ASTM D7473/D7473M-21

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D7473 − 12 D7473/D7473M − 21
Standard Test Method for
Weight Attrition of Non-floating Plastic Materials in the
Marine Environment by Open System Aquarium
Incubations
This standard is issued under the fixed designation D7473;D7473/D7473M; the number immediately following the designation indicates
the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope Scope*
1.1 This test method is used to determine the weight loss as a function of time of non-floating plastic materials (including
formulation additives), when incubated under changing, open, marine aquarium conditions, which is representative of aquatic
aerobic environments near the coasts and near the bottom of a body of water in the absence of sunlight, particularly UV and visible
portions of the spectrum. The goal of this test is to obtain data that will predict real world experiences based on the extent and
rate of biodegradation data of the same materials obtained from the laboratory Test Method can be used D6691. The aquarium
incubated films are examined for visual degradation and dry weight loss over time. This test is not a replacement to Test Methodto
assess the D6691, but rather an additional ASTM method for weight attrition. The standard addresses weight loss of the plastics
in a marine environment and cannot be used for demonstrating biodegradation for which Specificationpotential for physical
degradation of the test material. Such potential for physical degradation will be affected D7081 needs to be used.by real life
environmental conditions.
1.2 In particular this test method does not take into consideration the possible effects of solar irradiation.
1.3 The aquarium-incubated plastic materials are examined for visual degradation and dry weight loss over time. This test does
not provide information on ultimate biodegradation (that is, it is not a replacement for Test Method D6691), but it is an ASTM
method for weight attrition. The standard addresses only weight loss as a function of time of the plastics materials in a marine
environment and shall not be used for demonstrating ultimate biodegradation.
1.4 This test method does not provide information regarding the potential formation of microplastics due to the physical
degradation of the samples.
1.5 Plastic film pieces of known size and thickness are used at levels so as not to exceed the availability of micronutrients essential
for and therefore limit the microbial biodegradation process.processes.
1.6 The aquarium incubation test method allows for representative indigenous microorganisms present in seawater and marine
sediment to be enriched for and carry out the biodegradation. It is recommended that the test be carried out in the geographical
vicinity (latitudinal area) where the test film ismaterials are likely to be used and potentially disposed of in the marine environment
if biodegradable criteria are met. used. These Aquarium studies are conducted in indoor environments, hence any sunlight-induced
effects on degradation, or biodegradation, or both, are not taken into account.
This test method is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.96 on Environmentally Degradable
Plastics and Biobased Products.
Current edition approved May 1, 2012March 1, 2021. Published June 2012March 2021. DOI:10.1520/D7473–12.Originally approved in 2012. Last previous edition
approved in 2012 as D7473 – 12. DOI:10.1520/D7473_D7473M–21.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7473/D7473M − 21
1.4 Prior to conducting this aquarium test method (weight loss data) for the verification of biodegradability, Test Method D6691
shall be run on the same materials to establish quantitative levels of the plastic organic carbon oxidation and levels of carbon
dioxide recovered there from. If Test Method D6691 achieves 30 % mineralization, then apply this Aquarium test and perform it.
If the results from Test Method D6691 do not achieve 30 % mineralization, then aquarium incubation testing need not be done and
the material shall be considered non-biodegradable in the marine environment.
1.7 This test by itself shall not be used as the basis for claims, such as “Biodegradable in Marine Environments” since it is only
a weight loss test method. This test method is solely a means for measuring a characteristic (physical degradation) under standard
conditions. It does not assess the general environmental impact of plastic products.
1.8 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in
each system are not necessarily exact equivalents; therefore, each system shall be used independently of the other. Combining
values from the two systems has the potential to result in non-conformance with the standard.
1.9 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
NOTE 1—There is no known ISO equivalent to this standard.
1.10 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D883 Terminology Relating to Plastics
D6691 Test Method for Determining Aerobic Biodegradation of Plastic Materials in the Marine Environment by a Defined
Microbial Consortium or Natural Sea Water Inoculum
D7081 Specification for Non-Floating Biodegradable Plastics in the Marine Environment (Withdrawn 2014)
3. Terminology
3.1 Definitions—Definitions of terms applying to this test method appear in Terminology D883.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 absence of light—absence of electromagnetic radiation with the focus on visible and ultraviolet portions of the spectrum of
sunlight or other light with similar wavelength frequencies from artificial sources.
3.2.2 natural seawater (NSW)—seawater unamended with any additives.
3.2.3 indigenous microbes—those microbes naturally occurring in a seawater or sediment sample.
3.2.4 mesophilic—temperature range from approximately 20 to 40°C over which microorganisms adapted to moderate conditions
maintain active metabolic rates.
3.2.5 psychrophilic—temperature range from approximately 2 to 20°C over which microorganisms adapted to cold conditions
maintain active metabolic rates.
3.2.6 sulfate reduction—the anaerobic microbial process whereby sulfate acting as an electron acceptor is converted to hydrogen
sulfide as an end product.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
D7473/D7473M − 21
3.2.7 surface marine sediment—sediment (SED)—the upper few millimetresmillimeters to several centimetrescentimeters of
oceanic bottom sediments containing the natural indigenous microbial populations and ranging from oxic to potentially anoxic
conditions with increasing sediment depth.
4. Summary of Test Method
4.1 This test method consists of the following:
4.1.1 Selecting, characterizing and preparing plastic filmsmaterials for testing (formulation, carbon content, molecular weight, film
thickness and uniformity).
4.1.2 Running short term short-term (4 days) sterile seawater controls of the films plastic materials to determine level of loss due
to soluble components (plasticizers etc).etc.). See Section 11.
.
4.1.3 CollectingCollection and storage in the absence of light of marine sediment from the local coastal marine environment for
use in aquarium incubations.
4.1.4 Having access to a continuous flow of natural seawater.
4.1.5 Exposing film plastic material pieces in the absence of light to natural flowing seawater or sediment surfaces under natural
flowing seawater in open tray incubations in a marine aquarium at seasonally varying water temperatures. See Section 8.
4.1.6 Harvesting film plastic material pieces at varied time intervals to assess visual impacts of exposure and degradation and
determining the percentage loss in dry weight and weight loss per unit area.
4.1.7 The film material is related for its attrition and weight loss in this realistic open system aquarium incubation, to the prior
determination of its organic carbon biodegradability to CO based on the outcome of Test Method D6691 testing of the same film.
4.2 Conventional plastics are not allowed to be disposed of at sea, and yet the use of such materials aboard ships has increased
in recent years. A technological goal is to develop a test method for plastics, designed to biodegrade safely in the marine
environment (conversion to carbon dioxide by means of microbial metabolism). These can be used in place of conventional plastics
which will fulfill the criteria for allowing them to be disposed of in the marine environment. This aquarium incubation test method
has been developed and is used to assess the rate and extent of attrition of biodegradable plasticsplastic materials as a loss in dry
weight during incubation exposure to indigenous marine microorganisms. The test assesses weight loss under continuous flow
(open system) aquarium conditions in which microbial growth processes rely on the naturally occurring supply of nutrients (for
example, nitrogen and phosphate) in the incoming seawater and use the plastic as the carbon source. Aquarium testing is more
realistic of the actual marine environment than a closed flask laboratory test (that is, Test Method D6691) as it allows flushing,
exposure to a diverse population of microbes, removal of metabolic end products, re-supply of oxygen, exposure to anoxic
conditions in sediment, and exposure to seasonal temperature variation of the incoming seawater and natural concentration of
macro- and micronutrients. The This dynamic test is carried out as close to the geographical vicinity (latitudinal area) where the
test filmtested material is likely to be used in product form.
4.3 The test does not quantify the conversion of plastic organic carbon to carbon dioxide, but rather the loss in dry weight of the
material over time. Therefore, other test methods, such as Test Method D6691, must be run prior to this test in order to determine
the maximum CO production from the test filmsample and therefore indicate the degree of biodegradation under the more
optimum conditions of the laboratory but which are less realistic of the actual marine environment.laboratory.
4.4 Conducting Test Method D6691 initially as a closed system test in the laboratory will determine if the plastic items meet
criteria of acceptable biodegradability to the pass level for mineralization specified in 1.4 and if so, the open system aquarium test
is warranted. The rate of biodegradation can be expected to be faster under laboratory conditions compared to the Aquarium test
since the latter is conducted under changing and often colder temperatures and a more limited supply of nutrients relative to the
available carbon.
D7473/D7473M − 21
5. Apparatus
5.1 Borosilicate Glass Beakers,glass beakers, varied sizes, (250 mL to 4 L as needed for sediment).
5.2 Autoclave capable of steam sterilizing.
...