Scholarly record
NATURAL REGENERATION OF THE ENVIRONMENT IN THE AREA OF THE OLD KRUMOVO IRON MINE IN SOUTHEAST BULGARIA
Abstract
The ore extraction from Krumovo deposit, located at the northern periphery of the Manastir heights in Southeast Bulgaria started in 1906 and continued till 1986. The ore comprised Fe3O4 with admixtures of sulfides such as pyrite, pyrrhotite, marcasite and chalcopyrite. Open pits and underground workings were used. The excavations severely degraded the habitats, vegetation and waters on an area of about 3 km2. By 1986 waste rock (comprising hydrothermally altered basic magmatic rocks, such as gabbro or diorites, magnesium skarn fragments, poor grade ore and various sulfide rich alteration products) and small open pits of various sizes were spread all over the area. The underground workings were connected with inclined galleries, from which waste waters drained. Since 1986 the waste rock has been subjected to secondary extraction for use as a construction material, which resulted in its nearly entire removal. It is worth seeing how 114 years after mining commencing, and 34 years after its stopping, the nature has managed to cope with the damage. Environmental components have been studied with emphasis on water. In previous years, the authors performed hydro chemical studies in this region and the data can be used to compare the water quality in Krumovo deposit area with the overall regional water properties. Water from two ponds in the Krumovo iron deposit was studied. These ponds differ in the water residence time as one is seasonal, while the other keeps water yearly. Data on integral water characteristics (such as pH, Eh, conductivity, and dissolved oxygen), water macro components, as well for micro components (such as Co, Cu, Fe, Mn, Ni, Cr, PO43-, NO3-) are presented in the paper. It has been found that the water in Krumovo is reasonably pure compared with the surface water from the region. There are reasons for this observation: (i) The regional waters are influenced by the parent rock material, and especially by the calcrete deposits, which are found immediately under the organic soil layer. As a result, water neutralization (sometimes alkalization) is observed - causing precipitation not only of carbonates but also of heavy metals - pollutants; (ii) The water sources contacting with the agricultural land in the region are affected by fertilizers' use. The Krumovo deposit is located in a hilly area, which is naturally forested and thus not subjected to the pollution from the agriculture. After the end of mining, bushes and trees germinated in nearly every crevasse in the rock and concrete wastes, providing nearly continuous vegetation cover. This contributes to the quality of the waters and provides conditions for recovering of the lost soil; (iii) Nearly 40 million tons of waste rock, as well as the abandoned concrete structures, were removed, thus eventual continuous pollution sources were withdrawn.
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References8
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