Biological properties of selected overburdens of Singrauli coalfields

Abstract

Coalfield mine overburden or abandoned mine sites is a major environmental concern. Overburden materials are nutrient-poor, loosely adhered particles of shale, stones, boulders and cobbles and are devoid of true soil character. Eco-restoration or natural transformation of overburden materials to soil for cultivation is a time taking process. In the present study, we focused on how the OB materials are different from nearby natural soil and explored the characterization of physical, chemical and biological properties of different aged overburden undergoing the process of eco-restoration. Further, we have analysed various microbial population, enzymatic activities and microbial respiration process in different aged overburdens vis-a-vis nearby soil. Microbial population was more in 16 year old overburden among different aged OB but less than nearby soil. Dehydrogenase, Urease activity showed an increasing trend with maturity age of overburden representing higher microbial population, while alkaline phosphatase activity is not following any trend. Soil microbial respiration was found to be increased with age of overburden. Carbon mineralization rate constant in all overburden lied in a narrow range (0.020-0.011) day-1 and it did not show any significant variation as compared to native forest soil (0.03 day-1). Mineralizable carbon was found more in native soil (7.95 mg C/kg of overburden) and 16 year old overburden (5.56 mg C/kg of overburden). Cumulative CO2 evolved was more in native forest soil (8.67 mg C/kg), and was comparable with 16 year old overburden (5.4 mg C/kg). Microbial population, enzymatic activity and carbon mineralization can act as an indicator for analysing changes in overburden spoil properties due to ecorestoration.