Spatio-temporal distribution of microplastics in a Mediterranean river catchment: The importance of wastewater as an environmental pathway

Embargo until June 25, 2023Microplastics (MPs) are considered to be ubiquitous contaminants in freshwater ecosystems, yet their sources and pathways at the river catchment scale need to be better determined. This study assessed MP (55–5000 µm) pollution in a Mediterranean river catchment (central Spain) and aimed to identify the importance of wastewater as an environmental pathway. We sampled treated and untreated wastewaters, and raw and digested sludge from five WWTPs during two seasons. River water and sediments were sampled at three locations with different anthropogenic influences during three seasons. On average, 93% (47–99%) of MPs were retained by WWTPs. Concentrations in river water and sediment ranged between 1 and 227 MPs/m3 and 0–2630 MPs/kg dw, respectively. Concentrations strongly depended upon land-use, with pollution levels increasing significantly downstream of urban and industrial areas. Seasonality influenced the observed MP concentrations strongly. During high flow periods, higher water but lower sediment concentrations were observed compared to low flow periods. We estimate that 1 × 1010 MPs are discharged into the catchment via treated and untreated wastewater annually, which constitutes up to 50% of the total MP catchment discharge. Thus, we conclude that the wastewater system represents a major environmental pathway for MPs into Mediterranean rivers with low dilution capacity.acceptedVersio

Time-course biofilm formation and presence of antibiotic resistance genes on everyday plastic items deployed in river waters

The plastisphere has been widely studied in the oceans; however, there is little information on how living organisms interact with the plastisphere in freshwater ecosystems, and particularly on how this interaction changes over time. We have characterized, over one year, the evolution of the eukaryotic and bacterial communities colonizing four everyday plastic items deployed in two sites of the same river with different anthropogenic impact. α-diversity analyses showed that site had a significant role in bacterial and eukaryotic diversity, with the most impacted site having higher values of the Shannon diversity index. β-diversity analyses showed that site explained most of the sample variation followed by substrate type (i.e., plastic item) and time since first colonization. In this regard, core microbiomes/biomes in each plastic at 1, 3, 6 and 12 months could be identified at genus level, giving a global overview of the evolution of the plastisphere over time. The measured concentration of antibiotics in the river water positively correlated with the abundance of antibiotic resistance genes (ARGs) on the plastics. These results provide relevant information on the temporal dynamics of the plastisphere in freshwater ecosystems and emphasize the potential contribution of plastic items to the global spread of antibiotic resistanceThe authors acknowledge the financial support provided by the Spanish Government (Ministerio de Ciencia e Innovacion, ´ MICIN): PID2020–113769RB-C21/22, PLEC2021–007693 (Funded by MCIN/ AEI/10.13039/501100011033 and by the European Union “NextGenerationEU”/PRTR”), the IMPASSE project (PCIN-2017–06) belonging to the EU JPI-Water initiative, and the Thematic Network of Micro- and Nanoplastics in the Environment (RED2018–102345-T, EnviroPlaNet Network). SMC thanks the Universidad de Alcala ´ for the award of an FPI contract. A. Rico thanks the Talented Researcher Support Programme - Plan GenT (CIDEGENT/2020/043) of the Generalitat Valenciana. The authors gratefully acknowledge the Genomics Unit of the “Parque Científico de Madrid” for qPCR experiments and Illumina sequencin

Retention efficiency for microplastic in a landscape estimated from empirically validated dynamic model predictions

Soils are recipients of microplastic that can be subsequently transferred to the sea. Land sources dominate inputs to the ocean, but knowledge gaps about microplastic retention by land hinder assessments of input rates. Here we present the first empirical evaluation of a dynamic microplastic fate model operating at landscape level. This mechanistic model accounts for hydrology, soil and sediment erosion, particle characteristics and behavior. We predict microplastic concentrations in water and sediments of the Henares river (Spain) within the measurement uncertainty boundaries (error factors below 2 and 10, respectively). Microplastic export from land and discharge by river fluctuates in a non-linear manner with precipitation and runoff variability. This indicates the need of accurate dynamic descriptions of soil and stream hydrology even when modeling microplastic fate and transport in generic scenarios and at low spatio-temporal resolution. A time-averaged landscape retention efficiency was calculated showing 20–50% of the microplastics added to the catchment over a multiannual period were retained. While the analysis reveals persistent uncertainties and knowledge gaps on microplastic sources to the catchment, these results contribute to the quantitative understanding of the role of terrestrial environments in accumulating microplastics, delaying their transport to the sea

Large-scale monitoring and risk assessment of microplastics in the Amazon River

Microplastics (MPs) are one of the most widespread contaminants worldwide, yet their risks for freshwater ecosystems have seldom been investigated. In this study, we performed a large monitoring campaign to assess the presence and risks of MPs in Amazonian freshwater ecosystems. We investigated MP pollution in 40 samples collected along 1500 km in the Brazilian Amazon, including the Amazon River, three major tributaries, and several streams next to the most important urban areas. MPs in the 55–5000 µm size range were characterized (size, shape, color) by microscopy and identified (polymer composition) by infrared spectroscopy. Ecotoxicological risks were assessed using chronic Species Sensitivity Distributions for effects triggered by food dilution and tissue translocation using data alignment methods that correct for polydispersity of environmental MPs and bioaccessibility. This study shows that MPs are ubiquitous contaminants in Amazonian freshwater ecosystems, with measured concentrations (55–5000 µm) ranging between 5 and 152 MPs/m3 in the Amazon River and its main tributaries, and between 23 and 74,550 MPs/m3 in urban streams. The calculated Hazardous Concentration for the 5% of species (HC5) derived from the SSDs for the entire MP range (1–5000 µm) were 1.6 × 107 MPs/m3 (95% CI: 1.2 × 106 – 4.0 × 108) for food dilution, and 1.8 × 107 MPs/m3 (95% CI: 1.5 × 106 – 4.3 × 108) for translocation. Rescaled exposure concentrations (1–5000 µm) in the Amazon River and tributaries ranged between 6.0 × 103 and 1.8 × 105 MPs/m3, and were significantly lower than the calculated HC5 values. Rescaled concentrations in urban streams ranged between 1.7 × 105 and 5.7 × 108 MPs/m3, and exceeded both calculated HC5 values in 20% of the locations. This study shows that ecological impacts by MP contamination are not likely to happen in the Amazon River and its major tributaries. However, risks for freshwater organisms may be expected in near densely populated areas, such as the cities of Manaus or Belem, which have limited wastewater treatment facilities.Large-scale monitoring and risk assessment of microplastics in the Amazon RiverpublishedVersio

Effects of Polyester Fibers and Car Tire Particles on Freshwater Invertebrates

Microplastic ingestion has been shown for various organisms, but knowledge of the potential adverse effects on freshwater invertebrates remains limited. We assessed the ingestion capacity and the associated effects of polyester fibers (26–5761 µm) and car tire particles (25–75 µm) on freshwater invertebrates under acute and chronic exposure conditions. A range of microplastic concentrations was tested on Daphnia magna, Hyalella azteca, Asellus aquaticus, and Lumbriculus variegatus using water only (up to 0.15 g/L) or spiked sediment (up to 2 g/kg dry wt), depending on the habitat of the species. Daphnia magna did not ingest any fibers, but low levels of fibers were ingested by all tested benthic invertebrate species. Car tire particle ingestion rose with increasing exposure concentration for all tested invertebrates and was highest in D. magna and L. variegatus. In most cases, no statistically significant effects on mobility, survival, or reproductive output were observed after acute and chronic exposure at the tested concentrations. However, fibers affected the reproduction and survival of D. magna (no-observed-effect concentration [NOEC]: 0.15 mg/L) due to entanglement and limited mobility under chronic conditions. Car tire particles affected the reproduction (NOEC: 1.5 mg/L) and survival (NOEC: 0.15 mg/L) of D. magna after chronic exposure at concentrations in the same order of magnitude as modeled river water concentrations, suggesting that refined exposure and effect studies should be performed with these microplastics. Our results confirm that microplastic ingestion by freshwater invertebrates depends on particle shape and size and that ingestion quantity depends on the exposure pathway and the feeding strategy of the test organism.publishedVersio

Effects of Polyester Fibers and Car Tire Particles on Freshwater Invertebrates

Microplastic ingestion has been shown for various organisms, but knowledge of the potential adverse effects on freshwater invertebrates remains limited. We assessed the ingestion capacity and the associated effects of polyester fibers (26–5761 µm) and car tire particles (25–75 µm) on freshwater invertebrates under acute and chronic exposure conditions. A range of microplastic concentrations was tested on Daphnia magna, Hyalella azteca, Asellus aquaticus, and Lumbriculus variegatus using water only (up to 0.15 g/L) or spiked sediment (up to 2 g/kg dry wt), depending on the habitat of the species. Daphnia magna did not ingest any fibers, but low levels of fibers were ingested by all tested benthic invertebrate species. Car tire particle ingestion rose with increasing exposure concentration for all tested invertebrates and was highest in D. magna and L. variegatus. In most cases, no statistically significant effects on mobility, survival, or reproductive output were observed after acute and chronic exposure at the tested concentrations. However, fibers affected the reproduction and survival of D. magna (no-observed-effect concentration [NOEC]: 0.15 mg/L) due to entanglement and limited mobility under chronic conditions. Car tire particles affected the reproduction (NOEC: 1.5 mg/L) and survival (NOEC: 0.15 mg/L) of D. magna after chronic exposure at concentrations in the same order of magnitude as modeled river water concentrations, suggesting that refined exposure and effect studies should be performed with these microplastics. Our results confirm that microplastic ingestion by freshwater invertebrates depends on particle shape and size and that ingestion quantity depends on the exposure pathway and the feeding strategy of the test organism

Fate of microplastics in agricultural soils amended with sewage sludge: Is surface water runoff a relevant environmental pathway?

Embargo until November 18, 2023Sewage sludge used as agricultural fertilizer has been identified as an important source of microplastics (MPs) to the environment. However, the fate of MPs added to agricultural soils is largely unknown. This study investigated the fate of MPs in agricultural soils amended with sewage sludge and the role of surface water runoff as a mechanism driving their transfer to aquatic ecosystems. This was assessed using three experimental plots located in a semi-arid area of Central Spain, which were planted with barley. The experimental plots received the following treatments: (1) control or no sludge application; (2) historical sludge application, five years prior to the experiment; and (3) sludge application at the beginning of the experiment. MPs were analyzed in surface water runoff and in different soil layers to investigate transport and infiltration for one year. The sewage sludge used in our experiment contained 5972–7771 MPs/kg dw. Based on this, we estimated that about 16,000 MPs were added to the agricultural plot amended with sludge. As expected, the sludge application significantly increased the MP concentration in soils. The control plot contained low MP concentrations (31–120 MPs kg−1 dw), potentially originating from atmospheric deposition. The plot treated five years prior to the experiment contained 226–412 and 177–235 MPs kg−1 dw at the start and end of the experiment, respectively; while the recently treated plot contained 182–231 and 138–288 MPs kg−1 dw. Our study shows that MP concentrations remain relatively constant in agricultural soils and that the MP infiltration capacity is very low. Surface water runoff had a negligible influence on the export of MPs from agricultural soils, mobilizing only 0.2–0.4% of the MPs added with sludge. We conclude that, in semi-arid regions, agricultural soils can be considered as long-term accumulators of MPs.publishedVersio

Gender and academic writing

The relationship between gender and discourse has been a focus of theoretical and empirical attention in the fields of applied and sociolinguistics for some 30 years (for overviews see Cameron, 2006, 2007, 2010; Coates, 2004; Litosseliti & Sunderland, 2002; Talbot, 2010; Wodak, 1997), with debates continuing around the extent and specific ways in which language and discourse are gendered and how such gendering is enacted and sustained, often taking spoken language as the empirical object (Swann, 2002; for recent examples, see; Baxter, 2014; Grohosky, 2014; Hultgren, 2017). The significance of gender for writing and specifically academic writing has received less attention in sociolinguistic and discourse studies but there are a number of important strands of work which this Special Issue seeks to bring together. These include: a) feminist writings on what it means to ‘write’ across all discourses and genres, particularly what it means to inscribe and re-inscribe as a woman (e.g. de Beauvoir 1997; Irigary,1993; pender,1980; Threadgold,1997; Liu, Karl, & Ko, 2013) and as a feminist (Belsey, 2000; Handforth & Taylor, 2016); b) academic writing research which has foregrounded gender as a key aspect of identity work in the production, reception and teaching of academic writing (e.g. Flynn, 1988; Nye, 1990; Kirsch, 1993; Dixon, 1995; Haswell & Haswell, 1995; Holbrook, 1991; Ivanic, 1998; Lillis, 2001; Belcher, 2009; Tse & Hyland, 2008, 2012); c) academic writing research which has explored the specific ways in which the labour surrounding the production of academic writing, notably the teaching of student writing, is gendered (e.g. Blythman & Orr, 2006; Horner, 2007; Schell, 1998; Tuell, 1992; Turner, 2011); d) research which documents the material conditions of academic work, including scholarly writing, and their continuing gendered impacts on career trajectories (e.g. Acker & Feuerverger, 1996; Appleby, 2014; Grummell, Devine, & Lynch, 2009; Hey, 2001; Leathwood and Read, 2009; Moi, 2008; Prozesky, 2008)