Calcium airborne

Maleic Anhydride. The ACGIH threshold limit value in air for maleic anhydride is 0.25 ppm and the OSHA permissible exposure level (PEL) is also 0.25 ppm (181). Maleic anhydride is a corrosive irritant to eyes, skin, and mucous membranes. Pulmonary edema (collection of fluid in the lungs) can result from airborne exposure. Skin contact should be avoided by the use of mbber gloves. Dust respirators should be used when maleic anhydride dust is present. Maleic anhydride is combustible when exposed to heat or flame and can react vigorously on contact with oxidizers. The material reacts exothermically with water or steam. Violent decompositions of maleic anhydride can be catalyzed at high temperature by strong bases (sodium hydroxide, potassium hydroxide, calcium hydroxide, alkaU metals, and amines). Precaution should be taken during the manufacture and use of maleic anhydride to minimize the presence of basic materials. 

Half-lives span a very wide range (Table 17.5). Consider strontium-90, for which the half-life is 28 a. This nuclide is present in nuclear fallout, the fine dust that settles from clouds of airborne particles after the explosion of a nuclear bomb, and may also be present in the accidental release of radioactive materials into the air. Because it is chemically very similar to calcium, strontium may accompany that element through the environment and become incorporated into bones once there, it continues to emit radiation for many years. About 10 half-lives (for strontium-90, 280 a) must pass before the activity of a sample has fallen to 1/1000 of its initial value. Iodine-131, which was released in the accidental fire at the Chernobyl nuclear power plant, has a half-life of only 8.05 d, but it accumulates in the thyroid gland. Several cases of thyroid cancer have been linked to iodine-131 exposure from the accident. Plutonium-239 has a half-life of 24 ka (24000 years). Consequently, very long term storage facilities are required for plutonium waste, and land contaminated with plutonium cannot be inhabited again for thousands of years without expensive remediation efforts. 

In may be of interest to compare the fluxes of elements in biogeochemical cycles of Oak Forest ecosystem with exposure to airborne deposition input. The latter were (inkg/ha/yr)forN, 17.7 forCa, 14.7 forMg, 1.8 for K, 4.2 for Na, 1.4 forP, 1.1 for Fe, 0.07 and for Zn, 0.14. The deposition input of these elements fall into a range of 20% (calcium) to 4.5% (potassium) relative to the respective biogeochemical fluxes (see Table 9). The airborne Fe input accounts for a mere 2.5%. Simultaneously, for some heavy metals, like zinc, the deposition input is commensurate with the fluxes of biogeochemical cycle. 

Sodium tripolyphosphate manufacmre generates no process wastes. Wastewaters from the manufacture of calcium phosphates are generated from a dewatering of the phosphate slurry and wet scmbbing of the airborne solids during product operations. 

Sources of Airborne Calcium in Rural Central Illinois... 

The objective of this work was to identify calcium sources and their relative contributions in rural central Illinois as a step toward understanding the role of airborne alkaline... 

The problem is exacerbated in large and crowded communities. For example, there are well over 50 hospital incinerators in New York City. Most local hospital incinerators are not equipped with acid-gas scrubbers, which convert harmful airborne substances into harmless calcium salts. Nor are most incinerators equipped with electrostatic precipitators to capture particles that have adsorbed toxic flue gases. 

Geochemical modeling is often used to identify the compounds that primarily control the chemistry of arsenic in aqueous solutions. Modeling studies indicate that the arsenic concentrations of Kelly Lake, Ontario, Canada, are controlled by the precipitation and dissolution of Fe(II) arsenates rather than calcium or Fe(III) arsenates (Sadiq et al., 2002). The arsenic in the lake originated from runoff from the nearby Sudbury mining district and airborne particles from local ore smelters (Sadiq et al., 2002). 

In a study of 71 workers exposed to airborne white phosphorus for intermediate or chronic durations, 4.5% and 44%, respectively, developed phossy jaw (Ward 1928). Forty-eight male workers with exposure to white phosphorus ranging from 1 to 17 years were found to be normal and healthy with regards to many parameters, including serum levels of calcium and phosphorus, and bone density none of the men developed phossy jaw (Hughes et al. 1962). 

Wear nitrile rubber gloves, laboratory coat, and protection. To reduce risk of forming airborne dust, cover spill with a 1 1 1 mixture by weight of sodium carbonate or calcium carbonate, clay cat litter (bentonite), and sand. Scoop the solid into a container and transport to the fume hood. Slowly, while stirring, add the solid to household bleach (50 mL/g of chromium hexacarbonyl). Allow the solid to settle, decant the liquid to the drain with at least 50 times its volume of water. Dry and package the solid for disposal in accordance with local regulations.5,6... 

Airborne dusts and grit Waterborne mud and silts Calcium and magnesium salts Iron oxide... 

One non-standard desulfurisation technique, used on a rotary kiln by a producer of calcined dolomite, is to include finely divided dolomite in the feedstone. The fines calcine, become airborne as a result of the action of the kiln internal fittings (i.e., trefoils and lifters), and remove a significant amount of the sulfur dioxide. It is not known whether this technique would be as successful with high calcium limestone, which calcines at higher temperatures than dolomite. Other techniques will no doubt be evaluated, such as the injection of hydrated lime into the back-end of the kiln. The cost-effectiveness of such techniques in relation to alternatives, and their effects on kiln operation, would need to be assessed. 

Fergusson JE, Stewart C. 1992. The transport of airborne trace elements copper, lead, calcium, zinc, and manganese from a city into rural areas. Sci Total Environ 121 247-269. 

Airborne contaminants, in the form of dust, corrosion products, and residues from paints, etc., can introduce many different elements into a sample, e.g., sodium, potassium, calcium, magnesium, and aluminum. This is a significant threat where open reaction vessels are used, and can be avoided by simple precautionary measures such as covering the dissolution vessel with a dish or beaker equipped with a side arm through which a stream of filtered air or gas is passed. More stringent measures include the use of a clean air room kept imder positive pressure, with the reaction itself carried out imder a laminar flow hood. Gaseous contaminants can be eliminated from the reaction vessel s air supply using appropriate adsorption filters. 

Dustproofing. Oil is commonly used for dustproofing coal. When coal is sprayed with oil, the film causes some dust particles to adhere to the larger pieces of coal and others to agglomerate into larger lumps not easily airborne. Calcium chloride absorbs moisture from the air, providing a wet surface to which the dust adheres. 

That fallout of trace elements from atmospheric pollution is widespread and far from confined to urban and industrial areas, is also borne out by data published by the UK Atomic Energy Authority, who determined, by neutron activation analysis, about 30 trace elements in airborne dust, rainwater and dry deposition, sampled at regular intervals in north-west England [188]. The highest concentrations measured in air were for chlorine, sodium, calcium, aluminium, iron, lead and zinc, and there were also measurable levels of antimony, arsenic and mercury, usually in the winter months, when there was a general increase in trace-element concentration. Further data were published on the atmospheric content and total deposition of a wide range of trace elements at seven non-urban sites (one in Shetland) in the UK in the years 1972 and 1973 [189]. Data have also been published for the North Sea and the Firth of Clyde [190]. 

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