Dust Deposition Rates Research Articles

Dust Deposition at Zhurong Landing Site From Multispectral Camera Observations

AbstractDust deposition is one of the most predominant processes occurring on Mars. Until now, just a few in situ observations have been conducted to investigate the Martian dust. The Multispectral Camera (MSCam) onboard the Zhurong rover with its calibration target can be used to monitor dust deposition, providing a new ground observation. In this work, we focused on the observations of the MSCam calibration target to retrieve atmospheric optical depth and dust deposition rate over the first 300 sols. The derived atmospheric optical depths are around 0.44, suggesting relatively low airborne dust. The estimated dust deposition rate reveals a distinctive deposition process compared with that of other rovers or landers. Notably, no evident dust is presented during the initial 110 sols, after which dust starts to accumulate. Combining in situ meteorological measurements and numerical modeling, wind speed could be a critical factor to control the dust deposition rate.

A novel four-stage integrated GIS based fuzzy SWARA approach for solar site suitability with hydrogen storage system

The hydrogen storage system is a suitable solution to solve the periodic nature of solar energy. In this study, a new four stage comprehensive framework based on Geographical information system (GIS) and fuzzy multicriteria decision-making (MCDM) is presented to identify suitable areas for developing solar power plant (SPP) in one of the dust-prone areas of Iran, Yazd province. High-resolution remote sensing data along with organization datasets are used to exclude inappropriate areas using GIS approach. Also, a new application of the SWARA method is introduced to prioritize solar sites by considering the uncertainty in the fuzzy environment. The considered criteria include economic (proximity to the settlements, roads and transmission lines), geography (slope and aspect) and technical criteria (global horizontal irradiance, temperature, dust optical thickness and dust deposition rate). The results showed that 55% of the area is unsuitable for the development of a SPP due to environmental, dust characteristics and topography limitations. Also, 13.8%of the area has a moderate suitability, 26.8% of it has a good suitability and only 4.5% of it has an excellent suitability. In addition, the building SPP in suitable areas in Yazd province has the potential to produce 6926.2 TWh/yr of electricity and 112 Mton/yr of hydrogen.

Dust temporal and spatial deposition affected by climate and soil mineralogical and chemical properties in a semi-arid area

The important process of aerosol dusting is of economic, environmental and heath significance. The objective was to investigate the climatic parameters including rainfall (R), wind speed (WS), temperature (T), and relative humidity (RH), as well as soil mineralogical and chemical properties affecting dust deposition rate (DDR), in a unique and rarely studied area, the Kuhdasht watershed (456 km2) of Lorestan province, Iran. Data were collected seasonally using glass-traps inserted in ten research stations to indicate DDR seasonal and spatial variations using ARC-GIS. The spatial distribution of organic matter (OM), clay and CaCO3, and the mineralogical properties (using diffractograms obtained by XRD) of the dust and soil samples were determined. The city had the highest DDR decreasing toward the mountains. Spring (3.28–4.18 ton/km2) and autumn (1.82–2.52 ton/km2) resulted in the highest and the least DDR, respectively. The diffractograms indicated the sources of dust were local or from out of the borders. The clay minerals (kaolinite and illite) and the evaporating minerlas (gypsum, calcite, dolomite, and halite), detected in the soil and dust samples indicated their contribution to the process of DDR. According to the regression models and the correlation coefficients, DDR was highly and significantly correlated with R (R2= 0.691), WS (0.685) and RH (0.463) indicating such parameters can importantly affect DDR in the semi-arid areas.

Numerical investigation of the effect of dust shields on accumulation of dust over PV panels

Dust accumulation on photovoltaic panels represents a major challenge for the operation of solar panels especially in the regions known by their high rate of dust and low frequency of rain. The objective of this study is to minimize dust accumulation on PV panels operating street light posts using dust shields. A novel dust shield having the same width of the panel, and subtending an angle of 120° with the panel, is proposed for dust mitigation. Numerical simulations are carried out to evaluate the influence of the dust shield on dust accumulation over the panel’s surface. It is found that using a dust shield decreases the dust deposition rate by more than 44%. Moreover, extending the panel’s surface at the lower edge with an extension plate together with the dust shield decreases the dust deposition rate better than using a dust shield only. Also, the effect of adding an air gap between the shield and the added extension plate is investigated, and it is found that the air gap induces air drafts over the panel’s surface, which acts as an air barrier that obstructs the approach of dust particles to the panel’s surface. These drafts get stronger as the air gap thickness increases, accordingly, less particles deposit on the panel. Finally, it is found that using a dust shield with a length smaller than the panel’s length in addition to an extension plate together and increasing the thickness of the air gap is an effective and efficient solution for dust mitigation, such that the percentage decrease in the dust deposition rate that might be more than 88%.

Aeolian dust distribution, elemental concentration, characteristics and its effects on the conversion efficiency of crystalline silicon solar cells

Exposure of PV modules to ambient environmental conditions like dust deposits, has some deleterious effects on peak power (Pmax) and overall conversion efficiency (η). This study investigates the effect of module height, tilt, and orientation on the rate of dust deposition on the surfaces of PV modules. Consequently, the effect of different dust categories on Pmax and η are investigated. North facing module surfaces are observed to exhibit higher deposition rates in southerly winds. A significant decrease in conversion efficiency of 1.30%, 1.74%, 4.05%, 2.74% and 1.38% after a fortnight are observed in modules installed in five randomly selected study sites. A higher decrease in efficiency on average after a fortnight is observed in sites having traces of anthropogenic particles on dust samples collected from the PV surfaces with minimal effects observed in sites having biogenic and geogenic particles. Abundance of anthropogenic dust particles coupled with mild tilt and leeward orientation led to a higher maximum power and efficiency degradation rate.

Human exposure to dust and heavy metals in industrial regions and its relationship with the prevalence of multiple sclerosis disease.

In recent decades, multiple sclerosis (MS) diseases have been significantly prevalent in some industrial areas of Iran, such as steel industrial areas in Isfahan province (central Iran). In this study, the environmental impacts of two steel mill factories in Isfahan province and their effects on the spread of MS in the region were investigated. To examine the extent of exposure, seasonal dust samples were collected from 15 sites around the two investigated factories. The annual dust deposition rate (DDR) was then determined and the concentrations of lead (Pb), cadmium (Cd), nickel (Ni), cobalt (Co), and manganese (Mn) in the dust samples were measured. Furthermore, the concentration of the mentioned elements was determined in the nail samples taken from 40 MS patients and 40 healthy people (control) living in the study region. The interpolated map extracted from the DDR values showed the highest dust deposition around the two studied steel factories, which decreases with increasing distance from them. The enrichment factor (EF) of heavy metals was the highest at the distance between the two steel factories, decreasing by moving away from them which indicate that these two steel factories are the source of investigated heavy metals in the region. The statistical analysis also revealed significant differences (P < 0.01) between the concentration of heavy metals measured in nail samples taken from MS patients and healthy people. The mean Pb concentration measured in the nail sample taken from MS patients was more than 18 times that of healthy people (93.45 and 5.02mg/kg, respectively). These results revealed a buildup of heavy metals in the body of MS patients much more than usual, originating from the activities of two investigated steel companies in the region.

Numerical Modeling of Dust Deposition Rate on Ground-Mounted Solar Photovoltaic Panels

Abstract Despite the growth in the global cumulative installed photovoltaic (PV) capacity, the efficiency of PV panels is greatly reduced due to dust accumulation and soiling. To enhance this efficiency, consideration must be given to the factors that affect dust deposition ranging from panel configuration to weather conditions. This research aims to determine which of those factors contribute significantly to dust accumulation and model this behavior. Numerical experiments were performed to study those factors based on a planned Design of Experiments (DOE). Dust particle size, dust amount, wind speed, wind direction, and the solar panel tilt angle are the five factors examined using computational fluid dynamics (CFD) simulations. Statistical and regression analyses were then used to determine the most significant factors and model their effect on the deposition rate. Results revealed that the dust diameter, panel tilt angle, and wind speed influence the deposition rate the most. Dust diameter is positively correlated to the dust deposition rate. Larger dust particles have a lower deposition rate as the wind velocity increases. In addition, smaller dust particles will always give the lowest dust deposition rate irrespective of the tilt angle. It was also seen that the maximum dust deposition rate occurs at a panel’s tilt angle of approximately 50 deg regardless of the wind speed or the dust particle size. The developed mathematical model shows the factors contributing to soiling and panel efficiency reduction over exposure time. This model can be used further to optimize panel cleaning frequency.

The effectiveness of the wind barrier in mitigating soiling of a ground-mounted photovoltaic panel at different angles and particle injection heights

Soiling is one of the most important factors that reduce the efficiency of photovoltaic (PV) solar panels. An increase in the amount of dust particles resting on the surface of the PV panel leads to a significant reduction in efficiency and serious damage to the solar panel. In this research, a numerical study of the behavior of dust particles under different conditions was performed. Based on the CFD method, the dust deposition rate and wind flow domain around a ground-mounted PV panel were predicted. The current research also includes an optical study of the negative effect of the barrier by shading the PV panel, to ensure the correct placement of the barrier before proceeding with the numerical study. Seven tilt angles of the panel were considered, for all configurations the maximum is taken by the 50 μm particles, thus, it is concluded that the particle deposition rate is maximum on the PV when the tilt angle is 40° followed by 30°. The addition of a wind barrier at the front of the system reduced the quantity of particles that reached the surface of the PV, especially for large particles when the force of gravity is not taken into account. To ensure the validity of this barrier, the injection level of the particles was increased, the results were really interesting, the effectiveness of soiling reduction was not affected by a high rate, which is promising.

Influence of terrigenous supply from the African continent on sedimentary CaCO3 distribution in the Southeast Atlantic Ocean

AbstractTerrigenous materials are transported to the ocean via various pathways, which can modify the weight contents of calcium carbonate (wt% CaCO3) in marine sediment and mask CaCO3 dissolution profiles, especially in ocean margins. Although the effect of terrigenous dilution on marine CaCO3 has long been established, there is still a lack of quantitative assessment on how the terrigenous input shapes sedimentary CaCO3 depth distribution features. In this study, we focus on the CaCO3 depth distribution patterns on the seafloor in the Southeast Atlantic Ocean. Based on an up‐to‐date compilation of surficial sedimentary CaCO3 content data and a simple conceptual model, the regional dilution effect of terrigenous supply from the African continent on the basinal sedimentary CaCO3 depth distribution is quantified. Our results show that the flux of noncarbonate materials needed to reproduce the carbonate distribution decreases with distance to the African continent. The noncarbonate flux to pelagic sediment in the Southeast Atlantic Ocean is on the same order of magnitude of the dust deposition rate, while the flux to marginal sediment is intensified as a consequence of the fluvial discharge. Moreover, enhanced dissolution of CaCO3 is found in marginal regions, which is due to faster rates of deep (boundary) currents than those in the pelagic ocean. These new insights help to distinguish the dilution impact from carbonate dissolution patterns and will advance research on land–ocean interaction and paleoclimate/environment reconstructions in ocean margins.

Eurasian Ice Sheet derived meltwater pulses and their role in driving atmospheric dust activity: Late Quaternary loess sources in SE England

The role of Quaternary ice sheet fluctuations in driving meltwater pulses and ocean circulation perturbations is widely acknowledged. What is less clear is the role of these processes in driving changes in past atmospheric dust activity, and possible wider links between dust and climate. Terrestrial windblown dust (loess) deposits along the northern fringe of the European loess belt potentially record past atmospheric dust emission from regions close to the former Eurasian Ice Sheet (EIS) and provide a means to evaluate the role of ice sheet fluctuations in the past dust cycle. Numerical loess chronologies across this region generally agree on greatly enhanced dust deposition rates during MIS 2, when the EIS reached its maximum extent. Yet, uncertainties over the sources of this material prevent understanding of the precise causes of this greatly enhanced atmospheric dustiness, and any potential link to ice sheet fluctuations and climate. In southeast England, loess accumulation dominantly occurred in two phases centered on 25–23.5 ka and 20–19 ka, matching the timing of coalescence of the Fennoscandian and British-Irish ice sheets and specifically advances and retreats of nearby ice lobes in the western North Sea. As such, these deposits provide an ideal test of the role of ice sheet fluctuations in atmospheric dust dynamics. Here we undertake such a test through a detailed provenance study of loess in southeast England and potential dust source sediments across the North Sea region. We group extensive new and published data sets of detrital zircon U–Pb ages from basement rocks and Cenozoic sediments in the North Sea area, which not only provide new insight into both loess source, but also the nature of sediment transport over NW Europe into the North Sea basin more widely. Multi-proxy evidence allows us to unambiguously identify ice sheet derived sediments in the exposed North Sea basin as the dominant source of loess in southeast England, while fluvial sediments delivered by rivers draining Continental Europe possibly contributed additional source material to the first loess accumulation phase. We propose that sudden retreats of the North Sea Lobe released substantial amounts of sediment rich meltwater into the southern North Sea and Channel basins, driving accelerated dust emission, loess deposition and provenance variability in NW Europe during MIS 2. Moreover, we propose that this model of dust activity driven by proglacial sediment availability may be applicable for EIS marginal regions more widely, even where resultant loess cover is rarely preserved due to extensive erosion and reworking along the ice marginal spillway. This implies the role of ice sheets in controlling wider dust emission may be underestimated. In addition to driving changes in ocean circulation through meltwater pulses, ice sheet dynamics in the Quaternary may have also driven substantial and abrupt changes in atmospheric dust activity. This mechanism may in part explain the coupling between dust and climate events widely seen in Quaternary dust sediment records and suggests a possible major role of high latitude dust emission in MIS 2 dustiness across Europe and beyond.

Experimental Investigation of Mineral Particle Deposition in the Cement Production Process.

This study aims to improve the understanding of the formation and prevention of deposits caused by the introduction of alternative fuels in the cement industry. Experiments were conducted with cement mineral materials in a laboratory-scale entrained flow reactor. To simulate the temperature conditions in a cement calciner, two different deposit probe systems were used: a high probe surface temperature (HPST) deposit system with a probe surface temperature range of 700–1200 °C and a low probe surface temperature (LPST) deposit system with a probe surface temperature range of 500–700 °C. The effects of fed materials (raw meal, hot meal, bypass dust), flue gas temperature (700–1200 °C), deposit probe surface temperature (550–1200 °C), gas velocity (0.9–2.7 m/s), and experimental duration (5–60 min) on the deposit formation rate were investigated. The results revealed that the concentration of KCl in the fed materials has a large influence on deposit formation. In HPST experiments with furnace temperatures ranging from 700 to 1100 °C, the bypass dust has a higher deposition rate than hot and raw meals, due to a large amount of K and Cl (>10 wt %) in the bypass dust, which forms melts and increases the stickiness between impacting particles and deposits. In LPST experiments, the presence of KCl facilitated the deposit formation rate by providing a sticky layer on the deposit probe via condensation, resulting in a higher deposition rate of bypass dust than the raw meal. An increase in gas velocity showed a negative effect on the deposit formation rate due to an increase in rebound. The present study suggests that keeping the calciner wall temperature at 900–1100 °C and a low level of KCl content would effectively reduce the deposit formation, thereby increasing the equipment life and reducing the operating cost during cement production.

Hot exozodis: cometary supply without trapping is unlikely to be the mechanism

ABSTRACT Excess near-infrared emission is detected around one fifth of main-sequence stars, but its nature is a mystery. These excesses are interpreted as thermal emission from populations of small, hot dust very close to their stars (‘hot exozodis’), but such grains should rapidly sublimate or be blown out of the system. To date, no model has fully explained this phenomenon. One mechanism commonly suggested in the literature is cometary supply, where star-grazing comets deposit dust close to the star, replenishing losses from grain sublimation and blowout. However, we show that this mechanism alone is very unlikely to be responsible for hot exozodis. We model the trajectory and size evolution of dust grains released by star-grazing comets, to establish the dust and comet properties required to reproduce hot-exozodi observations. We find that cometary supply alone can only reproduce observations if dust ejecta has an extremely steep size distribution upon release, and the dust-deposition rate is extraordinarily high. These requirements strongly contradict our current understanding of cometary dust and planetary systems. Cometary supply is therefore unlikely to be solely responsible for hot exozodis, so may need to be combined with some dust-trapping mechanism (such as gas or magnetic trapping) if it is to reproduce observations.

Computational prediction of dust deposition on solar panels

This research is concerned with performing computational fluid dynamics (CFD) simulations to investigate the air flow and dust deposition behavior around a ground-mounted solar PV panel. The discrete phase model (DPM) is adopted to model the gas-solid flow. The influence of the wind speed, the dust particle size, and the dust material on the dust deposition rate was investigated based on the environment of Cairo, Egypt. The wind speeds range between 1 and 11.5 m/s with an average of 3.7 m/s. It is found that increasing the wind speed decreases the dust deposition rate. For wind speeds higher than 2 m/s, it is found that increasing the dust particle diameter or the dust density increases the dust deposition rate. For wind speeds lower than 2 m/s, it is found that there is a critical particle size before which increasing the dust density causes dust deposition rate to increase and after which increasing the dust density decreases the dust deposition. The maximum percentage of deposition rate equals 10.8% and occurs for the dolomite dust material at a wind speed of 2 m/s and particles diameter of 150 μm.

Analyzing the Impact of Dust Accumulation on Power Generation and Bifacial Gain

Dust accumulation on PV modules, influenced by a variety of environmental parameters, such as relative humidity, wind speed, and particulate matter (PM) concentration, is one of the most common detrimental factors in reducing the power output. An investigation is conducted to quantify the impact of dust accumulation on power generation and bifacial gain in this work. Based on the experiments, the daily dust deposition rate as well as its correlation with relative humidity, wind speed, PM concentration, and ambient temperature is determined. Furthermore, the soiling loss (SL%) and soiling rate (SR) are analyzed over the period of the study. At the end of the test period, the SL% and SR are reported to be 6.86% and 0.233, respectively. This percentage loss is further used to simulate the annual energy yield and bifacial gain. A clean bifacial PV system recorded a higher performance ratio (0.83) and lower collection loss <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L_C</i> (0.8 kWh/kW <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> /day) compared to the lower performance ratio (0.78) and greater collection loss <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L_C</i> (1.12 kWh/kW <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> /day) of a soiled bifacial PV system. The yield of the monofacial PV system is far lower under the soiled state, and this discrepancy allows for greater bifacial gain (BG) (7.11%) to be realized under the soiled state of the modules. Although a bifacial module under soiled state will generate lower output than its cleaner counterpart, BG under soiled state is governed by the difference in yield from a monofacial system at a greater extent than a bifacial system.

Predicting continuous dispersion and deposition of explosive dust in confined spaces using a discrete phase model

Dust dispersion and deposition are of great concern when designing dust control systems. In this study, suspension and deposition of dust in an enclosed chamber was simulated using a computational fluid dynamics (CFD) - discrete phase model (DPM) with a particle-wall stick-rebound feature. The dispersion and deposition of dust at explosive concentrations of 15, 30, and 45 g/m 3 were simulated in this study. The dust rebounding at particle-wall interaction and particles sticking to wall were also simulated. The rate of dust-deposition and particle-size distribution of settled dust were obtained during simulation from selected locations within the chamber. The results showed that the larger particles tend to settle closer to the dispersion nozzle when compared with the smaller particles. The suspended dust concentration increased with the rate of dispersion, but after 30 s of continuous dispersion, the rate of dispersion did not alter the suspended dust concentration changing rate. The low prediction errors showed that the CFD-DPM model is accurate in predicting the rate of dust-deposition in confined chambers by tracking the particle motion. • A CFD-DPM approach was used to simulate the dust dispersion and deposition. • With time, the rate of dust dispersion did not influence suspended dust concentration. • Tracking particle motion aids in accurate prediction of dust-deposition.

Assessment of soiling impacts and cleaning frequencies of a rooftop BAPV system in composite climates of India

As one of the pioneers in solar photovoltaic (SPV) installations, India has witnessed several challenges related to performance; dust accumulation is one among them which needs attention. On the other side, most installers and SPV system owners do not have informed knowledge of dust accumulation rates (DAR) and optimum cleaning frequencies (OCF). It is also a well-known fact that DAR varies based on the SPV system (e.g., ground-mount, roof-mount, building applied/attached, building integrated and many other types). Hence, this paper analyses the effect of soiling specific to rooftop building-applied photovoltaics (BAPV) systems, and the main objective is to estimate the OCF driven by DAR. A rooftop BAPV system installed in India's composite climate zone is chosen as a case study, and its daily performance is monitored. Also, the on-site DAR is measured with micro slides help each day. It is observed that the system has different DAR for different seasons, clearly showing the relationship between energy outputs and DAR. The annual average daily deposition rate of dust was measured as 0.122 gm/m2/day. The maximum soiling loss of 0.39%/day was recorded in spring, followed by 0.34%/day in winter. The minimum soiling loss of 0.24%/day was measured in monsoon owing to heavy rainfall. The rooftop BAPV optimum cleaning frequency has been determined based on the energy lost due to soiling and cleaning cost. Overall, this study reveals that the rooftop BAPV system needs cleaning twice a year, first in spring and second in winter.

3D CFD modelling of dust deposition characteristics and influences on building-mounted photovoltaic system

Airborne dust deposition on the solar photovoltaic panels can significantly decrease the photovoltaic efficiency performance. Dust deposition characteristics and influences on building-integrated photovoltaic panels were studied by shear stress transfer k-ω turbulence model with inlet profiles and discrete particle model. The influences of dust size, wind velocity, and building roof inclination on the dust deposition behaviors were studied carefully. The air flow fields, the dust particle trajectories, the deposition rate on solar photovoltaic panels and the photovoltaic efficiency decrease by dust deposition were obtained and analyzed in the study. The three-dimensional simulation has great difference on the wind flow structures compared with two-dimensional simulation. The size of the separation vortex in the three-dimensional simulation is significantly smaller than that in two-dimensional simulation. The secondary flow structures become more significant in the rear of the building. The dust deposition rate is firstly increased and then decreased with the increasing of dust diameter. The maximum deposition rate is 2.54% for 150 μm particles. The minimum deposition rate is just 0.03% for 500 μm particles. The maximum deposition rate is 1.39%, 2.54% or 3.74% for the roof inclination angle of 16.7°, 22.6°or 36.9°, respectively. When particle size is 150 μm, the dust motions are determined by the air flow fields, mass inertia and gravitational settling. The photovoltaic efficiency reduction is significantly higher with increasing of dust size. The present model can conveniently estimate the photovoltaic efficiency decrease by dust deposition in realistic engineering application.

Relation between regional drought and mountain dust deposition revealed by a 10-year record from an alpine critical zone

Mineral dust was collected with a network of passive samplers in the Uinta Mountains (Utah, USA) over a 10-year period to evaluate the relation between regional drought and dust deposition. A total of 72 samples from eight collectors were analyzed for flux, grain size distribution, mineralogy, geochemistry, and their Sr and Nd isotopic fingerprint. The dust is primarily very fine silt, with an average median grain size of 11.6 μm. The clay minerals illite and kaolinite are common in the dust, along with quartz, potassium feldspar, and plagioclase. The most abundant elements (after Si) are Al > Fe > K > Ca > Mg > Ti. The trace elements Cd, Sn, Sb, Zn, Cu, As, and Pb are present at abundances greatly in excess of normal levels in upper crustal rocks. Dust fluxes average 14.4 mg/m2/day, generally decrease at higher elevations and toward the eastern end of the range, and are significantly higher in summer. Annual fluxes range from 1.4 to 5.8 g/m2/yr with a decadal average of 3.4 g/m2/yr. Rates of dust deposition are significantly correlated with regional drought severity from the Standardized Precipitation-Evapotranspiration Index (SPEI) for the southwestern US over 2, 3, and 6-month time scales. Previous work has demonstrated a connection between drought in the southwestern US and the abundance of fine (PM2.5) material aloft. This work is the first to use long-term monitoring of annual dust deposition to confirm that the flux of silt-sized dust to mountain ecosystems is significantly correlated with regional drought severity.

Annual and seasonal variability in high latitude dust deposition, West Greenland

AbstractHigh latitude regions (≥ 50°N and ≥ 40°S) are thought to contribute substantially to contemporary global dust emissions which can influence biogeochemical cycling as well as geomorphic, cryospheric and atmospheric processes. However, there are few measurements of the emission or deposition of dust derived from these areas that extend beyond a single event or season. This article reports the deposition of locally‐derived dust to an ice‐free area of West Greenland over 2 years from 23 traps distributed across five sampling sites. Local dust sources include glacial outwash plains, glacially‐derived delta deposits and the reworking of loessic soils. Annual dust deposition is estimated at 37.3 to 93.9 g m−2 for 2017–2018 and 9.74 to 28.4 g m−2 in 2018–2019. This annual variation is driven by high deposition rates observed in spring 2017 of 0.48 g m−2 d−1 compared to the range of 0.03 to 0.07 g m−2 d−1 during the rest of the monitoring period. The high deposition rates in spring 2017 were due to warmer than average conditions and high meltwater sediment supply that delivered large quantities of sediment to local outwash plains in 2016. For other seasons, dust deposition was lower over both autumn–winter periods (0.03 g m−2 d−1) than during the spring and summer (0.04–0.07 g m−2 d−1). When sediment availability is limited, dust deposition increases with increasing temperature and wind speed. Secondary data from dust‐related weather type/observation codes and visibility records were found to be inconsistent with measured dust deposition during the period of study. One possible reason for this is the complex nature of the terrain between the observation and sample sites. The dust deposition rates measured here and the infidelity of the observed dust with secondary data sources reveal the importance of direct quantification of dust processes to accurately constrain the dust cycle at high latitudes.

Toward Constraining Sources of Lithogenic Metals in the Northern Gulf of Mexico

AbstractNorth African dust is known to be deposited in the Gulf of Mexico, but its deposition rate and associated supply of lithogenic dissolved metals, such as the abiotic metal thorium or the micronutrient metal iron, have not been well‐quantified. 232Th is an isotope with similar sources as iron and its input can be quantified using radiogenic 230Th. By comparing dissolved 232Th fluxes at three sites in the northern Gulf of Mexico with upwind sites in the North Atlantic, we place an upper bound on North African dust contributions to 232Th and Fe in the Gulf of Mexico, which is about 30% of the total input. Precision on this bound is hindered by uncertainty in the relative rates of dust deposition in the North Atlantic and the northern Gulf of Mexico. Based on available radium data, shelf sources, including rivers, submarine groundwater discharge, and benthic sedimentary releases are likely as important if not more important than dust in the budget of lithogenic metals in the Gulf of Mexico. In other words, it is likely there is no one dominant source of Th and Fe in the Gulf of Mexico. Finally, our estimated Fe input in the northern Gulf of Mexico implies an Fe residence time of less than 6 months, similar to that in the North Atlantic despite significantly higher supply rates in the Gulf of Mexico.