Prognosis of the stability of arsenic in the biotop of the brown-coal dump

Abstract

In the nature there is a large number of various microorganisms which participate in the process of transformation of minerals and other materials, in their corrosion, disintegration decomposition or even formation of new components. Many of the microorganisms gain the energy for their metabolic processes trough oxidation of anorganic compounds. Interaction of microorganisms or their metabolites with deposited components, which may be toxid, can take place directly in the dump biotop. In fly-ashes produced by burning the Slovak brown coal a higher arsenic content is present, the arsenic in the original coal being bound in a very stable FeAsS compound (arsenopyrite). However this compound is decomposed by burning and so we were interested in the stability of newly formed arsenic compounds found in the fly-ash. Their stability was tested by leaching experiments in an environment of nutrient medium for bacteria Thiobacillus ferrooxidans 9KA (pH 1.5) at a concentration of cells 7x10 ml and simultaneously also without bacterial culture at the same condition. Apart from this, the extraction of arsenic from fly-ash was monitored also in the environment of metabolites of fungi Aspergillus niger (citric acid) at pH 1.8.