Biochemistry of mercury in an impacted gold mining tropical aquatic system: the Pra River Basin in Southwestern Ghana

2005·8.2 MB·English

by  Donkor, Augustine Kwame

BIOGEOCHEMISTRYOFMERCURYINANIMPACTEDGOLDMINING
TROPICALAQUATICSYSTEM:THEPRARIVERBASININSOUTHWESTERN
GHANA
By
AUGUSTINEKWAMEDONKOR
ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOL
OFTHEUNIVERSITYOFFLORIDAINPARTIALFULFILLMENT
OFTHEREQUIREMENTSFORTHEDEGREEOF
DOCTOROFPHILOSOPHY
UNIVERSITYOFFLORIDA
2005
Copyright2005
by
AugustineKwameDonkor
TOMYLORDBETHEGLORY
ACKNOWLEDGMENTS
IammostgratefultotheMostHighGodforseeingmethroughthisprogram.
I am very much indebted to my advisor Dr. Jean-Claude Bonzongo under whose
guidanceandadviceIundertookthisproject.Hisinvaluableideasandwisdomheshared
gavemetheneededinspirationtocompletethisresearch.Hewillalwaysberemembered
forhissupport,love,concernandclosecooperation.Mywarmestthanksalsogotomy
supervisorycommitteemembers,Dr.JosephDelfino,Dr.ThomasCrismanandDr.James
Winefordner(ChemistryDepartment)whocarefullyreadthemanuscriptandmademany
usefulsuggestions.Theiroutstandingeffortsbroughtthisdissertationtoareality.
I wish to express my profound gratitude to Dr. Vincent Nartey (Chemistry
Department)UniversityofGhana,Accra-Ghana,forhiskeyroleinthesamplingand
transportingofsamplestoUSA. Hisunderstanding,closecooperation,encouragement
and moral support “kept me going and the completion ofthis research”. I am also
thankfulfortheservicesofhisstudent,Mr.DennisAdotey.
MysincerethankstoDr.BenjaminSmith(ChemistryDepartment);hisservices
andassistanceindiversewayswillnotbeforgotten.Iwouldalsoliketothankallmy
colleaguesinthedepartmentespeciallythoseinDr.Bonzongo’sgroup,Mr.B.K.Dubey
ofDr. Townsend’s groupfor1CP-AES analysis andtheadministrativestafffortheir
assistancealways.IwishtoacknowledgethegreathelpprovidedbymygoodfriendsDr.
YawSolomonObengandDr.RexMaimait.
iii
ManythankstoUniversityofFloridaforaComptonFellowshipawardandthe
InstituteofHealthandConservation,SantaRosa,Californiaforagrantforthisresearch.
SpecialthankstoAnneFitzgeraldofFitzgeraldAssociatesforherassistance.
Finally,IsayabigthankyoutomywifeAliceandthethreekids,Glory,Joyand
Peacefortheirloveandsupportthroughouttheperiod.
IV
91
TABLEOFCONTENTS
page
ACKNOWLEDGMENTS
iii
LISTOFTABLES viii
LISTOFFIGURES x
ABSTRACT
xiii
CHAPTER
GENERALINTRODUCTION
1
1 GOLDMININGANDMERCURYPOLLUTION 5
2.1Introduction 5
2.1.1BriefHistoryofGoldMiningandMercury 9
2.1.2GoldRushesAroundtheWorld 1
2.2GoldMiningProcessesandAmalgamationTechnology 14
2.2.1MercuryDischargestotheEnvironmentduetoPastandPresentGold
MiningActivities 1
2.4MercuryandHumanHealthImpacts 32
2.4.1DirectExposureviaInhalation 32
2.4.2ExposureviaDiet 33
2 MERCURYINDIFFERENTENVIRONMENTALCOMPARTMENTSoFTHE
PRARIVERBASIN,SOUTHWESTERNGHANA 36
3.1Introduction 36
3.2StudySite 41
3.3MethodsandMaterials 44
3.3.1Sampling 44
3.3.2Analysis 47
3.3.2.1Totalandmethyl-Hgintheaqueousphase 47
3.3.2.2Totalandmethyl-Hginsedimentsandsoils 47
3.3.2.3Totalandmethyl-Hginfish 48
3.3.2.4Totalandmethyl-Hginhair 48
3.3.2.5DeterminationofothertracemetalsbyICP-AES 49
v
3.4 ResultsandDiscussion 50
3-4.1Mercuryintheaqueousphase 50
3-4.2MercuryinSediments 55
3.4.3ImpactofAGMonLevelsofTraceElementsotherthanMercuryin
Sediments 59
3.4.4AssessmentoftheContaminationLevelofPraRiverSediments 67
3.4.4.1Mercuryenrichmentinthesediments 69
3.4.4.2Co-variationofmercuryandothermetalswithA1 74
3.4.5.MercuryinSoils 87
3.4.6MercuryinBiologicalTissues 90
3.4.6.1.MercuryinFishTissues 90
3.4.6.2MercuryinHumanHair 92
3.5Conclusions 96
4 MERCURYTRANSFORMATIONANDMETHYLMERCURY
PRODUCTIONINSOILSANDSEDIMENTSOFTHEPRARIVERBASIN 98
4.1Introduction 98
4.2Materialsandmethods 102
4.2.1StudyAreaandSampling 102
4.2.2DeterminationoftheEffectofWaterContentonMethyl-HgFormation
inSoil 103
4.2.3DeterminationofthePotentialRatesofHgMethylationandMethyl-Hg
DegradationinRiverineSediments 104
4.2.4DeterminationofHgSpeciationinSoilandSedimentSamples 104
4.3ResultsandDiscussion 107
4.3.1EffectofWaterContentonInorganicHgPresentinSoilsandonHg
NewlyAddedtoSoils 107
4.3.2ProductionandDegradationofMethyl-HgandthePotentialfor
Mercury AccumulationinRiverSediments 121
5 ASSESSINGTHEROLEOFSOLARRADIATIONONMERCURY
TRANSFORMATIONANDCYCLING 127
5.1Introduction 127
5.2ChangesinIn-comingSolarRadiationandMercuryCycling 131
5.2.1OrganicMatterandHgAssociationinTerrestrialandAquaticSystems132
5.2.2DirectImpactofUV-RadiationonOrganicMatter 135
5.2.3IncreasingSolarUV-RadiationandHgBioaccumulation/Toxicity 137
5.3PotentialImpactsofUV-RadiationonHgCycling 138
5.3.1Photo-reduction 139
5-3.2Photo-oxidation 142
5.3.3DirectEffectofSolarRadiationonAqueousMethyl-Hg-Degradation
andHg-Methylation 142
5.4PreliminaryLaboratoryStudytoAssesstheIndirectEffectofUV-BonHg
Transformation 143
5.4.1Methods 143
vi
5.4PreliminaryLaboratoryStudytoAssesstheIndirectEffectofUV-BonHg
Transformation 143
5.4.1Methods 143
5.4.2ResultsandDiscussion 144
5.5Summary 145
6 CONCLUSIONSANDRECOMMENDATIONS 148
6.1Conclusions 148
6.2Recommendations 149
APPENDIX
A QA-QCFORTHESEDIMENTANDSOILANALYSESFROMTHEPRA
RIVERBASIN 150
A.lTotal-Hg 150
A.2Methyl-Hg 151
B TOTALMERCURY(THg)CONCENTRATIONS(ngg1DRYWEIGHT)AND
PERCENTAGEOFSPECIESCONTRIBUTIONINTHEINVESTIGATED
SEDIMENTS 155
C MERCURYMETHYLATIONANDMETHYLMERCURYDEMETHYLATIONIN
SEDIMENTS 156
LISTOFREFERENCES 159
BIOGRAPHICALSKETCH 199
vii
2-
LISTOFTABLES
3-
Table page
1EstimatedMercuryInputtotheEnvironmentDuetoGoldandSilverMining 23
1MineralproductionfromGhanaiansmall-scaleminingsectorfrom1989to2003....37
3-2Concentrationsoftotal-Hg(THg),methyl-Hg(MeHg),anddissolvedorganic
carbon(DOC)inwatersamplescollectedduringJune2002rainyandJanuary
2003dryperiods,(nd=notdetermined) 52
3-3Totalandmethyl-Hgconcentrationsinmg/kginsedimentssamplescollected
duringtheJune2002rainyandJanuary2003dryperiods 55
3-4Totalmetalconcentrationsinmg/kgdryweight(ppm)andorganicmattercontent
determinedaslossonignition(LOI)onriversedimentscollectedfromthePra
Riverbasinduring“June2002rainyseason” 61
3-5Totalmetalconcentrationsinmg/kgdryweight(ppm)andorganicmattercontent
determinedaslossonignition(LOI)onriversedimentscollectedfromthePra
Riverbasinduring“January2003dryseason” 63
3-6Pearsoncorrelationcoefficientsforsedimentdatacollectedduringthedryseason.
Lead(Pb)andcobalt(Co)arenotincludedastheirconcentrationswerebelow
instrumentanalyticaldetectioninsamplescollectedinJanuary2003dryseason...65
3-7PearsonCorrelationcoefficientsforsedimentdatacollectedduringtheJune2002
wetseason 66
3-8Calculatedenrichmentfactors*(EF)foranalyzedelementsinsedimentsamples
collectedintheJune2002rainyseason.Shalereferencevaluesweretakenfrom
TurekianandWedepohl(1961) 70
3-9Calculatedenrichmentfactors(EF)foranalyzedelementsinsedimentsamples
collectedduringtheJanuary2003dryseason.Shalereferencevaluesweretaken
fromTurekianandWedepohl(1961).*ND=notdetected 72
3-10Totalandmethyl-Hgconcentrationsinmg/kgandpercentOrganicMatter(%
OM)insoilsamplescollectedduringJune2002rainyandJanuary2003dry
periods 88
viii
3-11Averagetotalandmethyl-Hgconcentrationsintissues(dryweight)fromfour
differentfishspeciesthatarecommoninlocalpeople’sdietcollectedalongPra
RiverduringJanuary2003dryseason 91
33--12THgandMeHgconcentrationsinmg/kginheadhairsamplescollectedfrom
indigenouspeoplealongthePraRiverduringtherainyperiodofJune2002.
Sampleswerecollectedfromvillagescorrespondingtothelistedsitenumbers.
4- Thenumberofindividualspersiteislistedincolumn2 93
13THgandMeHgconcentrationsinmg/kginheadhairsamplescollectedfrom
indigenouspeopleatthesamplinglocationnumber6duringthedryperiodof
January2003 95
1Totalmercuryconcentrations(ngHgg'1dryweight)andpercentageofspecies
contributionintheinvestigatedsoils,alongPraRiverBasin 119
4-2Potentialratesofmercurymethylationandmethyl-Hgdemethylationinsediments
ofthePraRiverBasin 121
4-3SpecificratesofHgmethylationandmethyl-Hgdemethylationdeterminedas
percentageoftheaddedinorganicHg(formethylationexperiments)andmethyl-
Hg(fordemethylation)transformedperincubationhour 122
A-l.MajorionsalongthecourseofthePraRiverBasininppmduringJune2002
rainyandJanuary2003dryperiods 152
B-l. Totalmercury(THg)concentrations(ngg'1dryweight)andpercentageof
speciescontributionintheinvestigatedsediments 155
IX