Kg Of Dust Research Articles

Energy balance of the Deep Impact experiment

We present results on the energy balance of the Deep Impact experiment based on analysis of 180 infrared spectra of the ejecta obtained by the Deep Impact spacecraft. We derive an output energy of 16.5 (+9.1/−4.1) GJ. With an input energy of 19.7 GJ, the error bars are large enough so that there may or may not be a balance between the kinetic energy of the impact and that of outflowing materials. Although possible, no other source of energy other than the impactor or the Sun is needed to explain the observations. Most of the energy (85%) goes into the hot plume in the first few seconds, which only represents a very small fraction (<0.01%) of the total ejected mass. The hot plume contains 190 (+263/−71) kg of H 2O, 1.6 ± 0.5 kg of CO 2, 8.2 (+11.3/3.1) kg of CO (assuming a CO/H 2O ratio of 4.3%), 27.9 (+25.0/−8.9) kg of organic material and 255 ± 128 kg of dust, while the ejecta contains ∼10 7 kg of materials. About 12% of the energy goes into the ejecta (mostly water) and 3% to destroy the impactor. Volatiles species other than H 2O (CO 2, CO or organic molecules) contribute to <7% of the energy balance. In terms of physical processes, 68% of the energy is used to accelerate grains (kinetic energy), 16% to heat them, 6% to sublimate or melt them and 10% (upper limit) to break and compress dust and/or water ice aggregates into small micron size particles. For the hot plume, we derive a dust/H 2O ratio of 1.3 (+1.9/−1.0), a CO 2/H 2O ratio of 0.008 (+0.009/−0.006), an organics/H 2O ratio of 0.15 (+0.29/−0.11) and an organics/dust ratio of 0.11 (+0.30/−0.07). This composition refers to the impact site and is different from that of the bulk nucleus, consistent with the idea of layers of different composition in the nucleus sub-surface. Our results emphasize the importance of laboratory impact experiments to understand the physical processes involved at such a large scale.

The distribution of dust devil activity on Mars

Martian dust devil activity, inferred from their tracks, is mapped globally and compared to surface and atmospheric properties. Dust devils are estimated to lift 2.3 ± 1 × 1011 kg of dust each year, mostly from two narrow bands near 60°N and 60°S, during their respective spring and summer. Approximately 55% of the dust lifted by dust devils in the northern hemisphere is removed from within 45 and 75°N, while 65% of that lifted in the south is from within 45 and 75°S. The southern band is an order of magnitude more populated with tracks than in the north, likely a result of Mars' orbital eccentricity. The equator is the location of a lesser peak, while few dust devil tracks are found at the poles and middle latitudes. During the fall and winter in both hemispheres, few tracks are observed. Dust devil and track formation does not appear to be controlled significantly by elevation, topographic slope, dust cover, or surface physical properties. Dust devils annually lift approximately half as much material as local and regional dust storms and are therefore significant contributors of dust into the Martian atmosphere.

Alkaline leaching of zinc from electric arc furnace steel dust

Electric arc furnaces (EAF) generate about 10–20 kg of dust per metric ton of steel, which constitute a hazardous waste, known as EAF dust. This dust contains a remarkable amount of non-ferrous metals, which include zinc, cadmium, lead, chromium and nickel that could be recovered, reducing the environmental impact of the leachable toxic metals, and generating revenue. In this paper, different alkaline leaching techniques were tested in order to dissolve the zinc present in an EAF dust: (i) conventional agitation leaching; (ii) pressure leaching; (iii) conventional leaching following a microwave pretreatment and (iv) leaching with agitation provided by an ultra-sonic probe. Temperature and sodium hydroxide concentration were the variables tested. The highest zinc recovery from the EAF dust, containing about 12% of zinc, was about 74%. This was achieved after 4 h of leaching in a temperature of 90 °C and with a sodium hydroxide concentration of 6 M of the leaching agent.

Method for determining plutonium in air filters in detection of nuclear activities

Summary A method was developed to determine activities and isotope ratios of plutonium and uranium. The method includes dry and wet ashing of air filters and separation of plutonium and uranium from each other and from other nuclides on Eichrom®´s extraction chromatography resins UTEVA and TRU. Interferences in plutonium separation caused by thorium and polonium were investigated and eliminated. A field trial was performed in Kurchatov, Kazakhstan, to test the aerosol sampling and radiochemical methods developed for plutonium and uranium. In the air samples collected, the activity of 239,240Pu varied between 0.67 and 228 Bq/kg of dust, the activity of 238Pu from 0.20 Bq/kg to 16.4 Bq/kg of dust, and the isotopic ratio 238Pu/239,240Pu between 0.011 and 2.4. Concentrations of Pu isotopes in the air were 13.4-2490 nBq/m3 for 239,240Pu and 7.2-960 nBq/m3 for 238Pu. Radioactivity of 239,240Pu in air filters from Astana varied between 0.075 and 0.72 Bq per kg of dust and that of 238Pu between 0.038 and 0.14 Bq/kg of dust. Activity concentration of 239,240Pu in the air of Astana was 5.0-130 nBq/m3.

House dust in seven Danish offices

Floor dust from Danish offices was collected and analyzed. The dust was to be used in an exposure experiment. The dust was analyzed to show the composition of the dust which can be a source of airborne dust indoors. About 11 kg of dust from vacuum cleaner bags from seven Danish office buildings with about 1047 occupants (12 751 m 2) was processed according to a standardized procedure yielding 5.5 kg of processed bulk dust. The bulk dust contained 130.000–160.000 CFU g −1 microorganisms and 71.000–90.000 CFU g −1 microfungi. The content of culturable microfungi was 65–123 CFU 30 g −1 dust. The content of endotoxins ranged from 5.06–7.24 EU g −1 (1.45 ng g −1 to 1.01 ng g −1). Allergens (ng g −1) were from 147–159 (Mite), 395–746 (dog) and 103–330 (cat). The macro molecular organic compounds (the MOD-content) varied from 7.8–9.8 mg g −1. The threshold of release of histamine from basophil leukocytes provoked by the bulk dust was between 0.3 and 1.0 mg ml −1. The water content was 2% (WGT) and the organic fraction 33%. 6.5–5.9% (dry) was water soluble. The fiber content was less than 0.2–1.5% (WGT) and the desorbable VOCs was 176–319 μg g −1. Most of the VOC were aldehydes. However, softeners for plastic (DBP and DEHP) were present. The chemical composition includes human and animal skin fragments, paper fibers, glass wool, wood and textilefibers and inorganic and metal particles. The sizes ranged from 0.001–1 mm and the average specific density was 1.0 g m −3. The bulk dust was resuspended and injected into an exposure chamber. The airborne dust was sampled and analyzed to illustrate the exposures that can result from sedimented dirt and dust. The airborne dust resulting from the bulk dust reached concentrations ranging from 0.26–0.75 mg m −3 in average contained 300–170 CFU m −3. The organic fraction was from 55–70% and the water content about 2.5% (WGT). The content of the dust was compared to the similar results reported in the literature and its toxic potency is estimated to be relatively low. The storage of the bulk dust during the experiment had little effect on the specific biological and chemical composition.

Toxicity of Crotoxyphos Insecticide to Brahman Calves and Brahman and Crossbred Yearling Steers

Crotoxyphos (Ciodrin) insecticide was applied to Brahman calves and Brahman and crossbred (Hereford-Angus) steers to determine its effect on blood cholinesterase. Brahman calves treated with 946 ml of 1% crotoxyphos spray showed inhibition in whole blood and red cell cholinesterase (p < .01). Two out of 4 calves exhibited severe toxicosis and 1 developed skin lesions. Brahman calves treated with 946 ml of 0.5% crotoxyphos spray or 3% crotoxyphos dust showed cholinesterase inhibition (p @? .01) but no observed toxicosis. Whole blood and red cell cholinesterase of Brahman and crossbred steers were inhibited (p @? .01) when treated with 1.9 1 of 0.5% crotoxyphos spray per head at weekly intervals for 11 weeks. Brahman animals had a greater (p .01) inhibition than crossbred steers. The 3% crotoxyphos dust offered as free-choice in a self-applicating dust bag produced no cholinesterase inhibition in Brahman and crossbred steers; 2.7 kg of dust were depleted from the dust bag during the 11-week period.