Concentration and association of minor and trace e

ConcentrationandassociationofminorandtraceelementsinMukahcoalfromSarawak,Malaysia,withemphasisonthepotentiallyhazardoustraceelementsSay-GeeSia⁎,WanHasiahAbdullahGeologyDepartment,UniversityofMalaya,50603KualaLumpur,MalaysiaabstractarticleinfoArticlehistory:Received1June2011Receivedinrevisedform17September2011Accepted18September2011Availableonline2October2011Keywords:CoalHealthandenvironmentalconcernsMixedlayerclaysPyriteTraceelementsTheashyieldandconcentrationsoftwenty-fourminorandtraceelements,includingtwelvepotentiallyhazard-oustraceelementsweredeterminedinMukahcoalfromSarawak,Malaysia.ComparisonsmadetotheClarkevaluesshowthatMukahcoalisdepletedinAg,Ba,Be,Cd,Co,Mn,Ni,Se,U,andV.Ontheotherhand,itisenrichedinAs,Cr,Cu,Pb,Sb,Th,andZn.Amongthetraceelementsstudied,VandBaareassociatedpredominantlywiththeclayminerals.Manganese,Cr,Cu,Th,andNiaremostlyboundwithinthealuminosilicate,sulphideand/orcarbonatemineralsinvaryingproportions,thoughaportionoftheseelementsarealsoorganicallybound.Arse-nic,PbandSbaremostlyorganicallybound,thoughsomeoftheseelementsarealsoassociatedwiththesulphideminerals.Zincisassociatedwithboththeorganicandinorganiccontentsofthecoal.Amongthepotentiallyhaz-ardoustraceelements,Be,Cd,Co,Mn,Ni,Se,andUmaybeoflittleornohealthandenvironmentalconcerns,whereasAs,Cr,Pb,SbandThrequirefurtherexaminationfortheirpotentialhealthandenvironmentalconcerns.OfparticularconcernaretheelementsAs,PbandSb,whicharemostlyorganicallyboundandhencecannotberemovedbyphysicalcleaningtechnologies.Theyescapeduringcoalcombustion,eitherreleasedasvapourstotheatmosphereorareadsorbedontothefineflyashparticles.©2011ElsevierB.V.Allrightsreserved.1.IntroductionCoalisacomplexcombustiblerockmadeupoforganicandinorganiccomponents.Bydefinition,coalmaycontainupto50%byweightand70%byvolumeofnon-carbonaceousmaterials(Schopf,1956),withasmanyas76ofthe92naturallyoccurringelementsoftheperiodictablehavingbeendetected(Schweinfurth,2003).Theconcentrationofele-mentsincoaldependsonthepropertiesofthecountryrocks,deposition-alenvironments,diagenesisandcoalificationprocesses,syngeneticandepigeneticmineralisation,aswellashydrological/hydrogeologicalcondi-tions(Arbuzovetal.,2011;ClarkeandSloss,1992;Cohenetal.,1984;Daietal.,2011a;Filippidisetal.,1996;Finkelman,1993;Gluskoteretal.,1977;Goodarzi,1995;GoodarziandSwaine,1994;Gürdal,2011;Mukhopadhyayetal.,1998;Sunetal.,2010;Swaine,1990;Valković,1983).Assuch,theconcentrationoftheelementscandiffergreatlybe-tweenandwithincoalseamsandcoalfields.Basedontheirconcentration,theelementscontainedincoalcangenerallybeclassifiedintothreegroups:(1)majorelements,generallywithconcentrationshigherthan1000ppm,consistingofthecoalformingelements(C,H,O,andN)andS;(2)minorelements,generallywithconcentrationbetween100and1000ppm,comprisingthemineralmatterformingelements(Si,Al,Ca,Mg,K,Na,Fe,MnandTi)andhalogens(F,Cl,Br,I);and(3)traceelements,generallywithconcentrationsbelow100ppm(Schweinfurth,2003;Xuetal.,2003).Elementsincoalcaneitherorganicallyassociatedincoal'sporewaterorboundorganicallywithcoalmacerals,orareinorganicallyboundwithdiscreteminerals(Ward,2002).Themodesofoccurrenceoftraceele-mentsvarygreatlyamongcoals.Inlow-rankcoalssuchassubbitumi-nousBofMukahcoal(SiaandDorani,unpublished),theelementsareusuallyorganicallybound,butwiththeprogressofcoalification,theele-mentsareremovedbyexpulsionofmoistureandchangesinthechemi-calstructureoftheorganicmatter(BensonandHolm,1985;GivenandSpackman,1978;KissandKing,1977;1979;Lietal.,2007;MillerandGiven,1986;Ward,1991;1992;2002).Elementswhichareboundwithdiscretemineralswill,however,remainunchanged(Ward,2002).Statisticalanalyses,particularlyPearsoncorrelationcoefficientsandclusteranalysis,havebeenwidelyappliedtostudythemodesofoccur-renceoftraceelements(Brownfieldetal.,2005;Daietal.,2005;2007;2008a;Duetal.,2009;EskenazyandStefanova,2007;GolabandCarr,2004;Huetal.,2006;Karayigitetal.,2000;Kimura,1998;MukherjeeandSrivastava,2005;Pentarietal.,2004;Shaveretal.,2006;SpearsandTewalt,2009;SpearsandZheng,1999;Suárez-Ruizetal.,2006;Sunetal.,2010;Wangetal.,2008;Wangetal.,2011).Statisticalrela-tionshipsbetweenanelementwiththeashyieldandash-associatedel-ementsarefrequentlyusedtoexploretheorganicandinorganicaffinitiesofanelement(Karayigitetal.,2000;SpearsandTewalt,2009;SpearsandZheng,1999;Wangetal.,2008).Elementsdisplayingsignificantpositiverelationshipwithashyieldandash-associatedele-mentsareinorganicallyassociated,andviceversa.NegativelycorrelatedInternationalJournalofCoalGeology88(2011)179–193⁎Correspondingauthor.Tel.:[phone];fax:[phone].E-mailaddress:[e-mail](S.G.Sia).0166-5162/$–seefrontmatter©2011ElsevierB.V.Allrightsreserved.doi:10.1016/j.coal.2011.09.011ContentslistsavailableatSciVerseScienceDirectInternationalJournalofCoalGeologyjournalhomepage:(y)andtheashyield(x),theinter-ceptoftheregressionlineontheordinatereveal