What can be special in ordinary dust?
What it is possible to speak about dust, about such household trifle which only requires attention during each next cleaning? Dust - it is also dust. Whether the subject is so interesting that it can devote the whole article? However, if to reflect yes to become interested in opinion of scientists and to glance in the past, it is possible to learn quite interesting things.
On August 26, 1883 the volcano of Krakatau released into the atmosphere on huge height (to 32 kilometers) about 6,5 cubic kilometers of the smallest ashes. This cloud gradually shrouded all globe; it settled only many months later.
The volcanic dust which is long remaining in the atmosphere in a suspension causes many surprising phenomena. So, the dust clouds which are thrown out on June 6, 1912 on height to 50 kilometers by Mount Katmai (Alaska) appeared already on June 17 over St. Petersburg and then were condensed so that absorbed up to 70 percent of all solar heat.
By the way, somewhere I read that unusually light St. Petersburg nights about which A.S. Pushkin in " wrote; Bronze Horseman “ were caused by the atmospheric dust which is thrown out by a volcano in Sicily.
But all this state of emergency. And usually, in normal conditions how many dust is over the earth? From where it undertakes? What its value in the nature and human life? And in general, what is dust?
Atmospheric dust are smallest parts of various salts, minerals, rocks, coal, the soil and other various mixes and chemical compounds of mineral and organic character; these are the remains of the vegetable and animal organisms lifted in the atmosphere by wind, whirlwinds and the ascending air streams.
From physics lessons to me evident and extremely simple experience was remembered. Set fire from below to a thick black thread and to the formed ashes allowed to fall freely. The white cindery thread settled beautifully and quickly enough; but once you placed on its way the burning match (even at rather long distance), the falling thread was picked up by the stream of warm air ascending from a match and quickly rose up, to a ceiling.
is Also transferred, without recognizing borders, and dust which is kicked up by wind, and is transferred to very long distances and with a high speed.
Ground layers of air contain such amount of dust that it is possible to speak about real “ to the dust atmosphere “. For example, in each cubic centimeter of air (even after a rain!) about hundred thousand particles from 0,0001 to 0,1 millimeters in size contain. They say that in emissions of land dust even a certain daily and annual frequency is observed: daily maxima fall on 14 - 15 hours, and year - for summer months. Certainly, it is connected with vigorous activity of the person.
And if we think that we can hide from dust where - nibud on a beach, then we are mistaken: defining purity of air over a surface of the seas and oceans, scientists found out what even in the central part of Atlantic in each cubic centimeter of air is on some thousands of motes.
Their source, it appears, water serves. Its smallest droplets lifted by wind quickly evaporate, and the salts of sodium, magnesium, calcium which are in them remain in the atmosphere in the form of microscopic kristallik and are carried away by air currents. Consider that beneficial influence of sea air on a human body is explained by this salt dust.
Scientists, as we know, like to classify everything. They carried such dust to a look “ dust land “. But on the land and a surface of the water dust of other sort gets. It is the dust consisting from silicate and metal (iron, cobalt, copper) of balls with a diameter from 50 to 100 microns.
It is the space dust which is continuously coming from interplanetary space to the terrestrial atmosphere. Moreover, by means of rockets at the height of 75 - 160 kilometers the special belt consisting of space dust was found. Space dust accumulates on the earth in quantity (data are contradictory) from 16 thousand to 13 million tons per year and collects at the bottom of oceans with a speed about 4 centimeters for one million years.
At last, exists still “ live " dust;: bacteria, disputes, fungi. In the central regions of the cities their number reaches several tens of thousands in one cubic meter of air. But “ live " dust; is also in high layers of the atmosphere: even at the height of 15 - 20 kilometers at a temperature - 55 degrees in air live bacteria, however, in insignificant quantity, about 5 pieces on cubic meter.
Dust makes an integral part of the atmosphere. It reduces quantity of the sunbeams reaching the Earth`s surface. Heating up beams, dust heats also the atmosphere; absorbing radiation, it at the same time keeps also warmly terrestrial surface.
But dust plays a huge role and in human life. Researches of the atmosphere of the large cities showed that over them the constant dust cap which height reaches 500 meters and more always hangs.
If the villager inhales about 40 million motes a minute, then the citizen for the same time loads up to one billion motes into the lungs. And city industrial dust often contains arsenic, lead, manganese, selenium and other elements which can cause chronic poisonings. Motes with the sharp cutting sides (glass, quartz dust) cause development of chronic inflammatory processes in the top and average airways.
In a word, about dust is that to tell and eat of what to think, especially now when not just started talking about global warming, and we closely began to feel on ourselves its consequences. It is abnormal 40 - a-degree heat and the strongest drought which was endured by Moldova and Transnistria last year, and a large-scale flood of this year. And, at first sight, harmless, ordinary dust in it plays not the last role.