Microbial Characteristics of Young Soils on Disposal Sites of Coal Combustion Waste in Bosnia and Herzegovina

Abstract

Microbial communities are essential for a range of soil functions and adjust to soil development, environmental conditions and pollution level by community structure, abundance and activity. At desolated landfills of coal combustion waste (CCW) that were un-covered and covered with shallow soil material layers, soil microbial indicators were estimated for both the ecological and eco-toxicological evaluation. The young CCW sites with pH values of 9.5 and substantial coal-derived organic carbon showed significant microbial biomass content and nitrogen mineralization rates. At the 0 to 15 year old landfills, the microbial biomass content and activities increased significantly with age. However, large spatial variations occurred due to the variation of the cover material thickness, the degree of ash-aging and the tillage practices. Carbon dioxide was even sequestered at young CCW sites as indicated during laboratory incubation with an open apparatus purging continuously ambient air. In accordance, the respiratory quotient went down to 0.03 mol CO₂ evolution rate per mol O₂ uptake rate, indicating that the CO₂ evolution rate is limited as an overall quality indicator. Within 15 years, these ‘Technosols’ showed pH values of 7.7 and decalcified while changes in microbial biomass content and activity rates were mainly related to N availability. We concluded that the available As, B, Cr and Ni pollution at CCW sites seemed largely immobilised by organic matter and alkalinity and therefore did not to inhibit the microbial colonisation and development of high microbial activity within 15 years. However, the ash disposals pose a contamination risk by wind erosion and a future risk to human or environmental health when toxic metals will be released in soil at low pH values, low organic matter and low antagonistic ion contents.

Keywords:

• coal combustion waste
• carbon sequestration
• CO₂ evolution
• CO₂ absorption
• microbial biomass
• nitrogen mineralization
• pollution
• respiratory quotient
• soil development
• waste

ACKNOWLEDGMENTS

The authors are grateful to Helga Köller for the excellent technical assistance. Thanks to Louis Reid for the improvement of the English. The authors are also grateful to RECOAL partners (E.U. STREP ‘Reintegration of Coal Ash Disposal Sites and Mitigation of Pollution in the West Balkan Area—RECOAL’) for the support and the constructive comments. This work was in part supported by the E.U. IP ‘Sustainability Impact Assessment: Tools for Environmental, Social and Economic Effects of Multifunctional Land Use in European Regions—SENSOR’.