Dust Concentration Distribution Research Articles

The role of seasonality of mineral dust concentration and size on glacial/interglacial dust changes in the EPICA Dronning Maud Land ice core

AbstractWe present a record of particulate dust concentration and size distribution in subannual resolution measured on the European Project for Ice Coring in Antarctica (EPICA) Dronning Maud Land (EDML) ice core drilled in the Atlantic sector of the East Antarctic plateau. The record reaches from present day back to the penultimate glacial until 145,000 years B.P. with subannual resolution from 60,000 years B.P. to the present. Mean dust concentrations are a factor of 46 higher during the glacial (~850–4600 ng/mL) compared to the Holocene (~16–112 ng/mL) with slightly smaller dust particles during the glacial compared to the Holocene and with an absolute minimum in the dust size at 16,000 years B.P. The changes in dust concentration are mainly attributed to changes in source conditions in southern South America. An increase in the modal value of the dust size suggests that at 16,000 years B.P. a major change in atmospheric circulation apparently allowed more direct transport of dust particles to the EDML drill site. We find a clear in‐phase relation of the seasonal variation in dust mass concentration and dust size during the glacial (r(conc,size) = 0.8) but no clear phase relationship during the Holocene (0 < r(conc,size) < 0.4). With a simple conceptual 1‐D model describing the transport of the dust to the ice sheet using the size as an indicator for transport intensity, we find that the effect of the changes in the seasonality of the source emission strength and the transport intensity on the dust decrease over Transition 1 can significantly contribute to the large decrease of dust concentration from the glacial to the Holocene.

Analysis of dust distribution in silo during axial filling using computational fluid dynamics: Assessment on dust explosion likelihood

In this study, the dust distribution in a silo during axial filling was modelled using a commercial computational fluid dynamics (CFD) code. The work focused on the dust concentration distribution in the silo, for evaluating the likelihood of a dust explosion in the silo. The simulation was conducted using a combination of renormalized (RNG) k-epsilon and discrete phase models, with standard pressure interpolation and a second order upwind scheme. The predicted dust concentration distribution showed a good agreement with experimental data adopted from the literature. It was found that the dust concentration distribution was influenced by mean velocity and turbulence flow. The simulation results suggest that the cornstarch concentration inside the silo was always above the lower explosion limit (LEL), hence requiring a mitigating action or a control system to reduce the explosion risk.

Physicochemical impacts of dust particles on alpine glacier meltwater at the Laohugou Glacier basin in western Qilian Mountains, China

This work discusses the temporal variation of various physicochemical species in the meltwater runoff of Laohugou Glacier No. 12 (4260ma.s.l.) in central Asia, and their correlation with dust particles, based on a two-year field observation in summer 2012 and 2013, mainly focusing on dust concentration and size distribution, meltwater chemistry, particles SEM–EDX analysis in the meltwater, and MODIS atmospheric optical depth fields around the Qilian Mountains in central Asia. We find that, the volume–size distribution of dust particles in the meltwater is mainly composed of three parts, which includes fine aerosol particles (with diameter of 0~3.0μm, mainly PM 2.5), atmospheric dust (with diameter of 3.0~20μm), and local dust particles (20~100μm), respectively. Comparison of dust particles in the snowpack and meltwater runoff indicates that, large part of dust particles in the meltwater may have originated from atmospheric dust deposition to the snow and ice on the glacier, and transported into the meltwater runoff. Moreover, temporal variation of dust and major ions (especially crustal species) is very similar with each other, showing great influence of dust particles to the chemical constituents of the glacier meltwater. SPM and TDS implied significant influences of dust to the physical characteristics of the glacier meltwater. Results showed that, accelerated glacier melting may affect physicochemical characteristics of the meltwater at an alpine basin under global warming. MODIS atmospheric optical depth (AOD) fields derived using the Deep Blue algorithm, showed great influence of regional dust transportation over western Qilian Mountains in springtime. SEM–EDX analysis shows that dust particles in the glacier meltwater contain Si-, Al-, Ca-, K-, and Fe-rich materials, such as quartz, albite, aluminate, and fly ash, similar to that deposited in snowpack. These results showed great and even currently underestimated influences of atmospheric dust deposition to glacier meltwater physicochemistry at an alpine basin in central Asia.

Physicochemical characteristics and sources of atmospheric dust deposition in snow packs on the glaciers of western Qilian Mountains, China

Wind-blown dust derived from the arid and semi-arid regions is an important atmospheric component affecting the Earth's radiation budget. Dust storms are prevailing in central Asia. Deposition of atmospheric dust in snow was measured on Glacier No.12 (5040 m a.s.l.) in the Laohugou Basin and Shiyi Glacier (4510 m a.s.l.) in the Yeniugou Basin, of western Qilian Mountains, China, mainly focusing on dust concentration and size distribution, chemistry, SEM–EDX analysis and Nd–Sr isotopic composition. An analysis of spatial distribution of dust concentration and size distribution in the snow cover at two sites suggests that deposition of dust in western Qilian Mountains is different between sites as the environment changes from west to east. Mean mass concentration of dust with 0.57 < d<40 μm in the snow is 3461 μg kg−1 on Glacier No.12 and 2876 μg kg−1 on Shiyi Glacier, respectively. Annual flux of dust deposition to western Qilian Mountains has a range of 143.8–207.6 μg cm−2 yr−1 for particles with 0.57 < d<40 μm. Dust layers in the snowpit contain Ca- and Na-rich materials typically found in Asian dust particles. Number–size distribution indicated that most of the dust diameter is <2.0 μm, implying the significant influences of finer particles to alpine glacier regions of central Asia. Volume size distributions of dust particles showed single-modal structures having volume median diameters from 3 to 22 μm, which is comparable to the results of dust deposition on glaciers of the adjacent Tianshan Mountains in western China. SEM–EDX analysis suggested that dust particles were mainly composed of mineral particles, besides some fly ash particles and soot. EDX shows that mineral particles contain Si-, Al-, Ca-, K-, and Fe-rich materials, such as quartz, albite, aluminate, etc. The Nd–Sr isotopic composition of insoluble particles in two glaciers showed that Badain Jaran Desert and Qaidam Basin were the most possible source regions of dust in the western Qilian Mountains. Physicochemical constituents of dust indicated that the snowpack was influenced by both local atmospheric environment, e.g. local dust, and anthropogenic activities in central Asia.

Numerical simulation of dust concentration distribution regularities of down-the-hole drilling in open-pit mine

Numerical simulation of dust concentration distribution regularities of down-the-hole drilling in open-pit mine

Investigation of airflow and respirable dust flow behaviour above an underground bin

To mitigate the problem of dust contamination to the intake air of an underground coal mine, a study was carried out to understand the airflow and respirable dust flow behaviour for the development of effective dust suppression strategies. Three dimensional (3D) Computational Fluid Dynamics (CFD) modelling was used to predict airflow field around the crusher and transfer point above the underground bin and along the belt roadway. The CFD model was validated using average velocity and dust concentration profiles obtained from ventilation surveys in the belt roadway. The stochastic particle tracking model was adopted in the Lagrangian scheme to study the respirable dust dispersion behaviour and predict dust concentration distribution in the belt roadway. To overcome the uncertainty produced by the stochastic tracking, sufficient numbers of particles were employed to obtain a stable concentration field. Modelling results show that areas of airflow turbulence and circulation occur once the fresh ventilation emerges from the bin bottom and intercepts airflow from another intake. Dust particles from the underground bin will be dispersed extensively in the belt roadway once they become airborne, contributing to the high dust contamination in the intake fresh air. To mitigate dust contamination to the mine ventilation system, the dust clouds from the bin have to be intercepted and suppressed before they become airborne over the bin. Results from the CFD modelling will be used for the design and installation of a more effective dust control system.

Review of the occurrence of perfluorinated alkylated substances in house dust and evaluation of the exposure of toddlers to these compounds via house dust

Background and Aim: Perfluorinated alkylated substances are in focus of recent research activities because of their potential toxic properties and widespread occurrence in the environment. Within the frame of the PERFOOD project (KBBE-227525), an evaluation of exposure to perfluorinated alkylated substances from house dust has been performed by analysis of currently available literature in order to evaluate the importance of house dust as a carrier compared to the food pathway. Method: The evaluation has been focused on 16 different substances. Deterministic exposure estimations are based on average concentrations reported in house dust and standard assumptions of house dust intake from guidance documents. In addition, probabilistic calculations were done for PFOA based on publications that provide detailed information on the distribution of house dust concentrations. Results: The average exposure estimates considering median concentrations in house dust were 1 – 279 (PFBA), 2 – 2063 (PFBS), 1 - 44 (PFDA), 11 – 109 (PFDoDA), 6 (PFDS), 54 – 559 (PFHpA), 2 - 311 (PFHxA), 1 – 1379 (PFHxS), 7 - 132 (PFNA), 4 - 1724 (PFOA), 0.2 – 2756 (PFOS), 0.1 - 397 (PFOSA), 19 (PFTeDA), 39 (PFTrDA) and 7 – 868 (PFUnDA) (all in pg/kg b.w./d), showing the broad range of exposures. For PFOA, a detailed datasets in three publications allowed a probabilistic evaluation that also considered the range of house dust intake recommendations. Conclusion: A broad range of exposure via house dust was identified. The extent of the exposure estimates for each compound is not only a result of the widespread occurrence data in house dust but also based on the assumed amount of orally ingested house dust. The reliability of those data should be considered more in order to reduce the uncertainty in such assessments.

Uncertainty in Dust Budget over East Asia Simulated by WRF/Chem with Six Different Dust Emission Schemes

In this study, the dependence of dust budgets on dust emission schemes is investigated through the simulation of dust storm events, which occurred during 14–25 March 2002, over East Asia, by the Weather Research and Forecasting with Chemistry(WRF/Chem) model coupled with six dust emission schemes. Generally, this model can reasonably reproduce the spatial distribution of surface dust concentration; however, the simulated total dust budget differs significantly with different emission schemes. Moreover, uncertainties in the simulated dust budget vary among regions. It is suggested that the dust emission scheme affects the regional dust budget directly through its impact on the total emitted dust amount; however, the inflow and outflow of dust aerosols simulated by different schemes within a region also depend on the geographical location of the dust emission region. Furthermore, the size distribution of dust particles for a specific dust emission scheme has proven to be important for dust budget calculation due to the dependence of dust deposition amount on dust size distribution.

Optical method for continuous monitoring of dust deposition in mine’s entry / Optyczna metoda ciągłego pomiaru intensywności osiadania pyłu węglowego w wyrobisku górniczym

Abstract The paper presents factors determining dust explosion hazards occurring in underground hard coal mines. The authors described the mechanism of transport and deposition of dust in mines entries and previous research on this topic. The paper presents a method of determination of depositing dust distribution during mining and presents the way to use it to assess coal dust explosion risk. The presented method of calculating the intensity of coal dust deposition is based on continuous monitoring of coal dust concentrations with use of optical sensors. Mathematical model of the distribution of the average coal dust concentration was created. Presented method allows to calculate the intensity of coal dust deposition in a continuous manner. Additionally, the authors presented the PŁ-2 stationary optical dust sampler, used in the study, connected to the monitoring system in the mine. The article features the results of studies conducted in the return air courses of the active longwalls, and the results of calculations of dust deposition intensity carried out with the use of the presented method.

Numerical simulation study of dust concentration distribution regularity in cavern stope

Based on the theory of gas–solid two-phase flow and the characteristics of cavern stope a model of dust migration was established. The dust concentration changing of cavern stope by ventilation in 20min after blasting and the dust trajectory in different wind speed were simulated by Fluent Software. The results show that distribution of dust concentration is significantly affected by flow field of airway in cavern, and the dust concentration of inlet is higher than that of outlet and the highest one on the corner of inlet’s side. In the stope, the smaller the wind speed of inlet is, the shorter of dust can be captured, settled and discharged, the more obviously affected by the trajectory of gas flow field. It goes into the stage of clean cycle emissions after 60s, the speed of dust concentration dropped is the biggest between 0s and 70s, the main dust in stope is respirable dust after 70s, it needs much time to settlement.According to the measured data of metal mining, approximately 87% of dust was generated during the drilling and blasting in the mine (Wang, 1979). A lot of dust with high concentrations was produced during the cavern stope blasting and it was difficult to be discharged. It can help choose the right speed to rule out the dust quickly which produced during cavern blasting, if the dust concentration distribution and the dust migration law of different inlet velocity in the cavern can be verified, what’s more, the labor productivity can be increased. It has great significance for choosing reasonable ventilation parameters, reducing dust hazards of stope to researching the dust concentration distribution regularity in the stope.

MHD free convection flow of a visco-elastic (Kuvshiniski type) dusty gas through a semi infinite plate moving with velocity decreasing exponentially with time and radiative heat transfer

The present paper is concerned with the study of MHD free convective flow of a visco-elastic (Kuvshinski type) dusty gas through a porous medium induced by the motion of a semi-infinite flat plate under the influence of radiative heat transfer moving with velocity decreasing exponentially with time. The expressions for velocity distribution of a dusty gas and dust particles, concentration profile and temperature field are obtained. The effect of Schmidt number (Sc), Magnetic field parameter (M) and Radiation parameter (N) on velocity distribution of dusty gas and dust particles, concentration and temperature distribution are discussed graphically.

Estimation of the temporal and spatial distribution of dust concentration over China by combining PM10 and conventional meteorological observations

In this paper, we will present a simple algorithm to estimate the temporal and spatial distribution of dust mass concentration by combining PM10 and conventional meteorological observations. The efficiency of the algorithm has been demonstrated by applying it to analyze the dust source, transport, and dissipation of the dust storm which occurred in the west region of Pa-tan-chi-lin Desert at 0200 BST 27 March, 2004.

Saharan dust transport and deposition towards the tropical northern Atlantic

Abstract. We present a study of Saharan dust export towards the tropical North Atlantic using the regional dust emission, transport and deposition model LM-MUSCAT. Horizontal and vertical distribution of dust optical thickness, concentration, and dry and wet deposition rates are used to describe seasonality of dust export and deposition towards the eastern Atlantic for three typical months in different seasons. Deposition rates strongly depend on the vertical dust distribution, which differs with seasons. Furthermore the contribution of dust originating from the Bodélé Depression to Saharan dust over the Atlantic is investigated. A maximum contribution of Bodélé dust transported towards the Cape Verde Islands is evident in winter when the Bodélé source area is most active and dominant with regard to activation frequency and dust emission. Limitations of using satellite retrievals to estimate dust deposition are highlighted.

Development of an in situ ITER dust diagnostic based on extinction spectrometry: Dedicated light scattering models

The quantity of dust produced in fusion devices must be characterized in order to address their consequences on the operation of the machine as well as on safety issues. This paper presents the work currently in progress to develop light scattering models of dust as well as a light extinction spectrometer to monitor dust concentration and size distribution in the vacuum vessel.

Large-scale overview of the summer monsoon over West Africa during the AMMA field experiment in 2006

Abstract. The AMMA (African Monsoon Multidisciplinary Analysis) program is dedicated to providing a better understanding of the West African monsoon and its influence on the physical, chemical and biological environment regionally and globally, as well as relating variability of this monsoon system to issues of health, water resources, food security and demography for West African nations. Within this framework, an intensive field campaign took place during the summer of 2006 to better document specific processes and weather systems at various key stages of this monsoon season. This campaign was embedded within a longer observation period that documented the annual cycle of surface and atmospheric conditions between 2005 and 2007. The present paper provides a large and regional scale overview of the 2006 summer monsoon season, that includes consideration of of the convective activity, mean atmospheric circulation and synoptic/intraseasonal weather systems, oceanic and land surface conditions, continental hydrology, dust concentration and ozone distribution. The 2006 African summer monsoon was a near-normal rainy season except for a large-scale rainfall excess north of 15° N. This monsoon season was also characterized by a 10-day delayed onset compared to climatology, with convection becoming developed only after 10 July. This onset delay impacted the continental hydrology, soil moisture and vegetation dynamics as well as dust emission. More details of some less-well-known atmospheric features in the African monsoon at intraseasonal and synoptic scales are provided in order to promote future research in these areas.

Understanding dust explosions. The role of powder science and technology

Dust explosions in the process industries practically always start inside process equipment such as mills, dryers, mixers, classifiers, conveyors, and storage silos and hoppers. For any given dust type the ease with which dust clouds ignite and the rates with which they burn, vary considerably with factors well known in powder science and technology. The key factors include the primary particle size distribution of the dust, the degree of de-agglomeration of the dust particles in the cloud, the dust concentration distribution in the cloud, and the cloud turbulence. The last three factors are entirely dependent on the actual process situation in which the dust cloud is generated and sustained. The paper first discusses influences of these factors on the ignition sensitivity and explosion violence of dust clouds. Secondly, the concept of inherently safer process design to prevent accidental dust explosions is discussed, using design of hoppers and silos as an example. Then some consequences of the mentioned factors in design of mitigatory measures such as explosion isolation, explosion venting, and automatic explosion suppression, are discussed. The role of powder science and technology in understanding development and propagation of secondary dust explosions is also considered.

Data assimilation of dust aerosol observations for the CUACE/dust forecasting system

Abstract. A data assimilation system (DAS) was developed for the Chinese Unified Atmospheric Chemistry Environment – Dust (CUACE/Dust) forecast system and applied in the operational forecasts of sand and dust storm (SDS) in spring 2006. The system is based on a three dimensional variational method (3D-Var) and uses extensively the measurements of surface visibility (phenomena) and dust loading retrieval from the Chinese geostationary satellite FY-2C. By a number of case studies, the DAS was found to provide corrections to both under- and over-estimates of SDS, presenting a major improvement to the forecasting capability of CUACE/Dust in the short-term variability in the spatial distribution and intensity of dust concentrations in both source regions and downwind areas. The seasonal mean Threat Score (TS) over the East Asia in spring 2006 increased from 0.22 to 0.31 by using the data assimilation system, a 41% enhancement. The forecast results with DAS usually agree with the dust loading retrieved from FY-2C and visibility distribution from surface meteorological stations, which indicates that the 3D-Var method is very powerful by the unification of observation and numerical model to improve the performance of forecast model.

An integrated dust storm prediction system suitable for east Asia and its simulation results

An integrated dust storm modeling system is developed for the prediction of dust storms. The system couples a wind erosion scheme, a dust transportation model and the Penn State/UCAR modeling system (MM5) with a geographic information database. The system can be used for the prediction of dust emission rate and dust concentration associated with individual dust storm events. Two severe dust storm events occurred in spring 2002, one on the 19th–22nd of March and the other on the 6th–9th of April. The integrated modeling system is used to simulate the two events. The numerical results are compared with surface weather records and satellite images and good agreement is found between the model results and observation in dust concentration distribution and evolutions. The Gobi Desert in southern Mongolia and the Badain Jaran Desert, Tengger Desert and Hunshandake sandy land in Inner Mongolia (China) are identified to be the dust sources for the two events. The dominant modes of dust particles over western Inner Mongolia and Mongolia are from 2 to 11 μm in size, and 2 to 22 μm over Beijing and its surrounding area. The emission of particles in the 2–11 μm size range is found to be most important for Northeast Asian dust storms.

Ice core evidence for secular variability and 200-year dipolar oscillations in atmospheric circulation over East Antarctica during the Holocene

Two Holocene ice core records from East Antarctica (Vostok and EPICA-Dome C) were analysed for dust concentration and size distribution at a temporal resolution of 1 sample per ~50 years. A series of volcanic markers randomly distributed over the common part of the ice cores (from 9.8 to 3.5 kyear BP) ensures accurate relative dating (±33 years). Dust-size records from the two sites display oscillations structured in cycles with sub-millennial and secular scale frequencies that are apparently asynchronous. The power spectra of the composite sum (Σ) of the two dust-size records display spectral energy mostly for 150- to 500-year periodicities. On the other hand, the 200-year band is common to both records and the 200 year components of the two sites are out-of-phase (100-year lead or lag) over ~5.5 kyear, a phenomenon also reflected by a significant (>99% conf. lev.) band in the power spectra of the composite difference (Δ) of the two size records. During long-range transport, mineral dust originating from the Southern Hemisphere continents is graded to a variable extent depending on the altitude and duration of atmospheric transport. Relatively coarse dust is associated with air mass penetration from the middle–lower troposphere and conversely relatively fine dust with upper troposphere air masses or the influence of subsidence over the Antarctic plateau, a hypothesis already proposed for the changes that occurred during the Last Glacial Maximum to Holocene transition (Delmonte et al. 2004b). Moreover, we assume that the overall fluctuation of air mass advection over Antarctica depends on the meridional pressure gradient with respect to low latitudes, i.e. the Antarctic Oscillation (AAO). We therefore suggest a regional variability in atmospheric circulation over East Antarctica. The 150–500 year power spectrum of the composite (Σ) parameter represents the long term variability of the AAO, imprinted by secular internal oscillations probably related to the southern ocean-climatic system. On the other hand, the Δ dust composite parameter suggests a persistent atmospheric dipole over East Antarctica delivering coarser (finer) dust particles alternatively to Vostok and Dome C regions with a bi-centennial periodicity. Indeed, a seesaw phenomenon in dust size distribution was already observed at three East Antarctic sites during the last deglaciation (Delmonte et al. 2004b) and was interpreted as a progressive reduction of the eccentricity of the polar vortex with respect to the geographic south pole. Interestingly, the Δ parameter shows a pronounced 200-year oscillation mode, throwing new light on the unresolved question of a possible relationship between climate and solar activity.

Simulations of Asian Yellow Dust Incursion Over Taiwan for the Spring of 2002 and 2003

Dust storms that occurred in East Asia during the spring of 2002 and 2003 were simulated by a regional dust deflation and transport model. Particular focus was placed on dust incursion events over Taiwan. Two of the events were analyzed in detail to give a complete picture of the three dimensional transport patterns. The general characteristics of dust incursion events were summarized, including the source locations, transport route and distribution pattern in three dimensions, traveling time, duration of incursion, and the seasonal spatial distribution of dust concentration. Significant differences were also found in these characteristics between the two years, the main cause of which was a change in regional climate patterns. The performance of the model developed for this study was evaluated against other dust forecast models, and found to have superior capability for forecasting in the Taiwan area.