The enterprise intended to be carried out in Esquel will consist in open pit mining almost entirely, that is, the big holes where the material is extracted from will remain in the open air, and a cyanid heap leaching mining method will be employed, which involves using tons of chemicals.

This is why some authors (experts in the subject from Munich University) [1] consider this mining method a combination of the chemical and mining industries. An average of 180 tons of sodium cyanide, 12 tons of chlorydric acid , 12 tons of caustic soda and 1400 Kg. of litargirio, etc. will be used per month for this purpose. [2]

2- FUNDAMENTAL CYANIDE CHEMICAL PROPERTY

The most relevant property of cyanide is the way it combines with metals, which would explain both, its toxicity and usefulness in mining. Its combination with ferrum, present in all cells and essential for cellular breathing, accounts for its lethal effect in living criatures, even in small concentrations. Death of a human adult is produced by an averange of 150 mg of sodium cyanide ( salt volume comparable to a grain of corn) [3]. Cynide is used in mining due to its great power of combination with gold and silver. It is utterly efficient, given it extracts gold particules invisible for the human eye4 (96-99% of the metal present in ground rock), and it is immensely profitable: 1 cyanide ton extracts up to 6 Kg. of gold and the cost ratio is approximately 1,500 against 58.500 dollars[1].

3- WHY IS THIS AN ACTIVITY WHICH IMPACTS NEGATIVELY ON THE ENVIROMENT?

On the one hand, this is so because many tons of chemicals are used, as we can read in Estudio de Impacto Ambiental (EIA)- Enviroment Impact Study- (Chap. 4, figure 4.15, p. 22); there is no possible way of removing or isolating these chemicals from the enviroment. [5,6] In the case of the INCO process to be (supposedely) used in Esquel, not only does residual cynide remain in the enviroment (<3ppm), but also other more toxic derivates are produced (cyanides and thiocyanates), particularly affecting the fish [5]; and metal cyanide complexes are not destroyed [6]; besides, there is no telling what the efficiency of this detoxification process might be in the long term. [7]
On the other hand, from 42.000 to 45.000 tons of rock are removed per day from which 3000 tons are ground to a flour texture (70 microns). This rock powder is treated with cyanide. Among the dangerous products released from rock are heavy metals (like arsenic and mercury) and the sulphides generated (under water and air influence), sulphuric acid, known as acid mine drainage (AMD). Gradually, the cyanide degradation products or the ones produced as a result of the grinding of the rock reach superficial and deep waters according to EPA.[7]

4- WHY ARE HEAVY METALS TOXIC?

The toxicity of these metals is due to the fact that they cannot be metabolized naturally, they remain in the organism and have toxic effects when they combine with one or more reactive groups essential for norrmal fisiologic functions. In the case of the "cordón Esquel" there is a high persentage of arsenic (EIA, Annex I, p. 8) which will be released to the dump: 46 tons per day of a metal whose cronic effects include: vitiligo, generalized pruritus; or even more severe consequences, such as encephalopathy or spinal cord damage. [3] Besides, 30 ton/month of lead (another heavy metal) will be released. Lead in combiantion with rain water forms partially soluble lead hydroxide, which causes lead poisoning, especially in children, who may suffer from permanent brain damage. [3]

5- IS IT REALLY SAFE TECHNOLOGY?

The history of this technology shows that it has caused a great amount of enviromental damage around the world: Summitville, Colorado/USA 1993; Harmony Mine, South Africa 1994; Manila, Philippines 1995; Omai, Guayana 1995; Homestake Mine South Dakota, USA 1996; Gold Quarry Mine Nevada territory of Western Shoshone, USA 1997; Kumtor, Kyrgystan 1998; Baia Mare, Romania 2000. [8]

A 1998 EPA report [9] describes the 66 most relevant cases which took place in the United States. Especially in the State of Montana, the use of cyanide for gold leaching is currently prohibited due to the contamination produced in soil, aquifers and superficial waters as a consequence of 50 cyanide leakages from 1982 to 1998 (when it was prohibited). Ground water contamination is the most persistent. [10]

There are (recorded) cases of this type of contamination in Argentina, for example in Bajo La Alumbrera (Catamarca) [11].

Bibliography:

1- Korte et. al.(2000) Ecotoxicology and Environmental Safety 46, 241-245.
2- EIA - Empresa VECTOR (2002)
3- Gilman y Goodman (1994).Las bases farmacológicas de la terapéutica. Ed. Panamericana.
4- Morán, R., (1998) Cyanide Uncertainties. MPC Issue Paper N°1.
5- Morán, R. (2001) More Cyanide Uncertainties. MPC Issue Paper N°3.
6- Bellini, M. (2001) Degradación microbiana de cianuros. Tesis de Maestría de la U.N. San Juan.
7- EPA (U.S. Envinronmental Protection Agency) Technical Resource Document, Extraction and Beneficiation of Ores and Minerals, vol.2, GOLD, (1994).
8- Berlin-Declaration on Gold Mining Using Cyanide Proccess. Berlin (2000).
9- EPA, Human Health and Environmental Damages from mining and Mineral Processing Wastes. (1998)
10- Ley I-137 (1998) Estado de Montana.
11- Diario Clarín, lunes 7 de Diciembre de 1998. CATAMARCA: FILTRACIONES EN LA ALUMBRERA CONTAMINAN LAS AGUAS Y DAÑAN L0S CULTIVOS.