Dust in atmosphere

ABSTRACT The locations, magnitudes, variations and mechanisms responsible for the atmospheric C02 sink are uncertain and under debate. Previous studies concentrated mainly on oceans, and soil and terrestrial vegetation as sinks. Here, we show that there is an important C02 sink in carbonate dissolution, the global water cycle and photosynthetic uptake of DIC by aquatic ecosystems. The sink constitutes up to 0.82 Pg C/a 0.24 Pg C/a is delivered to oceans via rivers and 0.22 Pg C/a by meteoric precipitation, 0.12 Pg C/a is returned to the atmosphere, and 0.23 Pg C/a is stored in the continental aquatic ecosystem. The net sink could be as much as 0.70 Pg C/a, may increase with intensification of the global water cycle, increase in C02 and carbonate dust in atmosphere, reforestation/afforestation, and with fertilization of aquatic ecosystems. Under the projection of global warming for the year 2100, it is estimated that this C02 sink may increase by 22%, or about 0.18 Pg c/a. 

This sink, a negative climate feedback mechanism, may increase with the global-warming-intensified GWC, the increase in C02 and carbonate dust in atmosphere, reforestation/afforestation, and fertilization of the aquatic ecosystems. Using the global warming projection for the year 2100 by IPCC, it is estimated that the C02 sink by the GWC will increase by 22%, or 0.18 Pg c/a. 

Coal mines, determination of firedamp and of coal dust in atmosphere of 3 C367—C368... 

Coal Mines, Determination of Firedamp and of Coal Dust In Atmospheres of. Although many instruments have been designed to detect the presence of firedamp (or rather methane) in mine atmospheres, the principles of the flame safety lamp (Davy-type lamp) still form the basis of many detectors. The Davy lamp invented in 1815 is briefly described under COAL MINE EXPLOSIONS AND FIRES and it is stated that each US mine should have at least two Davy-type lamps to serve as detectors of firedamp or of lack of oxygen. If firedamp is present in small quantity, the flame of Davy lamp elongates and if the gas is present in considerable quantity, the lamp becomes filled with blue flame. For more definite detection of gas, the flame of the lamp is lowered until the yel part is at a minimum. Then the gas will be discernible as a small blue cap over the flame. This method is described in Refs 1, 9, 12 25. Some investigators consider that the safety lamp method of detection of firedamp is not very reliable (Ref 7)... 

Coal Mines, Determination of Firedamp and of Coal Dust in Atmospheres of. Although many instruments have been designed to detect the presence of firedamp (or rather methane) in mine atmospheres, the principles of the flame safety lamp (Davy-type lamp) still form the basis of many detectors. The Davy lamp invented in 1815 is briefly described under... 

AH operations producing dust require the usual measures to prevent dust in the atmosphere exceeding the allowable daily concentration. If this is not feasible, personal protection devices should be used. Especially when hydroquinone is present as a powder, adequate eye protection should be provided. 

Dust explosions are relatively rare but ean involve an enormous energy release. A primary explosion, involving a limited quantity of material, ean distribute aeeumulations of dust in the atmosphere whieh, on ignition, produees a severe secondary explosion. 

In addition to pollution episodes, risks may arise due to atmospherie oxygen eoneentrations fluetuating beyond its normal level of 21% posing health (page 72) or fire hazards. Eire and explosion dangers may also arise from the presenee of flammable gases, vapours, or dusts in die atmosphere (Chapter 6). 

Atmospheric dust concentration The dust burden present in atmospheric air measured in mg m ... 

How frequently the oil condition should be tested depends on operating and atmospheric conditions after the commissioning sample, further samples should be taken at three months and one year after the unit is first energized. After this, under normal conditions, testing should be carried out annually. In unfavorable operating conditions (damp or dust-laden atmospheres, or where space limitations reduce air circulation and heat transfer) testing should be carried out every six months. 

The name dust , is used in a variety of ways, and with different meanings. These range from the material that accumulates on the earth s surface, such as on streets and in living and working environments, to the particulate material suspended in the atmosphere. In this paper I wish to consider these two materials in terms of their chemical composition, sources and relationship between them. The names used for the two materials will be surface dust and atmospheric dust . The word aerosol may also be used for atmospheric dust but it more properly applies to the finer particles of atmospheric dust and includes liquid aerosol (i). Botfi surface and atmospheric dusts are increasingly seen to be a hazard to human beings as they are a source of intake of toxic materials such as heavy metals. For this reason study is important of the composition and sources of the dusts. 

It is remarkable that, except for local hot-spots such as around industrial sites, mining areas and volcanoes, the elemental compositions of atmospheric dust in similar locations, such as remote or rural or urban are relatively constant over the world. This suggests either common sources, or a dominant source, or good mixing and transport of the dust around the globe. In fact all three factors have a role in determining the uniformity. Because of the consistent composition it is possible to estimate the median concentrations of the elements in atmospheric dusts in similar, but widely separated, locations. These estimates are given in columns 2 to 7 in Table n. The concentrations of the elements in the atmospheric dust are expressed as mass per volume of air. For remote locations (columns 2 to 5) the concentrations are in ng m 3, whereas for rural and urban areas (columns 6 and 7) the elemental concentrations are in xg m-3. 

Diverse techniques have been employed to identify the sources of elements in atmospheric dust (and surface dust) (Table V). Some involve considering trends in concentration and others use various statistical methods. The degree of sophistication and detail obtained from the analyses increases from top left to bottom right of the Table. The sources identified as contributing the elements in rural and urban atmospheric dusts are detailed in Table VI. The principal sources are crustal material, soil, coal and oil combustion emissions, incinerated refuse emissions, motor vehicle emissions, marine spray, cement and concrete weathering, mining and metal working emissions. Many elements occur in more than one source, and they are classified in the... 

Since the majority of the elements in surface dust arise from deposited aerosol and added soil it is not surprising to find strong linear relationships between the concentrations of the elements in an atmospheric dust and street or house dust. This is illustrated by the two examples given in Fig. 8 for remote house dust vs urban atmospheric dust and street dust vs rural atmospheric dust. As discussed above crustal/soil material is a major component of atmospheric dust and the soil based elements in the atmospheric dust are Al, Ca, Fe, Mg, Mn, Ni, K, Si and Ti. The elements As, Br, Cd, Cl, Co, Cu, Pb, Rb, Se, V, and Zn are, on the other hand, enriched in atmospheric dust. The same elemental distribution applies to surface dust, but in this case their concentrations (compared on a mass basis) are reduced presumably due to dilution with soil. However, the elements enriched in the atmosphere remain enriched in the surface dusts. 

The atmospheric reservoir (8) represents P contained on dust particles. Because the mean residence time of dust in the air is very short, the standing stock of P in the atmosphere is rela-... 

As discussed in Chapter 4, chemicals can be a nuisance or pose health risks if they become airborne as a result of inadequate process control, operation and maintenance malpractice, inadequate maintenance, incomplete understanding of the process etc. Hazards may arise if the oxygen concentration in the air fluctuates beyond its normal level of 21% by volume, and fire/explosion dangers may arise from the presence of flammable gases, vapours or dusts in the atmosphere. Thus air quality tests may be required for a variety of purposes such as ... 

Silicon w is first isolated and described as an element in 1824 by Jdns Jacob Berzelius, a Swedish chemist. Silicon does not occur uncombined in nature, i.e.- as an element. It is found in practically aU rocks as well as in sand, clays, and soils, combined either with oxygen as silica (Si02= silicon dioxide) or with oxygen plus other elements (e.g., aliuninum, mcignesium, calcium, sodium, potassium, or iron) as silicates. Its compounds also occur in all natural waters, in the atmosphere (as siliceous dust), in many plants, and in the skeletons, tissues, and body fluids of some animals. 

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