1、Designation: D7473 12Standard Test Method forWeight Attrition of Plastic Materials in the MarineEnvironment by Open System Aquarium Incubations1This standard is issued under the fixed designation D7473; the number immediately following the designation indicates the year oforiginal adoption or, in th
2、e 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 is used to determine the weight loss asa function of time of non-floa
3、ting plastic materials (includingformulation additives), when incubated under changing, open,marine aquarium conditions, which is representative of aquaticenvironments near the coasts and near the bottom of a body ofwater in the absence of sunlight, particularly UV and visibleportions of the spectru
4、m. The goal of this test is to obtain datathat will predict real world experiences based on the extent andrate of biodegradation data of the same materials obtained fromthe laboratory Test Method D6691. The aquarium incubatedfilms are examined for visual degradation and dry weight lossover time. Thi
5、s test is not a replacement to Test Method D6691,but rather an additionalASTM method for weight attrition. Thestandard addresses weight loss of the plastics in a marineenvironment and cannot be used for demonstrating biodegra-dation for which Specification D7081 needs to be used.1.2 Plastic film pie
6、ces of known size and thickness are usedat levels so as not to exceed the availability of micronutrientsessential for and therefore limit the microbial biodegradationprocess.1.3 The aquarium incubation test method allows represen-tative indigenous microorganisms present in seawater andmarine sedimen
7、t to be enriched for and carry out the biodeg-radation. It is recommended that the test be carried out in thegeographical vicinity (latitudinal area) where the test film islikely to be used and potentially disposed of in the marineenvironment if biodegradable criteria are met. TheseAquariumstudies a
8、re conducted in indoor environments, hence anysunlight-induced effects on degradation, or biodegradation, orboth, are not taken into account.1.4 Prior to conducting this aquarium test method (weightloss data) for the verification of biodegradability, Test MethodD6691 shall be run on the same materia
9、ls to establish quanti-tative levels of the plastic organic carbon oxidation and levelsof carbon dioxide recovered there from. If Test Method D6691achieves 30 % mineralization, then apply this Aquarium testand perform it. If the results from Test Method D6691 do notachieve 30 % mineralization, then
10、aquarium incubation testingneed not be done and the material shall be considered non-biodegradable in the marine environment.1.5 This test by itself shall not be used as the basis forclaims, such as “Biodegradable in Marine Environments” sinceit is only a weight loss test method.1.6 This standard do
11、es 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.NOTE 1There is no known ISO equival
12、ent to this standard.2. Referenced Documents2.1 ASTM Standards:2D883 Terminology Relating to PlasticsD6691 Test Method for Determining Aerobic Biodegrada-tion of Plastic Materials in the Marine Environment by aDefined Microbial Consortium or Natural Sea Water In-oculumD7081 Specification for Non-Flo
13、ating Biodegradable Plas-tics in the Marine Environment3. Terminology3.1 DefinitionsDefinitions of terms applying to this testmethod appear in Terminology D883.3.2 Definitions of Terms Specific to This Standard:3.2.1 absence of lightabsence of electromagnetic radia-tion with the focus on visible and
14、 ultraviolet portions of thespectrum of sunlight or other light with similar wavelengthfrequencies from artificial sources.3.2.2 natural seawater (NSW)seawater unamended withany additives.3.2.3 indigenous microbesthose microbes naturally oc-curring in a seawater or sediment sample.1This test method
15、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 May 1, 2012. Published June 2012. DOI:10.1520/D747312.2For referenced ASTM standards, visit the ASTM
16、 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United
17、 States.3.2.4 mesophilictemperature range from approximately20 to 40C over which microorganisms adapted to moderateconditions maintain active metabolic rates.3.2.5 psychrophilictemperature range from approxi-mately 2 to 20C over which microorganisms adapted to coldconditions maintain active metaboli
18、c rates.3.2.6 sulfate reductionthe anaerobic microbial processwhereby sulfate acting as an electron acceptor is converted tohydrogen sulfide as an end product.3.2.7 surface marine sedimentthe upper few millimetresto several centimetres of oceanic bottom sediments containingthe natural indigenous mic
19、robial populations and ranging fromoxic to potentially anoxic conditions with increasing sedimentdepth.4. Summary of Test Method4.1 This test method consists of the following:4.1.1 Selecting, characterizing and preparing plastic filmsfor testing (formulation, carbon content, molecular weight, filmth
20、ickness and uniformity).4.1.2 Running short term (4 days) sterile seawater controlsof the films to determine level of loss due to soluble compo-nents (plasticizers etc). See Section 11.4.1.3 Collecting and storage in the absence of light ofmarine sediment from the local coastal marine environment fo
21、ruse in aquarium incubations.4.1.4 Having access to a continuous flow of natural seawa-ter.4.1.5 Exposing film pieces in the absence of light to naturalflowing seawater or sediment surfaces under natural flowingseawater in open tray incubations in a marine aquarium atseasonally varying water tempera
22、tures. See Section 8.4.1.6 Harvesting film pieces at varied time intervals toassess visual impacts of exposure and degradation and deter-mining the percentage loss in dry weight and weight loss perunit area.4.1.7 The film material is related for its attrition and weightloss in this realistic open sy
23、stem aquarium incubation, to theprior determination of its organic carbon biodegradability toCO2based on the outcome of Test Method D6691 testing of thesame film.4.2 Conventional plastics are not allowed to be disposed ofat sea, and yet the use of such materials aboard ships hasincreased in recent y
24、ears. A technological goal is to develop atest method for plastics, designed to biodegrade safely in themarine environment (conversion to carbon dioxide by means ofmicrobial metabolism). These can be used in place of conven-tional plastics which will fulfill the criteria for allowing themto be dispo
25、sed of in the marine environment. This aquariumincubation test method has been developed and is used toassess the rate and extent of attrition of biodegradable plasticsas a loss in dry weight during incubation exposure to indig-enous marine microorganisms. The test assesses weight lossunder continuo
26、us flow (open system) aquarium conditions inwhich microbial growth processes rely on the naturally occur-ring supply of nutrients (for example, nitrogen and phosphate)in the incoming seawater and use the plastic as the carbonsource. Aquarium testing is more realistic of the actual marineenvironment
27、than a closed flask laboratory test (that is, TestMethod D6691) as it allows flushing, exposure to a diversepopulation of microbes, removal of metabolic end products,re-supply of oxygen, exposure to anoxic conditions in sedi-ment, and exposure to seasonal temperature variation of theincoming seawate
28、r and natural concentration of macro- andmicronutrients. The test is carried out as close to the geographi-cal vicinity (latitudinal area) where the test film is likely to beused in product form.4.3 The test does not quantify the conversion of plasticorganic carbon to carbon dioxide, but rather the
29、loss in dryweight of the material over time. Therefore, Test MethodD6691 must be run prior to this test in order to determine themaximum CO2production from the test film and thereforeindicate the degree of biodegradation under the more optimumconditions of the laboratory but which are less realistic
30、 of theactual marine environment.4.4 Conducting Test Method D6691 initially as a closedsystem test in the laboratory will determine if the plastic itemsmeet criteria of acceptable biodegradability to the pass level formineralization specified in 1.4 and if so, the open systemaquarium test is warrant
31、ed. The rate of biodegradation can beexpected to be faster under laboratory conditions compared tothe Aquarium test since the latter is conducted under changingand often colder temperatures and a more limited supply ofnutrients relative to the available carbon.5. Apparatus5.1 Borosilicate Glass Beak
32、ers, varied sizes, (250 mL to 4 Las needed for sediment).5.2 Autoclave capable of steam sterilizing. The autoclave isrun at 121C for 20 min.5.3 Drying oven for obtaining constant dry weight ofsamples5.4 Analytical balance,(60.1 mg) for weighing testsamples5.5 Access to flowing natural seawater aquar
33、ium.5.6 Plastic boxes (lids removed) with open compartmentsfor holding samples incubated in open aquarium trays offlowing seawater.5.7 Nylon mesh screening,(18 to14 in. openings)5.8 Opaque plastic film or fabric.6. Hazards6.1 While there are no known specific hazards associatedwith this test procedu
34、re care must be taken in handling of allsamples. Latex gloves are used when handling the marinesediment.6.2 Before preparing chemical stock solutions read themanufacturers Material Safety Data Sheets.7. Inoculum7.1 Natural Seawater (NSW), as a continuous fresh supplyavoiding collections sites influe
35、nced by storm water runoff orhave major oil slicks on the surface.7.2 Surface Marine Sediment (SED), collected on or before(1 day) the day the Aquarium incubations are to be initiated.D7473 122Surface sediment, preferably of a muddy nature as opposed tosand, can be collected from any coastal locatio
36、n at or close tothe NSW source site.8. Procedure (Open System Aquarium Incubation)8.1 Film Preparation:8.1.1 Determine the average mil thickness of the film. Cutpre-dried film in 0.5 by 0.5 in. pieces. Weigh individual piecesof film and record weight.8.1.2 Samples shall not be subjected to any condi
37、tions ortreatments designed to accelerate weight loss prior to 8.3.2.8.2 Aquarium Inoculation Preparation :8.2.1 Collect surface SED from area of the NSW site andbring to aquarium incubation site. Keep sediment in place withabsence of light prior to incubation and testing. Collect enoughto half fill
38、 the needed number of sections in chosen incubationcontainers (for example, plastic boxes with 12 separate sec-tions and lids removedthese boxes will be placed in theflowing seawater aquarium trays). Sections of about 4 in. by 2in. are sufficient for each sample piece. The same types ofincubation co
39、ntainers and section size are used for the NSWincubation without any added sediment. Have enough boxsections to fulfill the needed number of samples for example, 2film samples 3 5 time points 3 3 triplicates 3 2 incubationconditions(NSW exposure alone and NSW-SED expo-sure) = 60 incubation container
40、 sections.8.3 Aquarium Incubation:8.3.1 Have a constant supply of natural seawater flowinginto and out of the aquarium tray. The incoming seawater canbe run through a coarse filter to reduce the amount ofsedimentation of particulates over time if necessary.8.3.2 Place the film samples in the plastic
41、 boxes intoindividual sections, with and without sediment in the sections,recording their location. Samples placed in box sections withadded sediment are placed just on top of the sediment surfacewith enough pressure to adhere them to the sediment. The topsof all boxes are covered with a large mesh
42、nylon screen (18 to14 inch openings) and secured with rubber bands around thebox. This prevents loss or exchange of any samples betweencompartment sections during incubation.8.3.3 Place all boxes containing sample films into theaquarium tray. Slowly fill all the boxes with seawater beforesubmerging
43、them in the aquarium tray to prevent shifting of thesediment adhered films. Cover the aquarium with opaqueplastic film or fabric to keep the plastic sample and sediment indark conditions.8.3.4 Record temperature of incoming seawater at zero timeand at each sampling point. Monitor samples over time f
44、or anyvisible signs of degradation and harvest samples at appropriatetime intervals over a maximum of 180 days. Report the totallength of the test period.9. Sample Harvesting and Processing9.1 At selected time intervals, samples (triplicates) areremoved from Aquarium box sections being careful not t
45、oloose delicate fragments if the test film has any tendency to doso. Aquarium incubation boxes are best lifted from theaquarium trays before this procedure and then replaced aftersamples are removed.9.2 Sampled film pieces are rinsed with distilled water toremove adhered sediment particles, adhered
46、bacterial slime ifpresent, and sea salts and then weight recorded after drying toconstant weight (35-40C).9.3 Note and report any blackening of the undersides ofAquarium samples, which are indicative of anoxic conditionsthat allow sulfate reducing microbes to play a significant rolein biodegradation
47、 of the films.10. Correction for Soluble Components10.1 In order to determine if significant soluble componentsare leached out during initial aqueous exposure, weighedpieces of film are incubated in pre-sterilized (autoclaved)distilled water for 96 hrs. They are then collected, dried andweighed to d
48、etermine the percentage of loss, if any, due tosoluble components, which would not be attributable to micro-bial action. The reported percentage in dry weight loss of testsamples is corrected for this solubilization loss if greater than0.5 %.11. Calculation11.1 Determine the percentage loss in dry w
49、eight of filmsamples over time (average of triplicate samples). Correct forany soluble losses from sterile controls if necessary.11.2 As microbial activity during exposure of the films isprimarily a surface action it is also important to calculate theweight loss per unit area of film. This is important whencomparing films of different mil thicknesses. A thicker filmcould lose as much or more weight per unit area but as it wouldhave had a higher initial dry weight than a thinner film, theactual percentage of dry weight loss can actually be less thanthe thinner fi
