Plastics in the Ocean
- 11:00 Accumulation of microplastics and associated contaminants in aquatic food webs
Authors: Noël Diepens ( Wageningen University ); Albert Koelmans ( Wageningen University )
We present a generic theoretical model (MICROWEB) that simulates the transfer of microplastics and hydrophobic organic chemicals (HOC) in food webs. Simulations with such models can drive experimental or field study designs and/or can be used for prospective risk assessments. We implemented the model for an Arctic case comprised of nine species including Atlantic cod, with polar bear as top predator. We used the model to examine the effect of plastic ingestion on trophic transfer of microplastics and persistent HOCs (PCBs) and metabolizable HOCs (PAHs), spanning a wide range of hydrophobicities. We performed scenario analyses to investigate the effect of (a) increasing share of plastic in the organisms’ diet, (b) equilibrium versus non-equilibrium states for the dissolved and plastic-bound HOCs, (c) chemical metabolisation on food web accumulation of plastic and contaminants, as expected from existing knowledge and theory. In a scenario where HOCs in plastic and water are at equilibrium, PCBs biomagnify less when more microplastic is ingested, because PCBs biomagnify less well from ingested plastic than from regular food. In contrast, PAH biomagnify more when more microplastic is ingested, because plastic reduces the fraction of PAH available for metabolisation. We also explore non-equilibrium scenarios representative of additives that are leaching out, as well as sorbing HOCs, quantitatively showing how the above trends are strengthened and weakened, respectively. The observed patterns were not very sensitive to modifications in the structure of the food web. The model can be used as a tool to assess prospective risks of exposure to microplastics and complex HOC mixtures for any food web, including those with relevance for human health.
- 11:15 Kinetics of POP sorption and additive release of a variety of polymers under Arctic conditions
Authors: Dorte Herzke ( NILU ); Kaori Sakaguchi-Soeder ( 2Institute IWAR, Technische Universität Darmstadt ); Andy Booth ( SINTEF )
The PLASTOX project investigates the ingestion, food-web transfer, and ecotoxicological impact of microplastics (MPs), together with the persistent organic pollutants (POPs), metals and plastic additive chemicals associated with them, on key European marine species and ecosystems. PLASTOX combines field-based observations, laboratory tests and manipulative field experiments to study the ecological effects of MPs. The use of common microplastic reference materials, including a marine litter-derived MP produced from an environmentally weathered fish box, allows a meaningful comparison of data generated by different partners and across the different activities of PLASTOX.
As part of a long-term field experiment conducted at marine locations across Europe (Mediterranean to Arctic), a range of different virgin polymer pellets (LDPE, PP, PS and PET), as well as post-use plastics and marine litter-derived MP particles, were deployed submerged in the small boat harbor at Tromsø, Northern Norway and Ny Ålesund, Svalbard for up to 12 months. The deployment device consisted of an empty stainless steel canister, with the various plastic types placed in reusable, empty teabags made of PP, placed separately in nylon netting. Sampling was conducted 1 week, 1 month, 3 months, 6 months and 12 months after deployment. Hydrophobic POPs including PCBs, DDTs, PBDEs and pesticides were measured to establish the adsorption kinetics in seawater under Arctic conditions. Samples were extracted using ultrasound and nonpolar solvents, followed by GPC and SPE clean up. Chemical analyses using GC/Orbitrap-HRMS and GC/qMS was done in the laboratories of the TU Darmstadt and NILU, Tromsø.
The concentrations for adsorbed POPs on the post-use polymers continued to change over the 12 month deployment period, indicating that an adsorption equilibrium could not be reached. Furthermore, PCB concentrations were typically between one and two orders of magnitude lower than concentrations observed for virgin polymer pellets deployed in temperate environmental conditions (San Diego Bay, US) (Rochman et al., 2013). This indicates that the environmental conditions in Arctic regions have a significant influence on adsorption processes and kinetics.
- 11:30 Microplastics as passive samplers of organic contaminants in the sea -- results from field studies in Norway
Authors: Katrin Vorkamp ( Aarhus University ); Anders Karlsson-Drangsholt ( Bellona Foundation ); Erik Burgerhout ( Nofima AS ); Noël Diepens ( Wageningen University ); Albert A. Koelmans ( Wageningen University ); Velmurugu Puvanendran ( Nofima AS ); Ivar Rønnestad ( University of Bergen ); Helge Tveiten ( Nofima AS ); André S. Bogevik ( Nofima AS )
Microplastics are polymer particles with a diameter of less than 5 mm. Their presence in the oceans results from use and discharge of commercial products or from the degradation of plastic debris in the sea. Several types of polymers, such as polyoxymethylen (POM), polydimethylsiloxane (PDMS) or polyethylene (PE), have been used as passive samplers to assess pollution in the marine environment. They accumulate organic contaminants over time until equilibrium is reached between the passive sampler and the surrounding seawater. Microplastics in the sea can act as passive samplers in the same way. Taken up by organisms, microplastics can thus become a source of contaminant exposure.
The project PlastiCod has studied the contaminant accumulation on microplastics in the sea and the subsequent uptake by Atlantic cod (Gadus morhua). For the field studies, industry PE was sieved to a particle size of 0.3-0.6 mm, filled in two permeable bags and placed in the sea at ten locations along the coast of Norway, including stations in northern Norway (Honningsvåg, Kirkenes). The positions of the bags were at least 50 m away from the shore and at a depth of at least 10 m. POM and PDMS sheets were deployed alongside the PE for comparison purposes. The samples were retrieved after about four months and analysed for polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCD), chlordane-related pesticides and toxaphene. The PE material was dried in the fume hood prior to Soxhlet extraction. The analysis of POM and PDMS followed previously published methods.
The contaminant concentrations in the PE were generally low. Amongst the PBDEs, for example, only BDE-47 and BDE-99 were widely detectable. The concentrations were generally highest for PCBs, ranging from about 0.1 to 3 ng/g dry PE for the sum of the seven indicator PCB congeners. PE samples from two bags differed considerably in their contaminant concentrations at some locations, while others showed good agreement. The highest concentrations were found in samples deployed in the inner Oslofjord and the lowest for samples from Kirkenes. Honningsvåg had generally higher concentrations than Kirkenes. The geographical distribution was similar for different contaminant groups, but not identical, indicating local phenomena.
The data will be further analysed, also in comparison to POM and PDMS concentrations. The results will contribute to our understanding of the role of microplastics as passive samplers of contaminants and thus of risks potentially associated with their uptake in the food web.
- 11:45 Is rubber from end-of-life car tires a source for pollutants and harmful effects in the Arctic marine environment?
Authors: Dorte Herzke ( NILU ); Claudia Halsband ( Akvaplan NIVA ); Lisbeth Sørensen ( SINTEF ); Andy Booth ( SINTEF )
Rubber microplastic (RMP) granules (≤ 5 mm in size) produced from discarded vehicle tires are used in large quantities on synthetic turf sports pitches. In Arctic coastal communities, RMP transport by wastewater effluents and terrestrial runoff is considered a significant source of MP to the Arctic marine environment. Their persistence and long residence time in the Arctic marine environment means RMP pose a potential health risk for Arctic wild life through direct ingestion, especially at the for organisms from the lower part of the marine food chain. Importantly, RMP may provide an exposure route to marine organisms for the additive chemicals and metals present in tires. In an interdisciplinary project, we studied the composition, additive leaching and environmental impacts of RMP from three sources: collected in situ from sports pitches in Trondheim and Tromsø; and 'fresh' granulate sourced directly from a producer. Arctic marine environments present special abiotic conditions for the release of additives from RMP, with cold water temperatures and long periods with unlimited sunlight. Over a 12 month period, RMP were deployed in the ocean in stainless steel containers and sub-sampled continuously to measure changes in the levels of metals and additives. To assess the release of additives from RMP into the seawater, leaching kinetics in seawater were established over a 14 day period under controlled laboratory conditions. Large quantities of metals (especially Zn) and additives (e.g. benzothiazole) leached from the RMP and were detected in the seawater. Although present in the RMP, only small quantities of polycyclic aromatic hydrocarbons (PAHs) were detected in the leachates. To assess the impacts of RMP additives, seawater leachates were produced under the same laboratory conditions for use in exposure experiments with two calanoid copepod species (Calanus sp. and Acartia longiremis) representing Arctic low-trophic organisms. Exposure experiments were conducted using serial dilutions of the leachates and mortality rate was the selected endpoint. A clear dose-response was observed, with high mortalities within 72 h at high (15-100%) leachate concentrations. Implications for ecosystem-level impacts will be presented in the conference.
Thursday 24th January 2019
11:00 - 12:00