Atmospheric Dust Research Articles

Research on the Physicochemical Properties of Fine Particulate Matter in Changchun, Northeast China

Objective: Air particulate matter concentrations in Changchun City, Jilin Province, may change around the autumn heating day. The aim of this study was to provide data references for environmental protection, detection and regulation in Changchun. Methods: Atmospheric particulate matter samples were collected using an airborne particulate matter sampler on the roof top of the Civil Engineering Teaching Hall on the campus of Jilin University of Construction; free settling dust of Atmospheric particulate matter was collected using metal trays. Atmospheric particulate matter concentrations were analysed by manual detection methods (weight method), carbonaceous fractions by total organic carbon analyser, and atmospheric fallout material composition and crystal structure by XRD diffractometer. The physicochemical properties of fine particulate matter around the autumn heating day in Changchun were investigated. Conclusions: (1) The daily average concentrations of various types of atmospheric particulate matter PM1, PM2.5 and PM10 generally increased after the start of the heating period. However, air quality is influenced by a combination of meteorological factors, of which emissions of air pollutants from urban heat generating plants during the heating period is only one aspect. So there is a situation where the average daily concentration of atmospheric particulate matter is lower after heating than before. (2) Analysis of the atmospheric its particulate matter PM2.5 samples collected around the heating day showed that the daily average concentrations of organic carbon (OC) and elemental carbon (EC) of atmospheric its particulate matter PM2.5 increased significantly after the heating day. (3) There was no significant difference in the main components of atmospheric dust fall before and after the heating day in Changchun, with the main components being crystalline SiO2 and a small Number of impurities.

Implications of strontium isotope and trace element variability in New Zealand kauri (Agathis australis)

New Zealand kauri trees are an important dendrochonologic resource in the southern hemisphere due to their long lifespans and the correlation of ring widths to El Niño - Southern Oscillation (ENSO)-events. This study represents the first chronology-constrained dendrochemical investigation of New Zealand kauri. Strontium isotope (87Sr/86Sr) and trace element analyses are combined to determine the potential for provenance (spatial) and environmental (temporal) dendrochemical investigations utilizing the geochemistry of kauri wood. Soil Sr isotopic measurements match 80% of the corresponding analyses from local trees and two of the four study sites have kauri isotopic compositions tightly clustered and distinctive, supportive of provenance investigations. The two sites which record inter-tree isotopic variability, a combination of variables, including geologic, atmospheric (dust and sea spray), and anthropogenic (land-use), all likely influence the isotopic and trace element variations. Discrete annual events or fluctuating conditions are difficult to observe from the isotopic tree ring record, reflecting the potential mobility of Sr within tree rings. However, the preservation of long term geochemical trends suggest processes such as climate change or anthropogenic soil modification may still be preserved in the kauri record.

Reliability assessment and paleo-oceanographic signals of geochemical and isotopic indicators in the North Pacific Subtropical Gyre

As the largest marine ecosystem on our planet, the North Pacific Subtropical Gyre (NPSG) plays an important role in global environmental and climate change. However, little is known about its environmental changes in an orbital scale. In this study, a constant flux model with excess 230Th was used to establish a time frame for our sediment core. Several geochemical and isotopic indicators were evaluated for their reliability in reconstructing paleoenvironment, including grain size distribution (GSD), Ti, Cu, Zn, Ba, total organic carbon (TOC), total nitrogen (TN), TOC/TN ratio, organic carbon and nitrogen isotopic composition (δ13C, δ15N). In addition, appropriate indicators were used to reveal changes in atmospheric dust deposition and biological productivity during the glacial and interglacial periods in the NPSG. Our results show that in such a low sedimentary environment, TOC, TN, TOC/TN ratio, δ13C, δ15N, Cu and Zn has been altered with the degradation of organic matter in the early diagenesis process. In contrast, GSD and Ti-derived eolian dust flux (Feolian) are suitable indicators for atmospheric dust deposition, and the mass accumulation rate of biogenic silica (MARBSi) and the deposition flux of excess Ba after correction for diffusion (Fexess Ba) are suitable for the reconstruction of biological productivity. The productivity during the glacial periods of Marine Isotope Stage (MIS) 2–4 and 6 is higher than the interglacial periods of MIS 1, 5, which corresponds well to the coarser dust particles and higher eolian dust supply. Therefore, we propose that different with former works in the subtropical Pacific, the fluctuations in productivity in the NPSG is mainly controlled by atmospheric dust deposition on a millennial scale.

Rare earth element geochemistry in soils along arid and semiarid grasslands in northern China

BackgroundRare earth elements (REE) are a group of trace elements that behave geochemically coherently. REE fractionation patterns normalized to reference materials provide a powerful tool for documenting pedogenesis. In-soil processes are particularly difficult to illustrate with respect to contemporary and past climate conditions. In this study, we characterize the rare earth element (REE) contents in bulk soils and respective geochemical fractions (e.g., exchangeable, carbonate-bound, reducible, and oxidizable fractions) and to decipher the relationships between REE geochemistry components and climatic factors across a large-scale northern China transect (NCT).ResultsAcross the NCT, bulk REE concentrations ranged from 55.2 to 241.1 μg g−1 with a main portion in the residual fraction (49–79%), followed by oxidizable fraction (2–40%), reducible fraction (3–22%), carbonate-bound fraction (0.1–16%), and negligible exchangeable fraction. The REE contents of geochemical components (carbonate-bound, reducible, and oxidizable) in topsoils correlated to climate factors (mean annual precipitation, mean annual temperature, potential evaporation, and aridity index (AI)). The normalized abundances to the upper continental crust (UCC) composition show that the middle REE was generally enriched than the light REE and heavy REE in topsoils along the transect. The overall UCC-normalized bulk REE patterns in topsoils and subsoils were similar, characterized by weak negative Ce anomalies and positive Eu anomalies.ConclusionsOur data in topsoils and depth profiles collectively suggest that cycling of REE was primarily regulated by abiotic processes in area with AI < 0.2, while the biological effect on REE circulation in soil played a more effective role in area with AI > 0.3. The similar UCC normalized patterns in topsoils suggest that the REE was originated from a common source with limited influences from other sources (e.g., atmospheric dusts and anthropogenic contributions). Our results to some extent provide evidence for climatic influence REE distribution patterns both in topsoils and subsoils across the continental-scale transect. Our investigation gives insights into future studies on vertical REE mobility and its associated biogeochemical pathways.

Surrogate atmospheric dust particles generated from dune soils in laboratory: Comparison with field measurement

Desert dust strongly influences the climate and the environment by altering the radiation budget, participating in atmospheric chemical reactions, and engaging the biogeochemical cycle. Studying its impacts requires knowledge of the physical and chemical properties of the original particles from the source origin. Unfortunately, the field collection of atmospheric samples in the desert is impractical. Fine surface soil is thus considered an alternative material from which to obtain the information applicable to dust particles from the desert soil. In this study, a laboratory system was set up to generate dust particles with simulated natural wind erosion processes from surface soils or directly from desert surfaces. Surface soils and field dust were simultaneously collected during a local blowing dust event. The comparison between the laboratory-generated dust and the field dust showed a consistent trend in particle size distribution and chemical composition. The chemical compositions were found to have explainable differences with the Certified Reference Materials for Asian dust (CJ-2). The laboratory-generated dust particles with the system could be applied as surrogates for soil-emitted dust in desert areas.

Influence of dust deposition, wind and rain on photovoltaic panels efficiency in Arequipa – Peru

ABSTRACT The present study the influence of dust, wind and rain on the performance of a photovoltaic was evaluated. To determine efficiency of panels influenced by external factors, a system was designed and installed, voltage, electric current, solar irradiance and temperatures were measured. Three types of dust were used to simulate the atmospheric dust; cement, ashlar and clay. Parameter considered for deposition of the powders was surface density (g/m2). Particle size was determined by granulometry, samples were analyzed by SEM/EDS. For the wind factor, three speeds were determined within a range of average speeds recorded in urban areas, tests were carried out in natural rain conditions. Results show that 06:00 a.m. to 5:30 p.m. energy generation efficiency of panels decreases due to increase of dust deposition. As well, it is shown that influence of wind increases efficiency slightly and that the performance of panels is directly influenced in rainy conditions.

Development and Evaluation of Dust Cleaning System for a Solar PV Panel

The most promising application of solar energy is the conversion of solar energy into electrical energy by using solar photovoltaic (PV) panel. The performance of solar based PV panel is definitely influenced by the amount of solar radiation, which are reaching on the panel surface. Since the solar PV panels are operating in open atmosphere dust particles get deposited on their surfaces and most of the times they have to work in this condition. These deposited dust particles create a layer of dust particles over the panel surface which prevents the 100% penetration of solar radiation into the panel surface. Therefore, proper cleaning of the panel surface becomes very necessary. In order to improve the performance of the PV panel an automatic microcontroller driven dust cleaning technique is developed which is capable of removing the accumulated dust particles from the PV panel surface. Moreover, an experimental study has been performed to analyse the efficiency of this developed techn ique. The developed cleaning system showed an improvement of 27.98% in the output power of PV panel when compared to the dusty panel.

Martian atmospheric water vapor abundances in MY26-30 from Mars Express PFS/LW observations

I report on retrievals of water vapor abundances in the Martian atmosphere using observations by Planetary Fourier Spectrometer Long Wavelength channel (PFS/LW) aboard the Mars Express (MEx) spacecraft. PFS/LW observations used in this work cover almost 4 Martian Years from Ls ~ 331° in MY26 (January 2004) to Ls ~ 209° in MY30 (December 2010). Vapor abundances were retrieved from nadir spectra collected over a range of latitudes, seasons and local hours. Most of the retrieved abundances correspond to daytime observations at local hours from 8 to 17 h. The spatial and temporal coverage of retrieved abundances varies significantly between years of observations, with the best coverage in MY27 and MY29. The average annual water vapor cycle observed by PFS/LW is qualitatively similar to the cycle observed by the Thermal Emission Spectrometer (TES) onboard Mars Global Surveyor (MGS), however the PFS/LW abundances are systematically lower. The likely reason for this difference is the difference in the respective water vapor absorption models. Comparison between PFS/LW abundances for time periods with low atmospheric dust opacity between different years of observations does not show significant interannual variability. PFS/LW abundances are significantly lower than the abundances retrieved from observations by Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on Mars Reconnaissance Orbiter (MRO) in MY29. The difference is likely due to the differences in retrieval models for different spectral regions used by CRISM and PFS/LW to retrieve water vapor abundances and due to different environmental parameters used in the retrievals. PFS/LW abundances are generally similar to abundances retrieved by the SPICAM IR instrument, except in the polar regions during summer. The difference likely arises because of non-uniform vertical distribution of water vapor in the summer polar atmospheres and different sensitivities of the two instruments to vertical distribution of vapor. The PFS/LW observed systematic longitudinal dependence of scaled vapor abundances in the northern tropics with two maxima at longitudes ~30–60°E and ~ 240–270°E. This longitudinal dependence resembles a standing wave forced in the local atmospheric flow by topography and surface thermo-physical properties. The longitudinal non-uniformity of water vapor possibly shows a seasonal dependence increasing around solstices and decreasing around equinoxes. During northern spring in the Northern Polar Region (NPR) PFS/LW observed an increase of vapor near the edge of the seasonal cap interpreted as a buildup of vapor by repeated cycles of water ice freezing and sublimation at the cap edge. Similar, but weaker and longitudinally non-uniform increase in vapor near the edge of the seasonal cap is observed in the Southern Polar Region (SPR) during spring. Tentative signs of water vapor diurnal variability were observed in the PFS/LW data over northern mid-latitudes during late spring and early summer, potentially reflecting vapor exchange between the regolith and the atmosphere.

Investigation of Indoor and Outdoor Fine Particulate Matter Concentrations in Schools in Salt Lake City, Utah

Although there is mounting evidence that suggests that air pollution is impactful to human health and educational outcomes, this is especially problematic in schools with higher air pollution levels. To understand whether all schools in an urban area are exposed to similar outdoor air quality and whether school infrastructure protects children equally indoors, we installed research-grade sensors to observe PM2.5 concentrations in indoor and outdoor settings to understand how unequal exposure to indoor and outdoor air pollution impacts indoor air quality among high- and low-income schools in Salt Lake City, Utah. These data and resulting analysis show that poor air quality may impact school settings and the potential implications with respect to environmental inequality. Based on this approach, we found that during atmospheric inversions and dust events, there was a lag ranging between 35 and 73 min for the outdoor PM2.5 concentrations to follow a similar temporal pattern as the indoor PM2.5. This lag has policy and health implications and may help to explain rising concerns regarding reduced educational outcomes related to air pollution in urban areas.

Impact of dust addition on the microbial food web under present and future conditions of pH and temperature

Abstract. In the oligotrophic waters of the Mediterranean Sea, during the stratification period, the microbial loop relies on pulsed inputs of nutrients through the atmospheric deposition of aerosols from both natural (e.g., Saharan dust), anthropogenic, or mixed origins. While the influence of dust deposition on microbial processes and community composition is still not fully constrained, the extent to which future environmental conditions will affect dust inputs and the microbial response is not known. The impact of atmospheric wet dust deposition was studied both under present and future environmental conditions (+3 ∘C warming and acidification of −0.3 pH units), through experiments in 300 L climate reactors. In total, three Saharan dust addition experiments were performed with surface seawater collected from the Tyrrhenian Sea, Ionian Sea, and Algerian basin in the western Mediterranean Sea during the PEACETIME (ProcEss studies at the Air–sEa Interface after dust deposition in the MEditerranean sea) cruise in May–June 2017. Top-down controls on bacteria, viral processes, and community, as well as microbial community structure (16S and 18S rDNA amplicon sequencing), were followed over the 3–4 d experiments. Different microbial and viral responses to dust were observed rapidly after addition and were, most of the time, more pronounced when combined with future environmental conditions. The dust input of nutrients and trace metals changed the microbial ecosystem from a bottom-up limited to a top-down controlled bacterial community, likely from grazing and induced lysogeny. The relative abundance of mixotrophic microeukaryotes and phototrophic prokaryotes also increased. Overall, these results suggest that the effect of dust deposition on the microbial loop is dependent on the initial microbial assemblage and metabolic state of the tested water and that predicted warming and acidification will intensify these responses, affecting food web processes and biogeochemical cycles.

Uranium Isotopic Composition and Constraints on the Provenance of the Qinghai‐Tibet Plateau's Surface Dust

AbstractThe production and emission of aeolian dust can provide key information on the contemporary and historical links between geological evolution and climate. Here we use 234U/238U isotope ratios and the uranium (U) comminution age method on samples collected from Qinghai‐Tibet Plateau (TP) surface dust and glacier snowpack/cryoconites to determine the erosion and potential transport provenance of the dust, regardless of petrological origin. The spatial variation of the (234U/238U) isotope ratios of TP dust showed relatively high values in the Songpan‐Ganzi‐Hoh Xil, Himalayan and the Kunlun‐Qaidam‐Qilian terranes, while showing relatively low (234U/238U) values in Lhasa and Qiangtang terranes, but among all samples the highest value appeared in the glaciation zone. Dust collected from nearby glacial areas with rugged terrain (e.g., the Qilian and Himalayan Mountains) have higher (234U/238U) values than those collected in the topologically flat non‐glacial areas. These differences are consistent with elevated erosion rates and dust comminution‐transport processes in glacial areas, which yield a major source for large quantities of fresh comminuted particles. Compared to sediments from other regions of the globe, the (234U/238U) values of the typical aeolian sinks (such as loess on the Loess Plateau and ice core dust, etc.) are generally lower in comparison to areas with high elevations where erosion rates are high. The (234U/238U) isotope values of TP dust tend to fall between the high‐elevation sites and the dust sinks, indicating the combined influence of short comminution times (tectonics, landscape dynamics, and glacial erosion) and long residence time on the TP. When compared with other central Asian dust sources, U‐Nd‐Sr isotope signatures in TP dust are distinct and can be thus used as an effective tracer of dust provenance. Using U isotopes, we show that dust originating from the TP undergoes long‐range transport and constitutes potentially significant component of the Asian and Northern Hemisphere atmospheric dust load.

Aerosol iron speciation and seasonal variation of iron oxidation state over the western Antarctic Peninsula

The iron (Fe) speciation and oxidation state have been considered critical factors affecting Fe solubility in the atmosphere and bioavailability in the surface ocean. In this study, elemental composition and Fe speciation in aerosol samples collected at the Palmer Station in the West Antarctic Peninsula were determined using synchrotron-based X-ray fluorescence (XRF) and X-ray Absorption Near-Edge Structure (XANES) spectroscopy. The elemental composition of coarse-mode (>1 μm) Fe-containing particles suggests that the region's crustal emission is the primary source of aerosol Fe. The Fe minerals in these aerosol particles were predominantly hematite and biotite, but minor fractions of pyrite and ilmenite were observed as well. The Fe oxidation state showed an evident seasonal variation. The Fe(II) content accounted for 71% of the total Fe in the austral summer, while this fraction dropped to 60% in the austral winter. Multivariate linear models involving meteorological parameters suggested that the wind speed, relative humidity, and solar irradiance were the factors that significantly controlled the percentage of Fe(II) in the austral summer. On the contrary, no relationship was found between these factors and the Fe(II) percentage in the austral winter, suggesting that atmospheric photoreduction and regional dust emission were limited. Moreover, the snow depth was significantly (p < 0.05) correlated with the aerosol Fe concentration, confirming the limiting effect of snow/ice cover on the regional dust emission. Given that the Antarctic Peninsula has experienced rapid warming during recent decades, the ice-free areas in the Antarctic Peninsula may act as potential dust sources.

Uranium isotopes of aeolian dust deposited in northern Tibetan Plateau glaciers: Implications for tracing aeolian dust provenance

Asian dust comprises a large portion of the northern hemisphere atmospheric dust load, thereby exerting substantial influence on the Earth's climate, global biogeochemistry and hydrological cycle through accelerated snow and ice melt. Dust deposited on alpine glaciers encodes information on broad scale atmospheric-environmental processes. The (234U/238U) values of dust fine particulates can reflect the comminuting time and intermediate processes; thus, it provides a new method for the provenance of aeolian dust in the glacial snowpack/cryoconite. Here we present results from a comprehensive survey of uranium isotopic concentrations in dust collected from cryoconites on the glaciers of the northern Tibetan Plateau (TP). These results indicate significant spatial heterogeneity in the (234U/238U) values associated with snowpack/cryoconite dust over a broad range of glaciers in the northern TP. The values of the (234U/238U) ratio in the glaciers of western Qilian Mountains (Qiyi Glacier, Shiyi Glacier, Laohugou Glacier No.12) were the highest, followed by the Tanggula (Dunkemadi Glacier) and Kunlun Mountains (Yuzhufeng Glacier), whereas these values were the lowest in the eastern Qilian Mountains (Jingyangling Snowpack, Dabanshan Snowpack, Lenglongling Glacier). By including the analysis of Sr-Nd isotopic compositions, we find the spatial isotopic distribution reflects a combination of local dust, which is associated with short comminuting times, and dust transported over long ranges. Meteorological data indicate that the dust production in the west and north TP, Alxa arid lands and Gobi Deserts, may have a significant impact on the TP glaciers. Moreover, U-Sr-Nd isotopic composition and end-member mixing models (EMMA) were used in our study to find out the relative contribution of distinct Asian dust sources to the dust budget in the TP glaciers. The results reveal that snowpack/cryoconite dust is derived from both local sources (low comminution signatures) as well as other dust sources in the Asian region. Our study demonstrates the potential of U isotope composition as a dust tracing method. In particular, by investigating this composition on dust collected from glacier snowpack and cryoconite holes, we arrive at a map of the distribution characteristics of (234U/238U) values in different regions of the TP. Our study is the first to deploy uranium comminution age for Tibetan dust source tracing, and the results are important to elucidate the multiple origins and dynamics of dust in the Tibetan Plateau.

The analysis of pre-monsoon dust storm over Delhi using ground-based observations

Three major sequential widespread dust events were experienced in the northern parts of India in May 2018. A significant impact of these pre-monsoon dust storms on the aerosol characteristics over the Indian National capital region (NCR) has been studied using remotely sensed ceilometer and ground-based measurements at Indira Gandhi International airport, New Delhi, India. The results show that after each dust activity, the significant inclusion of dust aerosols loaded in the free troposphere. Consequently, the direct impact on the lower atmospheric parameters like increase in daily average temperature (by 4–5 K), stepped up (stepped down) diurnal cycles of longwave fluxes (shortwave fluxes), has been recorded within 15 days of dust span. Mainly, the adverse meteorological and radiation features noticed before the first dust storm (DS1), which pinpoints the sudden dust intrusion over NCR, Delhi. However, this dust storm has extensively impacted on the atmospheric vertical dust loading, surface boundary layer mechanisms, and socioeconomic way. Therefore, the detailed analysis of vertical dust distribution and its interaction with mid-tropospheric processes has been carried by using the vertical normalized attenuated backscatter coefficients accompanying the radiosonde observation. The aloft floating dust layer up to 3–4 km has been noticed even after shallow rainfall and persisted at almost the same height for the next 34 h due to low-level clouds. Meanwhile, the sub-dust layer below 1 km is formed due to local activity, which also sustains for a long time.

Not all gravel deserts in northern China are sources of regionally deposited dust

Loess and dust deposits are the longest and best-preserved terrestrial record of climate changes available, and one of the most important records is the Chinese Loess Plateau. Ascertaining the provenance of the wind derived dust material is critical in our understanding of climate variations, atmospheric dust transport and controls on dust generation. To determine the dust sources of the CLP, major and trace element data have been obtained from 202 dust samples and compared to 122 published data of dust source regions throughout northwestern China. The results demonstrate that the northeastern Tibetan Plateau is the major dust source for the depositional desert, sandy land and loess regions (e.g. Badain Jaran Desert, Alxa Plateau, CLP). However, the Qilian Mountains causes some differences of dust sources for Lanzhou, Xi'an when compared with the CLP. The most important finding is that not all gravel deserts in north China are dust sources for loess sequences at Lanzhou, Xi'an and CLP, which means that previous dust emission quantity assessments may be overestimations. The northeastern Tibetan Plateau, Tarim, the middle and eastern area of the Hexi Corridor Desert, Heihe River Basin, Badain Jaran Desert, and the middle and east area of the Alxa Plateau are the main dust sources, supported by the geochemical characteristics of the samples, regional geomorphology, and near surface wind dynamics.

A North American dust emission climatology (2001–2020) calibrated to dust point sources from satellite observations

• Modelled Dust emission occurs mostly from the Great Plains and semi-arid deserts. • Wind friction changes spatially with varying vegetation roughness and surface winds. • Deserts relatively smooth, dust activated in areas prone to high wind speeds. • Great Plains relatively high winds, with dust vegetation roughness limited. Measurements of atmospheric dust have long influenced our understanding of dust sources and dust model calibration. However, assessing dust emission magnitude and frequency may reveal different dust source dynamics and is critical for informing land management. Here we use MODIS (500 m) albedo-based daily wind friction estimates to produce a new dust emission climatology of North America (2001–2020), calibrated by the novel use of dust point sources from optical satellite observations (rather than being tuned to dust in the atmosphere). Calibrated dust emission occurred predominantly in the biomes of the Great Plains (GP) and North American Deserts (NAD), in broad agreement with maps of aerosol optical depth and dust deposition but with considerably smaller frequency and magnitude. Combined, these biomes produced 7.2 Tg y -1 with contributions split between biomes (59.8% NAD, 40.2% GP) due to the contrasting conditions. Dust emission is dependent on different wind friction conditions on either side of the Rocky Mountains. In general, across the deserts, aerodynamic roughness was persistently small and dust sources were activated in areas prone to large wind speeds; desert dust emissions were wind speed limited. Across the Great Plains, large winds persist, and dust emission occurred when vegetation cover was reduced; vegetated dust emissions were roughness limited. We found comparable aerodynamic roughness exists across biomes/vegetation classes demonstrating that dust emission areas are not restricted to a single biome, instead they are spread across an ‘envelope’ of conducive wind friction conditions. Wind friction dynamics, describing the interplay between changing vegetation roughness (e.g., due to climate and land management) and changing winds (stilling and its reversal), influence modelled dust emission magnitude and frequency and its current and future climatology. We confirm previous results that in the second half of the 21st century the southern Great Plains is the most vulnerable to increased dust emission and show for the first time that risk is due to increased wind friction (by decreased vegetation roughness and / or increased wind speed). Regardless of how well calibrated models are to atmospheric dust, assuming roughness is static in time and / or homogeneous over space, will not adequately represent current and future dust source dynamics.

Thermal Structure and Aerosols in Mars’ Atmosphere From TIRVIM/ACS Onboard the ExoMars Trace Gas Orbiter: Validation of the Retrieval Algorithm

AbstractThe Atmospheric Chemistry Suite (ACS) onboard the ExoMars Trace Gas Orbiter monitors the Martian atmosphere through different spectral intervals in the infrared light. We present a retrieval algorithm tailored to the analysis of spectra acquired in nadir geometry by Thermal InfraRed channel in honor of professor Vassilii Ivanovich Moroz (TIRVIM), the thermal infrared channel of ACS. Our algorithm simultaneously retrieves vertical profile of atmospheric temperature up to 50 km, surface temperature, and integrated optical depth of dust and water ice clouds. The specificity of the TIRVIM data set lies in its capacity to resolve the diurnal cycle over a 54 sol period. However, it is uncertain to what extent can the desired atmospheric quantities be accurately estimated at different times of day. Here we first present an Observing System Simulation Experiment (OSSE). We produce synthetic observations at various latitudes, seasons and local times and run our retrieval algorithm on these synthetic data, to evaluate its robustness. Different sources of biases are documented, in particular regarding aerosol retrievals. Atmospheric temperature retrievals are found robust even when dust and/or water ice cloud opacities are not well estimated in our OSSE. We then apply our algorithm to TIRVIM observations in April–May 2018 and perform a cross‐validation of retrieved atmospheric temperature and dust integrated opacity by comparisons with thousands of colocated Mars Climate Sounder (MCS) retrievals. Most differences between TIRVIM and MCS atmospheric temperatures can be attributed to differences in vertical sensitivity. Daytime dust opacities agree well with each other, while biases are found in nighttime dust opacity retrieved from TIRVIM at this season.

Inferring iron-oxide species content in atmospheric mineral dust from DSCOVR EPIC observations

Abstract. The iron-oxide content of dust in the atmosphere and most notably its apportionment between hematite (α-Fe2O3) and goethite (α-FeOOH) are key determinants in quantifying dust's light absorption, its top of atmosphere ultraviolet (UV) radiances used for dust monitoring, and ultimately shortwave dust direct radiative effects (DREs). Hematite and goethite column mass concentrations and iron-oxide mass fractions of total dust mass concentration were retrieved from the Deep Space Climate Observatory (DSCOVR) Earth Polychromatic Imaging Camera (EPIC) measurements in the ultraviolet–visible (UV–Vis) channels. The retrievals were performed for dust-identified aerosol plumes over land using aerosol optical depth (AOD) and the spectral imaginary refractive index provided by the Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm over six continental regions (North America, North Africa, West Asia, Central Asia, East Asia, and Australia). The dust particles are represented as an internal mixture of non-absorbing host and absorbing hematite and goethite. We use the Maxwell Garnett effective medium approximation with carefully selected complex refractive indices of hematite and goethite that produce mass fractions of iron-oxide species consistent with in situ values found in the literature to derive the hematite and goethite volumetric/mass concentrations from MAIAC EPIC products. We compared the retrieved hematite and goethite concentrations with in situ dust aerosol mineralogical content measurements, as well as with published data. Our data display variations within the published range of hematite, goethite, and iron-oxide mass fractions for pure-mineral-dust cases. A specific analysis is presented for 15 sites over the main dust-source regions. Sites in the central Sahara, Sahel, and Middle East exhibit a greater temporal variability of iron oxides relative to other sites. The Niger site (13.52∘ N, 2.63∘ E) is dominated by goethite over the Harmattan season with a median of ∼ 2 weight percentage (wt %) of iron oxide. The Saudi Arabia site (27.49∘ N, 41.98∘ E) over the Middle East also exhibited a surge of goethite content with the beginning of the shamal season. The Sahel dust is richer in iron oxide than Saharan and northern China dust except in summer. The Bodélé Depression area shows a distinctively lower iron-oxide concentration (∼ 1 wt %) throughout the year. Finally, we show that EPIC data allow the constraining of the hematite refractive index. Specifically, we select 5 out of 13 different hematite refractive indices that are widely variable in published laboratory studies by constraining the iron-oxide mass ratio to the known measured values. The provided climatology of hematite and goethite mass fractions across the main dust regions of Earth will be useful for dust shortwave DRE studies and climate modeling.

Seasonal pollution and risk assessment of heavy metals in atmospheric dust from coal mining area

Seasonal pollution and risk assessment of heavy metals in atmospheric dust from coal mining area

Quantitative reconstruction of consecutive paleolake-level fluctuations by the groundwater recharged lake in the desert hinterland: A case study in the Badain Jaran Desert, Northwestern China

Quantitative reconstruction of consecutive paleolake-level fluctuations may help reconstruct lake evolution during the Holocene. However, the reconstruction of a groundwater recharged lake in a desert hinterland is challenging. In this study, 23 samples of lake bottom sediments were obtained from eight groundwater recharged lakes in the hinterland of the Badian Jaran Desert in northwest China to establish models between the grain size component and lake level. Our results showed that the four grain size components of the sediments could be separated using the Weibull function. The first two fine grain components (W1 and W2) were deposited in the atmospheric dust. The two coarser components (W3 and W4) could be interpreted as sediments transported by wind from the surrounding sand dunes, while W3 was subsequently redistributed by lake waves. Changes in the lake water depth could be expressed by the W1 and W2 component contents, as well as the modal size of W3. Using the above models, unmixing grain size components of the lake sediment obtained from the ZZH section located in a seasonal lake (Zhunzhahan Jaran Lake) in the desert hinterland were used to quantitatively reconstruct the lake-level fluctuations during the Holocene. The lake level frequently fluctuated between 3.82 and 9.21 m during 10.6–8.6 cal kyr BP, slightly fluctuated between 3.41 and 5.26 m during 8.6–4.7 cal kyr BP, and markedly declined from 6.09 m to 4.46 m during 4.7–3.5 cal kyr BP. Lake-level changes in the hinterland of the Badian Jaran Desert did not correspond to the effective moisture changes during the early Holocene. Instead, the rise in lake level during the early Holocene would have resulted from the input of groundwater from the meltwater in the mountains of the recharge area. The data reveal new methods for quantitatively reconstructing consecutive paleolake-level fluctuations by groundwater recharged lakes in the desert hinterland.