Transport Of Dust Particles Research Articles

Effects of thermophoresis on dust accumulation on solar panels

The dust accumulation on a solar panel may be one of the most serious losses in the energy yield of photovoltaic systems, especially in the desert environment. The transport of airborne dust particles onto solar panels is governed by various physical processes and described by particle dynamics in a fluid. Here we investigate how the temperature gradient between the solar panel and the ambient air affects the dust accumulation. This so-called thermophoresis, which drives particles moving from the hot solar panel to the cold air, is examined using the boundary layer approximation for non-isothermal laminar airflow along the solar panel. We find that a strong thermophoretic force is built up at the entry region of the solar panel. With the velocity and temperature profiles of non-isothermal laminar airflow, we simulate Lagrangian particle trajectories. We demonstrate that for submicrometer-size particles, the thermophoresis builds a region free of the dust accumulation on the solar panel. It is shown that the thermophoretic effect may decrease the accumulation of submicrometer-size particles on the solar panel whose temperature is a few tens of degrees higher than the ambient air in the daytime.

Dust dominates high-altitude snow darkening and melt over high-mountain Asia

Westerly driven, long-range transportation of dust particles in elevated aerosol layers (EALs) is a persistent phenomenon during spring and summer over the Indian subcontinent. During the snow accumulation season, EALs transport substantial amounts of dust to the snow-covered slopes of high-mountain Asia (HMA). Here we use multiple satellite-based estimates to demonstrate a robust physical association between the EALs and dust-induced snow darkening over HMA. Results from a fully coupled atmosphere–chemistry–snow model support these observations, revealing across HMA a signature of increasing dust-induced snow darkening with surface elevation that peaks near 4,500 m. Moreover, the influence of dust on snow darkening is greater than that of black carbon above 4,000 m. Our findings suggest a discernible role of dust in the observed spatial heterogeneity of snowmelt and snowline trends over HMA and highlight an increasing contribution of dust to snowmelt as the snowline rises with warming. Dust deposition in high-mountain Asia lowers snow albedo and hastens melt. Satellite data and models show that dust arrives via transport in elevated aerosol layers and outweighs black carbon impacts at high altitudes, suggesting a growing importance of dust on snowmelt as snowlines rise with warming.

Simulated regional dust cycle in the Carpathian Basin and the Adriatic Sea region during the Last Glacial Maximum

The climate and environmental conditions in the Carpathian Basin and the adjacent northern Italy/Adriatic region during the Last Glacial Maximum (LGM) exhibit some major differences, as compared to present-day conditions. For instance, high accumulation rates recorded in loess deposits point to an active dust cycle during the LGM. Here, we investigate the climate conditions and provide new insights into the regional dust cycle based on regional climate simulations for both LGM and present-day boundary conditions. The high-resolution model output (grid spacing of ~8.5 km) is in good agreement with available proxy data, showing much colder (particularly during winter) and drier conditions during the LGM over the model domain. Further, the simulated aeolian dust cycle of small grain size particles (<20 μm) is investigated in more detail for LGM conditions. Highest dust emissions are simulated to the east of the Alpine ice sheet and in the Kvarner Bay region. In the northern Carpathian Basin, dust deposition plumes indicate prevailing northerly (NW, N and NE) winds. Strong Bora winds flowing down the slopes of the Dinaric Alps appear to play a major role in the local to regional dust cycle in the northern Adriatic region. From a seasonal perspective, the dust cycle is most active during winter and spring. A closer look at climate and environmental conditions at key areas reveals that high mean wind speeds and low precipitation rates correlate well with the high dust emissions during winter and spring. In contrast, lower wind speeds, increasing precipitation and the greening of vegetation prevent high dust emissions during summer and autumn. An additional analysis of the occurrence frequency of cyclonic circulation patterns in the Adriatic shelf region reveals that individual passing cyclones played an important role in the transport of dust particles from the alluvial Po plain towards the eastern Adriatic loess stacks.

Mobility of Mn and other trace elements in Mn-rich mine tailings and adjacent creek at Kanye, southeast Botswana

Mine tailings rich in Mn and an adjacent creek at Kanye, southeast Botswana, have been investigated by total decomposition of solids, X-ray diffraction, EMPA techniques, sequential extraction, and water leaching to understand binding and mobility of Mn and other trace elements. The investigation revealed weathering of tailings close to the surface of the tailings and higher concentrations of Fe compared to Mn. There also are high concentrations of Ba and Pb in the tailings solids. The principal minerals of Mn and Fe are cryptomelane, K(Mn4+, Mn2+)8O16, and hematite, Fe2O3, respectively. Most Mn is bound to less crystalline phases dissolved in the reducible step of sequential extraction, suggesting high potential for release of Mn and related trace elements. The situation is very different for Fe, which is found mostly in the residual (Aqua Regia) insoluble fraction. This is in a good agreement with high concentrations of mobilized Mn and with low concentrations of mobilized iron in the water leaching test. The order of water-leached trace elements is Ba>Zn > As>V > Cu > Co > Pb where trace elements bound in Mn-oxyhydroxides are preferentially mobilized. In particular, As and V may represent a potential risk for the environment during rainy periods when mine tailings are probably flooded, and tailings material is transported by water in an ephemeral creek. Currently, sediments in the creek are contaminated at least to the boundaries of the Kanye settlement and they can be a source of groundwater contamination during the rainy period. Another possible source of contamination is wind transport and settling of dust particles from mine tailings with resulting ingestion when local farming products are consumed.

Transport control of dust particles by pulse-time modulated RF in dusty plasmas

Transport of dust particles was studied in radio frequency (RF) plasmas. Dust particles of two sizes were injected in the plasmas. The plasmas were generated by applying a pulse-time modulated RF voltage. The pulse-time modulation made it possible to change the electron temperature in the plasmas. The electron temperature dominates the charges of the dust particles and the electric fields around the sheath where the dust particles are levitated. The equilibrium position of the dust particles can be determined by forces on them derived from the charges and the electric fields. In this research, it was clearly shown to change the position of the dust particles and drop them from the plasmas by the pulsed-time modulation. Furthermore, the modulated RF plasma worked as sieves of the dust particles. It was possible to drop larger dust particles from the plasma, while smaller ones remain in the plasmas.

Performance of a dust model to predict the vertical mass concentration of an extreme Saharan dust event in the Iberian Peninsula: Comparison with continuous, elastic, polarization-sensitive lidars

An intense dusty event unusually occurred in wintertime over the Iberian Peninsula was detected over two Spanish NASA/MPLNET sites: the temporary Torrejón Observational Tower for Environmental Monitoring (TOTEM, 40.5°N 3.5°W) and the Barcelona station (BCN, 41.4°N 2.1°E). The highest dust incidence was observed from 22 to 23 February 2017; this two-day dusty scenario is examined in order to evaluate the performance of the operational NMMB/BSC-Dust model on forecasted mass concentration profiling in comparison with polarized Micro-Pulse (P-MPL) mass estimates for dust particles. First, the optical properties of the dust (DD) were effectively separated from the non-dust (ND) component by using the combined P-MPL/POLIPHON method. Lidar-derived DD optical depths reached maximums of 1.6–1.7 (±0.1) at both stations. Typical features for dust were obtained: linear particle depolarization ratios between 0.3 and 0.4, and lidar ratios in the range of 41–70 sr and 36–66 sr, respectively, for TOTEM and BCN. Lower AERONET Ångström exponents were reported for TOTEM (0.12 ± 0.04) than at BCN (0.5 ± 0.3). HYSPLIT back-trajectory analysis showed air masses coming from the Sahara region, mostly transporting dust particles. AERONET-derived Mass Extinction Efficiencies (MEE) under dusty conditions were used for the extinction-to-mass conversion procedure as applied to the P-MPL measurements: MEE values were lower at TOTEM (0.57 ± 0.01 m2 g−1) than those found at BCN (0.87 ± 0.10 m2 g−1). Those results reveal that dust particles were predominantly larger at TOTEM than those observed at BCN, and a longer transport of dust particles from the Sahara sources to BCN could favour a higher gravitational settling of coarser particles before reaching BCN than TOTEM. A comparative analysis between profiles as obtained from the lidar DD component of the mass concentration and those forecasted by the NMMB/BSC-Dust model (25 available dusty profiles) was performed. The degree of agreement between both datasets was determined by the percentage of dusty cases satisfying selected model performance criteria (favourable cases) of two proxies: the Mean Fractional Bias, MFB, and the correlation coefficient, CC. A good agreement is found (72% and 76%, respectively, of favourable cases); however, large discrepancies are found at low altitudes between the dust model and the lidar observations, mostly at early stages of the arrival of the dust intrusion. Higher model-derived centre-of-mass (CoM) heights are found in 60% of the cases (with differences < 15% w.r.t. the lidar CoM, whose values ranged between 1.8 and 2.3 km height). In addition, modelled mass loading (ML) values were generally higher than the lidar-derived ones. However, the evolution of the mass loading along the two days, 22 and 23 February, was rather similar for both the model forecasting and lidar observations at both stations. The relative ML differences (<50%) of the mass loading represented 60% of all cases. Discrepancies can be based on the uncertainties in the lidar retrievals (mainly, the use of single extinction-to-mass conversion factors). In general, a moderately good agreement is observed between the P-MPL-derived dust mass concentration profiles and the NMMB/BSC-Dust model ones at both sites; large discrepancies are found at lower altitudes, plausibly due to a lower sedimentation of dust particles coming from upper layers by gravitational settling than that introduced by the NMMB/BSC-Dust model in the simulations. The methodology described for the dust model evaluation against the continuous P-MPL observations can be easily adopted for an operational use of the NMMB/BSC-Dust model for forecasting the mass concentration profiling in frequently dust-affected regions with serious climate and environmental implications, as long as a typical MEE for dust could be accurately specified. Hence, a statistical analysis for determining AERONET-based MEE values over the Iberian Peninsula is on-going.

Transport of Dust Particles in Very Low-Pressure Magnetized Plasma Studied by Rapid Imaging

Incandescent dust particles are observed to the naked eye in pure acetylene plasmas excited at electron cyclotron resonance (ECR). Their transport in a plane parallel to the magnets is studied using fast imaging combined with a tracking algorithm. The dynamics of dust particles exhibit specific trends depending on the direction considered within the magnetic field ( $\vec {B}$ ), the position in the plasma reactor, and the time after plasma ignition. This transport is discussed considering the electric and the ion drag forces. Although the transport of dust particles is governed by the space-charge electric field in the direction parallel to $\vec {B}$ , it involves cross-field mechanisms in the direction perpendicular to $\vec {B}$ related, specifically, to the ambipolar $\boldsymbol { }\vec {E}\boldsymbol {\times }\vec {B}$ drift as supported by a simple model. However, to fully describe these transport phenomena, one would also consider spatial and time-evolutions of plasma parameters in the dusty plasma.

Aerosol clustering in an urban environment of Beijing during (2005–2017)

In depth and detailed study about various classes of aerosols over an urban city of Beijing has been carried out, with the help of cluster technique during the period from (2005–2017). Aerosol Robotic Network (AERONET), retrieved data for Aerosol Optical Depth (AOD), Angstrom Exponent (AE), Extinction Angstrom Exponent (EAE), Absorption Angstrom Exponent (AAE), Single Scattering Albedo (SSA), Real and Imaginary index of Refraction (RRI & IRI respectively), Asymmetry Parameter (ASY) has been utilized for discrimination of aerosols over the study site. Higher mean values of AOD and AE were found in winter and spring season as (0.86 ± 0.38, 0.85 ± 0.32) and (1.06 ± 0.36, 1.19 ± 0.21), while lower values (0.75 ± 0.33, 0.75 ± 0.33) and (0.97 ± 0.22, 0.85 ± 0.17) for summer and autumn season respectively, representing mixed anthropogenic aerosols over the site. Three main types of aerosol were reported in this study: Mixed Carbonaceous (MC), Biomass Residuals (BR), and coarse mode local and transported Dust Particles (DP). Various aerosol parameters and their inter-relationship were investigated in detail to analyze the dominant aerosol type and its seasonal variations. The EAE and AAE values ranged from (0.10–1.77 and 0.00–1.70 respectively), could mainly be attributed towards MC aerosols. Real and Imaginary parts of Index (RRI & IRI) were recorded in the range from (1.33–1.60 and 0–0.010) respectively. Similarly, the range for SSA and ASY was found as (0.79–0.99 and 0.43–0.78) respectively. Back-trajectories using Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model revealed transportation of air masses from Mongolian deserts, Gobi desert, and other neighboring regions (i.e. Russia and Kazakhstan).

Dust removal from solar concentrators using an electrodynamic screen

The electrodynamic screen (EDS), which transports particles by electrodynamic waves, is a promising technology to repel deposited dust from solar devices in places where water resources are scarce. As gravitational force may impede dust removal on concave or parabolic solar concentrators, this study aimed to determine the feasibility of the EDS to transport dust either upward or laterally, for application to concave solar devices. A discrete element method was used to computationally simulate the transport, collision, and adhesion of charged dust particles that were subject to traveling waves on an inclined EDS. High electric field strength (>2 kVp-p mm−1), short distance between electrodes, and a low adhesion circumstance resulted in the best cleaning efficiency with a wave that traveled up the incline. Over half of the particles moved up the incline successfully under this operational condition. To improve the cleaning efficiency, a new EDS configuration wherein the wave transported particles laterally along the surface (instead of up the incline against gravity) was proposed. With the new configuration, the performance clearly improved in all cases. Although some particles moved down the incline under most conditions, the application of EDS to clean dust off solar concentrators is achievable with optimal parameters.

Spatial distribution and temporal trend of airborne trace metal deposition in Albania studied by moss biomonitoring

This study describes the assessment of air quality in Albania using moss biomonitoring. The moss species, Hypnum cupressiforme (Hedw) sps., was used in this study. Mosses were collected during August and September 2015 at 55 sampling sites more or less homogeneously distributed over the entire territory of the country. The spatial distribution and temporal trends of trace metal atmospheric deposition were studied through the determination of twenty inorganic elements, Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Li, Mg, Mn, Na, Ni, Pb, Sr, V, and Zn. ICP-AES, AAS (As and Cd) and CV AAS (Hg) analysis were used to determine the concentration of the elements. The obtained data show significant differences in the spatial distribution of the elements derived from different emission sources. High emission loads of anthropogenic elements (Cr, Ni, Cu, As and Zn) were detected in the East, and of sea salt elements, particularly Na and K, in the Western coastal line. The distribution trend of the trace metals was studied by comparing the current data with the data of a similar study performed in 2010. Due to the differences in airborne metal concentrations, their scavenging ratios from the atmosphere to the terrestrial ecosystems, and their different uptake-leaching rates during wet and dry deposition respectively of 2015 and 2010 moss grown period, different concentration levels were found in 2010 and 2015 moss metal concentrations. The 2015 moss concentration levels of anthropogenic elements Cr, Ni, Cu, As, Zn and Na had increased, while K, Mg and Hg moss concentration data had declined. Other elements show non significant differences in mosses of both monitoring periods.The contamination levels that were evaluated by calculating the contamination factor (CF) for each element provided similar results for the 2015 and 2010 moss survey. Factor analysis (FA) was applied to identify the possible sources of elements in the 2015 moss samples. Five dominant factors were identified representing long-range and local atmospheric transport of wind-blown soil dust particles (F1); local emission from chromium industry and wind-blown mineral dust particles (F2); anthropogenic sources of traffic emission and wind-blown fine mineral dust particles derived from geogenic origin natural transport from the marine environment (F4); and long-range atmospheric deposition (F5). This study emphasis that moss biomonitoring combined with data analysis and inventory of emission sources are important tools to assess air quality in Albania.

О левитации пыли над поверхностью Луны

Determining the mechanisms of formation of lunar dust, the study of the dynamics and interaction of dust particles with plasma and with the surface of spacecraft are relevant, while there are several theoretical models for studying the formation of a plasma-dust sheath above the surface of the moon. The article presents a brief review of studies that have investigated the dynamics of dust particles in the plasma sheath above the lunar surface. A computational model of the dynamics of dust particles levitating above the surface of the moon was created on the basis of the molecular dynamics simulations. The distribution of the dust particle sшяу has been determined. We consider the physical conditions such as - the density of the regolith, particle size, parameters (density, temperature of electrons and ions, velocity) of the solar wind, which characterize the dynamics of dust particles near the lunar surface. Charging of dust particles was calculated taking into account the density of electrons, solar wind ions and photoelectrons in the orbital motion limited. The graph of the dust particle charge versus time is plotted. The processes of charging dust particles in a plasma medium near the surface of the moon can lead to levitation and the transport of dust particles across the surface of the moon under the influence of a gravitational and electric fields.

Numerical Simulation of Transport and Deposition of Dust Particles in Human Tracheobronchial Airways

Dust is a common pollutant of the air we breath. If dust particles are inhaled and deposited in human airways, they can cause a variety of respiratory disorders. The inhaled dust particles motion in human airways goes along with the airflow. The transport process can be considered as a two-phase flow of a gas phase and a particle phase. In this study, we investigated the airflow and dust particles transport and deposition in human tracheobronchial airways using computational fluid dynamics (CFD) techniques. A steady simulation was performed in asymmetric tracheobronchial airway mode consisting of 19 outlets to observe the characteristics of airflow fields. The discrete phase model (DPM) was employed to predict the particle trajectories and deposition in the airway model. Deposition resulted from inertial impaction and gravitational sedimentation was considered. In the simulation, the airflow characteristics differences in the right and left bronchial trees were observed. The influence of secondary flow on dust particles motion was great. More dust particles were deposited in the right bronchial tree than in the left. The deposition fraction of dust particles in human tracheobronchial airways was high. This study can provide awareness on deposition of dust particles passing beyond the larynx and enhance prevention of their entry into the respiratory system. It can also contribute a convenient way on the location of deposition of particles of a given type in human respiratory tract to be used for respiratory disease preventions.

The mysterious long-range transport of giant mineral dust particles.

Giant mineral dust particles (>75 μm in diameter) found far from their source have long puzzled scientists. These wind-blown particles affect the atmosphere's radiation balance, clouds, and the ocean carbon cycle but are generally ignored in models. Here, we report new observations of individual giant Saharan dust particles of up to 450 μm in diameter sampled in air over the Atlantic Ocean at 2400 and 3500 km from the west African coast. Past research points to fast horizontal transport, turbulence, uplift in convective systems, and electrical levitation of particles as possible explanations for this fascinating phenomenon. We present a critical assessment of these mechanisms and propose several lines of research we deem promising to further advance our understanding and modeling.

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

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

Large-scale coherent structures of suspended dust concentration in the neutral atmospheric surface layer: A large-eddy simulation study

Dust particles can remain suspended in the atmospheric boundary layer, motions of which are primarily determined by turbulent diffusion and gravitational settling. Little is known about the spatial organizations of suspended dust concentration and how turbulent coherent motions contribute to the vertical transport of dust particles. Numerous studies in recent years have revealed that large- and very-large-scale motions in the logarithmic region of laboratory-scale turbulent boundary layers also exist in the high Reynolds number atmospheric boundary layer, but their influence on dust transport is still unclear. In this study, numerical simulations of dust transport in a neutral atmospheric boundary layer based on an Eulerian modeling approach and large-eddy simulation technique are performed to investigate the coherent structures of dust concentration. The instantaneous fields confirm the existence of very long meandering streaks of dust concentration, with alternating high- and low-concentration regions. A strong negative correlation between the streamwise velocity and concentration and a mild positive correlation between the vertical velocity and concentration are observed. The spatial length scales and inclination angles of concentration structures are determined, compared with their flow counterparts. The conditionally averaged fields vividly depict that high- and low-concentration events are accompanied by a pair of counter-rotating quasi-streamwise vortices, with a downwash inside the low-concentration region and an upwash inside the high-concentration region. Through the quadrant analysis, it is indicated that the vertical dust transport is closely related to the large-scale roll modes, and ejections in high-concentration regions are the major mechanisms for the upward motions of dust particles.

Effects of atmospheric dust deposition on solar PV energy production in a desert environment

The effect of deposition of atmospheric dust onto photovoltaic modules is investigated using both field measurements and modeling. Energy yield, solar irradiance, ambient particulate matter concentrations, and meteorological data were monitored during a 12-month period at a solar test facility in the arid environment of Qatar. Dust concentration alone, is a weak predictor of PV soiling and performance, even for particles larger than 10 μm. Instead, a non-linear correlation between aerosol mass, RH and PV losses was observed. A dynamically resolved three-dimensional aerosol dispersion model coupled with online meteorology was employed to simulate the emissions and transport of dust particles in the surrounding environment. The advantage of using such a model is that most of the complexities of the deposition process are grouped together in a single parameter: the particle deposition velocity. The model predicts an average deposition velocity ranging between 1.1 cm s−1 and 3.3 cm s−1 during summer and 1.6 cm s−1 and 3.7 cm s−1 in winter for the different size ranges of coarse dust particles. A numerical weather prediction model coupled with an explicit treatment of aerosols could be a beneficial tool for comprehensive PV soiling predictive capabilities on an urban-to-regional scale. Results from the predicted geographical distribution of dust settling suggests that floating PV modules could benefit from significantly lower dust deposition.

Synoptic analysis of dust storm over Arabian Peninsula: a case study on February 28, 2009

Sand and dust storms are causing hazards and problems in aviation as well as the dangers and distresses they cause on living things. The low meteorological visibility, the presence of strong winds with gust, and the transport of dust and sand particles by the wind are dangerous on landing and departure of aircrafts, and even on planes that are parked. The main aim of the study is to examine the meteorological conditions causing the dust storm that took place in the Arabian Peninsula on February 28, 2009, and to determine the source of dust caused dust storm, sand storm, blown sand, and blown dust at the airports. Within the scope of the study, aviation routine weather report (METAR) and aviation selected special weather report (SPECI) reports have been assessed at many airports over Arabian Peninsula (AP), the northern part of the AP and North Africa. As model outputs; NCEP–DOE Reanalysis 2 data, BSC–DREAM8B, and HYSPLIT model were used. In the satellite images; METEOSAT MSG dust RGB images, MODIS, and Kalpana-1 data were used. According to obtained results, dust storms were detected in Bahrain, Kuwait, Saudi Arabia, and United Arab Emirates (UAE). At Al-Ahsa Airport in Saudi Arabia, the lowest visibility measured on February 28, 2009, dropping to 200 m, which was dominated by blowing sand. The source region of the dust observed at Dubai Airport in UAE is the eastern regions of the Rub’al Khali Desert located between Saudi Arabia, Oman, and UAE.

The collection efficiency of ESP model - Comparison of experimental results and calculations using Deutsch model

In spite of considerable progress in the field of numerical techniques, the models based on simplified equations are still in use in practice. In particular, the Deutsch model is often used for the description of transport and separation of dust particles in EHD–field inside electrostatic precipitator (ESP). The aim of the research presented in this paper was to compare the value of collection efficiency determined experimentally and calculated using the Deutsch model. Besides, an attempt to model the phenomena of transport of dust particles in laboratory ESP using the Deutsch model was undertaken. The rigid discharge electrode in the form of spiked pipe was used in these experiments. Overall and fractional collection efficiencies were determined for two kinds of fly ashes of different particle size distributions. The overall collection efficiency was determined experimentally and compared with the results obtained from Deutsch formula. The results have shown that the collection efficiency determined using two methods: experimental and calculated by the Deutsch model were consistent.

Influence of Dust Events on the Concentration and Size Distribution of Microorganisms in Bioaerosols

In order to study the influence of dust events on the airborne microbes in atmospheric bioaerosols, bioaerosol samples were continuously collected from March to April 2015 during two dust events using size-fractionated bioaerosol samplers in Lanzhou and Qingdao. The concentration of airborne microbes were measured using an epifluorescence microscope after staining with DAPI (4',6-diamidino-2-phenylindole). The results showed that the concentration of airborne microbes increased significantly during the period of dust (P<0.05). The average concentrations of airborne microbes on sunny days were 5.61×105 cells·m-3 and 2.08×105 cells·m-3 in Lanzhou and Qingdao, respectively, whereas the mean concentrations on dusty days were 14.8 times and 6.42 times those on sunny days, respectively. The concentration of airborne microbes presented a bimodal size distribution on sunny days in Lanzhou and Qingdao, with a peak at>7.0 μm and the lowest values ranging from 4.7 μm to 7.0 μm. However, the second peak appeared at 3.3-4.7 μm and 1.1-2.1 μm in Lanzhou and Qingdao, respectively. The size distribution of airborne microbes changed during the dust period. The size distribution of microbes still presented a bimodal distribution in Lanzhou; however, one peak shifted from>7.0 μm to 1.1-2.1 μm. The size distribution in Qingdao changed from a bimodal distribution to a skewed distribution with the predominant fraction in coarse mode. The background values of microbial load in PM10 before the dust were 2224 cells·μg-1 and 1550 cells·μg-1 in Lanzhou and Qingdao, respectively, and the highest value of such increased significantly to 26442 cells·μg-1 and 10250 cells·μg-1 during the dust events, respectively. This demonstrated that the high concentration of microbes in the dust events resulted not only from increased atmospheric particles but also from dust source and transportation path along with long-range transported dust particles.

An overview of mineral dust modeling over East Asia

East Asian dust (EAD) exerts considerable impacts on the energy balance and climate/climate change of the earth system through its influence on solar and terrestrial radiation, cloud properties, and precipitation efficiency. Providing an accurate description of the life cycle and climate effects of EAD is therefore critical to better understanding of climate change and socioeconomic development in East Asia and even worldwide. Dust modeling has undergone substantial development since the late 1990s, associated with improved understanding of the role of EAD in the earth system. Here, we review the achievements and progress made in recent decades in terms of dust modeling research, including dust emissions, long-range transport, radiative forcing (RF), and climate effects of dust particles over East Asia. Numerous efforts in dust/EAD modeling have been directed towards furnishing more sophisticated physical and chemical processes into the models on higher spatial resolutions. Meanwhile, more systematic observations and more advanced retrieval methods for instruments that address EAD related science issues have made it possible to evaluate model results and quantify the role of EAD in the earth system, and to further reduce the uncertainties in EAD simulations. Though much progress has been made, large discrepancies and knowledge gaps still exist among EAD simulations. The deficiencies and limitations that pertain to the performance of the EAD simulations referred to in the present study are also discussed.