Session Chairs: Patricia Corcoran, University of Western Ontario; Sarah Lowe, NOAA Marine Debris Program; Lorena Rios-Mendoza, University of Wisconsin-Superior

This session will gather experts in the field of freshwater plastic debris research to discuss and outline the current state of knowledge, share lessons-learned on techniques and challenges in freshwater systems, and educate the wider marine debris community about upstream effects.

Distribution and impacts of plastic pollution and other marine debris have been well documented in the world’s oceans and marine ecosystems. Researchers have only recently begun to explore the abundance and impacts of plastic debris in freshwater environments, including lakes, tributaries, effluents, and their associated sediments. Although there are similarities between plastics in marine and freshwater environments, recent research suggests that marine-specific protocols and results may not be entirely relevant to freshwater systems, especially in regard to debris size, toxicology pathways, and the role of wind and currents in debris distribution. Plastic particles, whether large or small, have the potential to cause environmental and human health consequences. In addition, the lack of harmonization of analytical methodologies from sampling to analysis hinder the comparison of existing quantitative results.

This session will gather experts in the field of freshwater debris research to discuss and outline the current state of knowledge, share lessons-learned on techniques and challenges in freshwater systems, and educate the wider marine debris community about upstream effects. Plastic debris has been identified on every continent, including Antarctica, and thus, the global scope of the issue will attract speakers from numerous countries. The pervasiveness of plastic and its use on a global scale will incite members of the research community, government and not-for-profit organizations to attend the conference. The session will be an appropriate companion to concurrent oceanic and other marine-focused sessions. Following the conclusion of the session and conference, chairs will develop a summary paper of the current state of research in freshwater environments to be published in a peer-reviewed journal.




Microplastics in riverine sediments and the factors affecting their accumulation

presenting: Patricia Corcoran (University of Western Ontario, Canada); authors: Patricia Corcoran (University of Western Ontario, Canada), Sara Belontz (University of Western Ontario), Kelly Ryan (University of Western Ontario), Paul Helm (Ministry of the Environment and Climate Change)

Reports of microplastic debris in marine and fresh surface waters provide a glimpse into the extent of plastics pollution on a global scale. Microplastics buried in benthic sediment, however, are relatively poorly document because of the challenges faced in separation procedures. The Thames River in Ontario, Canada flows approximately 400 km through agricultural and urban regions before emptying into Lake St. Clair in the Laurentian Great Lakes system. Thirty-five samples and duplicates were collected from river bottom sediment using a petite ponar grab in November and December of 2016. Microplastics were separated from sediment and organic debris by splitting, wet sieving, sodium polytungstate density separation, and microscopy. The 63 μm to 2 mm grain size grade was retained for examination. Every sample contained microplastic particles. Counts ranged from 16 to >10,000 particles/kg dry sediment with an overall fragment-fiber-microbead ratio of 27:67:6. The most abundant fragments were blue and red, whereas fibers were mainly blue and black, and beads were mainly black and gray. A weak correlation was noted between river flow and microplastics abundance, with moderate flow regions averaging greater counts than low and high. Preliminary grain size analysis shows that original samples composed of a considerable mud, clay, and organic matter contained the greatest number of microplastics. Greater particle counts were noted in samples from urban versus rural areas. The results indicate that microplastics abundance in riverine systems is influenced by a variety of factors, including, but not limited to sources, land-use, population density, grain size, and flow rate.


Plastic pirates sample macroplastic litter along rivers from Germany – riverside litter and sources estimated by schoolchildren

presenting: Martin Thiel (UNEP, Chile); authors: Martin Thiel (UNEP, Chile), Katrin Knickmeier (Kieler Forschungswerkstatt), Katrin Kruse (Kieler Forschungswerkstatt), Dennis Brennecke (Kieler Forschungswerkstatt), Alice Nauendorf (Kieler Forschungswerkstatt), Martin Thiel (Universidad Catolica del Norte)

Rivers receive important loads of litter by visitors and terrestrial runoff, but the particular sources of riverine litter have not been identified. Here we used a citizen science approach where schoolchildren examined riverside litter and identified possible sources at over 200 sites along large and small rivers of Germany, covering all large river systems. Abundances of shoreline litter ranged from 0 to 6.08 items m-2 with an average of 0.64 items m-2. Litter comprised plastics (31%), cigarette butts (22%), glass (14%), paper (13%), metal (12%), and other items (such as food leftovers, 8%), indicating mostly contributions from visitors. Along many rivers there were also accumulations of litter that were deposited in the vicinity of the riverside, underlining the fact that visitors leave or directly dump litter along the river. Among the items found was also a high proportion of items potentially dangerous to people, including broken glass, sharp metal objects, used hygiene articles and items containing chemicals (such as batteries and aerosol cans). In the search for litter sources, the schoolchildren likewise identified mainly people who use the rivers as leisure areas (in contrast to people who live in the vicinity or the river itself bringing litter from upstream sources). These results indicate that a large proportion of riverside litter is directly left behind by visitors, highlighting the urgent need for better education in order to protect river environments and reduce input of riverine litter to the marine environment. Financial support: Kiel Science Factory, Federal Ministry of Education and Research, Lighthouse Foundation


Floating macro litter input from rivers to the European Seas

presenting: Daniel Gonzalez Fernandez (University of Cadiz, Spain); authors: Daniel Gonzalez Fernandez (University of Cadiz, Spain), Georg Hanke (Joint Research Centre – European Commission)

Despite the expected high importance of land-based sources of litter to the marine environment, the existing literature shows an important lack of field data and knowledge on this subject. Particularly, riverine litter input data have not been acquired and only estimates are available. Floating macro litter input to the seas is relevant because of its potential direct impact on wildlife through ingestion and entanglement, long range transport and as precursor to microplastics.

The JRC exploratory project RIMMEL was therefore set-up to deliver information about plastic waste entering the European Seas through river systems. A tablet computer application was developed for the harmonized monitoring of floating macro litter. The project operated an international network of scientific observers for field data collection across Europe. Data was acquired by visual observation during monitoring sessions, using the tablet computer application from bridges or other vantage points. The network has collected 800 datasets from 48 rivers in all European Regions over a period of one year, building up a unique database. These datasets correspond to 453 hours of monitoring. This is the first time such data is collected at large scale (17 countries) following a harmonized approach for monitoring and reporting.

Results indicate litter occurrence and type. Most frequent floating macro litter items entering the European seas include plastic fragments and single use items such as plastic bottles and bags. Riverine floating macro litter input over time has a great variability, with an average value of 20 items/hour per river for the whole set of data. These results provide support to European policies such as the Marine Strategy Framework Directive and the EU Circular Economy (Plastic Strategy).


Predicting microplastic behavior in rivers on a US national scale

presenting: Albert Koelmans (Wageningen University, Netherlands); authors: Albert Koelmans (Wageningen University, Netherlands), Christopher Holmes (Waterborne Environmental), Scott Dyer (The Procter & Gamble Company)

Whereas the small scale aquatic behaviour of microplastic particles is rather well understood and large scale models exist for traditional chemicals, no existing models unify these areas of knowledge. Here we provide the first deterministic model that combines the key features of microplastic settling, with a large scale US national model implementation of river network hydrology. We derived depth dependent in-stream first order removal rate constants for microplastics from the Besseling et al. (2017) NanoDUFLOW model and used these as input for the iSTREEM® model (Kapo et al., 2016). NanoDUFLOW provides removal rates while accounting for heteroaggregation, thus gaining realism especially for nanoplastic behavior. Subsequently, the iSTREEM model was used to simulate the emission, transport and water column concentrations of microplastics in rivers on a US national scale. Simulations were based on monitored microplastic data from wastewater treatment plants (WWTPs) and used these to estimate loading rates into WWTPs and receiving rivers in iSTREEM®. River flow rates and estimated depths for over 200,000 individual river sections provided realism with respect to the variability in hydrodynamics within the whole US river network. Our results illustrate that the nested modeling approach provides a powerful tool for prospective scenario analyses. River dynamics appear to lead to a high spatial variability in microplastic concentrations among sections in a river, dependent on their flow, retention time and depth, and on inputs from WWTPs and tributary rivers. Generally, microplastic concentrations decrease with increasing river order. However this is less pronounced for nanoplastics, which are carried much further in the network. Microplastic size thus drives retention with important implications for transport to the oceans.


Analysis of microplastic pollution in Slovenian watercourses and lakes

presenting: Andreja Palatinus (Institute for Water of the Republic of Slovenia, Slovenia); authors: Andreja Palatinus (Institute for Water of the Republic of Slovenia, Slovenia), Mitja Centa (Institute for Water of the Republic of Slovenia), Manca Kovač Viršek (Institute for Water of the Republic of Slovenia), monika Peterlin (Institute for Water of the Republic of Slovenia)

Research focused on microplastic sampling in the Ljubljanica River and Lake Bled using three different methods through the entire water column. We have developed and tested the sampling methodology using a water pump for assessing microplastic and mesoplastic concentrations in water column. 38 samples were collected using three sampling methods: a) surface – epi-neuston net, b) water column – water pump, c) sediment – Van Veen grab. Samples were analyzed thoroughly in a laboratory using two different methods according to the sampling method. Microplastics or mesoplastics were separated from the samples and analyzed according to European Master List of litter. Results show that water pump sampling methodology is more suitable in lakes than in watercourses. The comparison of the microplastic sampling results obtained by an epi-neuston net in the Ljubljanica River and Lake Bled with the sampling results in certain watercourses and lakes around the world demonstrates that the results obtained in Slovenia are comparable to the ones around the world. On the basis of the results of this research, it can be concluded that microplastics are already present in Slovenian watercourses and in lakes which leads to potential ecological problems.


Spatiotemporal Distribution and Characteristic of > 20 μm Microplastics and Annual Load on Nakdong River in South Korea

presenting: Soeun Eo (Korea Institute of Ocean Science and Technology, South Korea); authors: Soeun Eo (Korea Institute of Ocean Science and Technology, South Korea), Young Kyoung Song (Korea Institute of Ocean Science and Technology), Gi Myung Han (Korea Institute of Ocean Science and Technology), Sang Hee Hong (Korea Institute of Ocean Science and Technology), Won Joon Shim (Korea Institute of Ocean Science and Technology)

River is an important pathway for transporting plastics to the oceans. Nevertheless, abundance, composition and load of riverine microplastics, especially less than 300 μm in size, is limited. The Nakdong River, the second largest river, in Korea was investigated spatially and seasonally. Surface water sampling was done in upstream (US), midstream (MS) and downstream (DS) in February (dry season), May (intermediate) and August (wet). Bottom water (DB) was also sampled in downstream. Each 100 L of river water was analyzed in triplicate and >20 μm microplastics was identified using micro-FTIR. Mean abundance of microplastic on Nakdong River was in range of 293 (US, February)-4,760 (DS, August) n/m3. Abundance of microplastic on surface increased downstream in February and August, and DS > US > MS in May. Microplastic abundance was 1.8-3.7 times higher in surface than bottom water in all seasons. Microplastic less than 300 μm accounted for 66%, 81%, 72% of the total abundance in February, May and August, respectively. Dominant polymer type was polyester in February (32%), polypropylene in May (66%) and in August (38%). Fragment was most abundant shape (62-80%), and it was followed by fiber (20-38%). The annual microplastic load in Nakdong River was estimated as 1.2×10¹³ n/y. Top 20 cm surface water transported 9.9×10¹¹ n/y, 1.1×10¹³ n/y was discharged by subsurface water.


Macro and Microplastics: St Louis River Estuary and Lake Superior

presenting: Lorena Rios Mendoza (University of Wisconsin Superior, United States); authors: Lorena Rios Mendoza (University of Wisconsin Superior, United States), Cera Johnson (University of Wisconsin Superior), Maryelle Nyeck Nyeck (University of Wisconsin Superior)

Microplastic particles are a new type of pollution reported in the Great Lakes with unknown impacts in the ecosystem and human health. Little information is currently available on the composition, distribution, or fate of microplastic debris in special in the western end of Lake Superior and St. Louis River Estuary. The aims of this research were to identify possible sources, abundance, and the potential of microplastics to be ingested by fish. Identification and quantification of organochlorine pesticides, polychlorinated biphenyls, and polycyclic aromatic hydrocarbons adsorbed on the surface of plastic particles were determined. In this study, there were 58 samples collected (creeks, rivers, lake water, effluents water from four wastewater treatment plants, and beaches around Lake Superior) during the summers of 2016-17. A manta trawl was used to collect the samples with a duration of one hour. The identification of the type of synthetic polymer was determined using a Fourier transform infrared (FTIR) Micro Spectrophotometer. The microplastics were classified by color, size, pellets, fibers, and fragments. Preliminary results from effluent water from four wastewater treatment plants showed a range of 0.1 to 17.5 plastic particles per liter. The main plastic particles were fibers (cotton, synthetic plastic and mixed cotton-plastic).


Microplastic and anthropogenic litter in rivers: Sources, retention, export, and biological interactions

presenting: Timothy Hoellein (Loyola University Chicago, United States); authors: Timothy Hoellein (Loyola University Chicago, United States), Rachel McNeish (Loyola University Chicago), Samuel Dunn (Loyola University Chicago), Lisa Kim (Loyola University Chicago), Amanda McCormick (University of Wisconsin Madison), Sherri Mason (State University of New York at Fredonia), John Kelly (Loyola University Chicago)

While rivers are considered a conduit of microplastic (particles < 5mm) and anthropogenic litter (AL) to oceans, less is known about its abundance, transport, and biological interactions within freshwater ecosystems. We conducted 2 sets of projects to examine the ecological dynamics of microplastic and AL in rivers. First, we measured microplastic in water column, sediment, macroinvertebrates, and fish in the 8 largest tributaries of Lake Michigan, completed seasonally for 1 year. Watersheds spanned a gradient of urban land-use. Microplastic was found at all sites, but those with agricultural and urban land use had greater concentration and export of particles. Sediment concentrations were higher than water column, suggesting deposition as a sink of microplastic in rivers. Almost all fish and macroinvertebrates collected had microplastic ingestion, with differences by taxon and feeding group. Our second set of projects examined the abundance, distribution, and biofilm colonization of AL in urban rivers. AL abundance and composition was different between benthic and riparian habitats. Within stream reaches, most AL accumulated in debris dams, where it interacts with microbes and macroinvertebrates critical for leaf breakdown. Finally, experimental incubations of different types of plastic revealed the influence of polymer type on microbial primary succession. Results will directly inform policy and engineering advances to prevent or mitigate the effects of microplastic and AL in rivers. Synthesizing research across freshwater and marine disciplines is critical to quantify the physical and biological factors driving the ‘life cycle’ of plastic at a global scale.


Microplastic Ingestion By Several Species of Fish from the Great Lakes

presenting: Keenan Munno (University of Toronto, Canada); authors: Keenan Munno (University of Toronto, Canada), Paul Helm (Ontario Ministry of the Environment and Climate Change), Donald Jackson (University of Toronto), Chelsea Rochman (University of Toronto), Dave Poirier (Ontario Ministry of the Environment and Climate Change), Satyendra Bhavsar (Ontario Ministry of the Environment and Climate Change), Richard Chong-Kit (Ontario Ministry of the Environment and Climate Change), Steve Petro (Ontario Ministry of the Environment and Climate Change)

Microplastics, plastics less than five millimetres in size, come from several sources including industry, consumer products and the breakdown of larger plastic debris, with greater abundances of plastics found near major urban centres. We collected fish in 2015 from nearshore waters of Lake Ontario adjacent to the cities of Toronto and Hamilton, Ontario, to investigate the prevalence of microplastics in fish subjected to inputs from the most populated Canadian region of the Great Lakes. The fish included several species varying in size, feeding strategy (benthic and pelagic) and trophic level. Some of the species are also sportfish which are caught and consumed locally. Abundance and type of microplastics (>125 µm) contained in fish digestive tracts were determined. Preliminary results show that bottom-feeding fish species, with counts ranging up to 223 particles, have a greater abundance of microplastics in their digestive tracts than fish feeding near the surface of the water. Fibers are found to be the most prevalent particle type. Particle abundances and character will be compared to those in water samples collected from the same locations to determine whether certain shapes are more prevalent in fish digestive tracts relative to the surrounding environment, and which sources may contribute most to abundances in fish. This study provides an indication of the role of lake sediments in the exposure of fish to microplastics, and provides information regarding the most abundant types of microplastics and their potential sources. These results, which are the first from highly impacted areas of the Great Lakes, will inform management decisions and policy development to address microplastics.


Microplastics from waste-water treatment plants in Portugal. Preliminary data

presenting: Joana Antunes (FCT UNL, Portugal); authors: Joana Antunes (FCT UNL, Portugal)

Two WWTP were analysed, regarding microplastics: a mixed domestic and industrial wastewater (WWTPA) and a mostly domestic wastewater (WWTP B). Samples were collected at the entrance of the plant and from the treated effluent flowing to the environment. A NaCl saturated solution were added to samples and posteriorly filtered through GFC/C filters in a laminar flow chamber. Particles were sorted by type (fragments, beads, fibres, color and shape), counted, measured and analysed with FTIR (work in progress). A total of 4887 microplastics were observed in 18 samples. 99% of the microplastics analysed were fragments, mostly from treated effluent (average 404 items.100ml-1). Fibres presented a higher percentage in the affluent (85%). Comparing WWTP, the highest accumulation of fragments was registered in the WWTPB affluent. Fibres accumulation were similar in the both WWTP. Significant differences were observed in the treated effluent. WWTP A registered a higher number of fragments (average 783±1069items.100ml-1) in this effluent. This result was not expected and probably occurred due to fragmentation from bigger microplastics into reduced dimensions or probably due to a punctual contamination from the internal WWTP structures. Microplastics analysed had sizes between 89 μm and 3000 μm. Smaller microplastics were observed on the top fraction of samples and the bigger microplastics appeared on the bottom layer in the sludge. This is a work is in progress as part of a master thesis at FCT-NOVA, provides a perception into the impact of WWTP discharges on the environment and recommend a long-term monitoring in future studies.


Removing microplastic particles from samples with high organic matter content: a countrywide investigation of sewage sludge produced across Norway

presenting: Amy Lusher (Norwegian Institute for Water Research (NIVA), Norway); authors: Amy Lusher (Norwegian Institute for Water Research (NIVA), Norway), Rachel Hurley (Norwegian Institute for Water Research (NIVA)), Christian Vogelsang (Norwegian Institute for Water Research (NIVA)), Marianne Olsen (Norwegian Institute for Water Research (NIVA))

Developing methods to investigate the presence of microplastics in the aquatic environment began slightly later than those for the marine environment; however, we are closer to standardized methods having learnt from the challenges encountered in the marine realm. Most methods to extract microplastics from complex matrices rich in organic matter, such as sludge samples encounter difficulties and may not efficiently remove the high volumes of organic material. Furthermore, the lack of standardized methods for sampling and analysis complicates the comparison between the relatively few sludge studies available worldwide. NIVA were given the task to develop appropriate methods to qualitatively and quantitatively characterize microplastic particles in sludge and sediment from Norway. The main objectives were to characterize microplastics in sewage sludge collected from various wastewater treatment plants (WWTPs) in Norway applying different wastewater and sludge treatment technologies and compare the results. As the general sludge characteristics are very dependent on the applied technologies, both for wastewater and sludge treatment, it was first necessary to identify the most appropriate methods for analyzing collected samples. Additionally, these methods should be time- and cost-effective to facilitate future monitoring efforts. Results will be discussed under the framework of method development and inter-site comparisons. We will establish the effect of biosolid processing on microplastic concentrations, in addition to the influence of WWTP characteristics (secondary/tertiary treatment, population equivalent etc.). We also propose a standardized method for ongoing monitoring of WWTP sludge microplastic contamination.


Anthropogenic Contamination of Beer, Sea Salt, and Drinking Water

presenting: Mary Kosuth (University of Minnesota, United States); authors: Sherri Mason (State University of New York at Fredonia, United States), Mary Kosuth (University of Minnesota), Elizabeth Wattenberg (University of Minnesota)

The first peer-reviewed papers to document plastic pollution in the natural world were published over forty-five years ago. Since then, a robust body of work has accumulated and the ubiquity of synthetic polymers in the environment is undisputed. From abandoned gillnets hundreds of meters in length to plankton sized fragments, synthetic polymers have been extracted from remote corners of the Earth’s biosphere. Plastic have been quantified in marine environments that include segments of the pelagic biome, coastal habitats, deep sea sediments, as well as freshwater lakes and associated tributaries. Particles have also turned up in Arctic sea ice, ambient air, and a plethora of biota such as seabirds, aquatic mammals, fish, and benthic invertebrates. While evidence of plastic pollution in the natural world quickly mounts, few studies focus on synthetic polymer contamination in human consumables. This study investigates the presence of synthetic polymers in three specific consumable products: beer, sea salt, and drinking water. The first two studies (beer and salt) focused on consumables purchased within the United States in order to compare to similar studies conducted in other parts of the world. In the third study, 159 tap water samples were collected from seven geographical regions that span five continents. Results will be presented and discussed.