ACCUMULATON OF MICROELEMENTS IN TECHNOGENIC ECOSYSTEMS FROM THE VICINITY OF THE 'MEDET' OPENCAST MINE

摘要

Many studies have recently shown that phytocenosis in the reclaimed lands from the "Medet" mine region are poorly developed and do not provide a dense vegetation coverage.The purpose of this study is assess the accumulation rate and toxicity of some microelements acting as chemical barriers for the vegetation growth in the reclaimed "Sever" dump built in the vicinity of the "Medet" opencast mine. The achieved results showed that Technosols from the "Sever" dump form a geochemical zone with a high total copper content (determined after soil mineralization with aqua regia), which in the upper part of catena (the ridge of the dump) reaches 668.0 mg/kg. Thus it exceeds the threshold of 500 mg/kg, denned as intervention (toxic) concentration in Bulgarian legislation with 1.3 times. In comparison to typical concentrations of the element in Bulgarian soils these concentrations are on average 16 fold higher. Mobile concentrations of copper extracted with 1 M NH4N03 are also toxic and concentration into the birch leaves is comparable with the established in contaminated ecosystems (30.5 mg/kg). Lead, regardless of its high mobility in the studied soils slightly accumulates in plants.The plant species used for reclamation have selective ability to accumulate copper, lead, zinc and manganese and might diversely influenced their cycle in studied ecosystem. Birch is a vigorous phyto-extractor of zinc and manganese, since Acacia preferentially accumulates only copper.Fragmental rock texture of subsoil (below 25 cm) is both the physical and chemical barrier to plant development which restricts root penetration and retention of moisture and nutrients.