Scholarly record

MINERALOGICAL, GEOCHEMICAL AND MICROBIOLOGICAL STUDY OF METAL POLLUTED SOILS, SEDIMENTS AND DUMP MATERIALS IN THE VICINITY OF THE KCM PB-ZN SMELTER, PLOVDIV REGION, BULGARIA

R. Atanassova, T. Kerestedjian, G. Satchanska

Abstract

The predominant part of the soils in the studied area is alluvial soils with highly variable mechanical composition. According to their grain-size composition soils range from loamy sand, loam, to silty loam and in few cases clay loam. Analyses of the mineral composition of soils show that clay minerals and quartz are the dominant constitutions. Other registered minerals are Kfeldspar, plagioclase, calcite and dolomite with variable amounts. The distribution of heavy metals and As in soils is influenced by natural and anthropogenic factors. The distribution of concentrations of Pb, Zn, Cd, Cu and As indicates pollutions from the emissions coming from the smelter. The dispersion and deposition of elements are affected by the prevailing wind directions. The maximum of Pb, Zn and Cu near the new dump shows local influence. Cr, Ni, Co, Mn and Fe, beside input from KCM, have been naturally supplied within materials coming from the erosion of nearby metamorphic rocks. Surface sediments along Chepelarska River streambed before and after discharge of waste waters, sediments of Maritza River before and after confluence with Chepelarska River; sediments taken from waste water canals of Agria and KCM factories are studied. According to their grain-size composition sediments vary from sands to silty sands and silts. Metal content in sediments were determined in fraction < 63 mm. The results show extremely high metal concentrations in sediments of the waste water canals. The high increase of Zn, Pb and Cd content in river sediments after discharge of the waste waters is the demonstration that waste waters released by KCM are the major pollutant. Affected by pollution are also sediments of the Maritza River after the confluence with Chepelarska River. The information about the diversity and activity of the indigenous microflora in the metal-polluted soils and waters studied in the Pb-Zn smelter zone show a basic importance for understanding the bio-geo-chemical processes, occurring in the contaminated observed area. Significant changes were found in the structures of microbial community present in several Pb-Cu-Zn polluted soils and waters. Many bacterial strains were cultured from soil and water samples, most of which are resistant to heavy metals and herbicides. The results obtained and their analysis indicate that metal polluted soils and waters are a valuable reservoir for unusual microorganisms prospective for cheap bacteria-based bioremediation of heavy metal and pesticide pollutions and could prevent contamination of the environment. Clinker waste heaps in the vicinity of the smelter, expected to be relatively insoluble, and hence inactive, were found to be affected by active chemical processes. The old dump materials, after almost 30 years of coke burning and natural rain leaching, show concentrations of about 10 times above MPL; the worst situation is with the materials 5-20 years old (on the new dump) – the silicate-sulphide agglomerate (weltz clinker) with the burning coke in it represents an active chemical reactor, mobilizing the metallic contents from hardly soluble glasses into easily soluble recent phases on the heap. Deposited recent soluble phases have been identified. Most of these phases are sulphates of Cu, Zn, Fe, Mn and Al (chalcanthite, antlerite, bonattite, chalcocyanite, melanterite, copiapite, halotrichite and apjohnite) gypsum and native sulphur. The investigations are financed by the budget of NATO SfP 973739 “WATMETAPOL” Project of Science for Peace Program.

Publication details

Back to publication list