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ANTONIO L. DOADRIO VILLAREJO AN. R. ACAD. NAC. FARM.

The mercury is in the nature in form of cinnabar mineral that is a mercuric
sulphide, or mainly, in big bags of mercury metal. The mercuric sulphide is not
attack for the atmospheric agents (CO2, O2 and H2O) and it does not in the water
cycle.

The natural source of more important contamination is due to the sublimation
of the Hg metal.

The antropogenic sources are several; the use of the mercury like fungicide,
herbicide and preservative of seeds in agriculture; the wastebasket, the electroche-
mical industry, their use in paintings and piles, the industry of the catalysts, the
combustion of coal, those poured industrial and for the sewers, they are the most
important. It is necessary to highlight, mainly the source of industrial contamina-
tion, since supposes 83% of the total contamination of mercury approximately for
this source type.

The mercury is biotransform, especially in the rivers and oceans for microor-
ganisms, and incorporates to the trofic chains like methyl mercury, very toxic.

In the atmosphere, Hg2+ is the predominant species, formed starting from other
species of mercury, as the dimethylmercury, the HgO or the Hg metal, in different
chemical processes.

We can establish the following rules of behaviour of the mercury in the water:
All the forms of Hg become Hg2+ in the water for reaction with O2. Hg also
exists of its own incorporation through the water cycle.
The rusty species of mercury decrease to Hgº, for the action of bacterial pseu-
domonas in a anaerobic process.
The Hg2+ species are methylated in continental or coast waters, well for aerobic
methylation in numerous microorganisms and bacterial.
The Hg metal presents a clinical square of weakness, chills, metallic flavour,
nauseate, vomits, diarrheic, cough and thoracic oppression.
The Hg2+ precipitates proteins of the mucous and it gives an ashen aspect to the
mouth, pharynx and intestine, with intense pain and vomits for the corrosive effect
on the mucosa of the stomach that produces shock and death. The recovery takes
place alone with a quick treatment.
The organic derivates not usually produce sharp intoxications, and when these
take place they are unrecoverable and they produce the death.
Chronic intoxication of the Hg metal produce neurological effects and the call
syndrome vegetative astenic whose effects are takes place: goitre, tachycardia, low
pulse, gingivitis, irritability, tremors, loss memory and intense salivation. These
effects are reversible.

CARACTERÍSTICAS QUÍMICAS DE INTERÉS BIOLÓGICO

El mercurio se presenta en las cadenas tróficas en dos grupos de
especies químicas, inorgánicas y orgánicas, con características toxi-
cológicas diferentes, como después veremos. Las especies inorgáni-

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