Total Amount Of Dust Research Articles

Quantifying the contribution of dust to alpine soils in the periglacial zone of the Uinta Mountains, Utah, USA

Profiles of alpine soils in the Uinta Mountains (Utah, USA) were investigated to determine how long-term dust deposition has influenced soil properties in this environment. Field studies were focused on four above-treeline sites, all of which were apparently beyond the reach of erosive glacial ice during the Pleistocene. Modern dust, soil A and B horizons, and local bedrock were compared in terms of major and trace element geochemistry, along with Sr and Nd isotope compositions. In all cases, soil samples are a mixture of dust and local bedrock end members, with A horizons more closely resembling dust, and B horizons more similar to bedrock. Calculations estimate that these soil profiles contain ~50 to 80% dust, which is effectively mixed downward into the solum by cryoturbation. Because these landscape positions were not glaciated, the total amount of dust contained within soil profiles is large relative to sites at lower elevation within the glacial limit. In addition to altering physical properties of these soil profiles, including horizonation and texture, deposition of dust rich in base cations positively influences soil fertility.

METALLICITIES, DUST, AND MOLECULAR CONTENT OF A QSO-DAMPED Lyα SYSTEM REACHING logN(H I) = 22: AN ANALOG TO GRB-DLAs

We present the elemental abundance and H2 content measurements of a Damped Lyman-{\alpha} (DLA) system with an extremely large H i column density, log N(H i) (cm-2) = 22.0+/-0.10, at zabs = 3.287 towards the QSO SDSS J 081634+144612. We measure column densities of H2, C i, C i^*, Zn ii, Fe ii, Cr ii, Ni ii and Si ii from a high signal-to-noise and high spectral resolution VLT-UVES spectrum. The overall metallicity of the system is [Zn/H] = -1.10 +/- 0.10 relative to solar. Two molecular hydrogen absorption components are seen at z = 3.28667 and 3.28742 (a velocity separation of \approx 52 km s-1) in rotational levels up to J = 3. We derive a total H2 column density of log N(H2) (cm-2) = 18.66 and a mean molecular fraction of f = 2N(H2)/[2N(H2) + N(H i)] = 10-3.04+/-0.37, typical of known H2-bearing DLA systems. From the observed abundance ratios we conclude that dust is present in the Interstellar Medium (ISM) of this galaxy, with a enhanced abundance in the H2-bearing clouds. However, the total amount of dust along the line of sight is not large and does not produce any significant reddening of the background QSO. The physical conditions in the H2-bearing clouds are constrained directly from the column densities of H2 in different rotational levels, C i and C i^* . The kinetic temperature is found to be T = 75 K and the particle density lies in the range nH = 50-80 cm-3 . The neutral hydrogen column density of this DLA is similar to the mean H i column density of DLAs observed at the redshift of {\gamma}-ray bursts (GRBs). We explore the relationship between GRB-DLAs and high column density end of QSO-DLAs finding that the properties (metallicity and depletion) of DLAs with log N(H i) > 21.5 in the two populations do not appear to be significantly different.

Survey of dust formed in the TEXTOR tokamak: structure and fuel retention

A detailed survey of erosion and deposition on plasma-facing components was performed in the TEXTOR tokamak. Co-deposits and dust particles were collected from graphite limiters and from several locations on the Inconel liner. The total amount of dust (loose material), originating mainly from carbon-rich co-deposits detached from the limiters and the liner, was around 2 g, with sizes from 0.1 μm to 1 mm. The morphology and fuel retention was determined using microscopy methods, ion beam analysis and thermal desorption spectrometry. The study revealed differences in structure and fuel content between deposits from the toroidal and main poloidal limiters. There were also splashes, up to 1 mm in diameter, of molten metal (mainly nickel) on the toroidal limiters. Issues of the dust conversion factor (erosion-to-dust) are addressed and a comparison with results of previous dust surveys at TEXTOR is also briefly presented.

Environmental risks for gemstone miners with reference to Merelani tanzanite mining area, Northeastern Tanzania

Artisanal and small-scale gemstone miners are the workers with the highest health risk exposure in Tanzania. Gemstone mining at Merelani tanzanite mines which has gone to depths of 100 m or more in narrow straight and inclined shafts, underground artisanal miners work under a very harsh environment. Tanzanite deposits are located within sheared zones, lying along a deep-seated Lelatema fault zones. Rocks along these zones which are mainly graphitic and or/gypsum-bearing gneisses surrounded by limestone are soft, fractured and strongly weathered. Poor mining techniques, lack of geological background, chronic shortage of capital, and the lack of awareness on environmental pollution in the shafts have led to health and safety problems. In deep mines such as Merelani tanzanite mine, where the rocks are graphitic (C-rich), existence of poisonous gases is common. Dust exposure during drilling, blasting and shovelling indicates high average levels of overall respirable dust 15.5 mg/m3 whereby respirable quartz and graphite are 2.4 mg/m3 and 1.5mg/m3, respectively. The total amount of dust is 28.4 mg/m3. Supply of air (oxygen) to such depths by using small compressors is unreliable and inadequate, since they sometimes fail or deliberately are switched off. Further, lack of adequate ventilation for eliminating the toxic gases after blasting results in particles hazardous to the miners. Exposure to dust mixed with graphite; quartz and micas particles are harmful and may cause lung cancers or development of chronic silicosis. The workers and mine owners are supposed to adhere to mining rules, regulations and code of practice. Mines must be properly ventilated and back filling is necessary in mined out pits. Most of artisanal gemstone mining in Tanzania is sub-standard which results in fatal accidents. It is recommended that proper mining methods should be adhered to following the code of practice issued by the Ministry of Energy and Minerals. Tanzania Journal of Science Vol. 31 (1) 2005: pp. 1-12

Infrared 3–4 μm Spectroscopic Investigations of a Large Sample of Nearby Ultraluminous Infrared Galaxies

We present infrared L-band (3-4 μm) nuclear spectra of a large sample of nearby ultraluminous infrared galaxies (ULIRGs). ULIRGs classified optically as non-Seyfert galaxies (LINERs, H II regions, and unclassified) are our main targets. Using the 3.3 μm polycyclic aromatic hydrocarbon (PAH) emission and absorption features at 3.1 μm due to ice-covered dust and at 3.4 μm produced by bare carbonaceous dust, we search for signatures of powerful AGNs deeply buried along virtually all lines of sight. The 3.3 μm PAH emission, the signatures of starbursts, is detected in all but two non-Seyfert ULIRGs, but the estimated starburst magnitudes can account for only a small fraction of the infrared luminosities. Three LINER ULIRGs show spectra typical of almost pure buried AGNs, namely, strong absorption features with very small equivalent width PAH emission. Besides these three sources, 14 LINER and three H II ULIRGs' nuclei show strong absorption features whose absolute optical depths suggest an energy source more centrally concentrated than the surrounding dust, such as a buried AGN. In total, 17 out of 27 (63%) LINER and 3 out of 13 (23%) H II ULIRGs' nuclei show some degree of evidence for powerful buried AGNs, suggesting that powerful buried AGNs may be more common in LINER ULIRGs than in H II ULIRGs. The evidence of AGNs is found in non-Seyfert ULIRGs with both warm and cool far-infrared colors. These spectra are compared with those of 15 ULIRGs' nuclei with optical Seyfert signatures taken for comparison. The overall spectral properties suggest that the total amount of dust around buried AGNs in non-Seyfert ULIRGs is systematically larger than that around AGNs in Seyfert 2 ULIRGs. We argue that the optical (non)detectability of Seyfert signatures in ULIRGs is highly dependent on how deeply buried the AGNs are, and that it is essential to properly evaluate the energetic importance of buried AGNs in non-Seyfert ULIRGs.

Extinction correction for Type Ia supernova rates - I. The model

In this paper we present and discuss a new Monte Carlo approach aimed at correcting the observed Supernova (SN) rates for the effects of host galaxy dust extinction. The problem is addressed in a general way and the model includes SN position distributions, SN light curve and spectral library, dust properties and distribution as input ingredients. Even though the recipe we propose is in principle applicable to all SN types, in this paper we illustrate the use of our model only for Type Ia. These represent in fact the simplest test case, basically due to their spectroscopic homogeneity which, to a first approximation, allows one to treat them all in the same way. This test case shows that the final results do not depend critically on the spiral arm dust geometry, while the total amount of dust, its properties and the size of the galactic bulge do have a strong effect. With the availability of more complete spectral libraries and a more accurate knowledge of SN spatial distribution, the method we propose here can be easily extended to Core Collapses events.

ELEMENTAL COMPOSITION OF AIRBORNE DUST IN THE SHALE SHAKER HOUSE DURING AN OFFSHORE DRILLING OPERATION

During 2 days of an offshore drilling operation in the North Sea, 16 airborne dust samples from the atmosphere of the Shale Shaker House were collected onto filters. During this operation, drilling mud composed of a water slurry of barite (BaSO4) together with minor amounts of additives, among them chrome lignosulphonate and chrome lignite, was circulated between the borehole and the Shale Shaker House. The concentration of airborne dust in the atmosphere was determined and the elemental composition of the particles analysed by both PIXE (proton-induced X-ray emission) and ICP-MS (inductively coupled plasma-mass spectrometry). The total amount of dust collected varied from 0.04 to 1.41 mg m-3 with barium (Ba) as the single most abundant element. The open shale shakers turned out to be the major cause of generation of dust from the solid components of the drilling mud.

Time evolution of interstellar dust and far-infrared luminosity of disk galaxies

The evolution of interstellar dust in disk galaxies is modeled, assuming that dust forms predominantly in molecular clouds associated with star formation. Analytical solutions for the dust abundance in disk galaxies as a function of galaxy age are obtained for the prompt initial enrichment and accretion models of chemical evolution, consistent with observations of the heavy element abundance in the Galaxy. Star formation rates in the disks of galaxies are taken as either constant or decreasing exponentially with time. It is found that the total amount of dust in the early history of galaxies can be up to 4 times the value observed today. The total emission from dust in galaxies is calculated, using an average dust temperature derived from IRAS observations. In the strongly evolving models, the far-infrared luminosity from galaxies can be roughly two orders of magnitude larger than the current value.

Cleaning up industrial emissions

Metallurgical plants are a significant source of atmospheric pollution, these facilities being responsible for 12-15% of the quantity of harmful substances introduced into the air. The production of steel in open-hearth (OH) furnaces, moreover, is one of the "dirtiest" metallurgical operations from an enviromnental standpoint. While the current level of OH steelmaking has maximized the productivity of OH furnaces, it has also brought an increase in the discharge of hazardous substances: dust and oxides of sulfur and nitrogen. Open-hearth shop No. 1 at the Karaganda Metallurgical Combine evaluated the dust content of the outgoing gases and their concentration of harmful substances. The study revealed the process factors responsible for the deterioration in pollution control in the shop. It turned out that the escape of gases through the charging doors and leaks in the furnace superstructure account for 5-20% of the emissions registered. Moreover, while the concentration of nitric oxide is not above the MPC (maximum permissible concentration) in every section of the shop, the concentration of sulfur dioxide ranges from 0 to25.4 mg/m 3 -- with the MPC being 10 mg/m 3. The concentration of sulfur dioxide at work stations in the shop is 13.1 mg/m 3. The highest concentration of dust (45 mg/m 3) was found in the area of the tap hole during tapping. The MPC is 4 mg/ m 3. Dust concentration on the working platform of the furnace during cold-charging reaches 13.2 mg/m 3. Uncontrolled emissions could be reduced by increasing the draft, but this would require more powerful ventilating equipment. Also, increasing the amount of cold air brought into the system increases heat losses, disturbs the slag regime, and entails the consumption of additional heat carrier. An alternative solution is to install an aerodynamic screen, hoods, and other devices to control gaseous emissions. The total amount of dust generated by OH steelmaking is reduced 7% when two-level lances are used to blow the metal. The reduced dust formation is accompanied by improved operation of the regnerators, flues, and waste-heat boiler. The level of cleaning of the flue gases (controlled emissions) depends on the efficiency of the electrostatic precipitators in the gas-cleaning system. Their efficiency ranges within 85-99%. The efficiency of the gas-cleaning system as a whole is adversely affected by an increase in the quantity of gas (gas velocity) and an increase in gas temperature at the system inlet. Factors which tend to increase dust generation are: a reduction in the bulk weight of the scrap charge; overheating of the charge before the hot-metal addition; oxygen-blowing of the metal when its carbon content is below 0.15%. These findings suggest that, from an environmental standpoint, it would be helpful to change the OH shop over to the production of killed and low-alloy steels. Unfortunately, the existing gas-cleaning systems do not ensure the removal of oxides of sulfur and nitrogen from the flue gases. Since sulfur in the charge and the fuel is one factor contributing to the formation of sulfur dioxide in the steelmaking process, emissions of SiO 2 could be reduced by using pig iron and fuel oil that are low in sulfur. The concentration of oxides of nitrogen in flue gases depends on the method used to reduce fuel consumption and the extent to which the steelmaking operation is being forced.

Technogenic pollution of the snow cover on Svalbard

Abstract Quantitative aspects of technogenic pollution of the snow cover are reported, based on field measurements made in the vicinity of the Barentsburg coalmine, Spitsbergen, in 1987. The mean total contamination of the snow cover with solid aerosols, based on cores through the total depth of the snow pack, reached levels of 300 t/ km2 for the immediate area of the settlement of Barentsburg and 30 t/km2 for the surrounding area. The rate of dustfall within the settlement is estimated to be 480 t/ km2 per year. The total amount of dust falling throughout the area of contamination which is 6 times larger than that of the settlement per se reaches 6001 per year. The data recorded on pollution of the snow cover at Barentsburg are comparable with those from the Vorkuta coalmining region. It is concluded that the pollution is local in nature. The importance of studies of snow pollution within the framework of a wider program of environmental protection of the archipelago of Svalbard is demonstrated.