Geochemical and petrological studies of high sulfur coal and overburden from Makum coalfield (Northeast India) towards understanding and mitigation of acid mine drainage

Opencast coal mining produces trash of soil and rock containing various minerals,that are usually dumped nearby the abandoned sites which causes severe environmental concern including the production of acid mine drainage(AMD)through oxidation pyrite minerals.The current study entailed assessing the potential production of AMD from an opencast coal mining region in Northeast part of India.In order to have a comprehensive overview of the AMD problem in Makum coalfield,the physico-chemical,geochemical,and petrological characteristics of the coal and overburden(OB)samples collected from the Makum coalfield(Northeast India)were thoroughly investigated.The maceral compositions reveal that coal features all three groups of macerals(liptinite,vitrinite,and inertinite),with a high concentration of liptinite indicating the coal of perhydrous,thereby rendering it more reactive.Pyrite(FeS_(2))oxidation kinetics were studied by conducting the aqueous leaching experiments of coal and(OB)samples to interpret the chemical weathering under controlled laboratory conditions of various temperature and time periods,and to replicate the actual mine site leaching.Inductively coupled plasma-optical emission spectroscopy(ICP-OES)was operated to detect the disposal of some precarious elements from coal and OB samples to the leachates during our controlled leaching experiment.The Rare earth element(REE)enrichment in the samples shows the anthropogenic incorporation of the REE in the coal and OB.These experiments reveal the change in conductivity,acid producing tendency,total dissolved solid(TDS),total Iron(Fe)and dissolved Sulfate(SO_(4)^(2−))ions on progress of the leaching experiments.Moreover,the discharge of FeS_(2) via atmospheric oxidation in laboratory condition undergoes a significant growth with the rise of temperature of the reaction systems in the environment and follows pseudo first order kinetics.A bio-remediative strategies is also reported in this paper to mitigate AMD water by employing size-segregated powdered limestone and water hyacinth plant in an indigenously developed site-specific prototype station.Apart from neutralisation of AMD water,this eco-friendly AMD remediation strategy demonstrates a reduction in PHEs concentrations in the treated AMD water.

Geochemical characterization of shales of the Eocene Disang Group,Kohima Syncline,India:Inferences to hydrocarbon potential and depositional environment

The Kohima Syncline exposes the Eocene Upper Disang Formation in an extensive region that is composed of grey shales with subordinate sandstone and siltstone alterations.The shales contain low to fair amount of organic matters represented by Type IV/Type III terrestrial kerogens.The Biomarkers indicate presence of terrestrial angiosperms and microbially reworked organic matters with some marine phytoplankton.Rock-Eval maturity parameters indicate maturity within a wide range between immature to post mature wet gas window,while the biomarkers show maturity between immature to mid mature.The biomarkers indicate that the Disang shales deposited in an oxic deltaic-terrigenous environment.The trace elements characterize an oxic to suboxic warm and humid depositional environment.Few trace elements point to deposition in a low salinity continental rather than a marine environment.Thus,several biomarker and trace element parameters show that a continental milieu was already established during the deposition of the Upper Disang sediments.It indicates that either the Disang basin,that evolved as a marine basin,suffered rapid shallowing during the deposition of the Upper Disang sediments,or the Lower and Upper Disangs were coeval and Lower Disangs represented deep marine facies while the Upper Disangs represented peripheral shallow marine deltaic facies.Maturity parameters like Tmax and,sterane and hopane isomerization ratios indicate that the organic matters of the Disang Group were affected by sudden short duration thermal events followed by cooling.This is possible in an active tectonic region like the Kohima Syncline that bears many evidences of thrusting and folding.