ASTM_D_7991_-_15.pdf

Designation:D799115Standard Test Method forDetermining Aerobic Biodegradation of Plastics Buried inSandy Marine Sediment under Controlled LaboratoryConditions1This standard is issued under the fixed designation D7991;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()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method determines the biodegradation level ofplastic materials exposed to laboratory conditions that simulatethe environment found in the sandy tidal zone.1.2 The tidal zone,that is,the part of the coast affected bythe tides and movement of the waves,is the borderline betweensea and land,frequently a sandy area that is kept constantlydamp by the lapping of the waves.Stony and rocky shorelinesalso exist.1.3 Plastic marine debris is frequently washed up in thishabitat where it must be removed in order to restore theoriginal landscape.1.4 It is of interest to know the biodegradation behavior ofplastics when exposed to conditions simulating this habitat,because this information can help in predicting the time neededfor the biodegradation of the litter.1.5 Biodegradation is determined by measuring the CO2evolved by the plastic material when exposed to a sedimentkept wet with salt-water in a reactor,to simulate the tidal zone.1.6 Marine fresh-water habitats(for example,those found inbrackish waters and estuaries)are not considered by thisstandard.1.7 Reports shall clearly state the percentage of net CO2generation for both the test and reference samples at thecompletion of the test.Furthermore,in the laboratory reports,the results shall not be extrapolated beyond the actual durationof the test.NOTE1There is no known ISO equivalent to this standard.1.8 UnitsThe values stated in SI units are to be regardedas standard.No other units of measurement are included in thisstandard.1.9 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D5988 Test Method for Determining Aerobic Biodegrada-tion of Plastic Materials in Soil2.2 ISO Standards:3ISO 8245 Water quality Guidelines for the determination oftotal organic carbon(TOC)and dissolved organic carbon(DOC)3.Terminology3.1 Definitions:3.1.1 tidal zone,nthe part of the marine environment thatextends from the high tide line,which is rarely inundated withwater,to the low tide line,which is typically always coveredwith water.3.1.1.1 DiscussionSynonyms are:eulittoral zone,midlit-toral zone,mediolittoral zone,intertidal zone,foreshore.4.Summary of Test Method4.1 This test method consists of the following:4.1.1 Selection of plastic material for the determination ofaerobic biodegradation in a controlled laboratory system.4.1.2 Obtaining sediment and seawater from the shoreline.4.1.3 Exposing the plastic material to the wet sedimentunder controlled conditions.4.1.4 Measuring CO2evolved as a function of time.4.1.5 Assessing the degree of biodegradation by determin-ing the percentage of organic carbon in the plastic material thatis converted to CO2during the duration of the test.Thispercentage represents the percentage of mineralization and will1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.96 on EnvironmentallyDegradable Plastics and Biobased Products.Current edition approved Sept.1,2015.Published September 2015.DOI:10.1520/D799115.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute(ANSI),25 W.43rd St.,4th Floor,New York,NY 10036,http:/www.ansi.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 not include the amount of carbon converted to cell biomass thatis not in turn metabolized to CO2during the course of the test.4.1.6 Estimating the qualitative disintegration of the testmaterial by visual inspection at the end of the test.5.Significance and Use5.1 Plastic is sometimes carried by rivers or accidentallydischarged by ships into the sea;this plastic can then reachdifferent parts of the marine environment.Tides and waves alsofrequently deliver plastic marine debris into the sandy tidalzones.5.2 This test method simulates the environmental conditionsfound in the tidal zone.Plastic debris that reaches the sandytidal zone can settle there and become partially or totally buriedby sand and kept wet by waves or tides.It is of intere