Dust Intensity Research Articles

Scientific assessment of the quality of OSIRIS images

OSIRIS, the scientific imaging system on board the ESA Rosetta spacecraft, has been imaging the nucleus of comet 67P/Churyumov-Gerasimenko and its dust and gas environment since March 2014. The images serve different scientific goals, from morphology and composition studies of the nucleus surface, to the motion and trajectories of dust grains, the general structure of the dust coma, the morphology and intensity of jets, gas distribution, mass loss, and dust and gas production rates. Aims. We present the calibration of the raw images taken by OSIRIS and address the accuracy that we can expect in our scientific results based on the accuracy of the calibration steps that we have performed. Methods. We describe the pipeline that has been developed to automatically calibrate the OSIRIS images. Through a series of steps, radiometrically calibrated and distortion corrected images are produced and can be used for scientific studies. Calibration campaigns were run on the ground before launch and throughout the years in flight to determine the parameters that are used to calibrate the images and to verify their evolution with time. We describe how these parameters were determined and we address their accuracy. Results. We provide a guideline to the level of trust that can be put into the various studies performed with OSIRIS images, based on the accuracy of the image calibration.

Forward research on transmission characteristics of near-surface particulate-matter-polluted atmosphere in mining area combined with CFD method.

The optical radiation and radiation transfer characteristics of atmospheric particulate matter (PM) in mining area of northwest China were simulated and analyzed in this paper. Computational fluid dynamics (CFD) method was adopted to simulate the distribution of PM considering the local desertification and mining activities. The 1-D radiative transfer equation was solved using discrete ordinates method combined with Mie scattering model based on the CFD simulation results. The spectral aerosol optical depth and transmission characteristics of PM polluted atmosphere in the wavelength of 1-25μm under different intensity of dust releases, wind speeds and dust compositions were obtained and analyzed. The simulation results show that: the transmission characteristics are obviously enhanced with the increase of wind speed and sand particles' proportion but greatly decreased with the increase of the intensity of dust release.

DUST CONTINUUM AND POLARIZATION FROM ENVELOPE TO CORES IN STAR FORMATION: A CASE STUDY IN THE W51 NORTH REGION

We present the first high-angular resolution (up to 0.7", ~5000 AU) polarization and thermal dust continuum images toward the massive star-forming region W51 North. The observations were carried out with the Submillimeter Array (SMA) in both the subcompact (SMA-SubC) and extended (SMA-Ext) configurations at a wavelength of 870 micron. W51 North is resolved into four cores (SMA1 to SMA4) in the 870 micron continuum image. The associated dust polarization exhibits more complex structures than seen at lower angular resolution. We analyze the inferred morphologies of the plane-of-sky magnetic field (B_bot) in the SMA1 to SMA4 cores and in the envelope using the SMA-Ext and SMA-SubC data. These results are compared with the B_bot archive images obtained from the CSO and JCMT. A correlation between dust intensity gradient position angles (phi_{nabla I}) and magnetic field position angles (phi_B) is found in the CSO, JCMT and both SMA data sets. This correlation is further analyzed quantitatively. A systematically tighter correlation between phi_{nabla I} and phi_B is found in the cores, whereas the correlation decreases in outside-core regions. Magnetic field-to-gravity force ratio (Sigma_B) maps are derived using the newly developed polarization - intensity gradient method by Koch, Tang & Ho 2012. We find that the force ratios tend to be small (Sigma_B <= 0.5) in the cores in all 4 data sets. In regions outside of the cores, the ratios increase or the field is even dominating gravity (Sigma_B > 1). This possibly provides a physical explanation of the tightening correlation between phi_{nabla I} and phi_B in the cores: the more the B field lines are dragged and aligned by gravity, the tighter the correlation is. Finally, we propose a schematic scenario for the magnetic field in W51 North to interpret the four polarization observations at different physical scales.

The role of the clean development mechanism in achieving China’s goal of a resource-efficient and environmentally friendly society

This paper examines the impact of the clean development mechanism (CDM) on China’s progress in building a resource-efficient and environmentally friendly society, referred to as a dual-goal society. It presents China’s CDM activities from the perspective of policy directions, administrative arrangements and capacity building as well as outlines the regional trends and distribution of CDM projects across China’s 30 provinces. Based on regression analysis of 2006–2009 panel data, the research was able to provide estimates at provincial level of the impacts of CDM activities on China’s CO2 emission intensity, SO2 emission intensity and industrial dust emission intensity. The study concludes that the active CDM projects are mainly located in the less-developed central and west China where they have provided increased opportunities for sustainable development. Furthermore, the successful implementation of CDM projects across the country has significantly decreased the emission intensity of CO2, SO2 and industrial dust, which means that these activities have enhanced China’s ability to build the desired dual-goal society.

Past dust and GAS/FUME exposure and COPD in Chinese: The Guangzhou Biobank Cohort Study

The impact of occupational dust and gas/fume exposure on chronic obstructive pulmonary disease (COPD) in developing countries has not been quantified. We examined the relationship between past dust and fume exposure and prevalence of COPD and respiratory symptoms in a cross-sectional analysis of a large Chinese population sample. Participants in the Guangzhou Biobank Cohort Study (n=8216; 27.3% men, mean age 61.9±6.8 years) had spirometry and a structured interview including exposures, symptoms, and lifestyle. Self-reported intensity and duration of dust and gas/fume exposure was used to derive cumulative exposure. COPD was diagnosed from spirometry using lower limit of normal based on prediction equations. COPD was associated with high exposure to dust or gas/fume (exposed: 87/1206 v non-exposed: 191/3853; adjusted odds ratio: 1.41; 95% confidence interval (CI) 1.06, 1.87) with no evidence of effect modification by smoking. Respiratory symptoms were associated with exposures to dust and gas/fume, with adjusted odds ratios for chronic cough/phlegm of 1.57 (1.13, 2.17) and 1.39 (1.20, 1.60) for dyspnoea. The overall population attributable fraction for COPD due to occupational exposure was 10.4% (95% CI -0.9%, 19.5%). Occupational dust and gas/fume exposure is associated with an increased prevalence of COPD in this Chinese sample, independent of smoking. The population attributable fraction in Chinese is similar to that in Western populations.

A Novel Coal Water Content Measurement Method on Conveyor Belt

The coal dust storms create great harm to the environment and human health. The main source of coal dust is the low coal moisture on various types of coal conveying belt. The intensity of coal dust is heavy, especially in the coal-fired power plant, coal transportation coal conveyor belt and in areas, where various reprint point was heavy. In this paper, a measurement method on moisture content of coal conveying belt was proposed. The local group based on the probability can eliminate the factors affecting measuring accuracy such as the big piece of coal, the thickness of coal seam, and coal rock. The rationality behind the measurement was verified by simulation experiments. The proposed method gives an effective method to measure the moisture content of coal on the conveyer belt and provides technical support to prevent the spontaneous combustion and explosion of coal when the moisture content of coal is too low.

Transport pathways of Sahara dust over Athens, Greece as detected by MODIS and TOMS

This study analyses the Saharan dust (SD) events over Athens during 2000–2005 using daily Moderate Resolution Imaging Spectroradiometer (MODIS) and Total Ozone Mapping Spectrometer (TOMS) satellite data. The dust events were identified using the MODIS daily observations over Greece and the dates with detectable dust plumes were collected. The aerosol optical depth (AOD550) and fine-mode (FM) values from Terra-MODIS and Aerosol Index (AI) values from TOMS were obtained over Athens for the dusty days focusing on analysing the seasonality, intensity, transport pathways and mechanisms of dust. Seventy-nine dusty days were identified corresponding to SD events with duration from 1 to 4 consecutive days; the majority of SD events occur in April–May and July, with less during winter. The dust frequency presents large seasonal and intra-annual variation, with a maximum of 20 dust events in 2002 and a minimum of 7 in 2003. The use of TOMS-AI seems to be adequate for the characterization of dust over Athens despite the fact that 35% of the dusty days do not correspond to high AI values. The dust events are more intense during spring, mostly associated with dust transport from near surface to mid troposphere (vertical transport mechanism), while dust events detected only within the boundary layer have the lowest AOD values. On the other hand, the dust events in summer are of larger duration due to stable weather conditions and absence of precipitation and transportation at elevated heights.

OSL dating and lithological characteristics of loess deposits from Biały Kościół

Absolute dating using luminescence methods is widely applicable in geology, geomorphology, palaeogeography and in archaeology in establishing ages of sediments and archaeological artefacts. By creating absolute time scales for different events in the history of Earth scientists are able to reconstruct changes in climate and environment in the past, and the history of colonization and development of culture. Grain size is the most important loess lithologic property. Grain size composition depends mainly on factors connected with depositional processes (i.e. variety of source areas, distance from source areas, frequency and intensity of dust transporting winds). The influence of post depositional processes on changes in grain size composition seems to be of less importance with the exceptions for warm and long periods of intensive pedogenesis, which are favorable for formation of clay minerals. Therefore the grain size differentiation within thick loess sections may be used as a proxy record of climate changes during loess cover development. Here we present results for 12 samples dated at the profile at Biały Kościół. Obtained OSL results in some cases are quite different as compared with the OSL and TL dates obtained during last 10 years by other authors and presented in previous publications relating to this loess profile.

Lung function loss in relation to silica dust exposure in South African gold miners

ObjectiveTo estimate exposure-response relationships between respirable dust, respirable quartz and lung function loss in black South African gold miners.Methods520 mineworkers aged >37 years were enrolled in a cross-sectional study. Gravimetric...

Imprint of North-Atlantic abrupt climate changes on western European loess deposits as viewed in a dust emission model

Western European loess sequences of the last glaciation (∼100,000–15,000 years BP) exhibit strong, cyclic variations of the sedimentation rate, which are coeval to the Greenland stadial/interstadial cycles and the Heinrich events. These North-Atlantic rapid climate changes appear, thus, as a potential cause for the sedimentation variations, via changes in dust intensity cycle. Here we make a first step in testing this hypothesis, by modelling the impact of the North-Atlantic abrupt climate variations on dust emission. Our dust emission calculations use meteorological fields generated by the LMDZ atmospheric general circulation model at a resolution down to 60 km over Western Europe. Three numerical experiments are run, representing a Greenland stadial, an interstadial and a Heinrich event. Orbital parameters and ice-sheet configuration correspond to conditions from Marine Isotope Stage 3 (∼60,000–25,000 years BP), a period characterized by strong millennial-scale climate variability. The only differences we impose in the boundary conditions regard the North-Atlantic surface temperature and sea-ice cover in the latitudinal band 30°–63°N. The changes in wind, precipitation, soil moisture and snow cover from one simulated state to another result in small differences in dust emission intensity. In contrast, when the inhibition of the aeolian erosion by vegetation is taken into account, the dust fluxes for the cold climate states (Greenland stadial and Heinrich event) become generally more than twice higher than those for the relatively warmer Greenland interstadial, in agreement with the loess data. These results support the hypothesis that the North-Atlantic millennial-scale variability is imprinted in Western European loess profiles, and point to vegetation changes as the main factor responsible for millennial-scale sedimentation variations. An analysis for the English Channel and southern North Sea areas, major potential dust sources, shows that the seasonality of dust emission is not controlled by the wind speed, as in modern large deserts, but by the surface conditions. Consequently, the dusty season lasts from late winter to early summer, with maximum activity in April–May, and is shifted towards summer when the climate is colder.

Rhinite et asthme liés à l’exposition aux poussières de coton chez des apprentis en habillement

Respiratory allergies are the most common occupational diseases in the world. The aim of this study was to determine the prevalence of rhinitis and asthma among apprentices exposed to cotton dust in the clothing industry and to describe their epidemiologic and clinical profiles. We carried out a descriptive study of 600 apprentices in a textile and clothing vocational training centre in the Monastir area. The investigation comprised a questionnaire exploring risk factors and symptoms appearing during their training. Subjects who developed allergic respiratory symptoms at the work-place underwent a clinical examination, rhinomanometry and investigation of their allergic status and respiratory function. One hundred twenty apprentices (20%) developed allergic respiratory reactions due to exposure to textile dust (exclusively cotton) during their training, with a positive withdrawal-re-exposure test. Conjunctivitis (14.3%) and rhinitis (8.5%) were the most frequent allergic symptoms. Twenty eight apprentices (4.6%) presented symptoms of asthma. Rhinitis was associated with asthma in 45% of cases. Two cases of asthma were diagnosed clinically at the work-place following their exposure to textile dust. The prick test performed in 120 symptomatic apprentices was positive in 41.6% of cases. There was sensitization to pollens in 29 cases and to dermatophagoides in 13 cases. Cotton and wool allergy was noted in two cases. Allergic symptoms developing during the training were significantly more frequent in the atopic group, and they varied according to the intensity of textile dust exposure. In the textile and clothing industry the frequency of respiratory disorders caused by allergens remains high, especially in atopic apprentices who constitute a population at high risk.

Biomarkers of Airway Acidity and Oxidative Stress in Exhaled Breath Condensate from Grain Workers

Grain workers report adverse respiratory symptoms due to exposures to grain dust and endotoxin. Studies have shown that biomarkers in exhaled breath condensate (EBC) vary with the severity of airway inflammation. The purpose of the study was to evaluate biomarkers of airway acidity (pH and ammonium [NH(4)(+)]) and oxidative stress (8-isoprostane) in the EBC of grain workers. A total of 75 workers from 5 terminal elevators participated. In addition to EBC sampling, exposure monitoring for inhalable grain dust and endotoxin was performed; spirometry, allergy testing, and a respiratory questionnaire derived from that of the American Thoracic Society were administered. Dust and endotoxin levels ranged from 0.010 to 13 mg/m(3) (median, 1.0) and 8.1 to 11,000 endotoxin units/m(3) (median, 610) respectively. EBC pH values varied from 4.3 to 8.2 (median, 7.9); NH(4)(+) values from 22 to 2,400 microM (median, 420); and 8-isoprostane values from 1.3 to 45 pg/ml (median, 11). Univariate and multivariable analyses revealed a consistent effect of cumulative smoking and obesity with decreased pH and NH(4)(+), and intensity of grain dust and endotoxin with increased 8-isoprostane. Duration of work on the test day was associated with decreased pH and NH(4)(+), whereas duration of employment in the industry was associated with decreased 8-isoprostane. Chronic exposures are associated with airway acidity, whereas acute exposures are more closely associated with oxidative stress. These results suggest that the collection of EBC may contribute to predicting the pathological state of the airways of workers exposed to acute and chronic factors.

Eolian transport of salts—A case study in the area of Lake Ebinur (Xinjiang, Northwest China)

In the Ebinur region of Western Dzungaria, strong wind flows from Dzungarian Gate predetermine the widespread development of deflation processes. As a result of human-induced desiccation of Lake Ebinur, a new source of the loose material—the dry lakebed—has formed, which has intensified dust storms in this region. Annual dynamics of the frequency and intensity of dust storms and the amount and chemical composition of salts in the eolian material deposited in the area have been studied. The frequency of dust storms and the intensity of dust and salt deposition regularly decrease with an increase in the distance from the dry lake bottom (playa). The amount of dust deposition ranges from 600 (near the lake) to 70 (100–200 km from the lake) g/m 2/a. The amount of salts precipitating with dust is mainly from 14 to 27 g/m 2/a; the maximum registered amount of salt deposition is 77 g/m 2/a. As shown in our study, the farther from the lake, the higher the portion of sulfate and calcium and the smaller the portion of chloride and sodium ions in the composition of salts.

In Situ Transmissiometer Measurements for Real‐Time Monitoring of Dust Discharge during Orchard Nut Harvesting

Rapid assessments of operating conditions and field preparation on dust discharge from nut harvesters are needed to guide improved equipment design and grower practices for dust reduction. An industrial opacity sensor, typically used for industrial stack monitoring, was adapted for use on a nut harvester to measure relative dust intensity during nut pick-up operations in almond orchards. Due to the high volume of discharge air and the presence of large debris such as leaves, additional components were coupled with the sensor to enable subsampling of the air. Pre-harvest windrow preparation conditions were evaluated. Results indicated that relative dust intensity decreased by 32% during harvest activities after windrow preparation with proper nut sweeper adjustment. Conventional harvesting results indicated that under typical operating conditions, reducing the separation fan speed could reduce relative dust intensity by 54%. Ground speed also had a strong effect; reducing speed from 4.8 to 2.4 km h(-1) reduced opacity of discharged air by 50%. The measurement system was also mounted on a separate vehicle and used as a tool for comparing modifications in harvest machine designs where direct measurement of discharge may not be feasible due to mechanical constraints. A comparison between a conventional harvester and one modification in the harvester design found that the machine modification decreased relative dust intensity by 73%. The measurement tools described in this work can be used to provide rapid feedback on harvester operating conditions, orchard cultural practices, and machine design modifications.

Comparison of the dust distributions in the innermost comae of comets—1P/Halley and 19P/Borrelly spacecraft observations

We present a comparative study of the inner comae of comets 1P/Halley and 19P/Borrelly using data from the Halley Multicolour Camera (HMC) onboard Giotto and the Miniature Integrated Camera and Spectrometer onboard Deep Space 1 (DS1). We show that the dust brightness dependence as a function of radial distance is different for both comets. We suggest that optical depth or fragmentation effects dominate the brightness distribution at comet 1P/Halley whereas acceleration or non-point source geometry effects dominate at comet 19P/Borrelly. The nightside profiles of comet 19P/Borrelly suggest a continuing non-radial outflow from the nucleus out to several tens of kilometres. This modifies the observed dayside to nightside brightness ratio with distance and offers a further constraint on dust emission models. By setting up a linear system of equations to fit the dust intensity distribution, better fits could be obtained by incorporating acceleration into the equation of free-radial outflow. Finally, we estimate the dust production rate of 19P/Borrelly at the time of DS1 encounter as no higher than 324 kg/s based on comparisons with HMC intensity measurements.

Influence of Asian dust storms on air quality in Taiwan

In each year, dust storms triggered by cold air masses passing through northern China and Mongolia enhance the PM10 concentration over Taiwan region during winter and spring. On average, there are four to five dust events and 6.1 dust days in a year in Taiwan. Each event lasts for 1 day or even longer. A procedure to identify a dust event is rationalized and exercised on data collected during 1994–2005. Also, a ranking method named as the dust intensity rank (DIR) is developed to distinguish the intensity of each event affecting the local air quality. About 86% of dust days belong to ranks 1 and 2. In general, poorer air quality is associated with higher ranks. Ranks 4 and 5 correspond to a PSI (Pollution Standard Index) larger than 100. Linking DIR with the popular PSI is useful for both the public and the official forecasting system. It is also useful for inter-comparison between dust influences on air quality at different downstream regions in Taiwan. Composite analyses of the temporal and spatial variation of the hourly PM10 level indicate that dust particles usually arrive 12 h before the time of the peak PM10 concentration and last for 36 h at northern Taiwan, while the time of the peak concentration at eastern or western Taiwan, due to the evolution of the synoptic weather system, is about 3–12 h later. It is noted that the increase of PM10 level at the western side of Taiwan results from a mixture of upstream Asian dust inputs and local pollutants.

Water-soluble part of the aerosol in the dust storm season—evidence of the mixing between mineral and pollution aerosols

Six dust episodes were observed in Beijing in 2002. Both TSP (Total Suspended Particulate, particle size smaller than 100 μm) and PM 2.5 (particle size smaller than 2.5 μm) aerosol samples in these episodes were collected and their characteristics of water-soluble part were elaborated in demonstrating the mixing of mineral aerosol with pollution aerosol in the long-range transport of Asia aerosols with various sources and different paths. The dust storm peaked on 20 March, in which the highest concentrations of TSP and PM 2.5 were 10.9 and 1.4 mg m −3, respectively. The mass fraction of water-soluble part generally decreased with the increase of dust intensity. SO 4 2− contributed 38–70% to the total anions and Ca 2+ contributed 37–80% to the total cations, indicating that SO 4 2− and Ca 2+ were the most abundant anion and cation, respectively. The major ions of the water-soluble parts could be classified into three groups, i.e., the crust ions (Ca 2+, Na +, and Mg 2+), the pollution-crust ions (SO 4 2−, Cl −, and K +), and the pollution ions (NO 3 −, NH 4 +, NO 2 −, and F −). Crust ions and pollution ions were the main ion fractions in super dust and non-dust days, respectively, whereas the pollution-crust ions were the main ion fractions in both dust days of various dust intensity and non-dust days, which demonstrated clearly that the mixing between mineral and pollution aerosols was ubiquitous during the dust seasons (even in the super dust storm days) although it was more obvious in those normal and weak dust episodes. The main chemical species of the water-soluble part of the aerosols were CaCO 3 in the super dust storm, CaSO 4 in the normal and the weak dust events, and NH 4NO 3 in the non-dust event days. The secondary transformation of sulfate and nitrate occurred on dust particles both during and after dust days provided the strong evidence of the mixing between mineral and pollution aerosols during the long-range transport of dust.

Chemical composition and source signature of spring aerosol in Seoul, Korea

The measurement of atmospheric aerosol was made in Seoul during the spring of 1998. The objective of this study was to investigate the chemical characteristics of atmospheric aerosol with an emphasis on the effect of Asian dust. Total suspended particles (TSP) and particles smaller than 10 μm (PM10) were collected during March‐May 1998. For PM10, water‐soluble ions and trace elements were analyzed: NO3−, SO42−, Na+, NH4+, K+, Mg2+, Ca2+, Na, Mg, Al, Ca, Fe, Mn, Cr, Co, Cu, Zn, Cd, and Pb. All data were sorted into three groups on the basis of the intensity of Asian dust observed in Seoul: nondust, regular dust, and heavy dust. Chemical characteristics of aerosol were distinct for the heavy dust incidence compared to the other two cases. The average mass concentration of TSP and PM10 increased substantially during the heavy dust period. For water‐soluble ions, concentrations of SO42− and NO3− were the lowest, whereas Ca2+ and Mg2+ concentrations were remarkably enhanced. Concentrations and mass fraction of crustal elements such as Na, Mg, Ca, Fe, and Mn were highly elevated, but those of pollution‐derived heavy metals were appreciably decreased. Enrichment ratios of metallic components indicated that soil dust was the primary source of spring aerosols over Seoul. This was also confirmed by factor analysis. Trajectory analysis provided a convincing evidence for the air mass coming from the Asian desert areas, which are the source region of mineral dust. In contrast, the anthropogenic influence was more pronounced for the regular dust period: concentrations of heavy metals, NO3−, and SO42− were the highest. It could be associated with the transport of air mass over the industrialized regions of China, which is demonstrated by backward trajectory analysis. The result of factor analysis with high factor loadings in SO42− and NO3− implied the considerable influence of industrial emission on the composition of all spring aerosols over Korea.

Nuisance Concerns and Odor Control

Nuisance and odor control continue to be major challenges to livestock and poultry producers across the country. Dust and flies are the two most frequently mentioned nuisances after odors. Research and testing have devised systems that are capable of achieving reduced frequency and intensity of odors, flies, and dust; however, these systems are typically more expensive to build and operate than is the standard lagoon holding basin. Producers who operate close to sensitive odor perception sites are at a clear disadvantage to those located in more remote locations. In addition to the cost factor is the uncertainty associated with nuisance and odor control. Some dairies are able to co-exist with their neighbors despite frequent odor detection, but others find that their neighbors demonstrate much less tolerance. Odor control additives, either fed or applied to the manure, have generally been less than fully successful. Careful site selection, appropriate facility design, flawless management, and a generous amount of positive local relations have proved to be the most effective means of avoiding cost from odor confrontations.

A fragmentation model of dust grains in the inner coma of Halley. A possible explanation of the color effect

AbstractA model to describe the intensity of dust scattered light observed by the spectrometer TKS during the Vega/Halley encounter is presented. Good agreement is obtained when using a particle radius dependent mass density. The color effect is reproduced if the refractive index of tholin is adopted.