ISO 16623:2024
(Main)Plastics — Marine biodegradation testing — Preparation of optimized intertidal seawater and sediment
Plastics — Marine biodegradation testing — Preparation of optimized intertidal seawater and sediment
This document specifies procedures for preparing seawater and sediments used in test methods to assess the biodegradation of plastic materials in the marine environment. The screened sediment and sediment-rinsed seawater are prepared to sustain aerobic testing at laboratory scale. The described method is designed to separate sediment-rinsed seawater and sand-gravel sediments from intertidal sediments by wet filtration and seawater flotation. This document does not include steps to enhance the biodegradation of plastic materials by concentrating the natural seawater, adding nutrients to the seawater, and pre-culturing the inoculum. The methods described in this document are intended to be used in addition to issued ISO standard test methods for evaluating the biodegradation and disintegration of plastic materials. The applicable evaluation test methods are ISO 18830, ISO 19679, ISO 22404, ISO 23977-1, ISO 23977-2 and ISO 23832. NOTE The conditions described in this document do not always correspond to the optimum conditions for maximum biodegradation. This is a method of preparing test sediments from coastal seafloor sediments, not a method of preparing sediments from deep-sea seafloors.
Plastiques — Essais de biodégradation en milieu marin — Préparation d'eau de mer et de sédiments intertidaux optimisés
General Information
Standards Content (Sample)
International
Standard
ISO 16623
First edition
Plastics — Marine biodegradation
2024-12
testing — Preparation of optimized
intertidal seawater and sediment
Plastiques — Essais de biodégradation en milieu marin —
Préparation d'eau de mer et de sédiments intertidaux optimisés
Reference number
© ISO 2024
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 3
5 Apparatus . 4
6 Procedure . 4
6.1 General .4
6.2 Collection of sediment with less than 2 mm particle size and preparation of rinsed
seawater .5
6.3 Preparation of refined sediment .5
6.4 Purification of seawater for biodegradation test from suspended seawater .5
7 Validity of preparation . 6
7.1 Sediment for disintegration testing.6
7.2 Refined sediment for biodegradation testing .6
8 Preparation report of seawater and sediments . 6
Annex A (informative) Diagram of seawater and sediment preparation — Seawater and
sediment preparation by wet filtration and flotation . 8
Annex B (informative) Preparation of seawater and sediments from seafloor sediments: Wet
filtration and flotation of sediments . 9
Annex C (informative) Evolved carbon dioxide of seawater and sediment prepared from
seafloor sediments .11
Annex D (informative) Test validity of ISO 19679 — Validity of biodegradation test based on
carbon dioxide evolved .13
Annex E (informative) Example of biodegradation of reference material by ISO 19679 .15
Annex F (informative) Example of biodegradation of plastic films by ISO 19679 —
Biodegradation of plastic films using rinsed seawater and sand gravel sediments .16
Annex G (informative) Example of live and total cell count in sediment and seawater: Live and
total cell count in sediment and seawater by fluorescence method . 17
Annex H (informative) Example of biodegradation of plastic films by ISO 19679 . 19
Annex I (informative) Interlaboratory test ISO 19679 and ISO 18830 final report .20
Bibliography .21
iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
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this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
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related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 14, Environmental
aspects.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
Introduction
The assessment of the degree of biodegradation of plastics in marine habitats is one effective measure
to understand and evaluate the impact of reuse, recycling and environmental pollution of plastics. The
biodegradation of plastics is the process, in which plastics are decomposed by heterotrophic microorganisms,
such as bacteria and fungi, through enzymatic hydrolysis and subsequent metabolization. Marine
biodegradation proceeds mainly in microbial consortia that form at the interface between seawater and
plastics. This is because marine microorganisms live aerobically within biofilms at the interface between
the liquid phase of seawater and solid phases such as gravel and shells.
The diversity of microbial consortia in the marine environment is high, depending on their natural
environmental conditions. The species and number of microorganisms vary depending on the climate, ocean
currents, tides, and topography. Considering the diverse habitats of these microorganisms, three types of
biodegradation assessment methods have been developed:
— one-phase systems consisting of seawater or sediment and
— two-phase systems consisting of seawater and seafloor sediments.
However, due to the diversity of microorganisms even a biodegradable material such as cellulose, which is
used as a reference material, gave biodegradation results that ranged from 0 to 100 percent in ring tests
of these test methods. From the perspective of biodegradable plastic specification, it is thus necessary to
optimize the preparation of natural inoculum for the biodegradation tests to avoid those fluctuations in
experimental outcomes.
In order to reduce the impact of seasonal and regional variation in the marine inoculum composition, this
document describes a method for preparing seawater and seafloor sediments. The prepared seawater
and sediment can be used for the test methods defined in ISO 19679, ISO 18830, ISO 22404, ISO 23977-1,
ISO 23977-2 and ISO 23832.
Prepared seawater for biodegradation tests is obtained by rinsing seafloor sediments with seawater.
Sand and gravel mixtures with particle sizes from 250 µm to 2 mm are used as sediments to provide pore
water flow, oxygen supply, seawater filtration and biofilm growth. Through the preparation of defined
compositions of seawater and sediments in marine tests, the number of microorganisms and aerobic
conditions are stabilized, and reproducibility and comparability of biodegradation experiments (including
curves, lag time, etc.) are improved.
This document specifies methods for preparing seawater and sediments in the intertidal zone for estimating
the aerobic biodegradation of plastics in pelagic to coastal marine environments.
v
International Standard ISO 16623:2024(en)
Plastics — Marine biodegradation testing — Preparation of
optimized intertidal seawater and sediment
1 Scope
This document specifies procedures for preparing seawater and sediments used in test methods to assess
the biodegradation of plastic materials in the marine environment. The screened sediment and sediment-
rinsed seawater are prepared to sustain aerobic testing at laboratory scale. The described method is
designed to separate sediment-rinsed seawater and sand-gravel sediments from intertidal sediments by wet
filtration and seawater flotation. This document does not include steps to enhance the biodegradation of
plastic materials by concentrating the natural seawater, adding nutrients to the seawater, and pre-culturing
the inoculum.
The methods described in this document are intended to be used in addition to issued ISO standard test
methods for evaluating the biodegradation and disintegration of plastic materials. The applicable evaluation
test methods are ISO 18830, ISO 19679, ISO 22404, ISO 23977-1, ISO 23977-2 and ISO 23832.
NOTE The conditions described in this document do not always correspond to the optimum conditions for
maximum biodegradation. This is a method of preparing test sediments from coastal seafloor sediments, not a method
of preparing sediments from deep-sea seafloors.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 18830, Plastics — Determination of aerobic biodegradation of non-floating plastic materials in a seawater/
sandy sediment interface — Method by measuring the oxygen demand in closed respirometer
ISO 19679, Plastics — Determination of aerobic biodegradation of non-floating plastic materials in a seawater/
sediment interface — Method by analysis of evolved carbon dioxide
ISO 22404, Plastics — Determination of the aerobic biodegradation of non-floating materials exposed to marine
sediment — Method by analysis of evolved carbon dioxide
ISO 23977-1, Plastics — Determination of the aerobic biodegradation of plastic materials exposed to seawater
— Part 1: Method by analysis of evolved carbon dioxide
ISO 23977-2, Plastics — Determination of the aerobic biodegradation of plastic materials exposed to seawater
— Part 2: Method by measuring the oxygen demand in closed respirometer
ISO 23832, Plastics —
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