Session Chairs: George Papatheodorou, Department of Geology, University of Patras; Hrissi Karapanagioti, University of Patras
This session is focused on marine debris scientists dealing with environmental degradation and floating, beached and benthic plastic litter.
Plastics are ubiquitous in the marine environment and present even on the most remote areas of the planet. The boom in the global plastic production is reached up to 280 million tons in 2012. The imprudent use of plastics in our everyday life has elevated plastics into a major environmental threat. The generated plastic waste in 192 coastal countries in 2010, has been estimated at approximately 275 million metric tons (MT), from which 4.8–12.7 million MT have entered the oceans. For the synthetic polymers, the degradation process starts once they are deposited into the oceans, mainly due to the synergistic effect of environmental variables and the inherent material instability. Nonetheless, the degradation rate of the polymers is significantly slow, which makes them extremely persistent. Thus, plastics can last in the marine environment for decades or even hundreds of years when in surface; likely far longer when in deep sea.
Most synthetic polymers (polyethylene, polypropylene) are buoyant in waters while other (high-density polyethylene, polyethylene terephthalate) may sink. The torpid degradation of the large plastic items, will result in the formation of small fragments (< 5 mm); microplastics. Both plastics and microplastics have adverse effects on the marine biota. They may collocate with microorganisms, invertebrates and microbial communities, and even form plastiglomerates. Although there are many studies on the degradation of plastic in the laboratory by polymer scientists there are only limited studies on the environmental degradation of plastic in the marine and coastal environment. This session will address topics on identification and characterization of plastic, determination of the alterations, identification of possible mechanisms of degradation, dating of plastics and estimation of lifetime of plastics in the environment. This session will accept studies based on samples from field surveys and also studies from laboratory experiments. However, priority will be given to studies that provide characterization of plastic samples collected from the field.
Abstracts
Investigating Physical and Chemical Degradation of Plastics using Open Ocean Microplastic Samples and Laboratory and Field Weathering Experiments
presenting: Kara Lavender Law (Sea Education Association, United States); authors: Kara Lavender Law (Sea Education Association, United States), Jessica Donohue (Sea Education Association), Theophilos Collins (Sea Education Association), Katherine Pavlekovsky (Sea Education Association), Julia McDowell (Sea Education Association), Anthony Andrady (North Carolina State University), Giora Proskurowski (MarqMetrix)
There is currently no method to determine how long microplastics floating at the sea surface have undergone environmental weathering, how quickly fragmentation has occurred, and how these processes might vary according to polymer type in the marine environment. We conducted laboratory and field exposure experiments to address these questions, and also meticulously examined physical and chemical characteristics of more than 5000 open ocean microplastic particles for clues about their weathering history.
Microplastics collected using surface plankton nets by Sea Education Association in the western North Atlantic, eastern North Pacific, Mediterranean and Caribbean Seas since 1991 were analyzed to determine polymer type and particle size, mass and form. We hypothesized that particle characteristics, alone or in combination, are a relative indicator of age (time of exposure), where particles in subtropical gyre accumulation zones differ from those in regions closer to presumed sources, such as coastal areas and in enclosed marginal seas. A subset of collected particles whose original form is known – resin pellets – were also analyzed using FTIR-ATR and other methods for signatures of chemical degradation that are related to physical weathering characteristics. In parallel, exposure experiments on virgin plastic resins were conducted in laboratory experiments with seawater, and in two marine field exposure sites to evaluate changes in physical and chemical characteristics on a known exposure time scale. The major results of these combined studies offer clues to polymer-dependent degradation mechanisms and time scales in the marine environment.
Deterioration of plastics in air and sea water
presenting: Nicolas Biber (University of Plymouth, United Kingdom); authors: Nicolas Biber (University of Plymouth, United States), Richard Thompson (University of Plymouth), Andy Foggo (University of Plymouth)
Plastic an abundant solid contaminant in the marine environment. Despite their durability, plastics deteriorate into fragments due exposure to UV radiation and mechanical stress. This contributes to the accumulation of microplastics, which are defined as plastic particles smaller than five millimetres. Microplastic particles have been detected in the marine environment on a global scale. The occurrence of microplastic contamination can result from direct introduction of microplasticised pieces, for example form their use as abrasive particles in cosmetics, and from the fragmentation of larger items in the environment. A number of possible deterioration processes, such as mechanical wear and oxidation have previously been described. However, the rate and extent of deterioration of plastics in the natural environment remains largely unknown. This study aimed to describe deterioration of some commonly used types of plastics in the natural environment. Samples of polymers (biothene, polyethene, polystyrene and poly(ethylene terephthalate)) were deployed in seawater and air for 600 days . Subsamples of each material were collected from these environments at intervals over a twenty-month period. Their deterioration was measured through changes in tensile properties and molecular composition. Deterioration occurred much more rapidly in air than in sea water, which was attributed to reduced UV radiation and oxygen availability in water. Deterioration in air led to changes in tensile properties. With materials becoming more brittle their capacity for tensile extension was reduced. Tensile extension also decreased in material samples that were exposed in sea water even though no oxidation was measured. This suggests that the deterioration of plastics in marine environments can result from factors other than UV radiation.
presenting: Juan Carlos Alvarez Zeferino (Universidad Autónoma Metropolitana, Mexico); authors: Juan Carlos Alvarez Zeferino (Universidad Autónoma Metropolitana, Mexico), Alethia Vázquez Morillas (Universidad Autónoma Metropolitana), Margarita Beltrán Villavicencio (Universidad Autónoma Metropolitana), Lidia Silva Iñiguez (Universidad de Colima), Ojeda-Benitez Sara
The plastic wastes are problematic around the world, the problems associated with the environment in special the marine zones have been the center of attention lately from society, government, and academia.
The plastic residues remain for prolonged periods in the environment, causing affectation to the organisms, which can be ingested or entangled. Faced with this problem, new materials have been developed with the aim of reducing the impact on the environment, however, their designs have been developed to biodegrade or degrade under specific conditions and not in marine conditions.
In the present work, we studied the degradation of plastics in three marine conditions (buoy, boulders beach, and sand beach) in the port of Manzanillo Colima, México, for 60 days. We evaluated five different types of plastic: low-density polyethylene (LDPE), high-density polyethylene (HDPE), oxodegradable high density polyethylene (OXO-HDPE), oxodegradable high density polyethylene subjected to weathering (OXO-HDPE-W) and the compostable film ECOVIO® from BASF. The plastics were cut in strips of 1 x 10 cm and 30 samples of each plastic were placed in a PVC mesh cage.
The plastic that showed the major degradation was ECOVIO in all conditions, the beaches of boulders and sand presented the greatest degradation in comparison with the plastics that were in the buoy. The above allows assuming that the friction with sediments is one of the most important factors that contribute to the degradation of plastics
The degradation of plastics in marine environments must be prevented because when exposed to the weather the plastics are converted into microplastics, which are difficult and even impossible to remove.
Artificial ecosystem selection for marine polymer degradation
presenting: Robyn Wright (University of Warwick, United Kingdom); authors: Robyn Wright (University of Warwick, United Kingdom), Matthew Gibson (University of Warwick), Joseph Christie-Oleza (University of Warwick)
Up to 12.7 million tons of plastics are thought to enter the oceans every year, and this figure is likely to increase. As recalcitrant synthetic polymers, plastics are notoriously difficult to degrade in the marine environment and are therefore expected to persist for hundreds of years. To learn about the likely fate of these synthetic polymers in the ocean, we can investigate the fate of recalcitrant natural marine polymers, which are biodegraded by marine bacteria. Research has shown that microbial communities and consortia degrade environmental contaminants more efficiently than single strains, yet through artificial selection of whole communities, it is possible to attain consortia that are even more efficient at degrading contaminants. Here, we used an artificial selection method to evolve a community (isolated from coastal marine debris) to be better at degrading chitin, an abundant but recalcitrant natural polymer. We found that the evolved community exhibited higher chitinase activity, and therefore higher potential to degrade chitin, than the original community, and may be able to degrade chitin more completely and efficiently than an individual strain. This community is currently being characterised using MiSeq. We are also applying the same method to explore the degradability of the commonly used packaging plastic poly(ethylene terephthalate) (PET). Here, the community that is best at degradation is determined based upon its ability to grow with PET as the sole carbon source. The evolution is monitored via a combination of metabolic and enzyme activity assays, clear zone plates and changes in the chemical composition and weight of PET films exposed to these communities. The results of this study will inform us on the potential for microbial communities to develop the ability to degrade marine plastics.
A model study to explore the kinetics of polymer fragmentation in aquatic environment.
presenting: Fanon JULIENNE (IMMM, France); authors: Fanon JULIENNE (IMMM, France), Nicolas DELORME (IMMM), Taco NICOLAI (PCI), Christophe CHASSENIEUX (PCI), Fabienne LAGARDE (IMMM)
Degradation of non biodegradable polymers in the aquatic environment is a sum of complex phenomena such as photodegradation, thermal oxidation and hydrolysis. Importance of a specific factor such as temperature, biofouling, UV light, polymer chemistry and thickness and kinetics of fragmentation are relatively unknown. To provide a better understanding of these processes and to predict the evolution of microplastics environmental concentrations, laboratories experimentation are needed. The present study aimed to determine the kinetics of abiotic degradation and fragmentation of polymers as a function of environmental conditions. A first insight into the statistical analysis of the size distribution of generated fragments is obtained.
Polymer films were machined by blown extrusion to perfectly control their structure and thickness and were placed during several months in an aging chamber under controlled conditions. During all the experiment, the films were regularly analyzed through spectroscopy (UV-visible, IR, Raman) and water contact angle measurements to investigate kinetics of degradation. SEM and polarized light pictures were also taken to follow the fragmentation.
For polyethylene (PE), it appeared that weathering strongly affected all physico-chemical properties (chemical composition, hydrophobicity, crystallinity). Polymer breakdown occurred faster in water than at air and despite high carbonyl indices, fragmentation did not lead to nano-fragments in noticeable amount. The number of generated micro and milli-sized fragments did not increase linearly vs time. Moreover, some of the PE fragments exhibited an increase in their density leading to a sub-surface position in the water column, which might be of great importance in the mass balance budget of polymers at the oceanic surface.
Degradation of the Mulch Plastic in Soil Environment by photodegradation and biodegradation
presenting: Yüksel Ardali (Ondokuz Mayıs University, Turkey); authors: Yüksel Ardali (Ondokuz Mayıs University, Turkey)
Plastics as polyethylene are widely used in packaging and other agricultural applications. They accumulate in the environment at a rate of 25 million tons per year. Thus, the development and use of degradable plastics was proposed as a solution for plastic waste problem. Because of the ever-increasing use of plastic films, nowadays, biodegradability has become a useful characteristic for plastics. Conversely, the introduction of biodegradable plastics has generated a need for methods to evaluate the biodegradation of these polymers in landfills and solid waste treatment systems such as composting or anaerobic digestion treatment plants. The purpose of this study was to investigate climatic and soil factors responsible for the degradation of biodegradable plastics in soil environment were analyzed in soil 12 months. Degradation was determined every month by collecting sample specimens for the measurement of weight loss, percentage elongation, relative viscosity and FTIR spectrum. The tested plastic samples were found to be degradable in soil but the amount of total carbon, the pH, and the soil texture did not show a good correlation with the degradation of plastics.