Friday, 14 July 2006

Traditional Gold Mining in Apolobamba (Bolivia): Soil Pollution and Risk Assessment.

Mª Ángeles Muñoz García1, Ángel Faz Cano1, José Alberto Acosta1, Silvia Martínez Martínez1, R. Millán2, and R. Vera2. (1) Universidad Politécnica de Cartagena, Alfonso XIII, 52, Cartagena, Spain, (2) Centro de Investigaciones Energéticas Medioambientales y Tecnológicas, Av. Complutense, 22, Madrid, Spain

In the National Management Integrated Natural Area Apolobamba (Department of La Paz-Bolivia) it has been developed gold extraction mining activities around gold extraction, with a very poor engineering technology and the use of mercury. The Universidad Politécnica de Cartagena-Spain has carried out a research, in collaboration with the Agencia Española de Cooperación Internacional through the “Programa Araucaria” in Bolivia, in the most degraded zones in Apolobamba. The objective of this work is the quantification and qualification of the affectation degree in soils of the studied area, and both the environment and human health risk assessment. Four mining districts in Apolobamba have been selected: Sunchullí, Viscachani, Katantika and Sural, based of the extracted material volume and the lack of technology in the mining process. These districts are located in Apolobamba Mountain-range where altitudes above 5 000 m.s.n.m. are reached, and they are constituted of little cooperatives, with the exception of Sunchullí. The cooperatives are working the gold extraction, using a poor engineering and, as a consequence, producing high contamination levels. Samples of water, soil and sediments have been taken in the most representative soils of the studied area. In these samples mercury, lead, copper, zinc and cadmium have been analysed. The mercury content was determinated thorough AMA-254 method (limit = 0,5 ppb) with certificated standards BCR 62-BCR 281. Heavy metals (Pb, Cu, Zn and Cd) were determinate using nitric-percloric digestion; bio-available metals with Norwell (1984) method; and soluble metals using the extraction water technology. The results shows that the largest part of the studied soils, do not present high levels of heavy metals; however, some are contaminated by mercury, lead or zinc. The most polluted soils are near Sunchullí mining site, with high levels of mercury, where the operators and the mining population are in contact with these soils without any type of protection, which is a human health risk. In the other hand, many heavy metals in these soils are dumped to the rivers as happens in the case of Sunchullí, Katantika and Pelechuco rivers. They could also be incorporated to the trophic cycle through the flora and the fauna in their bio-available and soluble forms. Moreover, the water of the rivers is consumed by the human and used for irrigation of some vegetable gardens, inside and outside of the protected area. The high environmental and human health risk from the mining extractions in Apolobamba, could be reduced thorough the information and formation of the workers and, in general, the population of the mining communities. It could be recommendable to use safe treatments for the mining wastes and sediments and redirect the dumping to the less sensitive zones that not allow the metal sedimentation. These recommendations will reduce the metal pollution.

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