ISO 19679:2020 pdf free download.Plastics Determination of aerobic biodegradation of non floating plastic materials in a seawater/sediment interface Method by analysis of evolved carbon dioxide.
Products made with biodegradable plastics are designed to be recovered by means of organic recycling in composting plants or in anaerobic digesters. The uncontrolled dispersion of biodegradable plastics in natural environments is not desirable. The biodegradability of products cannot be considered as an excuse to spread wastes that should be recovered and recycled. However, test methods to measure rate and level of biodegradation in natural environments (such as soil or the marine environment) are of interest in order to better characterize the behaviour of plastics in these very particular environments. As a matter of fact, some plastics are used in products that are applied in the sea (e.g. fishing gear) and sometimes they can get lost or put willingly in the marine environment. The characterization of biodegradable plastic materials can be enlarged by applying specific test methods that enable the quantitative assessment of biodegradation of plastics exposed to marine sediment and seawater. Plastic products are directly littered or arrive with fresh waters in the pelagic zone (free water). From there, and depending on density, tides, currents, and marine fouling plastics can sink to the sublittoral, and reach the seafloor surface. Many biodegradable plastics have a density higher than 1 and therefore tend to sink. The sediment passes from aerobic to anoxic and finally anaerobic conditions going from the surface (the interface with seawater) into deeper layers, displaying a very steep oxygen gradient.
ISO 19679 specifies a test method to determine the degree and rate of aerobic biodegradation of plastic materials when settled on marine sandy sediment at the interface between seawater and the seafloor, by measuring the evolved carbon dioxide (C02). This test method can also be applied to other solid materials.
This test method is a simulation under laboratory conditions of the habitat found in different seawater/ sediment-areas in the sea, e.g. in a benthic zone where sunlight reaches the ocean floor (photic zone) that, in marine science, is called sublittoral zone
The determination of biodegradation of plastic materials and other solid materials buried in marine sediment is outside the scope of ISO 19679.
NOTE Measurement of aerobic biodegradation can also be obtained by monitoring the oxygen consumption, as described in ISO 18830.
The conditions described in this document do not always correspond to the optimum conditions for the maximum degree of biodegradation to occur.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
part of the organic carbon in water which cannot be removed by specified phase separation methods, for example by centrifugation at 40 000 ms-2 for 15 mm or by membranes with pores of 0,2 Itm to 0.45 lm diameter
3.4
pre-conditioning phase
pre—incuhation of an inoculum under the conditions of the subsequent test in the absence of test material, with the aim to consume potential organic matter present in excess that could disturb biodegradation measurement and to improve the acclimatization of the microorganisms to the test conditions
4 Principle
This test method is based on the determination of evolved CO2 and derives from Iso 14852. The testing medium Is based on a solid phase and a liquid phase. The solid phase Is a sandy marine sediment laid in the bottom of a closed flask; the liquid phase is a column of natural or artificial sea water, poured on the sediment. The test material is preferably in the form of a film to be laid down on top of the sediment, at the interface between the solid phase and the liquid phase. This is a simulation of an object that has sunk and finally reached the sea floor. The system is contained in a closed flask.
The CO2 evolved during the microbial degradation is determined by a suitable analytical method. The level of biodegradation is determined by comparing the amount of CO2 evolved with the theoretical amount (ThCO2) and expressed in percentage. The test result is the maximum level of biodegradation, determined from the plateau phase of the biodegradation curve. The principle of a system for measuring evolved CO2 is given in ISO 14852:2018, Annex A.
The details of interlaboratory testing based on the test method specified in this document are available in Reference [1.
5 Test environment
Incubation shall take place in the dark or in diffuse light in an enclosure which is free from vapours inhibitory to microorganisms and which is maintained at a constant temperature, preferably between 15 °C to 25 °C. but not exceeding 28 °C, to an accuracy of ± 2 °C. Any change in temperature shall be justified and clearly indicated in the test report.
6.3 Natural seawater/sediment.
Take a sample of a sandy sediment and seawater with a shovel beneath the low-water line into a bucket. Transfer the wet sediment together with seawater into sealed containers for transport and fast deliver it to the laboratory. After delivery, conserve the sediment at low temperature (approximately 4 °C) until use. The seawater/sediment sample should be preferably used within 4 weeks after sampling. Record storage time and conditions.
NOTE Seawater and sediment can also be sampled from large, well-running public marine aquaria.
Measure the TOC, pH and nitrogen content of the sediment and of the natural seawater if used instead of artificial seawater. The carbon content of sediment should he in the range of 0.1 % to 2%.
A preliminary oxidation can be applied to the sediment in order to decrease the organic matter content and the background respiration. Sediment and seawater are fluxed with air and gently stirred (max. 20 r/min to 30 r/min) in a large container for the desired period of time. Include this pretreatment process in the test report.
7 Apparatus
7.1 Test flasks.
Biometer flasks of the volume of about 250 ml are appropriate. Reactors with higher volumes can be used, if test conditions are not affected. The vessels shall be located in a constant-temperature room or in a thermostatic apparatus (e.g. water-bath). Stirring can be applied on seawater on condition that it does not disturb the sediment/seawater interface.
NOTE A suitable apparatus is shown in Eigi.ireAl. An example of a stirred apparatus is given in OECO TG 308:
2002, Annex 4171.
7.2 Container for the CO2 absorber.
A glass beaker to be located in the headspace of the reactor and filled with 10 ml of Ba(O[1)2 0.0125 rnol/l or with 3 ml of KOH 0,5 mol/l.
7.3 Analytical balance, shall have a sensitivity of at least 0,1 mg.
8.2 Reference material
Use ashless cellulose filters as a reference material’), If possible, the TOC, form, and size should be comparable to that of the test material. As a negative control, a non-biodegradable polymer (such as polyethylene) in the same form as the test material shall be used.
8.3 Preparation of the sediment
Filter the sediment in a funnel with a coarse filter paper to eliminate excess seawater. Sediment is ready for testing when dripping of sea water is ended. Sediment after filtering Is named “wet sediments hereafter.
8.4 Test setup
Provide several flasks, so that the test includes at least the following:
a) three flasks for the test material (symbol FT);
b) three flasks for the blank (symbol Fe);
c) three flasks for reference material (symbol Fc);
d) three flasks for negative control (symbol FN).
Two flasks for test material, blank, reference material, and negative control may be used instead of three for screening purposes.
8.5 Pre-conditioning phase
In a typical case, use a test flask with a volume of 250 ml. Put 30 g of the wet sediment on the bottom of the flask. Carefully pour 70 ml of natural or artificial seawater. Reactors with higher volumes can be used, if test conditions are not affected. The test should be performed with a water/sediment volume ratio between 3:1 and 5:1 and a sediment layer of about 0,3cm to 0,5 cm, depending on the granulometry of the sediment.