1、Designation: D5988 12Standard Test Method forDetermining Aerobic Biodegradation of Plastic Materials inSoil1This standard is issued under the fixed designation D5988; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last
2、 revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers determination under laboratoryconditions of the degree and rate of aerobic biodegradation ofplast
3、ic materials, including formulation additives, in contactwith soil.1.2 This test method is designed to measure the biodegrad-ability of plastic materials relative to a reference material in anaerobic environment.1.3 This test method is designed to be applicable to allplastic materials that are not i
4、nhibitory to the bacteria and fungipresent in soil.1.4 Claims of performance shall be limited to the numericalresult obtained in the test and not be used for unqualified“biodegradable” claims. Reports shall clearly state the percent-age of net gaseous carbon generation for both the test andreference
5、 samples at the completion of the test. Results shallnot be extrapolated beyond the actual duration of the test.1.5 The values stated in SI units are to be regarded as thestandard.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is therespo
6、nsibility 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. A specific hazardstatement is given in Section 8.1.7 This ASTM test method is equivalent to ISO 17556.2. Referenced Documents2.1 ASTM
7、Standards:2D425 Test Method for Centrifuge Moisture Equivalent ofSoilsD618 Practice for Conditioning Plastics for TestingD883 Terminology Relating to PlasticsD1193 Specification for Reagent WaterD1293 Test Methods for pH of WaterD2980 Test Method for Volume Mass, Moisture-HoldingCapacity, and Poroci
8、ty of Saturated Peat MaterialsD2989 Test Method for Acidity-Alkalinity of HalogenatedOrganic Solvents and Their AdmixturesD4129 Test Method for Total and Organic Carbon in Waterby High Temperature Oxidation and by Coulometric De-tectionD4972 Test Method for pH of SoilsD5338 Test Method for Determini
9、ng Aerobic Biodegrada-tion of Plastic Materials Under Controlled CompostingConditions, Incorporating Thermophilic TemperaturesD5511 Test Method for Determining Anaerobic Biodegra-dation of Plastic Materials Under High-Solids Anaerobic-Digestion Conditions2.2 APHA-AWWA-WPCF Standards:32540 D Total Su
10、spended Solids Dried at 103105C2540 G Total, Fixed, and Volatile Solids in Solids andSemi-Solid Samples2.3 ISO Standard:ISO 17556 PlasticsDetermination of the Ultimate Aero-bic Biodegradability of Plastic Materials in Soil by Mea-suring the Oxygen Demand in a Respirometer or theAmount of Carbon Diox
11、ide Evolved3. Terminology3.1 DefinitionsDefinitions of terms applicable to this testmethod appear in Terminology D883.4. Summary of Test Method4.1 The test method described consists of the selection ofplastic material for the determination of aerobic biodegradabil-ity, obtaining soil as a matrix and
12、 source of inoculum, exposingthe plastic material to the soil, measuring the carbon dioxideevolved by the microorganisms as a function of time, andassessing the degree of biodegradability.4.2 The CO2production measured for a material, expressedas a fraction of the measured or calculated carbon conte
13、nt, is1This test method is under the jurisdiction ofASTM 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. Originallyapproved in 1996. Last previous e
14、dition approved in 2003 as D5988 - 03. DOI:10.1520/D5988-12.2For 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.3
15、Standard Methods for the Examination of Water and Wastewater, 17th Edition,1989, American Public Health Association (APHA), 1015 Fifteenth Street NW,Washington, DC 20005.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C70
16、0, West Conshohocken, PA 19428-2959, United States.reported with respect to time, from which the degree ofbiodegradability is assessed.4.3 Alternatively, it is possible to determine the consump-tion of oxygen, or biochemical oxygen demand (BOD), forexample, by measuring the amount of oxygen required
17、 tomaintain a constant gas volume in the respirometer flask, or bymeasuring the change in volume or pressure (or a combinationof the two) either automatically or manually. The level ofbiodegradation expressed in percent is determined by compar-ing the BOD with the theoretical oxygen demand (ThOD). I
18、nusing this alternative approach, however, the influence ofpossible nitrification processes on the BOD must be consid-ered.5. Significance and Use5.1 The degree and rate of aerobic biodegradability of aplastic material in the environment determines the extent towhich and time period over which plast
19、ic materials aremineralized by soil microorganisms. Disposal is becoming amajor issue with the increasing use of plastics, and the resultsof this test method permit an estimation of the degree ofbiodegradability and the time period over which plastics willremain in an aerobic soil environment. This
20、test methoddetermines the degree of aerobic biodegradation by measuringevolved carbon dioxide as a function of time that the plastic isexposed to soil.5.2 Soil is an extremely species-rich source of inoculum forevaluation of the biodegradability of plastics in the environ-ment. When maintained appro
21、priately with regard to moisturecontent and oxygen availability, the biological activity is quiteconsiderable, although lower than other biologically activeenvironments, such as activated sewage-sludge or compost.6. Apparatus6.1 Soil-Contact Incubation Apparatus (see Fig. 1; biom-eter flasks are als
22、o appropriate). Ensure that all glassware isthoroughly cleaned and, in particular, free from organic ortoxic matter.6.1.1 Vessels, a set of vessels with approximately 2 to 4-Lofinternal volume with air-tight seal, such as 150-mm desicca-tors. Provide three vessels for soil only (known as “blanks” or
23、“controls,” these vessels show the background activity of thesoil), three vessels for a positive reference material (thesevessels show the viability of the soil microbial community),three vessels per test material, and three vessels as technicalcontrols. The technical controls contain only the absor
24、bingsolution and no soil. The ambient air which fills the headspaceof all the vessels introduces carbon dioxide into the system.The technical controls allow accounting for and subtractingthis introduced carbon dioxide. Additionally, the technicalcontrols indicate the air-tightness of the vessel syst
25、em byshowing possible infiltration of carbon dioxide into the sealedvessel.6.1.2 Beakers, sets of 150-mLand 100-mL, equal in numberto the soil incubation vessels.6.1.3 Perforated Plates or Other Support, a set to hold thebeakers above the soil inside each vessel. The support must bemade from a mater
26、ial that will not absorb carbon dioxide.6.1.4 Darkened Chamber or Cabinet, which allows selec-tion of a temperature between 20C to 28C, and allowsmaintaining the selected temperature at 62C.6.2 Analytical Equipment:6.2.1 Analytical Instrument, to measure the total carboncontent of the test specimen.
27、6.2.2 Analytical Balance, to weigh the test specimen.6.2.3 Burette, 100 mL.6.2.4 Bench-Top Centrifuge, for moisture-holding capacity(MHC) determination.6.2.5 Oven, set to 104 6 1C for moisture determinations.6.2.6 Muffle Furnace, set to 550C for ash determinations.6.2.7 pH Meter.6.3 Alternatively, i
28、t is acceptable to use a flow-throughapparatus or manometric apparatus as described in ISO 17566.7. Reagents and Materials7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents conform to the specifications of the Committe
29、e onAnalytical Reagents of the American Chemical Society wheresuch specifications are available.4It is acceptable to use othergrades, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.7.2 Ammonium Phos
30、phate, (NH4)2HPO4), 4.72 g/L.7.3 Barium Hydroxide Solution (0.025 N), prepared bydissolving 4.0 g anhydrous Ba(OH)2/L of distilled water. Filterfree of solid material, confirm normality by titration withstandard acid, and store sealed as a clear solution to preventabsorption of CO2from the air. It i
31、s recommended that 5 to 20L be prepared at a time when running a series of tests. Whenusing Ba(OH)2, however, care must be taken that a film ofBaCO3does not form on the surface of the solution in thebeaker, which would inhibit CO2diffusion into the absorbing4Reagent Chemicals, American Chemical Soci
32、ety Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopei
33、al Convention, Inc. (USPC), Rockville,MD.NOTE 1(1) Barium hydroxide solution or potassium hydroxide solu-tion, (2) soil, (3) water, and (4) perforated plate.FIG. 1 Soil-Contact Incubation ApparatusD5988 122medium. Alternatively, it is acceptable to use potassiumhydroxide solution (KOH, 0.5 N), prepa
34、red by dissolving 28 gof anhydrous KOH/L of distilled water and proceeding in thesame way as for the Ba(OH)2.7.4 Hydrochloric Acid, 0.05 N HCl when using 0.025 NBa(OH)2, or 0.25 N HCl when using 0.5 N KOH.8. Hazards8.1 This test method includes the use of hazardous chemi-cals. Avoid contact with che
35、micals and follow the manufactur-ers instructions and material safety data sheets.9. Soil9.1 Use natural, fertile soil collected from the surface layersof fields and forests. Make a laboratory mixture of equal parts(by weight) of soil samples obtained from at least three diverselocations (for exampl
36、e, an agricultural field, a forest, and apasture or meadow). Taking soil from multiple and diverselocations will maximize biodiversity. It is advisable to avoidsoils that have been exposed to pollutants that cause significantperturbations of the microbial population. The soils are pref-erably used f
37、resh from the field to assure active microbiota.Air-dried or frozen soils must be reactivated before use in thistest. It is preferable to use fertile soil classified as “sandy loam”in accordance with USDA classification, or “silty sand” inaccordance with the German DIN classification.9.2 The sources
38、 of the soils must be reported (see 14.1.1).Record the sampling site, its location, the presence of plants orcrops, the sampling date, the sampling depth, and, if possible,the history such as details of fertilizer and pesticide applica-tion.9.3 Sieve the soil to less than 2-mm particle size, andremo
39、ve obvious plant material, stones, or other inert materials.Store the soil in a sealed container at 4 6 1C for a maximumof one month.9.4 Analyze the soil for MHC by Test Method D425, TestMethod D2980, or another analogous test method for MHC orfield capacity.9.5 Determine the pH of the soil on a 5:1
40、 (distilled water-:soil) slurry using a glass combination electrode calibrated withstandard buffers, following the guidelines given inTest MethodD1293. Alternatively, it is acceptable to determine the soil pHby Test Method D4972. The pH must fall between 6.0 and 8.0.(Soil with a pH above 8.0 retains
41、 more of the CO2evolved bythe microorganisms than a neutral soil, while a soil with a pHbelow 6.0 has the potential to contain an atypical microbialpopulation.)9.6 Determine the moisture (total solidsdry solids) andash (total solidsvolatile solids) contents of the soil inaccordance withAPHA-AWWA-WPC
42、F 2540 D and G, respec-tively.9.7 It is acceptable for the test matrix to be a mixture ofnatural soil, as described in 9.1, and mature compost, such asobtained at the end of Test Method D5338. At a ratio of 1 gcompost to 25 g soil, which corresponds to a typical applica-tion in agriculture of approx
43、imately 120 tons of compost perhectare of agricultural land (assuming 20 cm of soil depth anda bulk density of 1.5 Mg m3).10. Test Specimen10.1 Test specimens shall be of known weight and havesufficient carbon content to yield enough carbon dioxide thatcan be measured accurately by the trapping proc
44、edure de-scribed in this test method (see 11.7 and 11.9). Determine thecarbon content of the test material by calculation or elementalanalysis, in accordance with Test Method D4129.10.2 It is acceptable for test specimens to be in the form offilms, pieces, fragments, powders, or formed articles, or
45、inaqueous solution, in accordance with Practice D618.Itisrecommended, but not required, to characterize any test speci-mens in the form of powders as to particle size distribution bysieve analysis.11. Procedure11.1 The test shall be performed in triplicate for each of thetechnical control, soil blan
46、k, positive reference material, andtest materials (triplicate for each test material).11.2 Place between 100 and 500 g of soil in the bottom ofthe vessel.11.3 Amend the soil with nitrogen to give a C:N of between10:1 and 20:1 (by weight) to the added carbon in the testspecimen by adding the appropri
47、ate volume of ammoniumphosphate solution. Add the same amount of nitrogen to thesoil blanks as to those that will receive a test material orpositive reference material.11.4 Add distilled water, prepared in accordance with Speci-fication D1193, to bring the moisture content to 80 to 100 % ofthe MHC o
48、f the soil (if the MHC is determined in accordancewith Test Method D425; if in accordance with Test MethodD2989, then 50 to 70 % of MHC is appropriate).11.5 Record the weight of the vessel and lid (with thenecessary amount of vacuum grease to seal air-tight) withamended soil.11.6 Add the test materi
49、al or positive reference material tothe soil (approximately 200 mg to 1000 mg carbon for 500 gsoil), and mix thoroughly into the soil.11.7 Place 100 mL of 0.025 N barium hydroxide solution ina 150-mLbeaker (or 20 mLof 0.5 N KOH in a 100-mLbeaker)and 50 mL of distilled water in a 100-mL beaker on theperforated plate inside the vessel; seal the vessel and place it inthe dark chamber or cabinet.11.8 Select a temperature between 20 to 28C, and maintainthat temperature at 62C.11.9 Carbon Dioxide Analysis:11.9.1 The carbon dioxide produced in each vessel reactswith Ba(OH
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