Preliminary assessment of heavy metals in water and sediment of Karnaphuli River, Bangladesh

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ContentslistsavailableatScienceDirect

Environmental

Nanotechnology,

Monitoring

&

Management

j o ur na l h o me pa g e :w w w . e l s e v i e r . c o m / l o c a t e / e n m m

Preliminary

assessment

of

heavy

metals

in

water

and

sediment

of

Karnaphuli

River,

Bangladesh

Mir

Mohammad

Ali

a

_,

_Mohammad

_Lokman

_Ali

a,b

_,

_Md.

_Saiful

_Islam

c,∗

_,

_Md.

_Zillur

_Rahman

d

a_Department_of_Aquaculture,_Patuakhali_Science_and_Technology_University,_Patuakhali_8602,_Bangladesh

b_Division_of_Genetics_and_{Microbiology,}_Institute_of_Biological_Sciences_University_of_Malaya,₅₀₆₀₃_Kuala_Lumpur,_Malaysia c_Department_of_Soil_Science,_Patuakhali_Science_and_Technology_University,_Patuakhali_8602,_Bangladesh

d_Fish_Inspection_and_Quality_Control_Chemistry_Lab,_Department_of_Fisheries,_Bangladesh

a

r

t

i

c

l

e

i

n

f

o

Articlehistory:

Received3September2015

Receivedinrevisedform

12December2015 Accepted4January2016 Keywords: Heavymetals Water Sediments Coastalriver Bangladesh

a

b

s

t

r

a

c

t

Contaminationofheavymetalsinsedimentisregardedasaglobalcrisiswithalargeshareindeveloping countrieslikeBangladesh.Fourheavymetalssuchasarsenic(As),chromium(Cr),cadmium(Cd)andlead (Pb)insedimentsandwaterwereinvestigatedfromKarnaphuliRiverinBangladesh.Thedecreasingtrend ofmetalswereobservedinwaterasCr>As>Pb>CdandinsedimentCr>Pb>As>Cd.Therangesofheavy metalsinwaterwere13.31–53.87,46.09–112.43,2.54–18.34and5.29–27.45␮g/Landinsedimentswere 11.56–35.48,37.23–160.32,0.63–3.56and21.98–73.42mg/kgforAs,Cr,CdandPb.Thelevelofstudied metalsinwatersamplesexceededthesafelimitsofdrinkingwater,indicatedthatwaterfromthisriver isnotsafefordrinkingand/orcooking.Contaminationfactor(CF)conﬁrmedthatthesedimentsamples weremoderatetohighcontaminationbyAs,CdandPb.Thepollutionloadindex(PLI)valueswereabove one(>1)indicatesadvanceddeclineofthesedimentquality.Thisstudyrecommendedthatcontinuous monitoringofAs,CdandPbinwater;sedimentandotheraquaticbiotaofKarnaphuliRivershouldbe directedtoassesstheriskofthesevitalmetalstosafetheecologyinthevicinityofthisriver.

1. Introduction

Contaminationofheavymetalsintheaquaticenvironmenthas attractedglobalattentionowingtoitsabundance,persistenceand environmentaltoxicity(Islametal.,2015a;Ahmedetal.,2015a,b). Bothnaturalandanthropogenicactivitiesareresponsibleforthe abundantofheavymetalsintheenvironment(WilsonandPyatt, 2007;Khanetal.,2008).However,anthropogenicactivitiescan effortlesslygenerateheavymetalsinsedimentandwaterthat pol-lutetheaquaticenvironment (Sanchez-Chardiet al.,2007).The increasingpollution byheavymetals havea signiﬁcantadverse healtheffectsforinvertebrates,ﬁsh,andhumans(Yietal.,2011; Islametal.,2014;Martinetal.,2015;Islametal.,2015b,d;Ahmed etal.,2015c).Themetalpollutionofaquaticecosystemsis increas-ing due to the effects from urbanization and industrialization (Sekabiraetal.,2010;Zhangetal.,2011;Baietal.,2011;Grigoratos etal.,2014;Martinetal.,2015).

∗Correspondingauthor.

E-mailaddresses:islam-md.saiful-nj@ynu.jp,msaifulpstu@yahoo.com

(Md.S.Islam).

Intheaquaticenvironment,sedimentshavebeenwidelyusedas environmentalindicatorsfortheassessmentofmetalpollutionin thenaturalwater(Islametal.,2015c).Theprincipalcomportment of metalsis a functionof thesuspendedsediment composition andwaterchemistryinthenaturalwaterbody(Mohiuddinetal., 2012).Duringtransportationofheavymetalsintheriverinesystem, it may undergofrequent changes due todissolution, precipita-tionandsorptionphenomena(Abdel-GhaniandElchaghaby,2007), whichaffecttheirperformanceandbioavailability(Nicolauetal., 2006;Nourietal.,2011).Sedimentis anessential anddynamic partoftheriverbasin,withthevariationofhabitatsand environ-ments(Morilloetal.,2004).Theinvestigationofheavymetalsin waterandsedimentscouldbeusedtoassesstheanthropogenic andindustrialimpactsandrisksposedbywastedischargesonthe riverineecosystems(Zhengetal.,2008;Yietal.,2011;Saleemetal., 2015).Therefore,itisimportanttomeasuretheconcentrationsof heavymetalsinwaterandsedimentsofanycontaminatedriverine ecosystem.

Nowadaysheavymetalpollutionisa mainprobleminmany developing countrieslike Bangladesh (Islam et al., 2015c).The unplannedurbanizationandindustrializationofBangladeshhave detrimentaleffectsonthequalityofwaterandsedimentaswellas http://dx.doi.org/10.1016/j.enmm.2016.01.002

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otheraquaticfauna.Thedisposalofurbanwastes,untreated efflu-entsfromvariousindustriesandagrochemicalsintheopenwater bodiesand rivershasreachedalarmingsituationin Bangladesh whicharecontinuallyincreasingthemetalsleveland deteriorat-ingwaterquality(Khadseetal.,2008;Venugopaletal.,2009;Islam etal.,2015a,c).InBangladesh,KarnaphuliRiveristhelargestand importantriverintheChittagongCityandseaportarea.Because oftheindustriallydevelopedareatheheavymetalpollutionofthe KarnaphuliRiverisincreasingdaybyday.Thestudiedriverreceives hugeamountofuntreatedeffluentsfromindustriessuchas spin-ningmills,dying,cotton,textile,steelmills,oilrefineriesandothers. Highconcentrationofheavymetalssuchasarsenic(As),chromium (Cr),cadmium(Cd)andlead(Pb)aredischargedintotheKarnaphuli Riverwhichpollutethewaterandsediments.Todate,noscientific researchregardingheavymetalpollutioninwaterandsedimentof thestudyriverhasbeenconductedsofar.Therefore,theobjectives ofthisstudyaretoevaluatethewaterqualityparametersofthe KarnaphuliRiver;todeterminethelevelsofheavymetalsinwater andsediment;andtoassesstheheavymetalpollutionstatusin sediments.

2. Materialsandmethods

2.1. Studyareaandsampling

ThisstudywasconductedontheKarnaphuliRiver,whichpasses throughChittagongCity,closetotheBayofBengal, Bangladesh (Fig.1).ThenameofthesamplingsiteswiththeirGIScoordinates ispresentedinTableS1.KarnaphuliRiverisoneofthemajorand mostimportantriversinChittagongandtheChittagonghilltracts, originatingintheLushaihillsinMizoramStateofIndia.Ittravels through180kmofmountainouswildernessformationofaslight circleatRangamatiandthenfollowsazigzagcoursebeforeitforms twootherprominentloops,theDhuliachhariandtheKaptai.Itruns overthedistrictinazigzagpathandafteracourseofabout170km fallsintotheBayofBengaland about16kmsouthwestof Chit-tagongtown.About40 compositesediment and watersamples werecollectedfrom10samplinglocationsofKarnaphuliRiverin September,2014(summer)andinMarch,2015(winter).During winter,thereisnorainfall,andriverwaterlevelsdecrease;during summer,riverwaterlevelsincreaseduetoheavyrainfall. Consid-eringthewaterflowinthestudiedriver,summerseasonexhibited higherthanwinterseasonwhichcancausethevariationofmetals concentrationinwaterandsediment.Watersampleswerefiltered (0.45␮mfilters, cellulose nitrate,Millipore) into polypropylene tubesusingaplastic syringe(BDPlastipak,50mL)fordissolved metalconcentrations.Sampleswereacidifiedto0.24MwithHNO3

(65%suprapure,Merck)andkeptat4◦Cinthedarkuntilanalysis. SedimentsampleswerecollectedbyEkmandredgefromdifferent stationsoftheKarnaphuliRiveratsamesitesofwatersamples.The collectedsampleswereputintothepolythenebag(sediment)and PVCbottle(water).Aftercollectionsampleswerebroughttothe FishInspectionandQualityControl(FIQC)ChemistryLaboratory, Khulna,Bangladesh.Thecollectedsedimentsamplesweredriedat roomtemperaturegroundandsievedwith2mmsieve.

2.2. Waterqualityparameters

Physico-chemical parameters like temperature, pH and dis-solved oxygen (DO) of the river water were measured. Water sampleswerecollectedonspotusingwatersamplerforthe detec-tionof physicochemical parameters.Temperature and pHwere determinedusingamicroprocessorpHmeter(ModelNo.HI98139, HANNA Instruments Ltd., Germany). Salinity was measured by potableRefractometer(Model:EXTECHRF20).Otherparameters

likehardness(mg/L),dissolvedoxygen(mg/L),alkalinity(mg/L), ammonia(mg/L),wereanalyzedonusingkits(HANNATestkits, HannaInstrumentsLtd.,Germany).

2.3. Chemicalsandsampledigestion

AllstandardsolutionfortargetelementwassuppliedbyMerck Germanywithhighestpuritylevel(99.98%).Ultra-pureHNO3was

usedforsampledigestion.Allotheracidsandchemicalswereeither suprapureorultra-purereceivedformMerckGermanyor Schar-lauSpain.Aftercollection,watersampleswerefilteredthrough MilliporeFiltrationAssembly,using0.45mmmembranefilter.The filtratewasthenacidifiedwithconcentratedHNO3tomakeapHof

<2.Measuredvolume(50mL)ofwellmixed,acidiﬁedsamplewas takeninabeaker.About5mLofconcentratedHNO3wasaddedand

boiledat130◦Conhotplatetillthevolumecametoabout25–30mL andlightcolor.AdditionofHNO3 andboilingwererepeatedtill

solutionbecomeslightcoloredorclear.Aftercooling,volumewas madetodesiredlevelwithDIWpassingthroughtheWhatmanno. 41ﬁlterpaper.About2.0gportionofdriedsedimentwastakenin 100mLbeakerand15mLofconcentratedHNO3 wasadded.The

contentwasheatedat130◦Cfor5huntil2–3mLremaininginthe beaker.AfterdigestionmaterialswerepassedthroughWhatman no.41ﬁlterpaper,washedwith0.1MHNO3solutionandmadeup

to100mLvolumewithdeionizedwater. 2.4. Analyticaltechniqueandaccuracycheck

AllthematrixeswereanalyzedforPb,Cd,CrandAsbyatomic absorptionspectrophotometer(ModelZEEnit700P#150Z7P0110, AnalytikJena,Germany)usingGF-AASandHydrideGenerator sys-tem.Allthemethodsarein-housevalidatedfollowingEC567/2002. Analyticalconditions for themeasurement oftheheavy metals in sample using AAS were tabulated in Table S2. The instru-ment calibration standards were made by diluting standard (1000ppm)suppliedbySigma–Aldrich,Switzerland. Theresults wereexpressedasmg/kgforfishandsedimentwhile␮g/Lforwater sample.De-ionizedultrapurewaterwasusedforthe experimen-talprocedure.Allglasswareandcontainerswerecleanedby20% nitricacid,finallyrinsedwithDe-ionizedultrapurewaterfor sev-eraltimesandoven-driedpriortouse.Theanalyticalprocedurewas checkedusingcertifiedreferencematerialDORM-4Fishproteinfor heavymetals.Thisfishsampleswerepreparedandprovidedbythe NationalResearchCouncil,Canada.Thestandarddeviationsofthe meansobservedforthecertifiedmaterialswerebetween0.65–8% andthepercentagerecoverywasbetween89and99%asshown inTableS3.Theresultsindicatedagoodagreementbetweenthe certifiedandobservedvalues.

2.5. Assessmentofheavymetalsinsediment

Intheinterpretationofgeochemicaldata,choiceofbackground valuesplaysa signiﬁcantcontribution.Severalresearchershave usedtheaverageshalevalues ortheaveragecrustalabundance dataasreferencebaselines(LoskaandDanuta,2003;Singhetal., 2005;Islametal.,2015a).Thedegreeofcontaminationfromheavy metalscouldbeevaluatedbydeterminingthecontaminationfactor (CF),pollutionloadindex(PLI)andgeoaccumulationindex(Igeo). 2.5.1. Pollutionloadindex(PLI)andcontaminationfactor(CF)

Toevaluatethesedimentquality,combinedapproachesof pol-lutionloadindexofthefourmetalswerecalculatedaccordingto Islametal.(2015c).ThePLIisdeﬁnedasthenthrootofthe multi-plicationsofthecontaminationfactorofmetals(CF).

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Fig.1.MapofthestudyareaofKarnaphuliRiver,Bangladesh.

whereCFmetalsistheratiobetweenthecontentofeachmetalto

thebackgroundvalues(backgroundvaluefromtheaverageshale value)insediment,CFmetals=Cmetal/Cbackground.Therefore,PLIvalue

ofzeroindicatesexcellence,avalueofoneindicatesthepresenceof onlybaselinelevelofpollutantsandvaluesaboveoneindicate pro-gressivedeteriorationofthesiteandestuarinequality(Tomilson etal.,1980).ThePLIgaveanevaluationoftheoveralltoxicity sta-tusofthesampleandalsoitisaconsequenceofthecontribution ofthestudiedfourmetals.Theratioofthemeasuredconcentration tonaturalabundanceofagivenmetalhadbeenproposedasthe contaminationfactor(CF)beingclassiﬁedintofourgradesfor mon-itoringthepollutionofonesinglemetaloveraperiodoftime(Islam etal.,2015c):lowdegree(CF<1),moderatedegree(1≤CF<3), con-siderabledegree(3≤CF<6),andveryhighdegree(CF≥6).Thus, theCFvaluescanmonitortheenrichmentofonegivenmetalin sedimentsoveraperiodoftime.

2.5.2. Geoaccumulationindex(Igeo)

Thedegreeofcontaminationfromtheheavymetalscouldbe assessedbymeasuringthegeoaccumulationindex(Igeo).Theindex

ofgeoaccumulationhasbeenwidelyusedtotheassessmentof sed-imentcontamination(SantosBermejoetal.,2003;Saleemetal., 2015).Inordertocharacterizethelevelofpollutioninthe sedi-ment,geoaccumulationindex(Igeo)valueswerecalculatedusing

theequation,

Igeo=Log2[ Cn

1.5Bn] (2)

whereC_n isthemeasuredconcentrationofmetalnin the sedi-mentandB_n isthegeochemicalbackgroundvalueofelementn in thebackgroundsample(Yuet al.,2011; Rahmanand Ishiga, 2012; Islamet al.,2015a).The factor 1.5is introducedto min-imize the possible variations in the background values which may be qualiﬁed to lithogenic effects. Geoaccumulation index

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(Igeo)valueswereinterpretedas:Igeo≤0—practically

uncontami-nated;0≤Igeo≤1—uncontaminatedtomoderatelycontaminated;

1≤Igeo≤2—moderately contaminated; 2≤Igeo≤3—moderately

to heavily contaminated; 3≤Igeo≤4—heavily

contami-nated; 4≤Igeo≤5—heavily to extremely contaminated; and

5<Igeo—extremelycontaminated. 2.5.3. Statisticalanalysis

Thedatawerestatisticallyanalyzedbythestatisticalpackage, SPSS16.0(SPSS,USA).Themeansandstandarddeviationsofthe heavymetalconcentrationsinwaterandsedimentswere calcu-lated.

3. Resultsanddiscussion

3.1. Waterqualityparameters

Thephysico-chemicalparameters of the water columnsuch as dissolved oxygen (DO), pH, temperature etc. are presented inTable1. Thephysicochemical parametersarevery important becausetheyhaveasignificanteffectonthewaterquality. Further-more,aquaticlifealsosuffersduetodegradationofwaterquality. Amongtheexternalfactorstemperatureisoneofthemost impor-tantfactorswhichinfluencetheaquaticecology(Huet,1986).The values oftemperature wereranged from28.8◦C to33.9◦C and 20.1◦C to23.9◦C during summerand winter, respectively. The meanvalueofwatertemperaturewasfoundwithinthe permissi-blelimitssetby(WHO,2004),whichwasbetween25and30◦C. TheaveragepHwas7.89and 8.17duringsummerand winter, respectively(Table1).Salinityisameasureofthesaltcontentofthe water.Thesalinityoffreshwaterisalwayslessthan0.5%.Thisrange ofsalinity isgenerally termedbrackishas distinctfrommarine orfreshwaters.Meanvaluesofsalinitywereobserved8.61pptin summerand9.06pptinwinter.Inthepresentstudy,thehighest hardness780mg/LwasobservedinsiteS10duringwinterdueto higherlevelofsalinitywherelowerhardness325mg/Lduring sum-merwasobservedin siteS3(Table1)duetothelowersalinity concentration(Lawson,2011).Dissolvedoxygenreferstothe oxy-gengasthatisdissolvedinthewaterandmadeavailabletoaquatic life.Thesolubilityofoxygenincreaseswithdecreasethe tempera-ture(Singhetal.,1990).AswasexpectedthehighestvalueofDO wasrecordedduringwinterseasonmightbeduetotemperaturein thisseasonwaslow(Macan,1980).Thedissolvedoxygen(DO)was found4.58–11.75mg/Lduringsummerand5.12–14.1mg/Lin win-ter.ThelowestvalueofDOwasobservedduringsummerthatcould beduetothelessornorainfallandincreaseintemperaturethatlead todecreaseindissolvedoxygenresultsduetotherateofoxygen consumptionfromaquaticorganismsandhighrateof decomposi-tionoforganicmatter.Josephetal.(1993)reportedthatasuitable rangeofalkalinityis20–300mg/Lforfish.Inthepresentstudythe highestalkalinityrangewas(114.4±3.782–189±16.355mg/L),it indicatesthatthelevelofalkalineisasuitablecondition.

3.2. Metalconcentrationinwater

Theresultsofheavymetalconcentrationsinsurfacewatersare showninTable2.Theaverageconcentrationofstudiedmetalsin waterfollowedthedecreasingorderof:Cr>As>Pb>Cd.Themean concentrationofCrinwaterwasobserved69.56and86.93␮g/L duringsummerandwinterseason,respectivelywhichwasmuch higherthantheWHOstandardlevelfordrinkingwater(Table2). TheaverageconcentrationofCdwasobserved6.46and10.64␮g/L duringsummerandwinterseason,respectively.Interestingly,the highestvalueofCdwasobservedatS6site(18.34␮g/Lduring

win-ter)whichmightbeattributedtothedomesticsewageandefﬂuents Table

1 Water quality parameters of Karnaphuli River of Chittagong district, Bangladesh. Sites Temperature ( ◦C) pH Salinity (ppt) Hardness (mg/L) DO (mg/L) Alkalinity (mg/L) Ammonia (mg/L) Su Wi Su Wi Su Wi Su Wi Su Wi Su Wi Su Wi S1 33.7 23.9 7.8 8.1 8.5 9.1 330 570 11.23 13.1 120 160 0.23 0.35 S2 32.4 21.4 7.8 7.9 8.7 9.1 350 595 7.11 8.31 115 145 0.31 0.51 S3 30.1 20.1 7.9 7.5 8.4 8.9 325 660 10.05 11.1 110 160 0.1 0.15 S4 31.6 21.2 8.1 7.8 8.7 9.3 360 725 5.1 7.24 115 150 0.13 0.27 S5 28.6 20.5 7.5 7.7 8.7 8.9 375 665 4.58 5.12 112 155 0.1 0.18 S6 32.1 22.7 7.3 8.5 8.5 9.1 335 585 10.11 12.21 130 170 0.33 0.43 S7 33.9 20.4 7.9 8.3 8.9 9.4 465 745 11.75 14.1 92 130 0.12 0.19 S8 29.8 20.3 8.2 8.1 8.8 8.9 430 690 7.1 9.2 125 165 0.13 0.28 S9 29.7 21.1 8.1 8.7 8.8 9.4 420 755 5.3 8.56 118 135 0.21 0.29 S10 28.8 20.6 8.3 9.1 8.9 9.5 450 780 8.45 10.29 110 140 0.27 0.35 Average ± SD 31.07 ± 1.94 21.22 ± 1.21 7.89 ± 0.31 8.17 ± 0.49 8.69 ± 0.17 9.16 ± 0.23 384 ± 52.64 677 ± 75.17 8.07 ± 2.63 9.92 ± 2.78 114.7 ± 10.25 151 ± 13.29 0.193 ± 0.09 0.3 ± 0.11 Note : Su—Summer, Wi—Winter season, respectively.

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Table2

Heavymetalconcentration(␮g/L)inwatersampleofKarnaphuliRiverandmaximumpermittedconcentrationinwater(␮g/L).

Sites As Cr Cd Pb

Summer Winter Summer Winter Summer Winter Summer Winter

S1 15.83 21.41 51.76 65.32 5.28 7.32 18.17 27.45 S2 32.43 41.53 63.91 78.54 6.87 13.49 7.32 12.67 S3 20.07 27.89 96.09 112.43 2.54 3.18 11.64 17.89 S4 27.13 33.48 46.09 55.43 3.12 6.59 9.89 13.45 S5 19.84 31.54 75.99 90.79 10.94 15.56 11.45 22.78 S6 17.29 29.83 69.27 87.45 11.71 18.34 5.73 11.56 S7 13.31 23.76 79.81 92.13 5.91 11.79 17.12 25.32 S8 30.44 53.87 93.14 107.57 4.38 8.93 5.29 10.69 S9 31.79 43.32 66.39 95.21 7.19 11.71 6.56 13.98 S10 25.49 37.98 53.18 84.38 6.62 9.53 5.34 12.49 Average±SD 23.36±6.99 34.46±9.87 69.56±16.95 86.93±17.39 6.46±3.00 10.64±4.49 9.85±4.75 16.83±6.17 DWSBa ₅₀ ₅₀ ₅ ₅₀ TRVb ₁₅₀ ₁₁ ₂ ₃ WHO(2004) 10 5 3 10

Note:SD,standarddeviation.

a_Drinking_water_standard_for_Bangladesh_proposed_through_ECR₍_Department_of_Environment,_Government_of_the_People’s_Republic_of_Bangladesh,₁₉₉₇_).

b_TRV_(toxicity_reference_value)_for_fresh_water_proposed_by_USEPA₍₁₉₉₉₎_.

fromtheportarea(Islametal.,2015a).Theaverage concentra-tionofAswashigherinwinter(34.46␮g/L)thanthatinsummer (23.36␮g/L)whichexceededtheWHOstandard(10␮g/L)(Table2). ArsenicoriginatesmostlyfromtheuplandHimalayancatchments or Chittagonghill tracts which are linkedwith thestudy river (Mitamuraetal.,2008).TheaverageconcentrationofPbinwater was9.85and16.83␮g/Lduringsummerandwinterseason, respec-tively,whichwerehigherthanthedrinkingwaterqualitystandard. Consideringthetoxicityreferencevalues(TRV)proposedbyUSEPA (1999)almostalltheheavymetals especiallyCrandCdgreatly exceededthelimitforsafewater,indicatedthatwaterfromthis riverisnotsafefordrinkingand/orcooking.Themetalsinwater wereseasonallyvaried,wherewinterseasonexhibitedhigherthan summer(Table2).Thelowerconcentrationofheavymetalsduring summermightbeduetothedilutioneffectofwater(Mohiuddin etal.,2012;Islametal.,2015a;Adamuetal.,2015).

3.3. Metalconcentrationinsediment

Heavy metal concentrations of sediments are presented in Table3.ConcentrationsofheavymetalsatsitesS4–S6weremuch higherthanothers sitesbecauseofthefact thatthesesitesare locatedattheseaportareaoftheriverandextensive discharg-ingofuntreatedeffluentsfromtheport.Metalsconcentrationsin sedimentwerehigherinwinter thansummerdue tothelower waterflow duringwinter whichcouldassistancetoaccumulate theheavymetalsinsediment(Islametal.,2015a,c).Theaverage concentrationofheavymetalsinsedimentswereinthe decreas-ingorderof:Cr>Pb>As>Cd.Chromiumconcentrationinsediment washigherthanothermetalsasaconsequenceofdirectdischarging untreatedwastesfrompetroleum,fertilizersandtextileindustries (Facettietal.,1998;Islametal.,2015a).However,highlevelofCr forsiteS5(131.09and160.32mg/kginsummerandwinter, respec-tively)indicatesitshigherinput,whichmightbeoriginatedfrom theurbanandindustrialwastes(Mohiuddinetal.,2012).Themean concentrationofAsinsedimentwasobserved13.57mg/kgin sum-merand19.87mg/kginwinterwhichwashigherthantheaverage shalevalue(ASV)(13mg/kg)(Table4).HighAsconcentrationin sedimentsmightbeattributedtotheanthropogenicactivitiessuch astreatmentfromthefertilizersandarsenicalpesticidesindustries (Fuetal.,2014;Ahmedetal.,2016),treatingofwoodby exhaust-ingcopperarsenate(Pravinetal.,2012;Baeyensetal.,2007)and tanningin relationtosomechemicalsespecially arsenicsulfide (Bhuiyanetal.,2011).

Theaverageconcentration ofCd was1.51mg/kg in summer and 2.50mg/kg inwinter(Table3).Highlevel ofCdwasfound during winter which might be due tothe differences in water capacityoftheriverwherelowwaterﬂowinwinterresultedthe precipitationofCdinsediment;therebyrisingitsconcentration (Islametal.,2015c).AverageconcentrationofPb wasobserved 38.33and49.04mg/kgduringsummerandwinterseason,about 2 times higherthan ASV value (20mg/kg)which could bedue totheeffect frompointand non-pointsources;suchasleaded gasoline,petroleum,municipalrunoffsandatmospheric deposi-tion(Mohiuddinet al.,2012;Shikazonoet al.,2012),chemicals andelectronicsmanufacturing,cables,oils,tireandcementfactory, andsteelworksnearbythestudyriverofChittagongdistrict.Asa whole,concentrationsofmostofthemetalsexceededsomewell documentedstandardvaluesandinagreementwithsomeprevious studiesinBangladeshandothercountries(Table4).

Pearson’scorrelation(PC)matrixforanalyzedsediment param-eterswascalculatedtoseeifsomeoftheparametersinterrelated witheachotherandtheresultsarepresentedinTable5.The ele-mentsinsedimentsdidnotshowanycorrelationwitheachother whereAsandCdshowedsignificantpositivecorrelation suggest-ingsimilarsourcesofinput(humanornatural)forthesetwometals intheriverwater(Bastamietal.,2012).Highcorrelationsbetween specificheavymetalsinwatermayreflectsimilarlevelsof contam-inationand/orreleasefromthesamesourcesofpollution,mutual dependenceandidenticalbehaviorduringtheirtransportinthe riversystem(Lietal.,2009;Chenetal.,2012;Sureshetal.,2012; Jiangetal.,2014).

3.4. Assessmentofmetalpollution

Thecalculated pollutionloadindex (PLI)values ofmetals in sedimentsaresummarizedinFig.2.ThePLIvalueswereranged from1.36to2.07duringsummerand1.83to2.91duringwinter conﬁrmingthatthesedimentofthestudiedriverwas contami-nated(PLI>1).HigherPLIvalueswereobservedinsamplingsites S4,whichmightbeduetotheeffectsofseaportactivities.The PLIcanprovidesomeunderstandingtothepopulationsaboutthe qualityofthesediment.Inaddition,italsodeliversessential infor-mationtothedecisionmakersonthepollutionstatusofthestudy area(Sureshetal.,2012).Thevaluesofcontaminationfactor(CF)for allmetalsshowedmoderatedegreeofcontamination(1≤CF<3), whereas,Cdshowedvery highdegreeofcontamination(CF>6) (Fig.3).Overall,theCFforallmetalswerethedescendingorder of:Cd>Pb>As>Cr.ThemeanCFvaluesofAs,Cd,CrandPbwere

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Table3

Heavymetalconcentrations(mg/kgdw)insedimentofKarnaphuliRiver,Bangladesh(n=3).

Sites As Cr Cd Pb

Summer Winter Summer Winter Summer Winter Summer Winter

S1 13.17 19.67 57.31 78.48 1.1 1.87 35.25 42.56 S2 25.39 31.53 37.23 53.27 1.53 3.21 27.76 31.73 S3 12.57 17.82 81.18 102.57 0.95 2.16 39.13 50.59 S4 13.38 19.67 111.48 135.93 1.4 2.55 61.86 73.42 S5 11.56 15.56 131.09 160.32 0.63 0.91 25.69 35.27 S6 18.39 26.79 65.89 80.53 1.12 1.61 56.03 67.38 S7 22.67 35.48 41.31 66.93 2.45 3.56 21.98 27.69 S8 19.38 26.32 68.11 91.47 1.34 2.91 35.73 48.59 S9 17.86 25.34 67.77 86.34 2.49 3.37 35.89 54.82 S10 13.57 19.87 39.18 65.27 2.11 2.89 43.97 58.39 Average±SD 16.79±4.70 23.81±6.39 70.06±30.93 92.11±33.16 1.51±0.64 2.50±0.85 38.33±12.74 49.04±15.06 Note:SD:standarddeviation.

Table4

Comparisonofmetalsinsediment(mg/kgdw)withdifferentinternationalguidelinesandotherstudiesintheworld.

River,Location Cr As Cd Pb References

KarnaphuliRiver(Bangladesh) 20.3(11.56–35.48) 81.09(37.23–160.32) 2.01(0.63–3.56) 43.69(21.98–73.42) Thisstudy

BangshiRiver(Bangladesh) 98 1.93 0.61 60 Rahmanetal.(2014)

BurigangaRiver(Bangladesh) 178 NA 3.3 70 Ahmadetal.(2010)

PairaRiver,Bangladesh 45 12 0.72 25 Islametal.(2015a)

Korotoa(Bangladesh) 109 25 1.2 58 Islametal.(2015c)

PadmaRiver,Bangladesh 97 NA NA 17 DattaandSubramanian(1998)

Jamuna(Bangladesh) 110 NA NA 19 DattaandSubramanian(1998)

GomtiRiver(India) 8.15 NA 2.42 40.33 Singhetal.(2005)

RiverGanges(India) 1.8–6.4 NA 0.14–1.4 4.3–8.4 Guptaetal.(2009)

YellowRiver(China) 41–128 14–48 NA 26–78 Liuetal.(2009)

OkumeshiRiver(Nigeria) 0.87 NA 1.32 0.45 Raphaeletal.(2011)

ASV 90 13 0.3 20 TurekianandWedepohl(1961)

TRV 26 6 0.6 31 USEPA(1999)

LEL 26 6 0.6 31 Persuadetal.(1993)

SEL 110 33 10 250 Persuadetal.(1993)

Note:ASV,averageshalevalue;TRV,toxicityreferencevalue;LEL,lowesteffectlevel;SEL,severeeffectlevel;NA,notavailable.

Table5

CorrelationbetweentheelementsinwaterandsedimentsofKarnaphuliRiver,Bangladesh.

As Cr Cd Pb Water(n=20) As 1 Cr 0.368 1 Cd 0.269 0.204 1 Pb −0.196 0.192 0.162 1 Sediment(n=20) As 1 Cr −0.324 1 Cd 0.731a ₋_0.280 ₁ Pb −0.079 0.320 0.102 1

a_Correlation_is_signiﬁcant_at_the_0.01_level_(2-tailed).

0

0.5

1

1.5

2

2.5

3

3.5 S1

S2

S3

S4

S5

S6

S7

S8

S9

S10

PL

I

val

u

e

Sampling location

Summ

er

Winter

Polluted Unpolluted

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0 2 4 6 8 10 As Cr Cd Pb CF v a lu e Metals Summer Winter

Very high degree

Considerable degree

Moderate degree Low degree

Fig.3.Contaminationfactor(CF)ofheavymetalsinsedimentofKarnaphuliRiver,Bangladesh.

Fig.4. Geoaccumulationindex(Igeo)ofheavymetalsinsedimentofKarnaphuliRiver,Bangladesh(su=summerseason,wi=winterseason).

1.29,0.78,5.04and1.92duringsummerand1.83,1.02,8.35and 2.45duringwinterseason.Thevaluesofgeoaccumulationindex (Igeo)ofthestudiedheavymetalsarepresentedinFig.4.Among

thestudiedmetals,theIgeo values showedthedecreasingorder

of:Cr>Pb>As>Cd.TheIgeovaluesforthestudiedmetalsindicated

unpollutedtoextremelypolluted.

4. Conclusions

HeavymetalpollutionisamajorproblemfortheKarnaphuli Riverbasin, Bangladesh. In thepresent studyconcentrations of As,Cr,Cdand Pbwerehigher thanthesafevalues which indi-catedthattheriverKarnaphuliispollutedbystudiedheavymetals andmightcreateanadverseeffectonthisriverineecosystem.The overallpollutionloadwasremarkablyhigherinwinterthanin sum-merseason.Thecontaminationfactor(CF),pollution loadindex (PLI) and geoaccumulation index (Igeo) exposed that sediments

wereunpollutedtoextremelypollutedbyheavymetals.Thisstudy suggestedthatpointsourcesofheavymetalsinthewaterand sed-imentsshouldbecloselymonitored;improvementofconditions andindustrialefﬂuentanddomesticsewagedischargeshouldbe reduced.

Conﬂictofinterest

Theauthorsdeclarethattherearenoconflictsofinterest.This studymainlyfocusesontheheavymetalscontentinsurfacewater andsedimentsandecologicalriskassessmentinacoastalriverof Bangladesh.Weextensivelymonitorthepresentpollutionstatusof tracemetalsinthesamples.Ourresearchmainlytheidentification ofenvironmentalproblemsrelatedmetalspollutionandnotreceive anyfinancialsupportsoranyotherrelationshipwithotherpeople ororganizations.

Acknowledgments

TheauthorswouldliketothanktheauthorityoftheFish Inspec-tionandQualityControl(FIQC)Laboratory,Khulna,Bangladeshfor providinglaboratoryfacilitiestocompletethisstudy.Theauthors alsodelightedtoexpresstheirgratefulnessandsincerestthanksto thestuffmembersofFIQCLaboratoryfortheirco-operationduring thesampleanalysis.Theauthorsaregratefulforﬁnancialsupport bytheNationalScienceandTechnologyFellowshipfromthe Min-istryofScienceandTechnology,TheGovernmentPeople’sRepublic ofBangladesh.Furthermore,wearethankfulforthekindhelpfrom themembersofPatuakhaliScienceandTechnologyUniversityand

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ChittagongVeterinaryandAnimalSciencesUniversity,Bangladesh, duringtheﬁeldsampling.

AppendixA. Supplementarydata

Supplementarydataassociatedwiththisarticlecanbefound, intheonlineversion,athttp://dx.doi.org/10.1016/j.enmm.2016.01. 002.

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