Quantification and characterization of macro- and mesoplastic items in the water column of the river Waal

Although studies on plastic concentrations mainly focus on the marine environment, recently, an increasing number of studies point out environmental consequences in freshwater environments around the world. However, there still is a paucity of field data on the abundance of riverine plastic items, in particular in the water column. In this study, we provide an overview of macro- and mesoplastic concentrations, categories, ages, and origin over several years in the water column of the river Waal, in the Netherlands. The river water column was passively sampled at two selected locations using a stow net at very low and low discharges (range 537 - 1345 m³.s^-1). The most dominant macro- and mesoplastic categories were 'Miscellaneous plastic waste', including "Plastic film 2.5 - 50 cm (soft)" and "Plastic film 0 - 2.5 cm (soft)" as main categories. Macro- and mesoplastic categories were found to show limited variability during several years of monitoring. The mean macroplastic concentration (± SD) ranged between 2.2 × 10^-3 ± 0.001 and 7.4 × 10^-3 ± 0.003 particles.m^-3 for October 2020 and November 2018, respectively. In 2020, the plastic concentrations showed a sharp decrease compared to the previous years, most likely as a consequence of the COVID-19 crisis. The origin of the plastics (e.g., countries) also showed little variability during monitoring. The consistency of several characteristics of the collected plastic suggests that the same sources were responsible for the macro- and mesoplastic input into the river Waal during low discharges and over multiple years. We present the first temporal assessment of macro- and mesoplastic concentrations and composition in the water column of the river Waal. The outcome of the current study can be used to support the development of management measures by decision makers.

Characteristics and fluxes of plastic debris based on socio-economic data for Patos Lagoon-a choked coastal Lagoon in South Brazil

Patos Lagoon, located in southern Brazil, is the world's largest choked coastal lagoon. Studies have revealed that plastic pollution affects lagoons; however, to date, they have only focused on a few limited regions of the lagoon. Top-down quantification methods based on socio-economic data from 2010 to 2017 were used to measure the amount of plastic reaching Patos Lagoon, thus broadening the perspective of plastic pollution in this area. According to the findings, Patos Lagoon's hydrographic regions produced an average of 4.54 Mton of plastic during the studied period. 1.86 Mton was consumed on average. High- and low-density polyethylene (HDPE and LDPE, respectively), polypropylene (PP), and polyvinyl chloride (PVC) were the main resins produced. Food-related activities were the largest consumer of plastic (17.98%), indicating a higher amount of single-use plastics being used in the basin. The preforms for plastic bottles, bags, and packaging were the most commonly manufactured plastic utensils. An estimated 8 to 14% of all plastics used to end up as mismanaged waste in the Patos Lagoon hydrographic basin. This resulted in 1.73 and 10.72 Kton, or 0.5 and 3.2 g/per person/per day, of plastic waste flowing into the waters of Patos Lagoon throughout the study period. These findings can help focus on management efforts by providing managers and policymakers with information for better plastic pollution mitigation in this environment.

Microplastics and co-pollutant with ciprofloxacin affect interactions between free-floating macrophytes

Microplastic and antibiotic contamination are considered an increasing environmental problem in aquatic systems, while little is known about the impact of microplastics and co-pollutant with antibiotics on freshwater vascular plants, particularly the effects of interactions between macrophytes. Here, we performed a mesocosm experiment to evaluate the impact of polyethylene-microplastics and their co-pollutants with ciprofloxacin on the growth and physiological characteristics of Spirodela polyrhiza and Lemna minor and the interactions between these two macrophytes. Our results showed that microplastics alone cannot significantly influence fresh weight and specific leaf area of the two test free-floating macrophytes, but the effects on photosynthetic pigments, malondialdehyde, catalase and soluble sugar contents were species-specific. Ciprofloxacin can significant adverse effects on the growth and physiological traits of the two test macrophytes and microplastic mitigated the toxicity of ciprofloxacin on the two free-floating plants to a certain extent. In addition, our studies showed that microplastics and co-pollutants can influence relative yield and competitiveness of S. polyrhiza and L. minor by directly or indirectly influencing their physiology and growth. Therefore our findings suggest that species-specific sensibility to microplastic and its co-pollutant among free-floating macrophytes may influence macrophyte population dynamics and thereby community structure and ecosystem functioning. And microplastics altered other contaminant behaviours and toxicity, and may directly or indirectly influence macrophytes interactions and community structure. The present study is the first experimental study exploring the effects of microplastics alone and with their co-pollutants on interactions between free-floating macrophytes, which can provide basic theoretical guidance for improving the stability of freshwater ecosystems.

Microplastic sampling techniques in freshwaters and sediments: a review

Pollution by microplastics is of increasing concern due to their ubiquitous presence in most biological and environmental media, their potential toxicity and their ability to carry other contaminants. Knowledge on microplastics in freshwaters is still in its infancy. Here we reviewed 150 investigations to identify the common methods and tools for sampling microplastics, waters and sediments in freshwater ecosystems. Manta trawls are the main sampling tool for microplastic separation from surface water, whereas shovel, trowel, spade, scoop and spatula are the most frequently used devices in microplastic studies of sediments. Van Veen grab is common for deep sediment sampling. There is a need to develop optimal methods for reducing identification time and effort and to detect smaller-sized plastic particles.

Microplastics in aquatic environment: characterization, ecotoxicological effect, implications for ecosystems and developments in South Africa

Microplastics are small-size plastic piece scales (particles < 5 mm) in sediments and waters which interact with environment and organisms by various means. Microplastics are becoming a universal ecological concern since they may be a source of hazardous chemicals to marine organisms and environments. Recent research suggests microplastics could enable the transfer of hydrophobic aquatic pollutants or chemical additives to biota. Even though microplastic presence and interactions are recently being detected in marine and freshwater systems, the fate of microplastics is still very poorly understood. This literature review is a summary of the sources and transport of microplastics, their interactions with toxic chemicals and the methodologies for chemical quantification and characterization of microplastics. The environmental outcome and impact of microplastics in wastewater treatment plants were assessed as well as the trends and update on microplastic research in the South African aquatic ecosystem.

Microplastics in a freshwater mussel (Anodonta anatina) in Northern Europe

Alarming amounts of microplastics have recently been shown to accumulate in the environment. Recent focus has been on synthetic material contaminating the marine environment, while effects on freshwater habitats and organisms have received less attention. We here confirm and analyse occurrence of microplastics in the duck mussel, Anodonta anatina, in a Swedish river. All analysed mussels contained microplastics, and the number of microplastic debris found in the mussels increased with mussel size. In addition, we demonstrate higher concentrations of microplastics downstream urban areas with wastewater treatment plants compared to a rural upstream location. Both fibres and particles were found in the mussels, indicating that the emissions of these pollutants may have varying origin. Our study indicates that microplastics can be suspended in the water column in streams and that concentrations are higher downstream anthropogenic activity. We discuss our results in light of potential pathways in rural versus surrounding arable land, and highlight a number of required research directions in the aquatic system.

Water Quality Monitoring to Support Cumulative Effects Assessment and Decision Making in the Mackenzie Valley, Northwest Territories, Canada

Project proponent- and government-led environmental monitoring are required to identify, understand, and manage cumulative effects (CE), yet such monitoring initiatives are rarely mutually supportive. Notwithstanding the need for a more integrated and complementary approach to monitoring, monitoring efforts are often less effective than intended for addressing CE. This paper examines current monitoring programs in the Mackenzie Valley, Northwest Territories, Canada, based on 7 attributes: consistency, compatibility, observability, detectability, adaptability, accessibility, and usability. Results indicate a tenuous link between and across proponent-led monitoring requirements under project-specific water licenses and government-led monitoring of regional baseline conditions. There is some consistency in what is monitored, but data are often incompatible, insufficient to understand baseline change, not transferable across projects or scales, inaccessible to end users, and ultimately unsuitable to understanding CE. Lessons from the Mackenzie Valley highlight the need for improved alignment of monitoring efforts across programs and scales, characterized by a set of common parameters that are most useful for early detection of cumulative change and supporting regulatory decisions at the project scale. This alignment must be accompanied by more open and accessible data for both proponents and regulators, while protecting the sensitivity of proprietary information. Importantly, there must be conceptual guidance for CE, such that the role of monitoring is clear, providing the types of CE questions to be asked, identifying the hypotheses to be tested, and ensuring timely and meaningful results to support regulatory decisions. © 2019 SETAC.

A new approach for the agglomeration and subsequent removal of polyethylene, polypropylene, and mixtures of both from freshwater systems - a case study

Based on a new concept for the sustainable removal of microplastics from freshwater systems, a case study for a pH-induced agglomeration and subsequent removal of polyethylene and polypropylene particles from water is presented. The two-step-based process includes firstly a localization and secondly an aggregation of microplastic particles (250-350 μM) in a physicochemical process. The research describes a strong increase in the particle size independent of pH of the aquatic milieu induced by the addition of trichlorosilane-substituted Si derivatives. The resulting Si-based microplastic aggregates (particle size after aggregation is 2-3 cm) could be easily removed by use of, e.g., sand traps. Due to the effect that microplastic particles form agglomeration products under every kind of process conditions (e.g., various pH, various polymer concentrations), the study shows a high potential for the sustainable removal of particles from wastewater.

Mountains to the sea: River study of plastic and non-plastic microfiber pollution in the northeast USA

Aquatic environments are sinks for anthropogenic contamination, whether chemical or solid pollutants. Microfibers shed from clothing and other textiles contribute to this problem. These can be plastic or non-plastic origin. Our aim was to investigate the presence and distribution of both types of anthropogenic microfibers along the length of the Hudson River, USA. Surface grab samples were collected and filtered through a 0.45μm filter paper. Abundance of fibers was determined after subtraction of potential contamination. 233 microfibers were recorded in 142 samples, averaging 0.98microfibersL^-1. Subsequent micro-FTIR showed half of the fibers were plastic while the other half were non-plastic, but of anthropogenic origin. There was no relationship between fiber abundance, wastewater treatment plant location or population density. Extrapolating from this data, and using available hydrographic data, 34.4% of the Hudson River's watershed drainage area contributes an average 300 million anthropogenic microfibers into the Atlantic Ocean per day.

Stability of single dispersed silver nanoparticles in natural and synthetic freshwaters: Effects of dissolved oxygen

Silver nanoparticles (AgNPs) are increasingly used in various commercial products. This increased use raises ecological concerns because of the large release of AgNPs into the environment. Once released, the local water chemistry has the potential to influence the environmental fates and behaviors of AgNPs. The impacts of dissolved oxygen and natural organic matter (NOM) on the dissolution and stability of AgNPs were investigated in synthetic and natural freshwaters for 7 days. In synthetic freshwater, the aggregation of AgNPs occurred due to the compression of the electric double layer, accompanied by the dissolution of AgNPs. However, once oxygen was removed, the highest dissolved Ag (Ag_dis) concentration decreased from 356.5 μg/L to 272.1 μg/L, the pH of the AgNP suspensions increased from less than 7.6 to more than 8.4, and AgNPs were regenerated by the reduction of released Ag⁺ by citrate. The addition of NOM mitigated aggregation, inhibited oxidative dissolution and induced the transformation of AgNPs into Ag₂S due to the formation of NOM-adsorbed layers, the reduction of Ag⁺ by NOM, and the high affinity of sulfur-enriched species in NOM for Ag. Likewise, in oxygen-depleted natural freshwaters, the inhibition of oxidative dissolution was obtained in comparison with oxygenated freshwaters, showing a decrease in the maximum Ag_dis concentration from 137.6 and 57.0 μg/L to 83.3 and 42.4 μg/L from two natural freshwater sites. Our results suggested that aggregation and dissolution of AgNPs in aquatic environments depend on the chemical composition, where oxygen-depleted freshwaters more significantly increase the colloidal stability. In comparison with oxic conditions, anoxic conditions were more favorable to the regeneration of AgNPs by reducing species (e.g., citrate and NOM) and enhanced the stability of nanoparticles. This indicates that some AgNPs will be more stable for long periods in oxygen-deprived freshwaters, and pose more serious environmental risks than that in oxygenated freshwaters.

Tributyltin bioaccumulation and toxic effects in freshwater gastropods Pomacea canaliculata after a chronic exposure: field and laboratory studies

Freshwater samples and gastropod mollusks (Pomacea canaliculata) were collected at 5 sampling stations located along the lower Río de la Plata basin, Argentina, to assess the extent of tributyltin (TBT) contamination. Determined data revealed the presence of TBT and some of its breakdown products (dibutyltin: DBT, and monobutyltin: MBT) in all freshwater samples and also in soft tissues of P. canaliculata gastropods. Chronic bioassays (6 months) were performed using female gastropods that had been reared under laboratory conditions and exposed to a similar TBT concentration than the value determined in freshwater samples (1 µg L^-1). The aims of this study were to evaluate the extent of TBT accumulation, the tissue distribution, and the effects on selected biomarkers (activity of superoxide dismutasa: SOD, activity of catalase: CAT, levels of total glutathione: t-GSH, lipid peroxidation, and activity of acetylcholinesterase: AChE). Gonads presented the highest accumulation, followed by the cephalopedal region, albumin gland, and finally hepatopancreas. Both metabolites, DBT and MBT, were also found. All exposed female animals presented development of a penis reflecting the potential of TBT as an endocrine disrupting chemical for this gastropod species. Results on the selected biomarkers confirmed additional adverse effects induced by TBT. An increase in CAT activity and changes in t-GSH levels are indicative of alterations on the cellular redox status. The inhibition of AChE could reflect signs of neurotoxicity. Altogether, these results reveal a negative impact on the health of this gastropod population.

Microplastics in freshwater systems: a review of the emerging threats, identification of knowledge gaps and prioritisation of research needs

Plastic contamination is an increasing environmental problem in marine systems where it has spread globally to even the most remote habitats. Plastic pieces in smaller size scales, microplastics (particles <5 mm), have reached high densities (e.g., 100,000 items per m(3)) in waters and sediments, and are interacting with organisms and the environment in a variety of ways. Early investigations of freshwater systems suggest microplastic presence and interactions are equally as far reaching as are being observed in marine systems. Microplastics are being detected in freshwaters of Europe, North America, and Asia, and the first organismal studies are finding that freshwater fauna across a range of feeding guilds ingest microplastics. Drawing from the marine literature and these initial freshwater studies, we review the issue of microplastics in freshwater systems to summarise current understanding, identify knowledge gaps and suggest future research priorities. Evidence suggests that freshwater systems may share similarities to marine systems in the types of forces that transport microplastics (e.g. surface currents); the prevalence of microplastics (e.g. numerically abundant and ubiquitous); the approaches used for detection, identification and quantification (e.g. density separation, filtration, sieving and infrared spectroscopy); and the potential impacts (e.g. physical damage to organisms that ingest them, chemical transfer of toxicants). Differences between freshwater and marine systems include the closer proximity to point sources in freshwaters, the typically smaller sizes of freshwater systems, and spatial and temporal differences in the mixing/transport of particles by physical forces. These differences between marine and freshwater systems may lead to differences in the type of microplastics present. For example, rivers may show a predictable pattern in microplastic characteristics (size, shape, relative abundance) based on waste sources (e.g. household vs. industrial) adjacent to the river, and distance downstream from a point source. Given that the study of microplastics in freshwaters has only arisen in the last few years, we are still limited in our understanding of 1) their presence and distribution in the environment; 2) their transport pathways and factors that affect distributions; 3) methods for their accurate detection and quantification; 4) the extent and relevance of their impacts on aquatic life. We also do not know how microplastics might transfer from freshwater to terrestrial ecosystems, and we do not know if and how they may affect human health. This is concerning because human populations have a high dependency on freshwaters for drinking water and for food resources. Increasing the level of understanding in these areas is essential if we are to develop appropriate policy and management tools to address this emerging issue.

Integrated study of metal behavior in Mediterranean stream ecosystems: a case-study

The objective of the present work was to assess the ecosystem status of Francolí river (Catalonia, Spain), a Mediterranean stream basin with contrasting human influences. An integrated approach was designed by combining physicochemical, biological and ecotoxicological analyses. The content of metals (As, Cd, Cr, Co, Cu, Hg, Ni, Pb, and Zn) was analyzed in samples of water, benthic sediments and aquatic macroinvertebrates. In addition, the potentially bioavailable fraction of metals in water and sediments was determined by using diffusive gradient in thin-films (DGTs) and sequential extraction of sediments (BCR), respectively. The biological quality was evaluated through aquatic macroinvertebrate communities, while the ecotoxicological status was assessed by Microtox(®) with Vibrio fischeri. Finally, an analysis of acid-volatile sulfide (AVS) and simultaneously extracted metals (SEM) was performed to evaluate the sediment toxicity associated to metal content. According to the results, DGTs and BCR are suitable methodologies to predict the potential bioavailable fraction of metals in freshwater systems. Moreover, ecotoxicity evaluation by means of V. fischeri, in combination with the chemical characterization and the biological quality assessment, should be complementarily used to get a better diagnose of freshwater systems.