ASTM_D_6692_-_01.pdf

Designation:D 6692 01Standard Test Method forDetermining the Biodegradability of Radiolabeled PolymericPlastic Materials in Seawater1This standard is issued under the fixed designation D 6692;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test is used to determine the degree of aerobicbiodegradation of polymeric compounds utilized in plasticmaterials by determining the level of respiration of suchradiolabeled carbon compounds to radiolabeled carbon diox-ide.1.2 The test is designed to utilize the naturally occurringmicrobes in seawater as the inoculum for the enrichment andsubsequent mineralization(biodegradation)of the test polymerusing it as a carbon and energy source resulting in a carbondioxide as an end product.1.3 The test method requires that the polymers to be assayedare synthesized using the radioisotope,carbon-14,and that thecompound or plastic material be uniformly labeled withcarbon-14.1.4 As controls,known biodegradable compounds,such asglucose or starch,also uniformly labeled with carbon-14,arerun in order to determine the biological activity of the naturalpopulation.1.5 The concentration of added polymers shall be kept lowso as not to cause limitation by oxygen,and the seawaterinoculum is amended with nitrogen and phosphorus com-pounds to ensure that growth in not limited by these nutrients.1.6 The safety problems and regulations associated withworking with radioactive materials are not addressed in themethod.It is the responsibility of the individual users toestablish and ensure adherence the proper safety,health,monitoring and all regulatory practices associated with the useof radioactive compounds.1.7 There is no similar or equivalent ISO standard.2.Referenced Documents2.1 ASTM Standards:D 883 Terminology Relating to Plastics2D 5296 Test Method for Molecular Weight Averages andMolecular Weight Distribution of Polystyrene By HighPerformance Size Exclusion Chromatography3D 6340 Determining Aerobic Biodegradation of Radiola-beled Plastic Materials in an A)Aqueous or B)CompostEnvironment33.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 disintegrations per minute(DPM),nthe degree ofradioactivity of an element given as the number of decaysoccurring per unit time.3.1.2 microcurie(Ci),na unit of radioactivity equal to/1,000,000 of a curie or 2.2 3 106DPM.3.1.3 millicurie(mCi),na unit of radioactivity equal to1/1000 of a curie.3.1.4 natural seawater(NSW),nseawater unamendedwith any additives.3.1.5 specific activity(SA),nthe level of radioactivity(Ci)per unit mass(for example,mg).4.Summary of Test Method4.1 This test method consists of the following:4.1.1 Obtaining samples of the test polymer in which thecarbon is uniformly labeled with carbon-14 and of knownspecific activity.4.1.2 Collecting a sample of natural seawater(NSW)from amarine source in which the material(non-radioactive)may beultimately disposed.4.1.3 Incubating,over a time course,weighed samples ofthe polymer in sealed vessels of NSW amended with nutrientsunder aerobic conditions at constant temperature.4.1.4 At varied time points,harvesting the microbiallyrespired radiolabeled carbon dioxide in absorbent traps.4.1.5 Determining the DPM of radiolabeled carbon dioxidein a liquid scintillation counter.4.1.6 Based on the recovered DPM,the specific activity andthe known amount of radiolabeled polymer added to the testincubation vessel calculate the amount and percentage of thepolymer which was respired(biodegraded)to carbon dioxide.1This test method is under the jurisdiction ofASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.96 on EnvironmentallyDegradable Plastics.Current edition approved June 10,2001.Published August 2001.2Annual Book of ASTM Standards,Vol 08.01.3Annual Book of ASTM Standards,Vol 08.03.1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.5.Significance and Use5.1 This method allows for a definitive determination con-cerning aerobic microbial biodegradation occurring for plasticcompounds of known uniform composition or of componentmaterials used in the production of non-uniform(that is,blend)plastics.5.2 The use of radioactive14C materials eliminates thepossibility of carbon dioxide measurement from anything otherthan the parent compound in question.5.3 The use of this assay relies on the enrichment andgrowth of naturally occurring microbes in marine samples tobiodegrade the radiolabeled plastic compounds generating cellmaterial and carbon dioxide as the radiolabeled end products.5.4 Time course(several days to several weeks)measure-ments allows for a biodegradation rate determination to bemade,but caution should be exercised in extrapolating thislaborato