Here, we present the results of hydrodynamic simulations of PPDs with the PLUTO code that include a more realistic thermal relaxation prescription, which enables us to study the VSI in the optically thick and optically thin parts of the disk under consideration of the thermal dust-gas coupling. We show the VSI to cause turbulence even in the optically thick inner regions of PPDs in our two- and three-dimensional simulations. The collisional decoupling of dust and gas particles in the upper atmosphere and the correspondingly inefficient thermal relaxation rates lead to the damping of the VSI turbulence. Long-lived anticyclonic vortices form in our three-dimensional simulation. These structures emerge from the turbulence in the VSI-active layer, persist over hundreds of orbits and extend vertically over the whole extent of the turbulent region. We conclude that the VSI leads to turbulence and the formation of long-lived dust traps within ±3 pressure scale heights distance from the disk midplane.

Evaluation of the dustiness of fugitive dust sources using gravitational drop tests

Handling of dry granular materials in quarries and mining processes are an important source of atmospheric dust characterized as fugitive sources. Fugitive dust sources may affect the health of operators in the facility or the inhabitants of nearby communities. During handling, the air-particle interaction eases the suspension of large amounts of dust. Some of the dust particles settle near the source while others are carried away by the air. The settled dust may be re-suspended into the air by windblown mechanisms or by traffic activity, increasing the impact on the surroundings. For middle and small-sized quarries in developing countries the direct field measurement of the environmental impact of fugitive sources is not affordable. This work proposes the utilization of a gravitational dustiness test to mimic fugitive dust sources that take place during handling of particulate materials and to evaluate the dustiness of the source. Two different gravitational dustiness tests devices were built and used to evaluate the dustiness of a granular material handling. The tests are simple, require low investment and can be used to study the influence of variables and remedy actions. The utilization of the tests allowed to estimate the amount of dust generated and to know the particle size distribution of the emitted dust. In addition, the tests allowed the exploration of the influence of the relative humidity and temperature of the surrounding air on the dust emission. Results suggest that dust emission is affected by the properties of the surrounding air due to the dependence of adhesion and inter-particle forces on the air humidity and temperature.

Evaluation of minerals being deposited in the Red Sea using gravimetric, size distribution, and mineralogical analysis of dust deposition samples collected along the Red Sea coastal plain

Abstract The effect of atmospheric dust on the Earth's climate and air quality is especially severe in the major dust-source regions of the globe, such as the Arabian Peninsula. To better quantify the impact of dust over this region, we established the dust deposition measurement sites at King Abdullah University of Science and Technology (KAUST) and an AErosol RObotic NETwork (AERONET) station. We measured and analyzed dust deposition for 61 months from 2014 to 2019, totaling 442 samples, in 6 different locations on the KAUST campus (22.3 N; 39.1E). The analyses include gravimetric measurements, X-Ray Diffraction (XRD) mineral analyses, and particle size distribution measurements. The intercomparisons of the samples collected from different sampling sites show that the dust deposition rates on campus are spatially uniform. Particle size and mass measurements of deposition dust samples are found to be uncorrelated with the concurrent AERONET measurements. Deposition sample sieving (D 20 µm are typically of local origin, since they deposit quickly. The annual mean deposition rate is about 11 g m-2 mo-1, with higher spring and fall rates and reduced rates in summer. The mineralogical analysis shows an abundance of quartz and feldspar with lesser amounts of micas, gypsum, clays, carbonate, halite, and iron oxides. Gypsum traces are probably produced either in the atmosphere or in the deposited sample by the reaction between carbonates and sulfur dioxide. The deposition of dust particles with D

Mineralogical and Chemical Tracing of Dust Variation in an Underground Historic Salt Mine

The aim of this study was to investigate the causes of the evolution of atmospheric dust composition in an open-to-public subterranean site (UNESCO-recognized historic mine) at increasing distances from the air intake. The role of the components imported with atmospheric air from the surface was compared with natural and anthropogenic sources of dust from inside the mine. Samples of deposited dust were directly collected from flat surfaces at 11 carefully selected sites. The morphological, mineralogical, and chemical characteristics were obtained using scanning electron microscopy (SEM), X-ray diffraction (XRD), and inductively coupled plasma spectroscopy (ICP). The study showed that the air in the underground salt mine was free of pollutants present in the ambient air on the surface. Most of the components sucked into the mine by the ventilation system from the surface (regular dust, particulate matter, gaseous pollutants, biogenic particles, etc.) underwent quick and instantaneous sedimentation in the close vicinity of the air inlet to the mine. The dust settled in the mine interior primarily consisted of natural geogenic particles, locally derived from the weathering of the host rock (halite, anhydrite, and aluminosilicates). This was confirmed by low values of enrichment factors (EF) calculated for minor and trace elements. Only one site, due to the tourist railroad and the associated local intensive tourist traffic, represented the anthropogenic sources of elevated concentrations of ferruginous particles and accompanied metals (P, Cr, Mn, Co, Ni, Cu, As, Mo, Cd, Sn, Sb, Pb, and W). The gravitational deposition of pollutants from these sources limits the effects of the emissions to the local range. The used methodology and the results are universal and might also apply to other mines, caves, or underground installations used for museums, tourists, or speleotherapeutic purposes.

Comparison of the influence of Martian and Earth's atmospheric environments on terahertz band electromagnetic waves

SummaryTerahertz waves have wide application prospects in space communication because of their strong penetration ability, wide band, and strong directional antenna. Therefore, it is necessary to study the propagation characteristics of terahertz waves in space, such as in the environment on Mars. In space near Mars, the terahertz link is mainly affected by the absorption attenuation of its atmosphere and the scatter attenuation of heavy dust storms. In this paper, the absorption of 0.1–1 THz waves in the Martian atmosphere is analyzed. The absorption coefficient is calculated based on the theory of atmospheric radiative transfer and the HITRAN database. The influence of temperature, pressure, and altitude on the absorption coefficient is analyzed, and the calculation results are compared with those of Earth's atmosphere. The size distribution of Martian dust particles is then fitted by lognormal distribution, and the transmission characteristics of terahertz waves with different wavelengths are studied based on Mie theory. The research results show the transparent window positions of the attenuation peaks of water vapor and oxygen, which are the main factors of atmospheric transmission attenuation in the 0.1–1 THz band. The attenuation of Martian dust is affected by the size parameter, and it decreases with the visibility of the dust storm. The results provide a reference for terahertz communications in a Martian atmospheric environment and clarify the range of Martian atmospheric fading and dust fading.

High Potential of Asian Dust to Act as Ice Nucleating Particles in Mixed‐Phase Clouds Simulated With a Global Aerosol‐Climate Model

AbstractMineral dust affects the microphysical and radiative properties of mixed‐phase clouds and hence the radiative balance of the Earth by acting as ice nucleating particles (INPs). However, the importance of Asian dust as INPs is not well understood. In this study, we examined the contribution of Asian dust to global dust INPs and its effect on cloud radiative forcing (CRF) using a global aerosol‐climate model with an ice nucleation parameterization that links INP number concentrations to ambient temperature and dust number concentrations. Our model well reproduces INP number concentrations measured over the Tokyo Metropolitan area in Japan during May 2017, when Asian dust was transported to Japan. Our simulation for the years 2013–2017 shows that Asian dust extends from its source regions (e.g., the Gobi and Taklimakan Deserts) to the North Pacific, North America, and the Arctic. Notably, Asian dust is transported to higher altitudes (i.e., to temperature regimes relevant for the formation of mixed‐phase clouds) more efficiently than dust from other regions. The annual‐mean simulated contribution of Asian dust to global dust INPs is 15%, which is 4.4 times higher than its contribution to global atmospheric dust loading (3.4%). These characteristics of Asian dust show its high potential to act as INPs in mixed‐phase clouds. Sensitivity simulations show that Asian dust INPs have a positive net CRF of 0.054–0.19 W m−2 in East Asia and the North Pacific during 2013–2017 (cf. 0.092–1.0 W m−2 for dust from other regions).

Assessing the bioavailability of dissolved rare earths and other trace elements: Digestion experiments with aquatic plant species Lemna minor (“duckweed” reference standard BCR-670)

Reference material BCR-670 (Lemna minor, “duckweed”) is one of the very few plant reference materials for which certified data for all rare earths and yttrium (REY) are available. However, biological samples like plants or fungi often include detrital inorganic material because substrate particles (e.g., soil or atmospheric dust) may be closely associated with the organic component. Hence, the digestion approach used may strongly affect element yields. We here present concentration data for major, minor and trace elements with a focus on REY (with and without off-line preconcentration and matrix separation) following high-pressure high-temperature HNO3-HCl-HF decomposition and low-pressure low-temperature HNO3 extraction, respectively.Rare earths and yttrium concentrations after HNO3-HCl-HF decomposition are in good agreement with certified data but corroborate that preconcentration and matrix separation prior to quadrupole ICP-MS analyses result in improved data quality compared to data obtained without preconcentration and matrix separation. The results of both the decomposition and the extraction protocol show excellent reproducibilities, respectively, but the REY concentrations of the HNO3 extractions are lower than the certified bulk data and are accompanied by considerably lower concentrations of Al, Zr and Th. This suggests that the HNO3 extraction does not dissolve trace elements from detrital (alumino)silicate particles associated with the plant material.Our results expand the existing data set for BCR-670 not only for REY but also for a range of other elements (e.g., Li, Co, Rb, Sr, Ba, Mg, Mn, Na, P) including elements for which no or hardly any information had hitherto been available. Therefore, our dataset helps to improve the overall characterisation of BCR-670.The new data obtained from HNO3 extraction may be used to assess analytical quality in studies focusing on the chemical composition of the biological component of plants and fungi, which is a prerequisite to quantify the bioavailability and bioaccumulation of trace elements such as the REY in plants and fungi.

Seasonality in Saharan Dust Across the Atlantic Ocean: From Atmospheric Transport to Seafloor Deposition

AbstractSaharan dust is transported in great quantities from the North African continent every year, most of which is deposited across the North Atlantic Ocean. This dust impacts regional and global climate by affecting the atmospheric radiation balance and altering ocean carbon budgets. However, little research has been carried out on time series of Saharan dust collected in situ across the open Atlantic. Here, we present a unique three‐year time series of Saharan dust along a trans‐Atlantic transect, sampled by moored surface buoys and subsurface sediment traps. Results show a good correlation between the particle‐size distributions of atmospheric dust and the lithogenic particles settling to the deep ocean floor, confirming the aeolian origin of the lithogenic particles intercepted by the subsurface sediment traps, even in the distal western part of the Atlantic Ocean. Dust from both dry and wet deposition as collected by the sediment traps, shows increased deposition fluxes and coarser grain size in summer and/or autumn that coincides with increased precipitation at the sampling sites as derived from satellite data. In contrast, both buoys that sampled dust during transport at sea level show little seasonal variation in both concentration and particle size, as the large amounts of dust transported in summer and early autumn at high altitudes are far above their sampling range. This implies that wet deposition in summer and autumn defines the typical seasonal trends of both the dust deposition flux and its particle‐size distribution observed in the sediment traps.

Influence of Dust on the Initiation of Neoproterozoic Snowball Earth Events

AbstractIt has been demonstrated previously that atmospheric dust loading during the Precambrian could have been an order of magnitude higher than in the present day and could have cooled the global climate by more than 10 °C. Here, using the fully coupled atmosphere-ocean general circulation model CESM1.2.2, we determine whether such dust loading could have facilitated the formation of Neoproterozoic snowball Earth events. Our results indicate global dust emission decreases as atmospheric CO2 concentration (pCO2) decreases due to increasing snow coverage, but atmospheric dust loading does not change or even increases due to decreasing precipitation and strengthening June-July-August (JJA) Hadley circulation. The latter lifts more dust particles to high altitude and thus increases the lifetime of these particles. As the climate becomes colder and the surface albedo higher, the cooling effect of dust becomes weaker; when the global mean surface temperature is approximately -13 °C, dust has negligible cooling effect. The threshold pCO2 at which Earth enters a snowball state is between 280 to 140 ppmv when there is no dust, and is similar when there is relatively light dust loading (~4.4 times present-day value). However, the threshold pCO2 decreases dramatically to between 70 to 35 ppmv when there is heavy dust loading (~33 times present-day value), due to the decrease in planetary albedo which increases the energy input into the climate system. Therefore, dust makes it more difficult for Earth to enter a snowball state.

Sources and Level of Rare Earth Element Contamination of Atmospheric Dust in Nigeria.

Background.Rare earth element (REE) composition of atmospheric dust has recently been used to trace potential sources of dust pollution.Objective.The present study aimed to determine the sources of atmospheric pollution in the study area using REE patterns and determine their level of pollution.Methods.Twenty-five (25) atmospheric dust samples were collected in the study area, with five samples each from an industrial area, traffic area, dumpsite area, residential area and remote area in Ibadan, southwestern Nigeria. In addition, five (5) topsoil and two (2) rock samples (granite gneiss) were collected for comparison. Concentrations of REE were determined by inductively coupled plasma mass spectrometry (ICP-MS).Results.The ratio of lanthanum/cerium (La/Ce), especially in some locations in industrial area (1.5), traffic area (1.5) and to some extent dumpsite area (1.1) was higher than in soil (0.2), upper continental crust (0.5) and the minimum value of fluid catalytic crackers (1.0). Generally, the respective average values of the ratios of La/praseodymium (Pr), La/neodymium (Nd) and La/samarium (Sm) in industrial area (32.1, 7.8 and 52.6) and traffic area (14.9, 4.4 and 26.8) were higher than their respective averages in soil (4.4, 1.1 and 6.2), rock (5.7, 1.9 and 14.1), upper continental crust (4.4, 1.1 and 6.6) and the minimum value in fluid catalytic crackers (5.8, 3.7 and 37.0). Meanwhile, their corresponding value in the dumpsite area, residential area and remote area were lower or similar to the geological background levels.Discussion.The contamination factors of REEs in the atmospheric dust of the industrial area and traffic area were classified as heavily contaminated, especially with light lanthanoid elements in REE. The degree of contamination of REEs in the atmospheric dust of industrial area (30.9) and traffic area (18.8) fell within the considerable contamination category. The high values of the light lanthanoid ratio and the contamination indices were attributed to their emission from the fired-power plant and vehicular exhaust.Conclusions.Most of the composition of the atmospheric dust was sourced from the local geology of the study area as observed in the residential area and remote area, while the contamination in the industrial area and traffic area was attributed to human activities.Competing Interests.The authors declare no competing financial interests.

Thermophysical Properties and Surface Heterogeneity of Landing Sites on Mars From Overlapping Thermal Emission Imaging System (THEMIS) Observations

AbstractOrbitally derived thermal inertia (TI) values of surfaces allow for remote interpretation of rock and sediment physical characteristics. The evolving local times of the Mars Odyssey Thermal Emission Imaging System (THEMIS) mission have enabled surface temperature data collection over multiple seasons and local times over ∼9 Mars years (MY). We utilize this higher temporal resolution data set to separate TI values of individual materials within THEMIS pixels (100 m sampling). In this study, we focus on geologic units within Gusev, Gale, and Jezero crater landing sites to determine their respective TI and ground‐truth our methods. We use the KRC model to predict temperatures for a range of homogeneous and two‐component thermophysical mixing scenarios (laterally and vertically heterogeneous), and compare those to THEMIS brightness temperatures. The Gusev and Gale crater results are consistent with rover‐based evaluations, indurated or clast‐covered sands. The best‐fit scenarios along the Jezero crater volcanic floor unit show low to moderate TI values representative of coarse sediment, volcaniclastic, or pyroclastic rocks. The light toned unit and western fan deposits both indicate sands and a moderate TI component; we interpret this as heavy fracturing within the rock. Difficulties in modeling some THEMIS temperatures are attributed to daily weather effects, local atmospheric dust variability, and real surface changes over time (e.g., dust deposition and removal); we also observe that some temperature observations lead to non‐unique modeled physical solutions. Nevertheless, these methods can still rule out a significant range of material properties and provide meaningful geologic information about Mars’ surface.

Temporal and spatial distributions and sources of heavy metals in atmospheric deposition in western Taihu Lake, China

Heavy metals in atmospheric dust can directly pollute the soil, water and sediment, causing serious harm to human health. In this study, the temporal and spatial distribution characteristics of heavy metals in atmospheric deposition in western Taihu Lake were studied. We established 10 sampling sites to collect atmospheric deposition for two years in different seasons. The atmospheric deposition flux follows the order urban area (95.6 g m−2·a−1) > suburban area (80.2 g m−2·a−1) > forestland (56.8 g m−2·a−1). The concentrations of heavy metals in atmospheric deposition show trends of high values in the winter and low values in the summer and are significantly negatively correlated with distance from the city. The pollution level of Igeo-Cd is 6, which is very high, and that of E-Cd is 219, which means high risk. Heavy metals in atmospheric deposition are mainly taken up via hand-mouth intake, and the harm to children is significantly higher than the harm to adults. The highest health risk assessment values for the four analyzed heavy metals in atmospheric deposition are located near the city and in suburbs (within 5 km of the city center), that is, in areas where human activities are concentrated. The health risk assessment values in areas outside the suburbs are low; these areas are less affected by human activities. The health risk assessment values of heavy metals in the winter and spring are higher than those in the summer and autumn. The Pb isotope ratios show that the main sources of heavy metals in atmospheric deposition and local soil are human activities, such as industry and coal combustion, with less input from natural sources. Heavy metals in atmospheric deposition in the western part of Taihu Lake not only directly threaten local human health but also enter Taihu Lake, posing a serious threat to the Taihu Lake ecosystem.

WRF-Chem Simulation for Modeling Seasonal Variations and Distributions of Aerosol Pollutants over the Middle East

Atmospheric aerosols and dust have become a challenge for urban air quality. The presented study quantified seasonal spatio-temporal variations of aerosols, tropospheric ozone, and dust over the Middle East (ME) for the year 2012 by using the HTAP emission inventory in the WRF-Chem model. Simulated gaseous pollutants, aerosols and dust were evaluated against satellite measurements and reanalysis datasets. Meteorological parameters, temperature, and wind vector were evaluated against MERRA2. The model showed high spatio-temporal variability in meteorological parameters during summer and low variability in winter. The correlation coefficients for all the parameters are estimated to be 0.92, 0.93, 0.98, and 0.89 for January, April, July, and October respectively, indicating that the WRF-Chem model reproduced results very well. Simulated monthly mean AOD values were maximum in July (1.0–1.5) and minimum in January (0.1–0.4) while April and October were in the range of 0.6–1.0 and 0.3–0.7 respectively. Simulated dust concentrations were high in April and July. The monthly average aerosol concentration was highest over Bahrain, Kuwait, Qatar, and the United Arab Emirates and Jeddah, Makkah. The contributions to urban air pollution were highest over Makkah city with more than 25% from anthropogenic sources.

Improving resolution in imaging through obscuring media with early-time diffusion signals.

A short pulse propagating through a medium consisting of randomly distributed scatterers, large compared to the wavelength, is expected to develop an "early-time diffusion" (ETD) behavior: a sharply rising structure in the time-resolved intensity, immediately following the coherent (ballistic) component. Since the ETD signal is attenuated at a rate substantially lower than the coherent wave, it offers a possibility of application in imaging through diverse scattering media, such as atmospheric obscurants (clouds, fog, mist), dust, aerosols, fuel sprays, or biological tissues. We describe here a two-way (reflection) imaging scenario utilizing the ETD phenomenon, and propose a specific image formation technique. We evaluate, by using the radiative transport theory, the resulting point-spread function (PSF) characterizing the image resolution. We show that the directly formed image has an angular resolution comparable to the width of the forward peak in the ensemble-averaged scattering cross section of the medium constituents. Subsequently, we show that, through the application of a regularized deconvolution technique enhancing higher Fourier components of the PSF, the resolution can be further significantly improved-at least by a factor of ${\sim}4$ for a medium layer of optical thickness of the order of 20. Such an improvement can be reached even if the noise level is a few orders of magnitude higher than the coherent (ballistic) image component.

Outdoor/Indoor Contaminant Transport by Atmospheric Dust and Aerosol at an Active Smelter Site

Activities associated with mining operations including smelting, ore handling, and mine tailings management have been identified as sources of dust and aerosol that may contain metal and metalloid contaminants, such as lead (Pb) and arsenic (As). Previous studies on contaminant transport have concentrated on the potential impact of these particulate emissions in outdoor environments. The purposes of this study were (i) to quantify the effect of dust and aerosol particle size on contaminant transport from outdoor-to-indoor environments and (ii) to document the changes in particle chemical composition during transport through the outdoor/indoor barrier. Outdoor and indoor particulate samples were collected at a high school equipped with mechanical air filtration systems from 2016 to 2019. The school is located near a set of mine tailings and an active copper smelter in Hayden, Arizona. Particle size segregated samples were collected using a ten-stage micro-orifice uniform deposit impactor (MOUDI). Results show that airborne fine particles (aerodynamic diameters less than 1 micron) can penetrate to the indoor environment but in a reduced amount due to mechanical filtration. Aerosol in the fine fraction particulate air concentrations was around 50% of the corresponding outdoor values, but their mass concentration of contaminants was similar to outdoor values. Indoor coarse particles (> 1 micron) comprised close to 20% of the levels found in outdoor coarse particles. These results highlight the need to consider the impact of particle diameter when assessing indoor exposure and potential health effects in communities living under the direct influence of mining and smelter activities.

ДОСЛІДЖЕННЯ МОДЕЛІ ПЕРЕДБАЧЕННЯ ПОТУЖНОСТІ, ЩО ГЕНЕРУЄТЬСЯ СОНЯЧНОЮ ЕЛЕКТРОСТАНЦІЄЮ

The question of determining the possible capacity of a photovoltaic power plant is very acute due to the growing demand for renewable energy, coupled with the fact that during the day we have limited time to generate energy from such a source. Thus, based on the obtained analytical data, which allows to predict weather conditions, it is possible to regulate the amount of energy supplied to the network in a certain way due to more maneuverable power plants. In previous years, electrical engineering scientists and researchers from different countries have developed and implemented methods for determining weather conditions, such as clouds, air temperature, atmospheric dust and others, as well as their impact on the energy output of a solar power plant. A photovoltaic panel is a complex nonlinear object with many variables. In addition to the structural features of the module, the output is most affected by solar radiation and panel temperature. When researching the prediction of the amount of energy produced, it is important to find sufficiently reliable and consistent data. At the forefront of these issues are US universities and research centers. For example, the University of Nevada in Las Vegas, in 2006 put into operation a set of measurements of weather conditions: the level of sunlight, ambient temperature, wind speed, humidity and others. When calculating the power generated by the panels, it is assumed that the system operates at the point of maximum power. The scheme works as follows: we set the values of temperature (Temperature) and irradiation (Irradiance); we apply voltage to the output terminals of the array by changing its value from 0 to Voc. We take current readings at each point, we find the power for each point, we find the maximum among the obtained array of points. Repeat over the entire range of input values. Thus, we obtain a graph of the output power of Figs. 4 pre-considering the losses in the inverter.

The Effect of Dust Transport on the Concentration of Chlorophyll-A in the Surface Layer of the Black Sea

This paper focuses on the atmospheric dust transport effect on the changes in chlorophyll-A concentration in the Black Sea surface layer. In order to assess the input of nutrients with atmospheric precipitations at the Crimean coast of the Black Sea, the collected samples were analyzed for the content of inorganic nitrogen, phosphates, and silicon. The samples were taken into a wet-only sampler and into a permanently open one, to assess the effect of dust on the nutrients concentration in dry depositions. Cases of multi-fold excess of the nutrients content in the open sampler collected precipitation over that in the wet-only sampler were identified. For such high concentration cases, the 7-day back-trajectories analyses was carried out using the model of the international network AERONET and the HYSPLIT model. The results of our research showed that the influx of nutrients with the atmospheric depositions can result in increasing of chlorophyll-A concentration in 11–36% in the surface layer of the Black Sea. After atmospheric depositions, concentration of phosphates in the surface layer can increase more than five times compared with the background concentration. The increase of silicon concentration can reach 30%. The influx of atmospheric precipitation containing significant amounts of nutrients into the bay can shifts the Redfield ratio compared with background value up to three times.

Spatiotemporal variations and long term trends analysis of aerosol optical depth over the United Arab Emirates

This research provides a comprehensive long term time series analysis of the spatiotemporal variability of aerosol optical depth (AOD) over the United Arab Emirates (UAE) using MODIS (Moderate-resolution imaging spectroradiometer) MAIAC (Multi-Angle Implementation of Atmospheric Correction) AOD (aerosol optical depth) product for the period 2003–2018. The UAE is located in one of the driest places on earth, the Arabian Peninsula, with two large extended desert regions that form major atmospheric dust sources in the world. The atmospheric dust emitted by these vast deserts is transported locally and regionally and it is the primary major contributor to the overall aerosol optical depth in this area. The investigation of the spatiotemporal trends of AOD over the UAE showed a significant obvious annual seasonal variability. Results showed a significant increase in AOD during summer due to high wind speed, resulting in scattered events of small to large scale haboobs within the study area, high temperature, and high relative humidity. The increased humidity levels are due to increased temperatures in the summer season leading to significant evaporation from the neighbouring water bodies (mainly the Arabian Gulf and the Sea of Oman) leading to a significant increase in water vapour levels in the atmosphere. Summar AOD values during the study period ranged between 0.42 – 0.73. The second highest AOD was observed in spring followed by winter. Spring AOD values ranged between 0.33-0.58 and winter values ranged between 0.25 – 0.41. The spatial distributions of AOD showed higher values over the coastal and desert areas. Coastal areas portrayed higher values as well likely due to the high levels of evaporation and increased anthropogenic activities such as coastal urban developments and automobile pollution. Time series analysis of the multitemporal dataset confirmed the SARIMA forecast model as the best fit which can be used to provide an accurate and reliable monthly forecast for the AOD concentrations in the UAE.

Diversity and Sources of Airborne Eukaryotic Communities (AEC) in the Global Dust Belt over the Red Sea

Airborne eukaryotic communities (AEC), rank among the least studied aerobiological components, despite their adverse impacts on human health and the environment. Here, we describe the AECs in the global dust belt, the area between the west coast of North Africa and Central Asia, which supports the highest dust fluxes on the planet. We sampled atmospheric dust over 14 months (fall 2015–fall 2016) from onshore and offshore locations of the Red Sea, the only waterbody that entirely encompassed in the global dust belt. We also sampled surface water samples to determine the potential transfer of taxa across the air-sea interface. To target the eukaryotes, we performed Miseq sequencing of atmospheric dust and surface water samples. Analysis of amplicon sequencing indicates a total pool of 18,816 sequence variants (SVs). Among 33 unique eukaryotic phyla in the AEC over the Red Sea, the most dominant taxa were Streptophyta, Apicomplexa, and Ascomycota. Aerosol eukaryotes originated from various sources and formed more diverse communities than eukaryotic communities of the Red Sea surface water. AECs were dominated by phylotypes released from plant material and soils, and including taxa reported to be harmful to human health. The AEC composition was significantly influenced by sampling locations and seasonal conditions but not by the origin of the air masses nor dust loads. This work is original and uses state-of-the-art methods and very powerful NGS- bioinformatics and statistical approaches. The selected study site has high interest and it has been well chosen because of the unique combination of high loads of dust deposition, being the only fully contained seawater body in the area acting as a sink for the atmospheric dust, and the lack of riverine inputs and watershed effects empathizing the role of atmospheric inputs in the ecology of the system.

Deforestation strengthens atmospheric transport of mineral dust and phosphorus from North Africa to the Amazon

AbstractPhosphorus contained in atmospheric mineral dust aerosol originating from Africa fertilizes tropical forests in Amazonia. However, the mechanisms influencing this nutrient transport pathway remain poorly understood. Here we use the Community Earth System Model to investigate how large-scale deforestation affects mineral dust aerosol transport and deposition in the tropics. We find that the surface biophysical changes that accompany deforestation produce a warmer, drier and windier surface environment that perturbs atmospheric circulation and enhances long-range dust transport from North Africa to the Amazon. Tropics-wide deforestation weakens the Hadley circulation, which in turn, leads to a northward expansion of the Hadley cell and increases surface air pressure over the Sahara Desert. The high pressure anomaly over the Sahara, in turn, increases northeasterly winds across North Africa and the tropical North Atlantic Ocean, which subsequently increases dust transport to the South America continent. We estimate that the annual atmospheric phosphorus deposition from dust significantly increases by 27% (P < 0.01) in the Amazon under a scenario of complete deforestation. These interactions exemplify how land surface changes can modify tropical nutrient cycling, which in turn, may have consequences for long-term changes in tropical ecosystem productivity and biodiversity.