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Strontium (Sr) and water

Strontium and water: reaction mechanisms, environmental impact and health effects

Seawater contains 8 ppm strontium on average. River water generally contains about 50 ppb of strontium and in oyster tissue 10 ppm of strontium (dry mass) was found.
When dissolved in water strontium mainly occurs as Sr2+ (aq). One other possible form is SrOH+ (aq).


In what way and in what form does strontium react with water?

Strontium reacts with water slowly, generally to strontium hydroxide and hydrogen gas. It reacts with water quicker than calcium, which is placed directly above strontium in the periodic chart, and slower than barium, placed directly below strontium.

The following reaction mechanism is applicable:

Sr (s) + 2H2O (g) -> Sr(OH)2 (aq) + H2 (g)


Solubility of strontium and strontium compounds

Strontium is water insoluble, but it does react with water. Strontium compounds can be water soluble. Examples include strontium carbonate with a water solubility of 10 mg/L, and strontium chromate with a water solubility of 9 mg/L.


Why is strontium present in water?

The most significant strontium mineral is celestite (strontium sulphate; SrSO4), followed by strontianite (strontium carbonate; SrCO3). At least 140,000 ton is exploited annually. This may produce strontium metal, which is not applied widely, but it may extract residue air from vacuum tubes. As a carbonate strontium is mainly applies for TV-screen production. This is the main application of the element. It insulates X-rays that occur from electric radiation in the cathode ray tube. This is however required less and less because of the increasing popularity of the flat screen TV. Strontium is applied for alloy refinery, and strontium sulphate was applied as imitation diamond. Because of its red inflammation it is suitable for application in fireworks. Strontium ferrite is applied in permanent ceramic magnets that are highly coercive and can be applied in small engines because of its resistance to heat and corrosion.
Radioactive 89Sris applied in nuclear physics and in nuclear medicine. 90Sr is a product of nuclear explosions. It strongly contaminated earth in the 1950's and 1960's, because above-ground test explosions were carried out. It is also a by-product of nuclear reactors and the highly energetic radiation is applied in for example space vehicles.


What are the environmental effects of strontium in water?

Strontium is only a dietary requirement in a few exceptional cases. A number of deep sea organisms apply strontium sulphate in shells, and stone corals also have a requirement for the element. Plants contains between 3 and 400 ppm strontium (dry mass). Strontium is usually immobile in the environment, because of rapid precipitation as strontium carbonate, or because it is applied in shells. The highest strontium concentrations are found in deserts and forest soils.
Strontium naturally occurs as four separate stable isotopes, and nineteen instable isotopes. 90Sr spread throughout the globe after nuclear test explosions in the 20th century, was washed out of the atmosphere, and ended up in soils, crops, grazing cows and other animals, and eventually in humans. It was taken up in measurable amounts by virtually every land organism. The extremity of the carcinogenic and mutagenic mechanisms was not described adequately so far.


What are the health effects of strontium in water?

The human body contains approximately 4.6 ppm strontium. It has no specific function, but it is absorbed because of its similarity to calcium. Consequently, the larger part of absorbed strontium is inserted in bones.
Strontium is non-toxic and a daily intake of about 0.8-5 mg through food is harmless, when it only contains non-radioactive strontium. In the 20th century this ended up in food and drinking water. Later, it was found mainly in infant's teeth.
The risk of radioactive strontium intake is mainly based on its carcinogenic and mutagenic mechanism, problems that occur in cell division, and possible increased infant mortality. 90Sr decays to radioactive yttrium, which accumulates in hypophysis and ovaries, and subsequently disrupts infant hormonal development, and infant growth.


Which water purification technologies can be applied to remove strontium from water?

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Literature and the other elements and their interaction with water







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