Designation:D7991−22StandardTestMethodforDeterminingAerobicBiodegradationofPlasticsBuriedinSandyMarineSedimentunderControlledLaboratoryConditions1ThisstandardisissuedunderthefixeddesignationD7991;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thistestmethoddeterminesthebiodegradationlevelofplasticmaterialsexposedtolaboratoryconditionsthatsimulatetheenvironmentfoundinthesandytidalzone.1.2Thetidalzone,thatis,thepartofthecoastaffectedbythetidesandmovementofthewaves,istheborderlinebetweenseaandland,frequentlyasandyareathatiskeptconstantlydampbythelappingofthewaves.Stonyandrockyshorelinesalsoexist.1.3Plasticmarinedebrisisfrequentlywashedupinthishabitatwhereitmustberemovedinordertorestoretheoriginallandscape.1.4Itisofinteresttoknowthebiodegradationbehaviorofplasticswhenexposedtoconditionssimulatingthishabitat,becausethisinformationcanhelpinpredictingthetimeneededforthebiodegradationofthelitter.1.5BiodegradationisdeterminedbymeasuringtheCO2evolvedbytheplasticmaterialwhenexposedtoasedimentkeptwetwithsalt-waterinareactor,tosimulatethetidalzone.1.6Marinefresh-waterhabitats(forexample,thosefoundinbrackishwatersandestuaries)arenotconsideredbythisstandard.1.7ReportsshallclearlystatethepercentageofnetCO2generationforboththetestandreferencesamplesatthecompletionofthetest.Furthermore,inthelaboratoryreports,theresultsshallnotbeextrapolatedbeyondtheactualdurationofthetest.NOTE1—ThereisnoknownISOequivalenttothisstandard.1.8Units—ThevaluesstatedinSIunitsaretoberegardedasstandard.Nootherunitsofmeasurementareincludedinthisstandard.1.9Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafety,health,andenvironmentalpracticesanddeter-minetheapplicabilityofregulatorylimi...
