Abstract

MONTERO, Ramón Luis  and  MARTINEZ, Manuel. Physicochemical composition of acidic waters from two coal mines: lobatera, Táchira State, Venezuela. Rev. Fac. Ing. UCV [online]. 2014, vol.29, n.4, pp.55-66. ISSN 0798-4065.

Groundwater pollution can derive from many sources, being acid coal mine drainage one of the most important. This work shows preliminary data obtained from a geochemical study of three water samples, two of which correspond to coal mine drainage from two different mines and one spring-water sample, all of them collected near Lobatera, Táchira State, Venezuela. The study included the measurement of the physicochemical parameters pH and electrical conductivity during the sampling, as well as the determination of the content of the chemical species Na⁺, K⁺, Ca²⁺, Mg²⁺, SO₄^2-, dissolved silica (SiO₂), Fe, Al, Mn and Zn in the laboratory. The results indicate that the waters discharged from coal mines are highly acid and have high electrical conductivity values, while the spring water showed a pH near neutrality and a low electrical conductivity value. The water samples associated with coal mines revealed a higher content of the determined chemical species than the spring-water sample. These results suggest that water pH drastically decreases during water-coal interaction, due to the dissolution of the pyrite from coal strata. Therefore, the water dissolution capacity increases. This phenomenon shall explain the high concentration of the analyzed chemical species in the water samples that have already penetrated the coal sequences and that have come into contact with the adjacent rocks.

Keywords : Acid waters; Water-coal interaction; Geochemical weathering; Pyrite; Leaching.

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