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Sympo+ium on SY,+~a Mining Rydrolopy, Sdnnmtobpy Md R~clcnutim <br />lUn,rn+ity of Kentucky. Le>, inpton, KentutiY WSOG-DeoemEer 1~5, 19801 <br />THE ASSESSMENT OF A STRATUM'S CAPABILITY <br />TO PRODUCE ACIDIC DRAINAGE <br />by <br />crank T. Caruccio, <br />Cwendelyn Ceidel <br />and <br />Armand Pelle tiers <br />Department of Geology <br />University of South Carolina <br />Columbia, South Carolina 29208 <br />Abstract. During the strip mining of coal in the bi- <br />t~vninous coal region of the United States, rock layers <br />of varying minera logic compositions overlying the coal <br />(the overburden) are disrupted and exposed, resulting <br />in accelerated weathering. The degree of which a <br />stratum will produce acidic or alkaline drainages is <br />dependent to a large extent upon the pyrite (as Fe52) <br />and calcareous (as Ca, Mg-CO3) content. The sulfide <br />minerals, which hitherto were isolated from the atmo- <br />sphere, oxidize to form a series of soluble hydrous <br />.iron sulfates, which in turn hydrolize to produce <br />acidity. Calcareous (Ca, Mg carbonate) materials, on <br />the other hand, have the capability to produce alka- <br />linity when exposed to water. <br />Through a series of experiments, samples of dark <br />shales collected from a strip mine in southwestern <br />Pennsylvania were exposed to simulated weathering con- <br />ditions. The samples having different calcareous- <br />pyrite ratios were periodically leached with deioni zed <br />water, simulated acid rain and simulated acid mine <br />drainage. The leachate quality was monitored and re- <br />lated to. the rock chemistry by vet chemical analysis <br />of a representative sample split. <br />It was found that the samples with low-neutrali- <br />zation potentials and low total-sulfur contents (re- <br />flecting pyrite content) produced mildly acidic <br />leachates when leached with water and acid rain. <br />Samples with high neutralization potentials and high <br />sulfur contents were found initially to neutralize the <br />simulated acid drainage and produce alkaline leachates. <br />However, with time, the samples ceased to neutralize <br />the simulated acid drainage and generated acidity. <br />These results show that the quality of the efflu- <br />ent generated by shales in southwestern Pennsylvania <br />can be predicted prior to disturbance and exposure to <br />the atmosphere by measuring two parameters. Although <br />a gross correlation exists between rock type and the <br />chemical weathering characteristics, a strong relation- <br />ship was found to exist between the effluent quality and <br />the carbonate-sulfur ratio. This ratio can be used to <br />monitor overburden characteristics in an active mining <br />operation and to identify toxic-acid producing strata. <br />'Currently with the S.C. Water Re SOUrCES Com- <br />mission, Columbia, South Carolina, 29204. <br />437 <br />