Concentration Of Dust Particles Research Articles

Assessment and recalibration of the Heliosat-2 method in global horizontal irradiance modeling over the desert environment of the UAE

Remote estimation of global horizontal irradiance (GHI) by Heliosat-2 model has been benchmarked against ground-based measurements in different locations. The obtained results have shown that the level of agreement between ground-based and model-based GHI values are location dependent. To our knowledge no similar studies have been carried out over the Arabian Peninsula. The unique climatic condition in the Peninsula, characterized by high concentrations of airborne dust particles and high humidity makes the region a particularly interesting case.In this study Heliosat-2 method was used to derive the ground surface GHI in the United Arab Emirates. Inputs to the model were monthly Linke turbidity factor normalized to an air mass of 2 and a cloud index derived from SEVIRI sensor onboard the European satellite Meteosat. The Linke turbidity factor was obtained from a ground network of seven stations distributed across the UAE. A SEVIRI-based technique was developed and used to derive cloud index from high-resolution visible channels. Ground surface GHI measurements were collected from four inland stations for a period ranging from mid-2007 to mid-2010. The obtained results show that the Heliosat-2 model underestimates the GHI. The obtained root mean square error (RMSE) and mean bias error (MBE) values ranged from 16.3% to 18.5% and −13.6% to −15.8%, respectively. A constant bias was observed between modeled and measured GHI throughout the four stations. To correct this bias, the empirical equation used in Heliosat-2 to estimate the clear sky diffuse horizontal irradiance (DHIclear) was recalibrated. With the new DHIclear empirical equation, the modified Heliosat-2 model becomes more adapted to desert and dusty environments such as that of the UAE. By applying the modified DHIclear equation, the RMSE and MBE values dropped to 9.5–10.3% and −1.2 to +0.8%, respectively.

Non‐Ideal Dust Structures in Cryogenic Complex Plasmas

AbstractThe possibility of the formation of dust structures in cryogenic environment at 4.2‐77 K was proved experimentally in the previous researches of cryogenic complex (dusty) plasma [1–5]. It was revealed from the experiments, among others, that the dust structures with high concentration of dust particles can be formed, in which interparticle distance is comparable with particle size ‐ super dense dusty plasma structures. Such structures had exotic properties such as globular (spherical) form, free boundaries, etc. In the present work new results on the experimental investigations of new phenomenon of spheroidizing ‐ process of the dust structure transition to compact globular shape at cryogenic temperatures ‐ were presented. Possible nature of such phenomenon is discussed (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Prediction of dust concentration in open cast coal mine using artificial neural network

Coal dust is a major pollutant in the ambient air of coal mining areas. The pollution due to open cast mining is more severe than pollution due to underground mining. Prediction of ambient concentration of pollutants should be known to implement any control techniques to reduce their concentrations. In this paper, three models were developed to predict the concentration of dust particles at various locations away from the source of pollution. These models are developed using Multilayer Perception Network and learning is done by back–propagation algorithm. The data for training and testing the network is collected from the field work done in North Karanpura Coal Mine in Jharkhand, India, which is an open cast mine. The meteorological data (wind velocity, dispersion coefficients, rain fall, cloud cover and temperature), geographical data (distance of the receptor point from the source in the direction of wind and distance of the receptor from source in the direction perpendicular to wind direction) and emission rate are used as inputs in the formation of models. The number of inputs for Model 1, Model 2, and Model 3 are six, seven, and nine, respectively. The output (dust concentration) is same for all the three models. The performance of the developed models was evaluated on the basis index of agreement and other statistical parameters i.e., the mean and the deviations of the observed and predicted concentrations, root mean square error, maximum deviation and minimum deviation, normalized mean square error, model bias and fractional bias. It was seen that the overall performance of Model 3 was better than Models 1 and 2. Artificial neural network (ANN) based dust concentration prediction model yielded a better performance than the Gaussian–Plume model.

Effect of Twist Drill Bit and Feeding Speed on Air Dust During Boring Process of Solid Wood and Wood-Based Composite Panels

A study was carried out to analyze the particles produced during drilling process with twist drills with one and two spirals (length 70 mm, diameter 8 mm) with different feeding speeds, executed in beech (Fagus sylvatica), pine (Pinus sylvestris) and oak (Quercus petraea) woods, and also, medium density fiberboard (MDF), particleboard and poplar plywood panels. Drilling of solid woods was performed by following its longitudinal and transversal directions. The measurement and counting of wood dust particles was performed with a Particle Scan Pro instrument that measures the concentration of wood dust particles (milligrams per cubic meter or particles/l) present in the air. This instrument is able to count particles with diameter equal to and larger than 0.3 μm. A total of 281 tests were made with an average number of repetitions of eight for each material. The larger quantity of particles was produced by the wood-based panels, followed by hardwoods and finally, softwood. All drilled woods produced more particles on the longitudinal direction than on the transversal direction. For lower feeding speed, the number of particles increased with the increase of the number of bit’s spirals. In general, the bits with one spiral produced a smaller number of pending particles than two spirals bits. Most of produced particles were registered in small sized categories (≤ 1 μm O), where most of them were occupied by micro fines particles with 0.3 to 0.5 μm diameter, which were produced massively during V22b work regime. Key words: Twist drill bit, feeding speed, drilling process, dust particles, solid wood, wood composite panels.

Thermal Diffusion and Mass Transfer Effects on MHD Flow of a Dusty Gas through Porous Medium

The present problem is concerned with the thermal diffusion mass transfer effects on MHD free convective flow of dusty gas through a porous medium induced by the motion of a semi-infinite flat plate moving with velocity decreasing “exponentially with time”. The effects of various parameters like magnetic parameter M thermal diffusion effect as soret number S1, permeability parameter K1, Schimdt number Sc are taken into account. The velocity profile, temperature field, and concentration of incompressible dusty gas and dust particles for several parameters are discussed numerically and explained graphically.

Size Differentiation of Individual Atmospheric Aerosol during Winter in Xi'an, China

Airborne particulate matter (including TSP, PM10, PM2.5, and PM1) were collected at an urban site in Xi’an during winter 2010. Individual particles were analyzed using scanning electron microscopy and energy dispersive X-ray spectrometer (SEM-EDX). The morphologies, size distributions, and relative abundance of aerosol particles in each size were summarized. The monomodal particle size distribution was found in all the samples under different weather conditions, with the peaks located at less than 1.0 μm. The majority of particles were composed of soot, mineral dust, and tar balls, with minor fly ash particles. Soot aggregates were the predominant species (in numbers), ranging from 56.6% in TSP on a sunny day to 86.3% in PM1 on a cloudy day, with an average of 73.2% in all the samples. The particle mass concentration and chemical composition, including water-soluble inorganic ions, elemental compositions, organic carbon (OC) and elemental carbon (EC) contents of 24-hr integrated PM2.5, were also subject to chemical bulk analysis. Soot was predominantly observed in the PM2.5 samples (from 74.7% to 82.7% in numbers), whereas EC accounted for only a small amount (< 8%) of the PM2.5 mass. Corresponding to the mass concentrations of geological materials (29.2%, 44.5%, and 37.3% on sunny, cloudy, and hazy days), the number concentrations of mineral dust and fly ash particles on the sunny, cloudy, and hazy days were 14.6%, 7.1%, and 7.7%, respectively.

Research on Protection Measures and Explosion about Aluminum Dust

The aluminum dust explosion is one of the most serious accidents of dust explosion. The oxidation reaction ability of aluminium dust enhances after processed into small grain powder, the energy produced during explosion is large, so the damage is serious, and the possibility of the secondary explosion exists.The influencing factors in the conditions of aluminium dust explosion are: certain dust particle size and concentration; air or oxidant; the initial igniting energy; state of aluminium dust. Certain measures to prevent the aluminum dust explosion are discussed in the paper, based on the hazardous characteristics and factors related to the explosion of aluminum dust.

SO-FDTD method of analyzing the reflection and transmission coefficient of weakly ionized dusty plasma layer

The complex permittivity of weakly ionized dusty plasma is presented as a fractional polynomial in j. A frequency-domain constitutive relation of weakly ionized dusty plasma is given by shift operator finite-difference time-domain (SO-FDTD) method in time domain. Also the recurrence relation on the electromagnetic properties of weakly ionized dusty plasma is deduced by the SO-FDTD. The reflection and transmission coefficients of the weakly ionized dusty plasma layer are calculated, and the influences which is caused by the change of the dust particle concentration and radius on reflection and transmission coefficients are also analyzed by the SO-FDTD method. The result shows that the reflection coefficient in the presence of dust particles is smaller than in the absence of dust particles, while the transmission coefficient in the former case is larger than in the latter case. Besides, it is found that the reflection coefficient decreases as the concentration or radius of dust particle increases.

Interaction between glow discharge plasma and dust particles

The effect of dust particle concentration on gas discharge plasma parameters was studied through development of a self-consistent kinetic model which is based on solving the Boltzmann equation for the electron distribution function. It was shown that an increase in the Havnes parameter causes an increase in the average electric field and ion density, as well as a decrease in the charge of dust particles and electron density in a dust particle cloud. Self-consistent simulations for a wide range of plasma and dust particle parameters produced several scaling laws: these are laws for dust particle potential and electric field as a function of dust particle concentration and radius, and the discharge current density. The simulation results demonstrate that the process of self-consistent accommodation of parameters of dust particles and plasma in condition of particle concentration growth causes a growth in the number of high-energy electrons in plasma, but not to depletion of electron distribution function.

Characteristics of Atmospheric Dust Deposition in Snow on Glacier No. 72, Mount Tuomuer, China

Wind-blown mineral dust derived from the crustal surface is an important atmospheric component affecting the Earth’s radiation budget. Deposition of dust particles was measured in snow on Glacier No. 72, Mount Tuomuer, in the western Tian Shan, China. The mean concentration of dust particles (measured as the number of particles) with 0.57 < d < 26 µm in the snow pack is 706 × 103 mL−1, with a mean mass concentration of 3806 µg kg−1. Dust number size distribution showed the dominant particles with d < 2 µm, while volume size distribution showed single-modal structures having volume median diameters from 3 to 25? µm. Results were compared with data from other sites in the Tian Shan and various Northern Hemisphere sites. A backward trajectory model was also employed to examine the transport process of dust particles in this region. Most of the air mass originated from southern China, e.g., the Taklimakan Deserts in springtime, during the Asian dust period. Transport of dust from southern Chinese deserts to adjacent mountains is in agreement with a growing body of evidence on the importance of dust inputs to alpine regions.

Parameters of the positive column of glow discharge with dust particles

We calculate the measured nonlocal parameters of the plasma of the positive column of direct current glow discharge in the presence of dust structures with different dust particle concentrations. The calculations are performed for typical conditions of the positive column of low-pressure glow discharge in air at which a collisional regime of maintaining discharge is achieved. The discharge plasma is described using the diffusion approximation; the flows to the surface of the dust particles are described in the orbital motion limited approximation. Calculation is carried out for micron-size particles with concentrations of up to 1011 m−3. The distribution of the dust component is assumed to be independent of the discharge parameters. Radial distributions of the plasma components and of the electric field component are obtained. The charges of dust particles for various concentrations and discharge parameters are calculated. It is demonstrated that for a certain particle concentration, the absorption efficiency of plasma particles becomes comparable with diffusion losses at the tube walls. The influence of the dust cloud on the electric field configuration at different dust particle concentrations in the cloud is analyzed. The current-voltage characteristics of the positive column of glow discharge are calculated. A higher discharge stability toward the perturbative action of dust particles at high discharge current values is demonstrated.

Electrical time resolved metrology of dust particles growing in low pressure cold plasmas

The electrical parameters of a capacitively coupled radiofrequency (CCRF) discharge change significantly when dust arises in the discharge. This work demonstrates the ability to follow in real time the evolution of the size and of the concentration of dust particles forming in a CCRF discharge from the variation of the electron density and of the self-bias voltage of the active electrode. According to experimental findings, it appears that the variation of this self-bias voltage depends on the surface of the dust particles. This trend is confirmed by an analytical modelling considering the low frequency behaviour of the phenomenon.

Physico-chemical characteristics and environmental significance of snow deposition on Haxilegen glacier No.51 in Tian Shan, China

Snow chemistry on the glaciers of alpine regions is a good indicator of atmospheric environmental change. We examine snow chemistry in three snowpits at different altitudes on the Haxilegen Glacier No. 51, in the Kuitun River source, Tian Shan, China, during July-September 2004 to 2007. We use correlation analysis, factor analysis and sea-salt tracing methods to examine the characteristics and sources of major ions and mineral dust particles in the snow. Results show that mineral dust particles and major ions in the snow pits vary seasonally. During the Asian dust period in springtime, the concentration of mineral dust particles and major ions deposited in snow is high, while the concentration is relatively low during the non-dust period of summer and autumn. This may be caused by dust storm activity in central Asia. The order of major ionic concentrations in the snow packs was determined to be Ca2+ > SO4 2− > NH4 + > NO3 − > Cl−> Na+ > Mg2+ > K+. Ca2+ was the dominant cation; SO4 2− was the dominant anion. We find, with the exception of NO3 −, that the variabilities of ionic concentrations are highly correlated. Results show that the glacier region was significantly affected by dust activity and anthropogenic source. The major ions, especially Na+, originate from dust sources of central Asia and from the Ocean, transported by the westerly winds.

MADE-in: a new aerosol microphysics submodel for global simulation of insoluble particles and their mixing state

Abstract. Black carbon (BC) and mineral dust are among the most abundant insoluble aerosol components in the atmosphere. When released, most BC and dust particles are externally mixed with other aerosol species. Through coagulation with particles containing soluble material and condensation of gases, the externally mixed particles may obtain a liquid coating and be transferred into an internal mixture. The mixing state of BC and dust aerosol particles influences their radiative and hygroscopic properties, as well as their ability of forming ice crystals. We introduce the new aerosol microphysics submodel MADE-in, implemented within the ECHAM/MESSy Atmospheric Chemistry global model (EMAC). MADE-in is able to track mass and number concentrations of BC and dust particles in their different mixing states, as well as particles free of BC and dust. MADE-in describes these three classes of particles through a superposition of seven log-normally distributed modes, and predicts the evolution of their size distribution and chemical composition. Six out of the seven modes are mutually interacting, allowing for the transfer of mass and number among them. Separate modes for the different mixing states of BC and dust particles in EMAC/MADE-in allow for explicit simulations of the relevant aging processes, i.e. condensation, coagulation and cloud processing. EMAC/MADE-in has been evaluated with surface and airborne measurements and mostly performs well both in the planetary boundary layer and in the upper troposphere and lowermost stratosphere.

The effect that coarse particles have on estimates of both optical and radiation characteristics of dust aerosol

Based on mathematical simulation, quantitative estimates of the effect that coarse dust particles have on the accuracy of retrieving the optical characteristics of aerosol have been obtained from the results of ground-based measurements of the spectral fluxes of both direct and scattered solar radiations. The results of verifying a retrieval algorithm (used at the AERONET ground-based network) based on special test models showed that the aerosol characteristics retrieved with this algorithm are unsuitable for calculating integral solar fluxes and for simulating space spectrometric IR measurements when the concentration of dust particles in the atmosphere exceeds their concentration in the well-known CONT model of continental aerosol by a factor of two or more.

Modeling of Dispersion and Settling of Micron-Sized Dust Particles in Pressure Regulator Used in Oxygen-Enriched Environment

Abstract It is essential to maintain cleanliness in an oxygen system as many accidents occurring in oxygen-enriched environment indicate contamination as a major source of ignition. Computational fluid dynamics (CFD) analyses show that valve seats, T-joints, elbows and spots with complex geometries are possible locations for accumulation of the dust particles. It is important to understand the mechanisms of contaminant accumulation, the initiation of fire and its propagation in valves and regulators in order to suggest ways for their prevention. As contaminant dust particles flow with oxygen through valves and piping systems, the solid dust particles impact or rub with the pipe wall or with each other. This results in the building up of static electric charges in them. These charged dust particles may eventually accumulate and lead to electrostatic discharge, thus creating a potential cause of initiation of fire. The aim of the present work is to develop a mathematical model based on CFD, of the dispersion and settling of micron-sized charged dust particles in the pressure regulator, commonly used in oxygen application. A two-dimensional numerical model of flow, dust particle dispersion and particle settling, utilizing finite volume approach, has been developed on FLUENT 6.3.26 platform. The results show that there is a possibility of electrical discharge due to the settlement of charged dust particles if a regulator is attempted to be reopened within a short time of it being closed. Since it is practically impossible to make all oxygen systems free of contaminants at all times, it may be worthwhile to analyze ways about how to avoid ignition even in presence of large concentration of dust particles. The present study may give an insight into the possibility of ignition and offer suggestions to avoid it through appropriate system configuration and operation timings.

Fully nonlinear solitary waves in a dusty electronegative multispecies plasmas

The formation and dynamics of fully nonlinear ion-acoustic solitary waves, which accompany electronegative plasmas composed of positive ions, two-negative ions, isothermal electrons, as well as a fraction of stationary charged (positive or negative) dust impurities are investigated. By using the hydrodynamic and Poisson equations, an energy-integral equation involving a Sagdeev pseudo-potential is derived. Using the latter, we have defined precisely the existence regions of the electrostatic localized pulses. The critical total negative ions concentration αc and critical second-negative ion density ratio νc thresholds, which indicate where the solitary pulses set in, have been determined for various regimes. Numerical calculations reveal that only supersonic pulses can exist. The total negative ions concentration, the second-to-total negative ions density ratio, electrons-to-positive ions temperature ratio, dust impurities concentration, positive-to-negative mass ratio, and Mach number have been investigated on the nonlinear wave profile. It is found that the total negative ion concentration as well as the dust particles concentration play the significant role in deciding the polarity of the propagating pulses. The results could be applied to investigate and predict the behavior of the nonlinear solitary structure in future laboratory plasma experiment having dusty electronegative multispecies plasmas as referred by Ichiki et al. [Phys. Plasmas 8, 4275 (2001)].

Temporal characteristics of mineral dust particles in precipitation of Urumqi River Valley in Tian Shan, China: A comparison of alpine site and rural site

Physico-chemical characteristics of mineral dust particles in the precipitation at both an alpine site and a rural site were determined in the Urumqi River Valley, Tian Shan, China. Results showed that the concentration, size distribution and chemical constitutes of dust particles in the precipitation varied seasonally at both two sites, though there existed obvious differences between them. Dust particle concentration in the precipitation increased during winter and springtime, but it decreased during summer and autumn, which had a positive correlation with strengthened wind speed and Asian dust activity, but a negative correlation with the seasonal variation of the precipitation amount, implying that aerosol dust in the precipitation of Urumqi River Valley in Tian Shan was very sensitive to the seasonal change of regional atmospheric environment in central Asia. Volume-size distribution of mineral dust particles showed larger modal size in Asian dust period of winter–spring, but relatively smaller modal size in non-dust period of summer–autumn. Moreover, the average modal size and mass concentration of dust particles at the rural site are larger than that of the alpine site. Chemical constitutes of dust indicated that the precipitation chemistry was mainly controlled by regional dust storms, local dust and anthropogenic activities in central Asia. HYSPLIT Model was also employed to examine the transport process of air mass and mineral dust particles in this region.

Indoor air quality improvement from particle matters for laying hen poultry houses

During breeding periods poultry production may produce harmful effects on the environment. Emissions of dust, odour and ammonia into the surrounding environment via the ventilation systems used in poultry houses create environmental hazards with the expulsion of large quantities of dust representing the main environmental concern. Indoor dust concentration in poultry houses must be controlled to provide adequate air quality for labourers and animals inside breeding enclosures. This study investigated the effects of diurnal change, seasonal breeding systems and housing style on indoor dust production and correlated this data with theoretical animal activity. Various ranges of indoor dust particle concentrations were measured within both aviary and cage systems containing laying hens. Measurements were taken throughout the whole day during two different seasons. An attempt was made to improve indoor air quality by purifying the recirculating air inside the poultry house. In order to select appropriate filtration system, and working conditions for the experiment, laboratory scale experiments were carried out. The efficiency of the designed filtering systems was tested in a floor housing system and finally a best performing filtering system was tested in a commercial floor housing system. During small scale barn measurements, a dry filter achieved the highest dust reduction efficiency in comparison to cyclone and wet filtration systems. Following these experiments, the designed dry filter was recommended for testing in a commercial farm. Reduction efficiencies were 55 and 72% for indoor concentration and dust emission rate, respectively. ► Dust concentration and emission estimated in two laying hen houses (cage and aviary). ► The measurements were taken over two year seasons (winter and summer) through the whole day. ► New dry filter was designed after selecting appropriate materials and working conditions. ► The reduction efficiency of dry and wet filter system was examined. ► The designed filter is recommended for use on commercial scale farms.

Indoor air pollution and health of children in biomass fuel-using households of Bangladesh: comparison between urban and rural areas

Indoor air pollutants from biomass combustion pose a risk for respiratory diseases in children. It is plausible that distinct differences in the indoor air quality (IAQ) exist between urban and rural areas in developing countries since the living environment between these two areas are quite different. We have investigated possible differences in IAQ in urban and rural Dhaka, Bangladesh and the association of such differences with the incidence of respiratory and some non-respiratory symptoms in children of families using biomass fuel. Indoor air concentrations of carbon monoxide (CO), carbon dioxide (CO(2)), dust particles, volatile organic compounds (VOCs), and nitrogen dioxide were measured once in the winter and once in the summer of 2008. Health data on 51 urban and 51 rural children under 5years of age from 51 families in each area were collected once a week starting in the winter and continuing to the summer of 2008. Mean concentrations of CO, CO(2,), dust particles, and major VOCs were significantly higher in urban kitchens than in rural ones (p<0.05). The incidence rate ratio (IRR) suggests that compared to the urban children, the children in the rural area suffered significantly more from respiratory symptoms [IRR1.63, 95% confidence interval (CI) 1.62-1.64], skin itchiness (IRR3.3, 95% CI 1.9-5.7), and diarrhea (IRR1.8, 95% CI 1.4-2.4), while fewer experienced fever (IRR0.5, 95% CI 0.4-0.6). No difference was observed for other symptoms. We found lower IAQ in the homes of urban biomass fuel-users compared to rural ones in Bangladesh but could not attribute the occurrence of respiratory symptoms among children to the measured IAQ. Other factors may be involved.