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Degradation and end-of-life of biodegradable plastic mulches in soils
Presenter: Marion Yvin
Université Bretagne Sud, IRDL, UMR CNRS 6027, Lorient, FRANCE
Among the various pathways by which microplastics enter into soils, mulching of farmland with plastic films has been identified as one of the main sources. There are three main types of plastic mulch films used in agriculture: conventional polyethylene (PE), oxodegradable and biodegradable films. Biodegradable plastic mulches are used as alternatives to PE and oxodegradable films. They are designed to be buried in the field after crop season. According to standard EN 17033, 90% of the initial film must be biodegraded in the soil after 2 years.
The BIOMALEG project aims to provide new insights about the behaviour and impact of biodegradable polymers in soils. Two experimental set-ups will be used to: i) Assess the plastic contamination level of 20-years mulched soils by comparing non-biodegradable and biodegradable mulches. First results show that the main polymers extracted were PE, PVC and biodegradable, corresponding to the main components of the mulches historically used. The plots where oxodegradable films had been used were the most contaminated by microplastics. ii) Monitor the degradation of biodegradable films in soil over 2 years. After 18 months of monitoring, a decrease of large (>2 mm) particles number was observed, while the quantity of smaller microplastics increase over time. This contribute to the growth of total plastic particle (>500 μm) quantity. The impact of the presence of microplastics from mulches in the studied field was also investigated in this project.
Microplastic contamination of organic fertilisers applied to agricultural soils
Presenter: Delphine Cirederf Boulant
Université Bretagne Sud, IRDL, UMR CNRS 6027, Lorient, FRANCE
Organic waste products such as composts, green waste or sewage sludge constitute a relevant alternative to chemical-based fertilisers, improving soil organic matter and microbial activity, and participating to circular economy. However, recent scientific papers suggest that plastics may end up in the terrestrial environment as a result of the organic fertilisers application ((Weithmann et al., 2018), (Crossman et al., 2020)). In order to assess the level of contamination, as well as to identify the polymers involved, a national unprecedent 3-year project was set up (2021-2023). The objectives are many: to determine the matrices acting as sources of microplastics (MP), to study the diversity, origins and amounts of these MP, and to estimate the annual potential flows to agricultural lands. Within this framework, the IRDL laboratory (Institut de Recherche Dupuy de Lôme) is responsible for setting up and validating a single MP extraction protocol applicable to various complex organic-rich matrices. 83 samples from as many sites in France were processed and analysed using μFTIR spectroscopy. Final results of this multi-stakeholder project will be presented and discussed. These unprecedented data indicate contamination of all matrices, at highly variable concentrations. Also, the most represented polymers in organic fertilisers are those the most commonly found in the environment (PS, PET, PE, PP). In addition, the level of contamination depends greatly on the incoming organic materials and the processes used. These overall results will allow us to quickly identify levers to limit microplastic pollution in organic soil improvers.
Evaluating policy solutions to address microplastic emissions to land
Presenter: Leah Mupas Seguit
The Pew Charitable Trusts
The impacts of microplastics in the environment are gaining attention, yet fewer solutions have been implemented for microplastics relative to macroplastics. Combining microplastic emissions from six sectoral uses of paint (architecture, general industrial, marine, automotive, industrial wood, and road markings) with microplastic pollution from tyres, pellets, textiles and personal care products, we model stocks and flows of microplastics from production, distribution to different pathways (e.g., wastewater treatment or run off) and their fates (e.g., managed waste or pollution) from 2016-2040. Additionally, we model the implementation of potential policies targeting upstream, midstream, and downstream sources of microplastic emissions to estimate their impact on reducing microplastic pollution. We found that annual rates of microplastic pollution to the environment are double previous global estimates, with the majority of microplastic pollution leaking to land. At these rates, microplastic emissions would make up nearly a quarter of total global macro- and microplastic pollution from sources quantified to date. For high-
and upper-middle income countries, the application of sludge from wastewater treatment facilities is a major pathway for microplastic pollution to land. Even if the policies modelled in this study are implemented, microplastic pollution in 2040 will still exceed todays rates, emphasizing the need for ambitious policies and innovation to solve the remaining microplastic pollution. Our findings underscore the urgency for policy action that is commensurate with the scale of microplastic emissions to the environment.
Studying the fate of biodegradable mulch films in the environment.
Presenter: Tommaso Nacci
Department of Chemistry and Industrial Chemistry, University of Pisa, via G. Moruzzi 13, 56124 Pisa, Italy
Agricultural mulching involves the covering of soil with special films to prevent crop contamination and to protect the soil from atmospheric agents. The complicated retrieval and landfilling of these materials caused significant environmental pollution. For this reason, biodegradable mulch films were introduced as an alternative to conventional ones, but their environmental impact is still unknown.
In this work the potential of analytical pyrolysis coupled to mass spectrometry in the life cycle assessment of agricultural mulch films was investigated. Two biodegradable mulch films composed of poly(lactic acid)/poly(butylene adipate-co-terephthalate) (PLA/PBAT) and Mater-bi (starch/PLA/PBAT) were selected to undergo natural ageing in the open environment together with a poly(ethylene) (PE) control sample. Subsamples were collected after 1, 3, 6, and 12 months of exposure to air, soil, and marine water. Scanning Electron Microscopy (SEM) was employed to monitor the morphology of the degraded samples, while the material composition was assessed by Attenuated Total Reflectance-Fourier Transform Infrared spectroscopy (ATR-FTIR), and Pyrolysis-Gas Chromatography-Mass Spectrometry (Py-GC-MS). SEM highlighted the formation of holes and damages on the surface of all degraded biodegradable mulch films starting from 1 month of exposure. For each biodegradable mulch film, Py-GC-MS showed similar aging trends for samples exposed to air and those buried in soil, featuring a progressive decrease in time of the relative abundance of PBAT and starch peaks. Py-GC-MS also pointed to the possible leaching in the environment of additives present in PLA/PBAT samples. No significant morphological and chemical changes were observed for PE samples up to 12 months.
Biodegradable Mulch Films Development: A case study for Africa
Presenter: Vincent Ojijo
Advanced Polymer Composites Group, Council for Scientific and Industrial Research (CSIR), Pretoria 0001, South Africa
Biodegradable mulch films (BDMs) are considered a better alternative to conventional plastic mulches as they partially address the issue of microplastics and land-based plastic pollution from agricultural activities. Apart from providing the known benefits for mulching, such as increased crop yield, enhancing early maturity, conservation of water, and weed control, the BDMs can be ploughed back into the soil at the end of crop-life cycle; thus saving on the cost for removal. The performance of the BDMs is however dependent on a number of factors, including climatic conditions. It is imperative that material solutions are tailored for specific conditions. In the AgriBioMulch film project, CSIR South Africa is partnering with Elizade University, Nigeria, to develop BDMs with tailored performance for sub-Saharan countries. We have developed formulations with enhanced local content, and prototyped BDMs at industry level for field trials in Nigeria. Herein, we present the experiences in the process, some technical results, and provide an outlook of post-field trials.
Distribution characteristics of microplastics in agricultural soils in two cities of Pakistan
Presenter: Zulfiqar Ahmad Saqib
Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad 38040, Pakistan
Plastic pollution in soils is now emerging issue globally, due to rapid urbanization and extensive use of plastic products. At present, the recognized sources of microplastics include compost, sewage sludge, irrigation, plastic mulching, littering, and atmospheric input. This study determines the spatial distribution of micro plastics (MPs) in different urban soils of Pakistan. Samples were collected from different land use type to determine the spatial distribution characteristics, main discharging sources of MPs and other factors. Abundance of MPs in soil ranged from 310-5698 items/kg, with an average value of 1450 items/kg. The MPs content with size of <0.5 mm in the first layer (10-15 cm) of agricultural soils was significantly higher (p < 0.05) than that in the upper crust (0–5 cm) of soil, which indicates possibility of MPs migration to deeper soil layers. Dominant shape of MPs were fragment and film, while chemically polypropylene (PP), polyvinyl chloride (PVC), and polyethylene (PE) were dominated compositions. Moreover, soil texture may affect MPs concentration in soil where MPs in sandy loam was significantly higher (p < 0.05) than that in silty loam or loam. In addition, age of plants and irrigation methods in agricultural soil had no effect on MPs content in soil where number of irrigations leads the leaching of MPs. The occurrence and impact of microplastic on the soil depend on the morphology, chemical components, and natural factors.
The fungal assemblage in soil polluted by plastics. Biodiversity, metabolism, and degradation potential
Presenter: Marta Elisabetta Eleonora Temporiti
Department of Earth and Environmental Science, University of Pavia, Via Sant’Epifanio14, 27100 Pavia, Italy
Microorganisms, and especially fungi, are a keystone of soil biodiversity and soil metabolic capacity. Therefore, changes in fungal community compositions and metabolisms could be an interesting point of view to evaluate the impact of plastic pollution on soil health. Moreover, the fungal possibility to produce exoenzymes involved in polymer degradation makes fungi possible actor for plastic degradation.
The aim of this study was to analyse the impact of plastic pollution on soil microorganisms’ metabolisms and soil fungal communities. Moreover, in order to create a useful collection, fungi with biodegradation potential were isolated and characterised basing on their enzymatic production and abilities to grow on plastic as sole carbon source. Finally, sub-micron x-ray technique was used to prove the penetrative and degradative activity of some fungal isolates.
The results showed a significant decrease in soil microbial metabolic ability in plastic polluted soil, and the soil fungal community composition was significantly different in pristine site when compared with polluted sites. In addition, a collection of 120 characterised fungal strains was created and tested on different plastic polymers. From the collection, interesting fungi were selected and studied for their ability to penetrate polyethylene terephthalate fragments. Indeed, new results on the geometry and morphology of the interaction between fungus and plastic substrate on a sub-micrometric scale were provided by X-ray microscopy. This study lays the foundation for further research on the effect of plastics on soil microbial communities and their activities.
Biodegradable plastics: effects on soil functionality and fertility
Presenter: Sara Guerrini
Department of Agricultural and Food Sciences, Alma Mater Studiorum University of Bologna, Bologna, Italy.
To understand the effect of biodegradable bioplastics (BDBP) on soil quality, increasing quantities (from 0.001 to 1%) of BDBP were added in two different soils (a loamy soil – Cambisol and a sandy soil –Arenosol) and compared to untreated soils. As expected, significant effects were observed only with the highest dose (1 %), resulting in higher growth of the microbial biomass, increase in the mineralization of dissolved organic carbon (OC) and increase in the available nitrogen (N) immobilization. The lower doses of BDBP (corresponding to the doses normally applied in agriculture) do not induce effects different from the untreated soils. To better investigate the magnitude of N immobilization, the experimentation was repeated on the loamy soil to which different doses of BPBD (from 0.01 to 1%) and marked N (15N) of mineral and organic origin were added at agronomic doses (i.e., 100 kg ha-1). A model plant (Lactuca sativa, variety Masaida) was also included to observe the effects of BDBP on plant growth. The addition of mineral N favoured plant growth regardless of the dose of BDBP added. The extractable C and N content and the microbial biomass N content were found to be significantly influenced only by the N source (mineral vs. organic) without significant effects due to the BDBP at agronomical doses. These results show that adding BDBP to the soil does not lead to adverse effects on soil biochemistry or plant growth.
Non-destructive detection and visualisation of microplastics in sandy soils by a novel 3D imaging approach
Presenter: Sascha E. Oswald
Institute of Environmental Science and Geography, University of Potsdam, Potsdam, Germany
Our understanding of how microplastics alter soil structure and function is still very limited. For example, it is largely unclear how microplastics modify the formation and stability of soil aggregates or rhizosphere processes. Various analytical detection methods are now available, but involve sampling or processing steps that destroy the integrity of the sample. Thus, essential information about the microplastic distribution inside the sample is irretrievably lost and the analysis of the influence of microplastic particles on local soil microstructure is hampered. We combine neutron and X-ray tomography to detect and localize different types of microplastics in sandy soil and simultaneously map the 3D structure of the soil matrix, and test its performance when removing organic matter by preprocessing or including a living root system. In this systematic study sandy soils with organic material were prepared and microplastics from different plastic types and shapes added, including particles, films, or fibres. For example, fragments of polyethylene films used in asparagus cultivation were mixed with soil collected from an asparagus field. Our three-dimensional imaging approach provides detailed information about the spatial distribution of the microplastics in the sample and can reproduce size and shape of particles, although it cannot distinguish between plastic types. Visualization showed how microplastic particles cause perturbations in the soil matrix that can affect its hydraulic and mechanical properties. Finally, we analyzed microplastics in the spatial context of plant-soil interactions for a lupine plant, making it also an attractive tool for in-situ studies of soil microplastic effects on plant roots.
Exploring Bioplastic Degrading Microorganisms for Enhanced Biodegradation and
Sustainable Waste Management
Presenter: Francesca Bandini
Dipartimento di Scienze e Tecnologie Alimentari per la sostenibilità della filiera agro-alimentare, Facoltà di Scienze Agrarie Alimentari ed Ambientali, Università Cattolica del Sacro Cuore, 29122 Piacenza, Italy
Bioplastics have emerged as promising alternatives to conventional plastics, but their disposal still poses significant challenges, such as the presence of residues at the end of anaerobic digestion and composting treatments, necessitating the development of new sustainable waste management strategies. Microorganisms capable of degrading bioplastics can provide invaluable insights into their breakdown mechanisms and hold promise for bioremediation approaches. By employing microbial enrichment technique from bioplastic residues of composted starch-based bioplastic (SBB) and polylactic acid (PLA), we isolated promising bacterial strains with plastic degrading capabilities. Enrichment microcosms provided an environment conducive to the growth of microorganisms utilizing bioplastics as a sole carbon source and with the capacity to degrade bioplastics. Over successive generations, microorganisms proficient in bioplastic degradation proliferated, outcompeting other strains. Characterizing these enriched microbial communities is critical for understanding the microbial diversity and functional dynamics associated with bioplastics degradation. Further analyses will cover molecular techniques, such as high-throughput sequencing and metagenomics, to enable the identification and classification of other uncultivable key microorganisms and their functional genes. Additionally, proteomic analyses will elucidate the specific enzymes involved in bioplastic breakdown, offering a unique opportunity to explore the metabolic pathways and enzymatic machinery involved in bioplastic degradation. The outcomes of this research will hold considerable implications for bioplastic waste management, promoting targeted strategies and consortia for enhanced biodegradation and recycling. These findings may contribute to developing bioremediation technologies and optimizing industrial processes, ultimately mitigating the environmental impact of bioplastic residues.
Release into the soil of additives contained in biodegradable mulching films during their life of use.
Presenter: Giuseppe Proietto Salanitri
CNR-IPCB, Via Paolo Gaifami 18, 95126 Catania, Italy
Agricultural plastic material is difficult to recycle and eliminate from the soil after use. In this view, the development of biodegradable plastic was a great advancement in the field of agriculture applications. In particular, biodegradable mulch films (Bio-Mul) are a sustainable alternative to fossil-based plastic ones. In fact, they are susceptible to rapid degradation in the soil during and after their use, eliminating the need for plastic film disposal. However, the non-biodegradable material counterparts such as additives, inorganic fillers, and stabilizers, could remain in the soil causing a serious threat to the flora and human health. To shed light on this aspect, commercial Bio-Mul films were investigated by chemical physical, morphological and mechanical analysis. The film was artificially exposed to UV light up to reaching the depletion of 50% in tensile strength, which is the limit of its useful life. Then, pieces of the sample were buried in a Mediterranean climate area (southern Italy), monitoring the climatic conditions, soil temperature, and water content. The as-treated films were subjected to additives quantification, and determination of inorganic contents by mass spectrometry analyses. The results obtained along with the exposure time, were compared with virgin materials.
Plastic metabolisation potential of the environmental microbiome following long-term exposure
Presenter: Guido Zampieri
Department of Biology, University of Padua, via U. Bassi 58/b, 35131 Padova, Italy
Plastic pollution of the soil is a global issue of increasing concern, with far-reaching impact on the environment and human health. To fully understand the medium- and long-term impact of plastic dispersal in the environment, it is necessary to define its interaction with the residing microbial communities and the potential for its metabolisation. Our study combines genome-centric metagenomics with gene expression and biochemical analysis to characterise microbial communities involved in polyethylene (PE) and polyethylene terephthalate (PET) degradation. Such microbiota were sampled from a landfill subject to decades-old contamination and were enriched through prolonged cultivation to select the microorganisms potentially involved in microplastic degradation. To pinpoint the response mechanisms against elevated plastic contamination of individual microorganisms, community composition and single-nucleotide variation were repeatedly analysed more than six months apart. Numerous enzymes with depolymerisation potential were identified in the metagenomes, such as PETases and MHETases, and putatively associated metabolic pathways were reconstructed. The microbial communities, especially those cultivated with PE, underwent a drastic change in composition over time associated with a marked accumulation of genomic variants in emerging species. Moreover, genome-centric metatranscriptomic patterns indicate a high transcriptional level of numerous genes characterised also by a marked accumulation of genomic variants, supporting the hypothesis that enzymes actively involved in PE and PET depolymerisation and metabolisation are under a strong selective pressure. Altogether, our results provide an improved characterisation of the impact of microplastics derived from common plastics types on terrestrial microbial communities and suggest potential biotic responses investing contaminated sites.
Marine invertebrates interaction with micro- and nanoparticles particles: size and morphology influence on ingestion-egestion
Presenter: Nora Exposito
Environmental Engineering Laboratory, Department of Chemical Engineering, University Rovira and Virgili, Paisos Catalans Avenue 26, 43007 Tarragona, Catalonia, Spain
Microplastics (MPs) have the potential to be ingested by organisms with adverse effects such as reduced growth and impaired on life-history. In addition, hazardous substances released from MPs could affect these organisms, with possible MPs transfer by consumption through trophic levels. The aim of this study is to understand the process of nano-and MPs ingestion, egestion and body interactions in adult and larvae of sea urchins (Paracentrotus lividus), amphioxus (Branchiostoma lanceolatum) and edible oyster (Ostrea edulis) and how it affects survival rates. The results showed that the adult sea urchin and amphioxus does not select the PE spheres and fibres, they feed depending on the concentration, distribution and individual conditions. The 53-63 μm and 125-150 μm spheres were more easily ingested and showed high interaction with other body parts and organs, however, but were not fully excreted within 48 h. Health and survival rates may have been affected at high particle concentrations. Spheres concentrations of 26 mg/L (53-63 μm) and 2.6 mg/L (80 nm) decreased the 24 h larval survival rate to 74 % and 78%, respectively and affected morphometric parameters. For oysters, after 48h of exposure and 24h of egestion, tended to accumulate MPs of up to 300 μm in the digestive tract, up to 150 μm in the abductor muscle and up to 53-63 μm in the gills and the mantle. Mortality was not significant. The smaller the MPs, the greater the bioacumulation.
Microplastics detection in food and beverages – Fast data processing and visualization approaches for μFTIR hyperspectral imaging based on machine learning
Presenter: Benedikt Hufnagl
Independent data scientist / chemometrician, Austria
Microplastics (MP) in food and beverages may be a possible human health hazard. Thus, recent studies put the topic into the focus of scientific and public discussions. Besides plastics leaked into the environment, food processing and packaging can be another possible entry path of microplastics into food and beverage products. In the cross-national CORNET (COllective Research NETworking) project ‘microplastic@food’, leading Austrian and German research institutions collaborate with 33 Austrian and 22 German SMEs from the food and beverage industry to develop analytical methods for detecting microplastics in their products.
The microplastics samples obtained by beverage or food-rinsing water filtration pose very different analytical challenges in comparison with environmental samples, as microplastics concentrations are considerably lower and dimensions are even smaller. Further, matrix remnants such as proteins, fats and waxes may lead to false positives and therefore can bias the results. μFTIR imaging allows for a fast measurement of samples concentrated on silicon filters, yet the large amounts of spectroscopic data created in a single measurement make fast, automated data analysis pipelines indispensable.
This presentation summarizes the insights for building fast and robust data analysis approaches based on machine learning and methods for visualizing and auditing results for report generation. The findings are compared to earlier studies which focused on environmental samples. We will show how machine learning can be leveraged to build broadly applicable data analysis models as well as how to extend them in the future to meet challenges in upcoming applications in food and beverage analysis.
Detection of microplastics, polymers and additives in mussels and large pelagic fishes in the Adriatic Sea
Presenter: Federica Di Giacinto
Istituto Zooprofilattico Sperimentale dell’Abruzzo e del Molise “G. Caporale” (IZSAM), Campo Boario, 64100 Teramo, Italy
Many studies detected microplastics (MPs) in the gastro-intestinal contents of animals. Further researches have shown that MPs can translocate through gastrointestinal tract to other tissues. Instead, few studies have investigated the presence of MPs in fish muscle. Concerning bivalves, since they are consumed without any type of evisceration, they represent for consumers an important route of exposure to MPs and their additives. We detected and characterized MPs, polymers and additives in the edible tissues of fishes (Thunnus thynnus and Xiphias gladius) caught in the Mediterranean Sea and in mussels (Mytilus galloprovincialis) farmed along the Italian-Croatian coasts. The tissues were digested in an alkaline solution and then the extracted MPs were quantified and characterized by stereomicroscopy and RAMAN spectroscopy. Furthermore, the presence of plastic additives (bisphenol a – BPA and paraphthalic acid – PTA) and polymers (PET and PC) was quantified by LC-MS/MS. The number of MPs per gram was 1 in the mussel, 0.20 in tuna and 0.22 in swordfish. The most abundant color and shape of MPs were black/filament in bivalves and blue/fragment in fishes. The most frequent polymer was polyester in mussel and polypropylene in fishes. A similar concentration of PTA and PET was detected in all animals, while BPA and PC were detected at an order of magnitude higher in molluscs than in fish. In conclusion, a general contamination by MPs were detected in all animals, with some differences in their morphology and chemical characteristics which depend on the dietary habits of the different species investigated.
Evaluation of microplastics in pigs samples intended for human consumption
Presenter: Claudia Favara
Environmental and Food Hygiene Laboratory (LIAA), Department of Medical, Surgical Sciences and Advanced Technologies “G. F. Ingrassia”, Catania University, Via Santa Sofia 87, 95123, Catania, Italy
The ubiquitous presence of microplastics (MPs) and in the light of new emerging studies, MPs represent a great concern for the environmental ecosystem, and for human health. Most of the articles in the literature analyse MPs in marine animals, but very few data are available for meats. The aim of the study was to investigate the presence of microplastics in local pigs intended for human consumption. After slaughter, samples of blood, urine, the entire colon and the entire rectum were taken to analyse the presence of MPs (<10 μm) and (>10 μm).
The extraction method applied is a nationally and internationally patented method. Identification, counting and measurement of particle diameters was done by SEM-EDX.
MPs were detected both in biopsies of colon (mean diameter 1.71 μm <10 μm and 15.37 μm >10μm) and rectum (mean diameter 1.72 μm <10 μm and 15.54 μm >10μm) and in urine samples (mean diameter of 1.68 μm <10 μm and 30.34 μm >10μm) and blood (mean diameter 1.18 μm <10 μm and 15.06 μm >10μm). These particles with a diameter of up to 15 μm enter the bloodstream and are then translocated throughout the body.
The amounts of MPs (p/g) in pigs represent the first data obtained from a pilot study, further investigations are required in the future. The preliminary results obtained open up a new scenario on food quality, this makes us reflect on the fact that man is exposed to the intake of microplastics also through the consumption of farmed meat
Effects of starch-PBAT blend microplastics on plant growth, soil organisms, microbial functioning and soil physicochemical properties in a mesocosm study
Presenter: Sam van Loon
Amsterdam Institute for Life and Environment (A-LIFE), Faculty of Science, Vrije Universiteit Amsterdam, De Boelelaan 1085, 1081 HV, Amsterdam, The Netherlands
To assess the environmental risk of microplastics (MPs), this mesocosm study investigated the effects of biodegradable starch-PBAT blend MPs on a community of soil microorganisms, plants, springtails and earthworms. Lufa 2.2 soil was spiked with the MPs at 0.025%, 0.05%, 0.2% and 0.8% (w/w dry soil), and incubated in climate-controlled mesocosms for up to 15 weeks (2 weeks incubation and 13 weeks experimental length). Plants (cress and lettuce) and animals (3 species of springtails, 2 species of earthworm) were introduced after 2 weeks of incubation. Springtail abundance was not affected by MP addition. Earthworm survival was not affected, but the total number of juveniles at 0.2% and 0.8% was significantly lower than at 0.025% and 0.05% MPs in the soil. Soil pH-CaCl2 was significantly (p<0.001) affected at all MP concentrations. At the two higher concentrations, small soil aggregate fractions became more dominant. Such changes in soil physicochemical properties may have implications fore.g., microbial community composition, soil invertebrate performance and nutrient availability.Measures of microbial activity (potential ammonification and nitrification, basal and substrate induced respiration) were affected by the MPs. Lettuce shoot length, percentage dry weight, total number oflettuce leaves, chlorophyll concentrations and oxidative stress biomarkers in the lettuce leaves wereaffected at the highest or two highest concentrations. This mesocosm study shows the added value oftesting more complex systems than single species tests, as many effects were observed atenvironmentally relevant concentrations of agricultural microplastics in soil.
Co-exposure to environmental microplastic and the pesticide 2,4- dichlorophenoxyacetic acid (2,4-D) induce distinctive alterations in the metabolome and microbial community structure in the gut of the earthworm Eisenia andrei
Presenter: Iteb Boughattas
Laboratory of Ecotoxicology and Agrobiodiversity, Sousse University, Tunisia
Given the wide use of plastic and pesticides in agriculture, microplastics (MP) and the herbicide2,4 dichloro-phenoxy-acetic acid (2-4-D) can be present simultaneously in soil. Nevertheless,little is known about their combined toxicity on soil organisms. In the present investigation,earthworms Eisenia andrei were exposed to microplastics (10 μg kg-1 of soil), the herbicide 2,4-D (7mgkg-1 of soil) and the mixture of the two for 7 and 14 days. Chemical loads in earthworms were quantified and the bacterial and archaeal diversity were examined in soil and earthworm gut as well as metabolomic profile. Furthermore, the integration between multi-omic data was performed in order to correlate changes in gut microbial diversity and the different metabolites. Our results demonstrated that MPs are ingested by earthworms and increased 2,4-D accumulation. More importantly, high-throughput sequencing revealed a shift in microbial diversity depending on single or mixture exposition. Metabolomic data demonstrated an important alteration of the metabolites related to oxidative stress, inflammatory system, amino acids synthesis, energy and DNA metabolism, being more pronounced in case of co-exposure. Collectively, ou rinvestigation revealed that the combined exposure to MPs and the herbicide 2,4-D poses potential risks to earthworms and consequently soil fertility, thus brooding our understanding about MPs toxicity and impacts on terrestrial environments.
Microplastic in agriculture soils irrigated with treated waste waters: ecotoxicological effects using Lumbricus sp.
Presenter: Sabrine Hattab
Laboratory of Ecotoxicology and Agrobiodiversity, Sousse University, Tunisia
The main objective of our study is to evaluate the toxicity of TWWs using Lombricus sp earthworms collected from irrigated soils with an increasing gradient over time (5 years, 16 years and 24 years). Chemical analysis of trace metal elements (TEMs) and microplastics in soil, as well as at earthworm were performed. Cytotoxicity, neurotoxicity and genotoxicity marker responses were also assessed at the earthworm tissue level. In this regard, we studied the stability of lysosomal membranes (LMS), the catalase (CAT) and glutathione-S-transferase (GST) antioxidant activities as well as the rate of accumulation of malondialdehyde (MDA) as markers of cytotoxicity. Acetylcholinesterase (AChE) activity was monitored as a marker of neurotoxicity and micronucleus (MNi) frequency as a parameter of genotoxicity. Our results showed that the use of TWWs induces alterations of the intestinal mucus and a bioaccumulation of MPs and TEMs in the tissues of earthworms, associated with annoyed cytotoxicity following the temporal gradient. At the genomic level, the pollutants caused genotoxicity that was manifested by a significant increase in MNi frequencies with increasing irrigation periods. Overall, this study highlights the ecotoxicological risk associated with microplastic from the use of TWWs.
Microplastic mediated transfer of Tetracycline resistance: unveiling the role of mussels in marine ecosystem
Presenter: Giovanni Milani
Università Cattolica del Sacro Cuore, Piacenza. Italy
Microplastic pollution has become a major environmental concern in aquatic ecosystems supporting the dissemination of antimicrobial resistance genes. Mussels, due to high susceptibility to microplastic accumulation, are now recognized as important indicators of marine microplastic pollution. In this study, we investigated the transferability of tetracycline resistance mediated by the conjugative transposon Tn916 from Enterococcus faecium UC7251 to two Listeria monocytogenes strains in a complex marine environmental model. Firstly, individual biofilms of the donor and recipients strains were created on microplastic particles. These biofilm-coated microplastics were then introduced into an aquarium housing Mytilus galloprovincialis, and the conjugation rate was evaluated after four and seven days of exposure. The transfer of tet(M) primarily occurred in mussels, exhibiting conjugation rates of 10-4 T/D. Interestingly, this phenomenon was also observed in the salt water, albeit at lower conjugation rates of 10-5 T/D. This study demonstrated that the transfer of the tet(M) gene from E. faecium to both Listeria strains was facilitated by the presence of microplastics combined with filtering effect of mussels.
True-to-life nanoplastics for toxicological and ecotoxicological studies
Presenter: Serena Ducoli
University of Brescia – Department of Mechanical and Industrial Engineering, Via Branze 38, 25123 Brescia (BS), Italy and INSTM
The need to understand the possible implications of microplastics and nanoplastics pollution on the environment and living organisms is becoming increasingly pressing. Given the complexity of separating nanoplastics from environmental samples, studies have been so far conducted using synthetic polystyrene nanobeads (NBs). There is an urgent need to create nanomaterials that better reflect the real characteristics of nanoplastics naturally formed, viz. true-to-life nanoplastics (T2LNPs), to close the gap between the laboratory parameters and the rules of nature, and to provide more realistic understandings of the toxicity and ecotoxicity of nanoplastics.
Here, we present a study on the production and characterization of T2LNPs and the investigation of bio-interfaces through the study of protein-corona and eco-corona formation on T2LNPs with respect to synthetic NBs. T2LNPs were produced from daily life plastic items subjected to mechanical fragmentation and characterized from both the chemical and the morphological points of view. The formation of protein-corona from human plasma, a well-established model fluid for toxicity tests, and the formation of eco-corona from humic acids, representative natural organic molecules for ecotoxicity assessment, were examined and compared between T2LNPs and NBs.
The differences detected in the coronas’ profiles of T2LNPs and NBs confirm the need to develop true-to-life materials as reasonable models for environmental nanoplastics. The broad heterogeneity in size and shape of fragmented T2LNPs gives the nanomaterial a peculiar and different behavior compared to the defined pristine nature of NBs, nominating T2LNPs as a more environmentally relevant material for naturally-occurring nanoplastics and opening the possibility to new and unexpected results in toxicological and ecotoxicological studies.
Bioplastic on marine sandy shores: degradation by supralittoral talitrid amphipods
Presenter: Alessandro Russo
Department of Biology, University of Florence, Via Madonna del Piano, 6, Sesto F.no, 50019 Florence, Italy
Supralittoral amphipods are known to play an important role in fragmentation and degradation of beached organic material, being detritivores and scavengers, and their ability to ingest microplastic has been assessed. The increasing production of various types of bioplastics could lead to their accumulation in the environment, particularly in the supralittoral zone of sandy beaches, similarly to conventional plastic products. Here, we evaluated the effective consumption of bioplastics and their effect on survival rate and pollutant transfer (phtalates) on a common species of supralittoral sandy shores: the amphipod Talitrus saltator (Montagu, 1808). We fed groups of 20 individuals with sheets of the two different starch-based bioplastics commonly used for production of disposable shopping bags for four weeks. Results demonstrated the possibility for talitrids to ingest bioplastic even in absence of a microbial biofilm, like previously suggested, and showed that different bioplastics can have different effects on survival rate of amphipods. Moreover, microtomographic analysis conducted on fecal pellets of T. saltator shows differences in the fragmentation of the two bioplastics. In addition, freshly collected individuals showed a higher concentration of phthalates than experimental individuals, suggesting an elevated presence of these pollutants in the environment, and the possibility of a scavenging effect of plastic during gut transit. Furthermore, preliminary data confirmed the ability of Orchestia montagui, another common talitrid amphipod species, to consume bioplastics and showed similar results in survival rate. In summary, results showed the potential role of T. saltator in the degradation of bioplastic in the supralittoral zone of sandy beaches, even if the material is not fouled by microbial biofilm.
Plastic mulch and pesticides residues effects on the lettuce growth
Presenter: Nicolas Beriot
Soil Physics and Land Management Group, Wageningen University & Research, Droevendaalsesteeg 4, 6708 PB Wageningen, The Netherlands.
Plastic mulch and pesticide residues are ubiquitous contaminants in agricultural soils. In the field, pesticide residues remain in the soil for months and can accumulate over time. However, most studies investigating the effects of these contaminants use pristine chemicals and test them in lab conditions. We tested 3 plastic mulches and 3 pesticides commonly used by farmers. Low-density polyethylene (LDPE), Pro-oxidant Additive Containing plastic (PAC) and biodegradable plastic (BIO) mulches were laid in a field for 4 months, shredded into micro- and macro-sized plastic pieces and then added to a mesocosm soil experiment along with the pesticides. Plastics and pesticides were left in the mesocosm to incubate for a year in field conditions before lettuce seedlings, Lactuca sativa, were planted. After a 14 week growing period, we measured the basal diameter, number of leaves, leaf area, fresh shoot biomass, dry shoot biomass and shoot water content. We observed decreased leaf area, fresh shoot biomass and dry shoot biomass in plants growing in soil where BIO plastic was present as compared to the control treatments. These results follow previous studies and call for a more detailed testing procedure before BIO mulches are approved for agricultural use and made available on the market.
Assessing the impact of Polyethylene Nano/Microplastic Exposure on Human Vaginal Keratinocytes
Presenter: Paola Pontecorvi
Department of Experimental Medicine, Sapienza University of Rome – Viale Regina Elena 324, 00161 Rome, Italy
The global rise of single-use throw-away plastic products has elicited a massive increase of the exposure rate to nano- and microplastics (N/MPLs) in humans. As regards women’s health, the potential threatening effects related to the use of disposable period products releasing N/MPLs have not been scientifically addressed. By using polyethylene (PE) particles (200 nm to 9 μm), we showed that acute exposure to high concentration of N/MPLs induced cell toxicity in vaginal keratinocytes after effective cellular uptake, as viability and apoptosis data suggest, along with transmission electron microscopy (TEM) observations. The internalised N/MPLs altered the expression of junctional and adherence proteins and the organization of actin cortex, influenced the level of genes involved in oxidative stress signalling pathways as well as that of miRNAs related to epithelial barrier function. When the exposure to PE N/MPLs was discontinued or became chronic, cells were able to recover in few days from the detrimental effects on viability, proliferation, and differentiation-related gene levels. However, in all cases, PE N/MPL exposure prompted a sustained alteration of DNA methyltransferase and demethylase expression, which might impact on epigenetic regulation processes, leading to accelerated cell aging and inflammation or to the occurrence of malignant transformation. Our results suggest that, apart from being potentially pollutant for the environment, the use of disposable period products may be dangerous for human health, hence, efforts should be made towards the substitution of plastic bulk material, preferring natural fibres such as cotton and cellulose.