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CharacterizationandAnalysisof Microplastics

AdvisoryBoard

JosephA.Caruso

UniversityofCincinnati,Cincinnati,OH,USA

HendrikEmons

JointResearchCentre,Geel,Belgium

GaryHieftje

IndianaUniversity,Bloomington,IN,USA

KiyokatsuJinno

ToyohashiUniversityofTechnology,Toyohashi,Japan

UweKarst

UniversityofMu¨nster,Mu¨nster,Germany

Gyro¨gyMarko-Varga

AstraZeneca,Lund,Sweden

JanuszPawliszyn UniversityofWaterloo,Waterloo,Ont.,Canada

SusanRichardson

USEnvironmentalProtectionAgency,Athens,GA,USA

Characterizationand AnalysisofMicroplastics

Editedby

TeresaA.P.Rocha-Santos

UniversityofAveiro,CESAM,Aveiro,Portugal

ArmandoC.Duarte

UniversityofAveiro,CESAM,Aveiro,Portugal

Elsevier

Radarweg29,POBox211,1000AEAmsterdam,Netherlands TheBoulevard,LangfordLane,Kidlington,OxfordOX51GB,UnitedKingdom 50HampshireStreet,5thFloor,Cambridge,MA02139,UnitedStates

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Thisbookandtheindividualcontributionscontainedinitareprotectedunder copyrightbythePublisher(otherthanasmaybenotedherein).

Notices

Knowledgeandbestpracticeinthisﬁeldareconstantlychanging.Asnewresearch andexperiencebroadenourunderstanding,changesinresearchmethods,professional practices,ormedicaltreatmentmaybecomenecessary.

Practitionersandresearchersmustalwaysrelyontheirownexperienceandknowledge inevaluatingandusinganyinformation,methods,compounds,orexperiments describedherein.Inusingsuchinformationormethodstheyshouldbemindfuloftheir ownsafetyandthesafetyofothers,includingpartiesforwhomtheyhaveaprofessional responsibility.

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ISBN:978-0-444-63898-4

ISSN:0166-526X

ForinformationonallElsevierpublications visitourwebsiteat https://www.elsevier.com

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ProductionProjectManager: VigneshTamil

Designer: MilesHitchen

TypesetbyTNQBooksandJournals

JoaoPintodaCosta,ArmandoC.Duarte,TeresaA.P.Rocha-Santos

Andre´sRodrı´guez-Seijo,RuthPereira

GerritRenner,TorstenC.Schmidt,JurgenSchram 1.IntroductiontoInfraredSpectroscopyofMicroplastics

PauloRibeiro-Claro,MarielaM.Nolasco,CatarinaArau´jo

2.1PrinciplesofRamanSpectroscopy120 2.2SpectrometersinaNutshell124

2.3CoherentAnti-StokesRamanScattering127

3.AdvantagesandLimitationsofRamanSpectroscopy

6. ApplicationofScanningElectronMicroscopy Energy DispersiveX-RaySpectroscopy(SEM-EDS)

AnaVioletaGirao,GianvitoCaputo,MartaC.Ferro

7. ApplicationofPyrolysis-GasChromatography/Mass Spectrometry(Py-GC/MS)

PeterKusch

1.Introduction

2.Pyrolysis-GasChromatography/MassSpectrometrytothe AnalysisofMicroplastics

2.1InstrumentationandMethod172

2.2CharacterizationofPolyethylene,Polypropylene, Poly(ethylene-co-propylene)andPoly (ethylene-co-vinylacetate)174

2.3CharacterizationofPolystyreneandPoly (acrylonitrile-co-1,3-butadiene-co-styrene)182

2.4CharacterizationofRubbers Poly(styrene-co-1, 3-butadiene)andPoly(acrylonitrile-co-1,3-butadiene)187

2.5CharacterizationofPolyamides190

2.6CharacterizationofPhenolicResin192

2.7CharacterizationofPolyurethanes193

2.8CharacterizationofPoly(ethyleneterephthalate)194

2.9CharacterizationofPoly(vinylchloride)197

2.10CharacterizationofSiliconeRubber200

3.Conclusion 206

8. AdvancedAnalyticalTechniquesforAssessingthe ChemicalCompoundsRelatedtoMicroplastics

LorenaM.RiosMendoza,SatieTaniguchi,HrissiK.Karapanagioti 1.Introduction

2.5BrominatedFlameRetardants213

3.EnvironmentalOrganicContaminantsSorbed

4.ExtractionofOrganicCompoundsFromMicroplastics

4.4AcceleratedSolventExtraction226

4.5ComparisonoftheDifferentExtractionMethods226

5.CleanUp PuriﬁcationandSeparationoftheCompounds

9. TheRoleofLaboratoryExperimentsinthe

CatherineMouneyrac,FabienneLagarde,Ame´lieChaˆtel, FarhanR.Khan,KristianSyberg,AnnemettePalmqvist

1.Introduction

2.MicroplasticsUsedinLaboratoryExperiments

2.1RepresentativenessofMicroplacticUsedinLaboratory ExperimentsforMicroplasticsFoundintheEnvironment243 2.2ValidatingtheMicroplastic‘VectorEffect’248

3.TypicalExperimentalDesignsforTestingEffects ofMicroplastics

4.ToxicologicalImpactsofMicroplasticExposures

Thispageintentionallyleftblank

ContributorstoVolume75

CatarinaArau ´ jo,CICECO,UniversityofAveiro,Aveiro,Portugal

GianvitoCaputo,IstitutoItalianoDiTecnologia,Genova,Italy

Ame´lieChaˆtel,Universite ´ Catholiquedel’Ouest,Angers,France

MonicaF.Costa,UniversidadeFederaldePernambuco,Recife,Brazil

Joa˜oPintodaCosta,UniversityofAveiro,CESAM,Aveiro,Portugal

ArmandoC.Duarte,UniversityofAveiro,CESAM,Aveiro,Portugal

MartaC.Ferro,CICECOandDepartmentofMaterialsandCeramicEngineering, UniversityofAveiro,CampusdeSantiago,Aveiro,Portugal

AnaVioletaGira ˜ o,CICECOandDepartmentofMaterialsandCeramicEngineering, UniversityofAveiro,CampusdeSantiago,Aveiro,Portugal

HrissiK.Karapanagioti,UniversityofPatras,Patras,Greece

FarhanR.Khan,RoskildeUniversity,Roskilde,Denmark

PeterKusch,Bonn-Rhein-SiegUniversityofAppliedSciences,Rheinbach,Germany

FabienneLagarde,Universite ´ duMaine,LeMans,France

CatherineMouneyrac,Universite ´ Catholiquedel’Ouest,Angers,France

MarielaM.Nolasco,CICECO,UniversityofAveiro,Aveiro,Portugal

AnnemettePalmqvist,RoskildeUniversity,Roskilde,Denmark

RuthPereira,InterdisciplinaryCentreofMarineandEnvironmentalResearch (CIIMAR/CIMAR),Porto,Portugal;FacultyofSciencesoftheUniversityofPorto, Porto,Portugal;GreenUP/CITAB-UP,Porto,Portugal

GerritRenner,NiederrheinUniversityofAppliedSciences,Krefeld,Germany; UniversityofDuisburg-Essen,Essen,Germany

PauloRibeiro-Claro,CICECO,UniversityofAveiro,Aveiro,Portugal

LorenaM.RiosMendoza,UniversityofWisconsin-Superior,Superior,WI, UnitedStates

TeresaA.P.Rocha-Santos,UniversityofAveiro,CESAM,Aveiro,Portugal

Andre´sRodrı´guez-Seijo,UniversidadedeVigo,Vigo,Spain

TorstenC.Schmidt,UniversityofDuisburg-Essen,Essen,Germany

JurgenSchram,NiederrheinUniversityofAppliedSciences,Krefeld,Germany

KristianSyberg,RoskildeUniversity,Roskilde,Denmark

SatieTaniguchi,UniversityofSa˜oPaulo,Sa˜oPaulo,Brazil xii ContributorstoVolume75

SeriesEditor’sPreface

IamdelightedtointroducethisnewCACtitleeditedbyTeresaA.P.RochaSantosandArmandoC.DuarteonCharacterizationandAnalysisof Microplastics.ThisbookisanexcellentadditiontotheCACseries,anditis ourﬁrstbookinthisseriesonthechallengingandwell-knownenvironmental problemofmicroplastics.

Plasticpollutionhasbeengivenconsiderableattentionsincetheendof 1980s,almost30yearsago.Becauseofitsnature,plasticcanbeeasily dispersedbywindbeingtransportedandfragmentedtolongdistances.Mostof usareawarethatplasticdebrisisoneofthemostubiquitousproblemsofour planet.Butitwasonly5 6yearsagothattheissueofmicro-andnanoplastics wasontheresearchagenda.Microplasticresiduesareaffectingtheaquatic organismsatdifferenttrophiclevelsbeingariskfortheaquaticlife.

Thevolumethatyouhavenowinyourhandscoversthemainpillarsof microplasticcharacterizationandanalysisinninechapters.First,an introductorychapteronoccurrence,fateandbehaviourintheenvironment describesanoverviewoftoday’sproblem.Nextchaptersaremorespecificon samplepreparation,morphologicalandphysicalcharacterization,andanalysis bydifferentspectroscopic,microscopicandgaschromatography/mass spectrometrictechniques.Thefinalchapterreportstheroleofcontrolled laboratoryexperimentsthatarealwaysneededtovalidatefielddatain environmentalstudies.

Thisbookoffersacomprehensiveviewofthecharacterizationand analyticalmethodologiesformicroplastics.Itisausefultoolfornewcomers andpractitionerswhowanttobeintroducedinthisnewresearchﬁeld.Senior marinechemistsandbiologists,environmentalchemists,ecologistsand hydrologistsstudyingfreshwatersystemswillenjoyreadingittoo.Recent literatureindicateswastewatertreatmentplantsassourceofmicroplasticsin theaquaticenvironment.

Thisbookwillcertainlycontributetoabetterunderstandingof microplasticpollutionproblemsatglobalscale.Inthisrespect,microplastic pollutionbringstheissuetothepublic’sattention,astheimpactsonaquatic lifecancreatemediainterestandpressureforgovernmentresponse.Certainly inthisparticularcase,pollutionpreventionmeasuresareneededandthe extremelyhighusageofplasticbagsinourdailylifeshouldbeavoidedassoon aspossible.

FinallyIwouldliketothankspeciallyTeresaandArmandofortheamount ofwork,timeandexpertisedevotedaseditorsofthisbook.Iwouldliketo acknowledgeaswelltothevariouswell-knownauthorsfortheircontributions incompilingsuchaworld-classandtimelybookfortheCACseries.

´ , IDAEA-CSIC,BarcelonaandICRA,Girona,December9,2016, EditorinChiefoftheComprehensiveAnalyticalChemistrySeries.

D.Barcelo

Preface

Microplasticsareplasticparticleswithlessthan5mminsizeandphysicochemicalproperties(e.g.,overallsize,density,colour,andchemicalcomposition)thatarekeycontributorstotheenhancementoftheirbioavailabilityto organisms.Mainlyduetotheirsmallsize,microplasticshavethepotentialof beingingestedbybenthicandplanktonicorganisms,thusenteringmarinefood webswithaverylowpotentialofbiodegradation.Therefore,adetailed qualitativeandquantitativemonitoringofmicroplasticsinthemarineenvironmentishighlyrequired,andinfactitisalreadyrecommendedwithinthe frameworkoftheMarineStrategyFrameworkDirective(MSFD).Duetothe methodologycurrentlyused,thescarcedataonmicroplasticsconcentrations aremostlybiasedtowardslargerparticles.Furthermore,differencesobserved indifferentstudiesintermsofconcentrationandcompositionbypredominant typesofmicroplasticscouldalsobeduetosignificantmethodologicaldifferences.Comparisonofthequantitativeresultsobtainedbypublishedworks wouldbeveryinterestingandofutmostimportance,butstillisaveryhardor evenimpossibletasktoperform.Therefore,reliabledataonconcentrationsof microplasticsinmarinesystemsandotherenvironmentalcompartmentsare stilllacking,whichmakesthisbookaverytimelyandusefulinstrumentfor dealingwithsuchahottopic.Thiscomprehensiveoverviewanddiscussion aimsmainlyatfulfillingthegapontheknowledgeabouttheanalyticaltechniquesandanalyticalmethodologiesformicroplasticsidentificationand quantificationbasedonpublishedworks.Thisoverviewincludestheassessmentofsamplingtechniquesandsamplehandling,morphological,physical andchemicalcharacterizationofmicroplastics,andtheroleoflaboratory experimentsinthevalidationoffielddata.Chapter1producesthestateofthe artontheoccurrence,fateandbehaviourofmicroplasticsintheenvironment, andithighlightstheneedforanalyticalmethodologiesfitforpurpose.Chapter 2introducesanddiscussesdifferentsamplingstrategiestobetakenintoaccountforensuringtheappropriatecollectionofmicroplasticsfromseveral environmentalcompartments.InChapter3themethodologiesusedforcharacterizationofthemorphologicalcharacteristicsofmicroplastics,suchas shapeand/orthecolour,andthephysicalcharacteristicsofmicroplastics,such assize,arediscussedandputintoperspective.Chapters4and5providean overviewanddiscusstheanalyticalmethodologiesassociatedwithinfrared spectroscopyandRamanspectroscopyforcharacterizationofmicroplastics.

Chapter6showstheapplicationofscanningelectronmicroscopy energydispersiveX-rayspectroscopyontheidentificationandcharacterizationof microplasticsandalsoonthecharacterizationofinorganicadditivesin microplasticsfragments.Chapter7introducestheuseofpyrolysisgaschromatography/massspectrometryforanalysisandidentificationofdegradation productsofcommerciallyavailablesyntheticpolymers/copolymersandtheir additives,andsubsequentapplicationonmicroplasticscharacterization. Chapter8isfocusedontheuseofadvancedanalyticaltechniquessuchasgas chromatographyhigh-resolutionmassspectrometryandliquidchromatographytandemmassspectrometryforassessingthecontaminantsrelatedto microplastics.Finally,Chapter9discussestheroleoflaboratoryexperiments inthevalidationoffielddata.

ThevolumeeditorswouldliketothanktheComprehensiveAnalytical Chemistry(CAC)serieseditor,Prof.Damia ´ Barcelo´,forgivingustheopportunityofcoordinatingsuchaninterestingthematicworkon‘CharacterizationandAnalysisofMicroplastics’.AllthehelpandadvicefromPoppy Garraway,theassociateacquisitionseditor,andShellieBryant,theeditorial projectmanager,arealsogratefullyacknowledged.Thanksarealsoduetothe authorswhohelpedustoassembleaclosesetofchaptersintoabooktargeting abroadspectrumofreadersrangingfromtheresearchersintheﬁeldtothe undergraduateandgraduatestudentsinterestedinanoverviewandaprimary sourceofinformationforpursuingfurtherstudies.

TeresaA.P.Rocha-Santos ArmandoC.Duarte

Chapter1

Microplastics e Occurrence, FateandBehaviourinthe Environment

Joa ˜ oPintodaCosta,* ArmandoC.DuarteandTeresaA.P.Rocha-Santos UniversityofAveiro,CESAM,Aveiro,Portugal

*Correspondingauthor:E-mails:jpintocosta@ua.ptandjoao.pinto.da.costa@gmail.com

ChapterOutline

1.Introduction1

1.1SourcesofMicroplasticsin theEnvironment4

1.2PrimaryMicroplastics5

1.3SecondaryMicroplastics5

2.FateofMicroplasticsinthe Environment6

2.1SpatialandTemporal Distribution6

2.2Degradation8

2.2.1Abiotic Degradation9

2.2.2Biodegradation10

2.3The‘MissingLink’in PlasticMassBalance11

1.INTRODUCTION

3.BehaviourandEffectsof Microplastics12

3.1PhysicalEffects12

3.2ChemicalEffects13

4.MethodologiesUsedforthe Identiﬁcationand Characterizationof Microplastics16

5.KeyChallengesand RoadMapforFurther Research19 Acknowledgements20 References20

Plasticsarematerialsmadeofawidenumberofsemisyntheticorsynthetic organiccompoundsthatcanbemouldedintoshapewhilesoft,andthenset intoaformveryrigidorslightlyelastic.TheInternationalUnionofPureand AppliedChemistry(IUPAC)deﬁnesplasticsasagenerictermusedinthecase of‘polymericmaterialthatmaycontainothersubstancestoimproveperformanceand/orreducecosts’ [1]

ComprehensiveAnalyticalChemistry,Vol.75. http://dx.doi.org/10.1016/bs.coac.2016.10.004

Themainfeatureofthesematerialsisreflectedintheiretymology:the wordplasticoriginatesfromtheGreekwords plastikos (plassiko ´ 2),meaning ‘capableofbeingshaped’,and plastos (plasso ´ 2),meaning‘molded’ [2]. Otherfeaturesincludeeaseofmanufacture,lowcost,imperviousnesstowater andchemical,temperature,andlightresistance [3].Thesecharacteristicshave ledplasticstoreplaceanddisplacemanymaterials,includingwood,paper, stone,leather,metal,glassandceramicand,currently,plasticsarepresentin ahugeandexpandingrangeofproducts,frompaperclipstospaceships [4] Thissuccesshasmanifesteditselfundermanyforms,includingthermoplastics,naturalandmodifiedpolymers,and,morerecently,duetoincreasing environmentalconcerns,biodegradableplastics [5].Themostcommonlyused typesofplastic,includingtheirspecificgravityandapplications,arehighlightedin Table1.Hence,consideringthisversatility,itisnotsurprisingthat thelastdetailedreportontheannualglobalproductionofplastics,for2015, showedittoexceed310milliontonnes [6]

Whilethebeneﬁtsofplasticsareundeniable,thiswidespreaduseofplastics, namelyindiscardableform,suchaspackagingmaterials,ultimatelyleadsto theiraccumulationintheenvironmentanditisestimatedthatplasticwaste constitutesapproximately10%ofthetotalmunicipalwasteworldwide [7]

Althoughafractionofthisplasticwasteisrecycled,mostofitendsupin landfills,wheretheymaytakeafewhundredyearstodecompose [9]. However,ofspecialconcernareplasticsthatenterthemarineenvironment, whichhavebeencalculatedtobe ca.10%ofthetotalplasticsproduced [10]. Theselargerplasticdebris,knownas ‘macroplastics’,havelongbeenthe focusofenvironmentalresearch,includinginspecificareasoftheocean, wheretheytendtoaccumulate,duetotheconvergenceofsurfacecurrents, theytendtoaccumulate [11],asisthecaseoftheGreatPacificGarbage Patch,illustratedin Fig.1

Thisfloatingdebrisiscontinuouslymixedbytheconcertedactionsofwind andwavesandbecomeswidelydispersedoverhugesurfaceareasandacross thetopportionofthewatercolumn [13].Besidestheobviousaesthetic consequences,whichmayhaveeconomicrepercussionsintourism,the environmentalimpactsoftheseparticlesincludeentanglement,ingestion, smothering,hangers-on,hitch-hikingandalieninvasion,asthesefloating debriscanconstitutenewroutesforinvasivespecies [3].Interestingly,ithas alsobeenreportedthatthespeciesfoundassociatedwiththeseplasticdebris, knownasthePlastisphere,cansometimesdiffergreatlyfromthefree-floating microbialcommunitiescommonlyfoundintheoceans [14].Nonetheless, thereareotherperhapslessfrequentlyrecognizedenvironmentalriskscaused byplasticdebris,includingriskstoshipping,fisheriesandothermaritime activities,suchasenergyproductionandaquaculture [15].Thesearehardly thesoledangersposedbyplasticlitteratseaand,inspiteofthelimitedstudies detailingitssocioeconomicimpacts,themainsectorsaffectedhavebeen identified,asdepictedin Fig.2.Theseconsequencesarenotconfinedto

TABLE1 TypesofPlasticCommonlyUsed,MainApplicationsandSpeciﬁcGravity [8]

TypeApplication

High-densitypolyethylene(HDPE)Milkcontainers,detergentbottles,tubing

Polystyrene(PS)Packagingfoam,disposablecups,foodcontainers,CDs,buildingmaterials1.05

Highimpactpolystyrene(HIPS)Electronics,cupsinvendingmachines,refrigeratorliners1.08

Polypropylene(PP)Packaging,bottlecaps,ropes,carpets,laboratoryequipment,drinkingstraws0.83

FIGURE1 TheGreatPacificGarbagePatch,alsocommonlyreferredtoasthePacifictrash vortex,isagyreofmarinedebrisparticles,mostlyplastic,inthecentralNorthPacificOcean. Discoveredaround1985,itislocatedroughlybetween135 Wto155 Wand35 Nto42 N [12] a Imagecredits:NOAA,GreatPacificGarbagePatch.MarineDebrisProgram,August19,2016. Availablefrom: https://marinedebris.noaa.gov/movement/great-pacific-garbage-patch

nationalboundaries,andthemultiscalarandtemporalmechanismsinvolvedin thefateandbehaviourofplasticsintheenvironmenthighlighttherelevanceof thisproblem.

1.1SourcesofMicroplasticsintheEnvironment

Microplastics,plasticparticlesassociatedwiththemillimetresizerange,have becomeofincreasingconcernduetotheirthreattoenvironmentalquality preservationandrelatedissues.Theseplasticparticlesareminutefragments, usuallywithasize <5mm [7,16],althoughotherstudieshaveconsidered microplasticsasparticlesthatfallwithinothersizeranges,including <1mm [17], <2mm [18],2 6mm [19] and <10mm [20].Microplasticsarealso colloquiallyreferredtoas‘mermaidtears’ [21],perhapsduetotheirsizeand thevastarrayofcoloursoftheseparticles.

AccordingtoColeetal. [9],microplasticscanbeclassiﬁedasprimaryand secondarymicroplasticsdependingontheiractualsource.

a.Inspiteofitssize,theGreatGarbagePatchisnotvisiblewhenresortingtosatelliteimagery. Thisisbecause,thoughcollectivelyverylarge,thepatchiscomposedofrelativelysmallparticles,sometimeslocatedjustbelowthesurface,and,therefore,notvisible.

FIGURE2 Thesocioeconomicimpactsoflitteratsea. AdaptedfromJ.P.daCosta,P.S.M. Santos,A.C.Duarte,T.Rocha-Santos,(Nano)plasticsintheenvironment sources,fatesand effects,Sci.TotalEnviron.566 567(2016)15 26.

1.2PrimaryMicroplastics

Primarymicroplasticsaremanufacturedtohaveamillimetricor submillimetricsize,andtheycanbefoundinhouseholditems,air-blasting media,personalhygieneproducts,suchasfacialcleansers,toothpasteand exfoliatingcreamsand,toasmallerextent,inmedicine,namely,asdrug vectors [3].Forexample,ithasbeenestimatedthatapproximately6%ofthe liquidskin-cleaningproductssoldintheEuropeanUnion,Switzerlandand Norwaycontainmicroplastics,ofwhichover93%consistofpolyethylene (PE) [22].Afteruse,microplasticspresentinsuchproductsarefrequently disposedofandcanreachtheenvironmentthroughwastewatercollectionand treatmentsystems.Thecurrentlywidespreaduseof3Dprintersalsoconstitutesasourceofthesepolymericmaterials,as3Dprintinghasbeenshownto releaseparticlesassmallas11.5nm [23].Anotherkeysourceofprimary microplasticsistherawmaterialsusedinthefabricationofplasticproducts. Accidentalloss,inadequatehandling,run-offfromprocessingfacilities,and residuesfromthemanufacturingofplasticmaterialscanalsoaccumulatein theenvironment [24,25].

1.3SecondaryMicroplastics

Secondarymicroplasticsresultfromthebreakdownoflargerplasticparticles. Whenexposedtotheelements,thephysical,biologicalandchemical

6 CharacterizationandAnalysisofMicroplastics

processestowhichthesepolymericparticlesaresubjecttocanculminatein thereductionofthestructuralintegrityofplasticdebris,leadingtotheir fragmentation.Thisfragmentation,however,canalsooccurbeforetheplastics entertheenvironment,asisthecaseofsyntheticﬁbresreleasedduringthe washingofclothes [3].

Themainsourcesofbothprimaryandsecondarymicroplasticsare summarizedin Table2,underliningthewiderangeofsourcesofthese materialsandhoweasilytheycanentertheenvironment.

2.FATEOFMICROPLASTICSINTHEENVIRONMENT

2.1SpatialandTemporalDistribution

Determiningthefateofmicroplasticsintheenvironmentisinherentlydifﬁcult, mainlyduetotheirsmallsize.Moreover,thevastarrayofwaysthroughwhich TABLE2 MainSourcesofPrimaryandSecondaryMicroplastics

PrimaryMicroplastics

Personalcareproducts,suchasexfoliants

Speciﬁcmedicalproducts,includingdentaltoothpolish

Industrialabrasives

Drillingﬂuids

Rawmaterialsforplasticproduction;processsubproducts

Improperhandling

Secondary Microplastics

Generallittering,dumpingofplasticwaste

Abrasioninlandﬁllsitesandrecyclingfacilities

Carelesslyhandledplasticﬁshinggear

Ship-generatedlitterordisposedoffafterrecreational activities

Plasticmaterialpresentinorganicwaste

Paintscontainingsyntheticpolymers/abrasionduringpaint removal

Polymersusedincompostingadditives

Fibresreleasedfromhygieneproducts

Fibresreleasedfromsynthetictextiles

AsreviewedbyK.Duis,A.Coors,Microplasticsintheaquaticandterrestrialenvironment:sources (withaspeciﬁcfocusonpersonalcareproducts),fateandeffects,Environ.Sci.Eur.28(1)(2016) 1 25.

thesematerialsentertheenvironment,aswellasthetimescalesnecessaryto ascertaintheirdegradation,maketheiraccuratequantificationratherdifficult [9].Theseconstraintsarefurtherexacerbatedbythelackofstandardized methodsinsampling,unitnormalizationanddataexpression,aswellasa unifieddefinitionandcharacterizationofmicroplastics [27].

Asanartificialproduct,plasticsourcesaremostlyinland.Nonetheless,due totheirdischargeindomesticandindustrialwastewaters,transportbywind andsurfacerun-off,upto80%ofthesematerialsendupintheoceans [3] Althoughcurrentwastewatertreatmentmechanicalprocesseshaveshown considerableefficiencyintheremovalofmicroplastics [28],thisgreatly dependsnotonlyonthetypesoftreatmentsusedinwastewatertreatment plants,butalsoonthenatureofthematerialspresentandtheirload [29].Itis generallyassumedthat,duetothelowdensityofthemajorityofplastic materials,asignificantproportionoftheseendupintheoceans [30].However, thismaynotnecessarilybetrue,as,owingtophenomenasuchasheteroaggregationwithotherdetritusandsuspendedsolids [31],thesematerialsmay besubjecttosettlinginriverbeds,anassumptionthathasbeensubstantiatedby recentfindingsdetailingsuchphenomena [32,33].Drivenbywindsandocean currents,plasticdebriscanbetransportedacrossvastdistancesandthese materialscanbefoundthroughouttheoceans,includingtheNorthandSouth Poles,remoteislandsandthedeepocean [34,35].Consequently,plasticlitteris hencecapableofpermeatingmarineecosystemsworldwide [9].Circulation modelssuggestthatallfivesubtropicalgyres,depictedin Fig.3,constitute

FIGURE3 Concentrationsofplasticdebrisinoceans’surfacewaters.Differentcoloursindicate distinctconcentrationranges.Theaverageconcentrationsin442sites(correspondingto1127 surfacenettows)areshown.Greyareasindicatetheoceangyres(accumulationzones)predicted bytheglobalsurfacecirculationmodeldevelopedbyMaximenkoetal. [37].Darkandlightgrey representinnerandouteraccumulationzones,respectively. FigurebyA.Co´zar,F.Echevarrıá,J.I. Gonza´lez-Gordillo,X.Irigoien,B.U ´ beda,S.Hernańdez-Leoń,A ´ .T.Palma,S.Navarro,J.Garcıáde-Lomas,A.Ruiz,M.L.Fernańdez-de-Puelles,C.M.Duarte,Plasticdebrisintheopenocean, Proc.Natl.Acad.Sci.111(28)(2014)10239 10244,copyright © bytheNationalAcademyof Sciences.Reprintedwithpermission. Microplastics Chapter j 1

zonesofaccumulationforthesedebris [36].Theselarge-scalevorticesactas ‘conveyorbelts’,and,sustainedbywhatareknownasEkmancurrents,collect theﬂoatingplasticdebrisreleased,whichissubsequentlyaccumulatedinto centralconvergencezones.Despitethetremendouscomplexityofthese distributiondynamics,directmeasurementsofmicroplasticsinthesurface havecorroboratedthesemodels [37,38]

However,microplasticshavebeenfoundtobeconsiderablymore preponderantincoastalareasthaninoffshoreregions [39],somethingthatcan beattributedtoanthropogenicactivities,namely,inpopulatedareaswith intensiveindustrialandcommercialactivities [40].

Inspiteofthelowdensityofthemostcommonlyusedplastics,including PE,low-densitypolyethylene(LDPE),high-densitypolyethylene(HDPE)and polypropylene(PP)(Table1),plasticdebriscanbefoundthroughoutthewater column.Whendirectlyreleasedintotheaquaticenvironment,particlesmade upofmaterialswithaspecificgravity >1tendtosinkandthosewithaspecific gravity <1tendtoremainbuoyant.Nonetheless,thesematerials’densities mayvaryalongthetimeduetoheteroaggregation,aspreviouslymentioned, andalsoduetootherphenomena,includingmicrobialcolonization (biofouling).Theformationofbiofilms,ultimatelyleadingtothepresenceof algaeand/orinvertebrates,hasbeendescribedashavingadramaticeffecton thedensityofthesematerialsinperiodsoftimeasshortas3weeks [41].Such events,combinedwiththenaturalturbulencefoundintheocean,aswellas withtheinteractionsofthesematerialswiththebiota,leadtoadistributionof plasticdebrisacrosstheentiretyofthewatercolumn,acomplexsystem highlightedin Fig.4.

2.2Degradation

Onceintheenvironment,microplasticscanundergodegradationthrough abioticorbioticprocesses,whichmayacteithersimultaneouslyorsequentially.However,thesemechanismsdonotdependsolelyontheenvironmental settingsalone,butalsoonthephysicalandchemicalcharacteristicsofthe polymericmaterials [42].Polyurethanes,forexample,aremorereadily biodegradedduetotheiresterlinkages,andadsorptionhasbeendescribedto favourpositivelychargedovernegativelychargedplasticbeads,owingtothe electrostaticattractionbetweenthechargedplasticparticlesandtheconstituentofthestudiedlivingsystems [43].Thismayalsoaffectthedegreeto whichmicroorganismsmayattachandformbiofilmsoverthesurfaceofthe microplastics,which,inturn,mayinfluencetherateofthebioticdegradation processes.Bothabioticandbiologicaldegradationmechanismsmayalsobe influencedbythecomplexityofthecompositionandpolymericstructureof thesematerials.AsnotedbyLambertetal. [42],plasticswithregularandshort repeatingunitswithhighsymmetries,suchasPP,PEandpolyethylene terephthalate(PET),oftenlimittheaccessibilityofenzymesandaretherefore

FIGURE4 Potentialfate,pathwaysandbiologicalinteractionsofmicroplasticsintheaquatic environment. AdaptedfromW.C.Li,H.F.Tse,L.Fok,Plasticwasteinthemarineenvironment:a reviewofsources,occurrenceandeffects,Sci.TotalEnviron.566 567(2016)333 349.

lesssusceptibletotheactionofthesebiomolecules.Hence,differentblendsof plasticmaterialshavebeendescribedasexhibitingdifferentsensitivitiesto ultraviolet(UV)-mediateddegradation [44].

2.2.1AbioticDegradation

Whenexposedtotheweatheringelements,plasticsundergomechanical disintegration,andexperiencefreeze thawcycles,pressurechanges,water turbulenceanddamagecausedbyanimals.Thismechanicalbreakdown, nonetheless,differsfromdegradation,asthemolecularbondsdonotchange andthematerialssimplyenduremorphologicalmodiﬁcations.

Photodegradationisgenerallyconsideredtobethemostefﬁcientabiotic degradationrouteoccurringintheenvironment.Plasticsexposedtoboth visible(400 700nm)andhigh-energyUVradiation(290 400nm)can absorbsuchradiation,leadingtoahigherreactivityoftheirelectrons,inducing oxidationandcleavage,degradationprocessesthataremediated,mostly,by chainscissionandcross-linkingreactions [44].

Thermaldegradationofplasticscausesbondscissionsofthemain polymericchain,leadingtochangesinthepropertiesofthematerial,including alterationsintensilestrength,molecularweight,crystallinityandevencolour. However,thehightemperaturesrequiredforthesemodiﬁcationsarehardly observedwheremicroplasticsoccurintheenvironment.Nonetheless,the