ESTIMATION OF MERCURY AND OTHER HEAVY METALS CONTAMINATION

IN TRADITIONAL GOLD-MINING AREAS OF SIBERIA

Tatyana G. Laperdina, Marina V. Melnikova, Tatyana E. Khvostova

Chita Institute of Natural Resources, Siberian Branch, Russian Academy of Sciences.

Butin Str., 26, P.O.Box 147, Chita, 672090, Russia

Tel: 7(3022)21-17-29, Fax: 7(3022)21-25-82, E-mail: ecogeo@cinr.chita.su

The mining of ore and placer gold is one of the most ecologically dangerous branches of mining industry. Deposits of placer gold are located, as a rule, in valleys of small and medium-sized rivers. Their mining is accompanied by extreme deterioration of river conditions and irreversible breakdown of natural landscapes. Processing of gold-bearing raw materials and concentrates are connected with the use of such toxic substances as mercury, cyanide, flotation agents at al. Gold-bearing ores and sands and country rocks include admixture of many toxic elements (mercury, lead, arsenic, antimony, copper, zinc, bismuth et al.) Therefore there is an extreme increasing of toxic metals content in the environmental components in zones affected by gold-mining industry. This increasing has a negative influence on conditions of water and terrestrial ecosystems and population health as well.

Maximum and, as a rule, stable mercury contamination is characteristic for places of treatment of gold concentrates. For example, the mercury content was registered: 50-2000 mg/kg in contaminated grounds; 5 and 27.8 ?g/l in dissolved and suspended forms in ground waters. The level of mercury content in the environment of residence territories may increase by 2-3 times.

In mouth parts of rivers in which watershed mining of placer gold is carried out the integral indices of water composition (pH, electric conductivity, turbidity) change significantly as well as the content of heavy metals increases by 2-15 times in comparison with background places. Besides, exceeding of maximum permissible concentration (up to 20 MPC) limiting the content of harmful substances in water of fishery water streams and reservoirs is registered.

A negative impact of mercury and other heavy metals on human health is strengthened considerably owing tounbalance of macro- and microcomponent composition of drinking water and food ration of population and natural endemic deficit of vitally necessary microelements such as iodine, selenium, fluoride et al. Environment contamination by mercury and lead provides binding of iodine getting into living organisms and its transformation into inactive forms. This still more impoverishes food ration with iodine and complicates treatment of iodine-deficit diseases.