FOCUSEDREVIEWDistributionofHeavyMetalPollutioninSurfaceSoilSamplesinChina:AGraphicalReview

QiannanDuan1•JianchaoLee1•YansongLiu1•HanChen1•HuanyuHu1

Received:16February2016/Accepted:14June2016ÓSpringerScience+BusinessMediaNewYork2016

AbstractSoilpollutioninChinaisoneofmostwideandsevereintheworld.AlthoughenvironmentalresearchersarewellawareoftheacutenessofsoilpollutioninChina,apreciseandcomprehensivemappingsystemofsoilpollu-tionhasneverbeenreleased.Bycompiling,integratingandprocessingnearlyadecadeofsoilpollutiondata,wehavecreatedcornerstonemapsthatillustratethedistributionandconcentrationofcadmium,lead,zinc,arsenic,copperandchromiuminsurficialsoilacrossthenation.Thesesum-marizedmapsandtheintegrateddataprovideprecisegeographiccoordinatesandheavymetalconcentrations;theyarealsothefirstonestoprovidesuchthoroughandcomprehensivedetailsaboutheavymetalsoilpollutioninChina.Inthisstudy,wefocusonsomeofthemostpollutedareastoillustratetheseverityofthispressingenviron-mentalproblemanddemonstratethatmostdevelopedandpopulousareashavebeensubjectedtoheavymetalpollution.

KeywordsHeavymetalÁDistributionÁSoilÁCadmiumÁChina

Today,soilpollutioninChinaisoneofthemostwideandseriousintheworld,andwilldirectChina’senvironmentalmanagementinnextseveraldecades(Bietal.2013;ChenandYe2014;Lietal.2014b;Tengetal.2014).TheChina

SoilPollutionSurveypublishedin2014indicatedthat16.1%ofarablelandispollutedandinorganicpollutants,particularlycadmium(Cd)isfoundinhighquantitiesin7%(MEP2014)ofsurveyedsites.Moreover,arsenic(As),copper(Cu),lead(Pb),chromium(Cr)andzinc(Zn)arealsofoundinthesoil,althoughinfewerareasandquan-titiesthancadmium.Itiswellknownthatthesoilinmanylargeandpopulouscities(includingGuangzhou,Shanghai,HongKong,Changsha,Hangzhou,Nanjing,Xuzhou,Qingdao,XiangtanandZhuzhou)hasbeensubjectedtoheavymetalpollution(Lietal.2014a;Tengetal.2014).Atpresent,heavymetalcontaminationposesincreasinglyserioushealthriskstolocalresidentsinmanyregionsofChina(Lietal.2014b)andalthoughtheseverityandharmofsoilpollutionhasreachedcriticallevelsacrosstheChinesemainland,thedistributionofnumerouspollutionpatchesremainsunknown.Ithastaken8yearsandonebillionChineseYuan(about161millionUSdollars)tocarryoutChina’sNationalSoilPollutionSurvey(Ma2006).Tocompletethesurvey,researchersadoptedasamplingmethodof898kmuni-formgrid,andacquiredtensofthousandsofsoilpollutantdataacrossthenation.Whilethisisalaudableandnec-essaryeffort,therearesomemethodologicalweaknesseswiththistechnique.Forexample,onesoilsampleper64km2unitmayprovidesufficientinformationinunpol-

lutedareas,therebyitishardtoavoidsamplingrisksofconcealingthepollutionandthecomplexityofheavymetaldistributioninmorepollutedareas(MEP2014).Besides,thesurveyworkinggroupshasnotattemptedtopresentsoilpollutiondistributionmapstodate.Toremedytheseweaknesses,wedrawonjournalarti-clesanddissertationsconductedbythousandsofresearchersworkingonsoilpollutioninChinaoverthelast10years.Ourworkconsistedinassemblingandmapping

ElectronicsupplementarymaterialTheonlineversionofthisarticle(doi:10.1007/s00128-016-1857-9)containssupplementarymaterial,whichisavailabletoauthorizedusers.

&JianchaoLeejianchaolee@snnu.edu.cn

1DepartmentofEnvironmentalScience,ShaanxiNormal

University,Xi’an710062,China

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BullEnvironContamToxicolDOI10.1007/s00128-016-1857-9thedatathusmakingessentialinformationavailable.Becausemostauthorspaymoreattentiontoheavilypol-lutedregions,thedataacquiredthroughthismethodwillprovidesomemoredetailedandobjectivepicturesofthepollutedareas.Inthisstudy,viacompilationandvisuali-sationofdata,someheavymetalsoilpollutionmapswereconstructedandaseriesofconclusionsaboutthedistri-butionofheavymetalpollutionacrossthecountrywereobtained.

MaterialsandMethodsWecollected12,970papersfocusingonChina’ssoilpol-lution,publishedwithinthecountryandabroad.Wenar-rowedouranalysisto2450papersthatfocusonsixheavymetals(As,Cu,Pb,Cr,ZnandCd)insurfacesoil.Somestudieswereexcludedforlackofsamplingmethodsorgeographiccoordinates,andeventually,850referenceswereincluded(Fig.S7).Accordingtothepresentformofsampledatainpapers,threemeansofdataseparationwasadopted.Insomepapers,directextraction,metalconcentrationsandgeographicalcoordinatesofsamplingsitescouldbeacquireddirectly,wasused.Meetingthosedocumentsonlyprovidedpollutionindexandcorrespondingformulas,webroughtbackcalculationtoobtainconcentrations.Besides,therealsoweresomepapersmerelydisplayedthepollutantdistribution,adigitalinversionofmapswasusedviaOrigin8.0(OriginLab,Northampton,Massachusetts,USA).Inaddition,WGS-84(WorldGeodeticSystem-1984Coordi-nateSystem),whichwasadoptedformostChineseresearchers,wasusedastheuniformgeographiccoordinatesystemintheprocessofdataextraction.Eventually,thenumberofobtainedsamplesitesofAs,Cu,Pb,Cr,ZnandCdare1340,1997,2489,1774,1789and2253,respectively.Andtheirprecisegeographiccoordinatesandheavymetalconcentrations(TableS1)wereextracted.Inconventionalenvironmentalandgeographicalinves-tigations,methodssuchasgridsamplingandspatialinter-polationprovidethespatialdistributionofsoilelements.However,duetotheiraggregatingcharacteristics,heavymetalpollutionsometimesfluctuatesinsoilonascaleofhundredsofmeters(Linetal.2010;Xieetal.2011).Mostheavymetalpollutionpresentsapatchydistributionoveralargeterritory.Therefore,inanareaasvastasChina,bringingoutahigh-precisioncontourmaprequiresenor-moussamplingunits.BasedontheGradeIIenvironmentalqualitystandardsforsoilsinChina(MEP2008),thoseoftheUSEnvironmentalProtectionAgency(USEPA1996,2002)andsomevaluesadoptedbypollutionexperts(Bhuiyanetal.2010;Maasetal.2010;Malandrinoetal.2011),weusethefollowingconcentrationlimitsforourchosensixmetals:cadmium(1mg/kg),lead(80mg/kg),