Phytoremediationofcadmiumpollutioninsoil

環科1101李康楠11320120

Background

Soilheavymetalpollutionisreferstotheproportionofgreaterthan5metalsortheircompoundsinthesoilenvironmentcausedbypollution.Atpresent,theHgemissionsabout15000tonsperyearonaverage,3.4milliontonsofCu,Pb,5milliontonsofMn15milliontons,tenthousandtonsofNi100.Inourcountrybycadmium,arsenic,chromium,leadandotherheavymetalpollutionofcultivatedlandareaofnearly20millionhm2,about1/5ofthetotalcultivatedlandarea.1.Soilheavymetalpollutionsources

Heavymetalconcentrationsinsoilbythedualeffectsofthenaturalsoilconditionsandhumanactivities.Generally,undertheconditionoflowconcentrationofheavymetalsinnaturalsoil,butinrecentdecades,humanactivitiesgreatlycontributedtotheaccumulationofheavymetalsinsoil.PollutionofthesoilUnreasonableuseofagriculturalinputs

SolidwasteSewageirrigation

圖1土壤中重金屬污染來源Atmosphericnaturalsedimentationandprecipitation

Soilcadmiummainlycomesfromthefollowingaspects::Theharmofcadmium

Cadmiumisakindofgreymetal,insolubleinwater,thedensityof8.64g/cm3,meltingtemperature331.03℃,boilingpointof767℃.Metalcadmiumtoxicitywaslow.Butitschemicaltoxicityisverylarge.Cadmiuminhumanbodysavingseffect,latentlangbutfor10to30years.Itisreportedthatwhencadmiuminwatermorethan0.2mg/L,residentsdrinkingwaterforalongtimeandcontainingcadmiumsubstancesfromfoodintake,canleadto"bonepaindisease".Accumulationofcadmiuminsoil

Cadmiuminsoilaccumulationof0~15cm.InthesoilmainlyCdCO3,Cd(PO4)2andCd(OH)2.GiveprioritytowithCdCO3againamongthem.Duetocadmiumcan'tbeinthesoilmicrobialdegradation,half-lifemorethan20years,asaresult,thepollutionistheaccumulationoftheirreversibleprocess.Themobilityandtransferofcadmiuminthesoil

Heavymetalscadmium,onceintothesoillongstrandedinmagnetism.Becauseitmovesslowly,sodon'tusuallyongroundwaterpollution.Thepresenceofcadmiuminsoilmorphologyaredividedintowater-solubleandwater-insolublecadmium.Ioncdcl2,CD(no3)2,cdco3andcomplexingstatesuchasCD(oh)2iswatersoluble,migration,anddon'tplantabsorption,anddifficulttosolublecadmiumcompoundssuchascadmiumcadmiumsediment,colloidabsorption,noteasymigrationandforplantabsorption.Butincertainconditionscanbemutualconversion.3.3.1植物修復技術(phytoremediation)

Patienceandsuperaccumulationinplantsbasedonthetheoryofsomeorcertainpollutants,usenaturalgrowthorgeneticengineeringbreedingofplants,andremovalofenvironmentalpollutantsinenvironmentalpollutioncontroltechnology.Includingplantextracts,plantvolatileandplantstablethreeways.植物提取(phytoextraction)

Theuseofplantsasaccumulationofheavymetals(hyperaccumulatorsabsorbmetalcontaminantsfromthesoil,thenharvestabovegroundandforcentralizedprocessing,growtheplantsinarow,toachievethepurposeofreducingorremovingthesoilheavymetalpollution.植物揮發(phytovolatilization)

Itsmechanismistheuseofplantrootsystemtoabsorbmetal,turningitintogaseoussubstancesvolatileintotheatmosphere,inordertoreducesoilpollution.ThepresentstudymoreisaSeandHg.植物穩定(phytostabilization)

Useafewplantstopromotetheprocessoftransitiontolowtoxicityofheavymetalsform.Inthisprocess,theheavymetalcontentofthesoilisnotreduced,justchangeform.圖1重金屬zn/cd超積累植物十字花科的天藍遏藍菜（thlaspicaerulescens）。圖2銅草（海洲香薷）4.PhytoremediationofsoilheavymetalpollutionresearchprospectsPhytoremediationhasirreplaceableadvantageinheavymetalpollutioncontrol,andinthegovernanceprocessofinsitu,governancecostslow,managementandoperationsimplicityandcompatibilityofenvironmentalaestheticsandincreasinglybroughttotheattentionofthepeople,andbecomeoneofhottopicsinthestudyofsoilbioremediation.Therefore,hasabroadapplicationprospect.Thefollowingaspectswillbethefocusofresearchinthisfield.4.1Superaccumulationplantselectionandcultivation

Superaccumulationplantisunderheavymetalstress,anadaptationofthemutanttendtogrowslowly,lowbiomass,climateadaptabilityisbad,haveverystrongenrichmentofspecificity.Therefore,screeningandbreedingofabsorptivecapacityisstrong,alsocanabsorbavarietyofheavymetalelements,andthebioremediationofbiomassofplantsisanimportanttask.Forgeneralrequirementsofaparticularheavymetalaccumulationplantstheabove-groundpartoftheheavymetalcontentisgreaterthanacriticalvalue(table1).元素CdNiPbCuZnMn臨界值1001000100010001000010000表1超積累植物重金屬含量臨界值

mg/kg-1

4.2Transgenicplants

Hasfoundthatmostoftheplantsasresourcesareinasmallrootshallow,biomassandthedisadvantageofslowgrowth,makeitsrepaircycleislong.Thismakestheengineeringapplicationofphytoremediationisrestricted,andthegeneticallymodifiedplantscanimproveitsapplicability.4.3Othermeasuresforstrengthening

Addingachelatingagent(suchasEDTA),cansignificantlyimprovetheactivityofmetalsinthesoilandpla