Despite various attempts by composting facilities to remove plastics from compost, high levels of particularly small microplastics (1 µm - 5 mm, MiPs) are detected in compost.

To elucidate the potential removal or enrichment of MiP during the composting process, we first analyzed the input of macroplastics (> 20 mm, MaPs) via bio-waste collection in an industrial composting plant. Then, we further determined MiPs at five different stages during the composting process (before and after distinct shredding and screening processes), as well as in the water used for irrigation.

We found varying total concentrations of MaP in the bio-waste collected from different municipalities, ranging from 0.36 - 4.72 kg ton^-1 bio-waste, with polyethylene (PE) and polypropylene (PP) being the most abundant types. Further, we found a similar presence of “foil” and “non-foil” plastics, with 0.824 ± 0.34 kg ton^-1 and 0.83 ± 0.34 kg ton^-1 bio-waste, respectively; only 0.3 ± 0.1 kg ton^-1 bio-waste of biodegradable plastic was found. The total concentration of MaP and MiP increased from 12 items kg^-1 before shredding to 34 items kg^-1 bio-waste in the final compost, indicating a relative enrichment of the number of particles during the process. Analyzing the rain water used for moistening the compost (collected on the roof of the compost facility) revealed that already high amounts of PE, polyamide (PA) and PP particles with sizes of 6 - 70 µm were found in rainwater (22,714 ± 2,975; 3,108 ± 748 and 685 ± 398 particles L^-1, respectively). These plastic loads were 1.4 to 5-fold lower in the process water collected after irrigation, indicating a co-contamination of compost by irrigation. 

This study highlights the importance of reducing plastic input via bio-waste, as it is one of the main sources for MiP contamination of compost, while also recognizing the challenges in effectively removing MiP during composting. The complex dynamics of MiPs, i.e. the enrichment of small MiPs, is problematic as small particles in particular have many ecotoxicological properties. We could identify irrigation water as a plastic source for compost, an input pathway that has been overlooked so far. Therefore, our results underline the need for comprehensive strategies to tackle plastic pollution throughout the composting cycle, from bio-waste input to final compost products.

How to cite: Peneva, S., Phan Le, Q. N., Munhoz, D., Wrigley, O., Wille, F., Macan, G. P. F., Doose, H., Amelung, W., and Braun, M.: Plastic input and dynamics in industrial composting, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7949, https://doi.org/10.5194/egusphere-egu24-7949, 2024.

Plastic films are essential in modern livestock and crop production. According to the Plastics Europe Report 2022, Light Polyethylene (LDPE) and Polypropylene (PP) are the primary plastic material demand in the agricultural sector. Especially for crop production, plastic mulching films cover arable soil to increase temperature, reduce evaporation, and prevent weed growth. However, mechanical and environmental weathering removes microplastics from the mulch film and can stock in the soil. Additionally, sewage sludge and compost use in agriculture lead to further microplastic contamination. Obviously, microplastic input to soils is critically high, but an accurate quantification is still lacking. This is partly caused by challenges in detection and analysis of microplastic in soils. First, it is challenging to extract microplastic from a matrix of organic and inorganic particles of similar size. Second, the well-established spectroscopic methods (e.g., Raman and FTIR) for detecting microplastics in water samples are sensitive to soil organic matter, and they are very time-consuming. Eliminating very stable organic particles (e.g., lignin) from soil samples without affecting the microplastic to be measured is another challenge. Hence, a robust analytical approach to detect microplastic in soils is needed. In this context, we developed a methodological approach that is based on a high-throughput (25 g soil sample) density separation scheme for measurements in a 3D Laser Scanning Confocal Microscope (Keyence VK-X1000, Japan) and subsequently using a Machine-Learning algorithm to classify and analyze microplastic in soil samples. Our aim is to develop a method for a fast screening of microplastic particle numbers in soils while avoiding the use of harmful substances (e.g., ZnCl₂) or prolonged organic carbon destruction. For method development, we contaminate three different soil types (sandy soil: 86.6% sand, 9.7% silt, 3.7% clay, 0.58% organic carbon; silty loam: 6% sand, 59% silt, 25% clay, 1.3% organic carbon analysis and loamy sand: 72% sand, 18% silt, 10% clay, 0.9% organic carbon) with transparent LDPE, black LDPE and PP microplastic in three different size ranges (< 50, 50 – 100 and 100 – 250 µm). Moreover, we test our method on microplastic fibers (PP, 1000 µm). The separated microplastic plus organic particles and some small mineral particles were scanned using a 3D Laser Scanning Confocal Microscope. For each sample, the 3D Laser Scanning Confocal Microscope generates three different main outputs: color, laser intensity, and surface characteristics with a pixel size of 2.72 µm. Based on these data outputs, a Machine-Learning algorithm distinguishes between the mineral, organic, and microplastic particles. It was found that color changes of microplastics due to soil contact challenge the classification but can be compensated by surface characteristics that become an essential input parameter for the detection. The presented methodological approach provides an accurate and high-throughput microplastic assessment in soil systems, which is critically needed to understand the boundaries of sustainable plastic application in agriculture.

How to cite: Scheiterlein, T. and Fiener, P.: Microplastic detection in arable soil using a 3D Laser Scanning Confocal Microscope coupled with a Machine-Learning Algorithm, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5018, https://doi.org/10.5194/egusphere-egu24-5018, 2024.

The continuous input of microplastics into terrestrial environments is altering the physico-chemical properties of soils. The wide variety of microplastic particles in terms of particle shape, size, polymer type and additives makes microplastic pollution a multifaceted problem. Recent research efforts aim to improve the mechanistic understanding of how microplastics change soil structure and function and how this affects plants and other soil biota. A number of analytical detection methods are now available, but these typically involve sampling or processing steps that destroy the integrity of the sample. As a result, essential information about the soil structure and the spatial distribution of microplastics in the sample is irretrievably lost. Non-invasive tools are needed to directly study the interplay between microplastic particles and the 3D structure of the soil matrix. We introduce a combination of neutron and X-ray tomography as a non-invasive method capable of detecting and localizing microplastic particles in sandy soils (by neutrons) and simultaneously analyzing the 3D microstructure of the surrounding soil (by X-rays). The feasibility and limitations were tested in a series of sandy soil samples containing organic matter and microplastics of different plastic types and shapes, including particles, films, or fibers. Pretreatment with H₂O₂ was tested to facilitate the image analysis for samples with higher organic content.

Our three-dimensional imaging approach can provide detailed information about the spatial distribution of microplastics in the sample and can reproduce the size, shape, and orientation of particles, although it cannot distinguish between plastic types. Visualization of embedded polyethylene film fragments as well as fibers revealed perturbations in the soil matrix that can clearly affect its hydraulic and mechanical properties. Finally, we analyzed microplastics in the spatial context of plant-soil interactions for the root system of a lupine plant, demonstrating that it is also an attractive tool for in-situ studies of soil microplastic effects on plant roots. Overall, this approach offers the opportunity to study the impact of microplastics on soil hydromechanical properties, the interaction of biota with microplastics, and possibly also microplastics local fate in sandy soil, albeit not as a screening or high-throughput tool, but suited as powerful tool for dedicated process studies.

How to cite: Tötzke, C., Kardjilov, N., and Oswald, S. E.: Non-invasive detection and visualization of microplastic particles, films and fibers in sandy soils , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15173, https://doi.org/10.5194/egusphere-egu24-15173, 2024.

It is a continuing challenge to analyze plastic in soil on an environmentally relevant level given the large variety and complexity of soil composition. Improvement of methods is required to: increase sample volume to meet soil heterogeneity, and simultaneously detect and quantify different types of plastic with high accuracy and precision independent of soil properties. A new combination of large-volume pyrolysis with thermal desorption-gas chromatography-tandem mass spectrometry (TD-GC-MS/MS) was used to detect a variety of polymer types without prior clean-up in larger (>1 g) soil samples. Characteristic MS/MS profiles for PA, PBAT, PE, PET, PLA, PMMA, PP, and PS were derived from plastic pyrolysis. Specifically developed rectangular, volume-defined reference micro-particles with respective weight (PE 0.48±0.12, PET 0.50±0.10, PS 0.31±0.08 µg), which can be directly introduced into solid samples for pyrolysis, were used as internal standards. For PE quantification in soil, we suggest a mathematical correction, PE_corrected, when analyzed without clean-up to account for organic matter contribution. In soil with organic carbon >1.5%, PE detection would require removal of organic matter. With a standard addition method, we quantified PS, PET and PE_corrected in complete soil matrices. To evaluate the reproducibility of plastic quantification for soils with different properties, sandy, clayey, oxide-rich and soils rich in organic matter were tested. We can now give recommendations for a simplified, more time-efficient quantification of various plastic types in a range of soil matrices and, hence, provide a robust base for future studies on the fate and effect of plastic in the environment.

How to cite: Bartnick, R., Rodionov, A., Oster, S. D. J., Löder, M. G. J., and Lehndorff, E.: Plastic quantification and limitations in different soil types using large-volume pyrolysis and TD-GC-MS/MS, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16832, https://doi.org/10.5194/egusphere-egu24-16832, 2024.

Composted biosolids are commonly used in agricultural lands as organic amendments. However, biosolids application also exposes the soil to pollution risk from various contaminants including microplastics (MPs). The MPs inevitably interact with the dissolved organic matter (DOM), which is the most active fraction of the soil organic matter. The physiochemical properties of the DOM, which vary based on the organic matter origin, are one of the key factors influencing these interactions. The majority of studies on DOM-MP interactions employ commercially available humic and fulvic acid as the DOM source and may not accurately represent the polydisperse nature of DOM released from organic amendments used in agricultural fields. The motivation for this study stems from recognizing the knowledge gap in understanding the interaction between the naturally occurring DOM in the soil and the MPs. It is imperative to investigate these interactions to determine consequential changes in DOM composition and to evaluate the fate and cotransport with other pollutants in the soils. For this purpose, we conducted adsorption experiments with various concentrations of biosolids-derived DOMs and different MP particles. We used the Excitation-Emission matrix (EEM) obtained by fluorescence spectroscopy to study the changes in the DOM due to its adsorption on the MPs. PARAFAC modeling of the EEMs was used to identify the preferential binding affinity of distinct fluorescent DOM components to the MPs. The results of the adsorption experiment and the EEM analysis will be presented and discussed.

Keywords: microplastics, dissolved organic matter, biosolids, adsorption, fluorescence spectroscopy, EEM

How to cite: Solomon, R. and Arye, G.: Interaction of biosolids-derived dissolved organic matter with microplastics: EEM analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8145, https://doi.org/10.5194/egusphere-egu24-8145, 2024.

Micro- and nanoplastics have become very common pollutants of soil ecosystems, yet their impact on soil microorganisms remains poorly understood. We exposed a model soil bacterium (Pseudomonas putida) and a model soil fungus (Coprinopsis cinerea) to different concentrations of nanosized polystyrene beads in microfluidic soil chips. The transparent micromodels allowed us to perform direct investigation of the effect of beads on abundance of the microbes and on interactions of individual cells with the nanobeads. Growth of both the bacteria and the fungi was reduced by the exposure to nanoplastics, along with a reduction in bacterial enzymatic activity. Nanobeads were strongly attracted to fungal hyphae, causing a high concentration of beads along the first hyphae to enter a pore space, and thus freeing the surrounding from a large proportion of the beads. We also found plastic particle accumulation along fungal hyphae in setups with soil inocula.  Chips with soil inocula also allowed us to investigate direct interactions of microbes with plastic particles, and particle aggregation under the influence of the microbe-affected soil solution over time. These studies contribute to our understanding of direct toxicity effects and interactions of nanoplastics and soil microbes.

How to cite: Hammer, E. C., Mafla-Endara, P. M., Beech, J., and Ohlsson, P.: Soil microbial responses to nanoplastic particles investigated in transparent soil micromodels, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19793, https://doi.org/10.5194/egusphere-egu24-19793, 2024.

The benefits of plastic mulch in agriculture, including higher crop yields, early seedlings development, and earlier harvests, are countered by challenges associated with their complete removal from the soil and proper disposal, ultimately contributing to plastic pollution. Plastic mulching is identified as a major source of microplastic pollution in agricultural soils, with an increasing number of reports indicating its impact on both soil and plant health. However, the causes of the adverse effects are still not clear. The risk posed by microplastics can arise from the plastic particles or as a consequence of the toxicity of chemical additives and plastic-derived compounds, which can be leached over time. In this study we assessed the impact of macro- and microplastic particles, along with their associated leachates, from both conventional (LDPE-based) and biodegradable (PBAT-based) mulch films on the germination of three plant species: arabidopsis (Arabidopsis thaliana), cotton (Gossypium hirsutum L.), and tomato (Solanum lycopersicum). We developed a comprehensive methodology for leachate extraction from macro and microplastics at concentrations of 0.2% and 2% w/w. This process involved monitoring various parameters over time including electrical conductivity (E.C), pH, total dissolved solids (TDS), and UV-visible absorbance indices. Additionally, we employed a semi-automated germination scoring pipeline, obtaining cumulative germination data that allowed the estimation of multiple germination parameters, including the maximum germination capacity (Gmax), the time required for 50% of the seeds to germinate (t50), and the area under the germination curve (AUC). Leachates from PBAT-based mulch showed a significant increase in the solution electrical conductivity (E.C), total dissolved soils (TDS), and absorbance indices for both macro and microplastics over time. Furthermore, a gravimetric weight loss of the biodegradable mulch samples occurred, indicating the release of certain compounds to the solution. Although there were no significant changes in the assessed proxies of leachates derived from LDPE-based mulch after one week, the leachates started to be released more pre-eminently after 35 days.  The seed germination assay revealed a negative effect of the leaching solution from the higher concentration of PBAT-based  leachates on the germination of arabidopsis seeds, as indicated by reduced Gmax(%), increased t50, and decreased AUC in comparison with the control. Although a slight reduction in germination was observed for the other plant species, the values were not statistically significant. When testing the impact of leached or new microplastic particles on the seeds, they did not significantly impact the seed germination parameters. This suggests a potential toxic effect of plastic leachates rather than the microplastics themselves. Further detailed characterization of leachate solutions will be conducted to gain a better understanding of the leaching process and the compounds released to determine the potentially hazardous substances affecting seed germination. These findings can offer valuable insights to the plastic industry, indicating the need to reduce or replace certain plastic building blocks and additives while exploring environmentally friendly alternatives. Moreover, the study underscores the need for increased attention to the environmental repercussions of plastic pollution in agriculture and its potential effects on plant health. 

How to cite: Macan, G. P. F., Munhoz, D. R., Willems, L. A. J., Harkes, P., Geissen, V., and Landa, B. B.: Impact of plastic mulch and their associated leachates on seed germination, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10326, https://doi.org/10.5194/egusphere-egu24-10326, 2024.

Microplastics (MPs) have emerged as a global environmental concern due to the uncertainties surrounding their occurrence, fate, and potential implications for environmental and human health. While research on the impact of MPs on aquatic systems is expanding, studies investigating their influence on terrestrial systems are limited. Agricultural soil acts as a dominant reservoir for MPs, with microfibers being a predominant form due to the application of organic amendments. Despite their ubiquity, the transport mechanisms of these particles and their effects on soil-plant systems remain largely unknown. This study addresses critical knowledge gaps by conducting a series of soil incubation experiments aimed at exploring the effects of polyester (PES) microfibers on soil quality and the growth of three common crops: lettuce, Chinese cabbage, and radish. Plants were cultivated in glass jars containing 100mg/kg fluorescent microfibers thoroughly mixed with the soil. Microfiber distribution was visualized using EVOS Auto FL 2. Soil endpoints revealed that the presence of microfibers induced significant alterations in soil bulk density, with minimal impact on soil carbon and nitrogen content across all plant treatments. Additionally, microfibers exerted a significant decrease in soil pH in lettuce-growing soil, while exhibiting a marginal pH increase in cabbage-growing and radish-growing soils. Microfibers were also found to diminish the formation of water-stable aggregates, particularly in the cabbage-growing soil. In terms of plant endpoints, the study observed accelerated germination of lettuce in the presence of microfibers, while the root length of radish was substantially affected. Microfibers led to a reduction in chlorophyll content in lettuce and cabbage leaves, whereas radish leaves exhibited an increase when exposed to microfibers. Microfibers were detected in both lettuce and radish roots and stems, and weak fluorescence was detected in lettuce leaves. Notably, the impact of microfibers varied among plant species, emphasizing the necessity for species-specific considerations. Furthermore, this study highlights the negative, positive, and neutral effects of microfibers on soil properties and plant performance and proves the potential uptake of microfibers by certain edible plants. The observed outcomes are attributed to the distinctive characteristics of fibers, including their unique shape, surface area, and flexibility, which may interact with soil particles and crops. Given the widespread distribution and accumulation of microfibers in agricultural soil, this study provides crucial insights for ecotoxicological assessments related to soil and terrestrial higher plants. It also holds implications for stakeholders in environmental pollution, food safety, and human health.

How to cite: Chen, Z., Banwart, S. A., Kay, P., Pramanik, D. D., Ashley, D., Feng, W., and Nash, T.: Transport Mechanisms of Microfibers and Their Effects on Soil-Plant Systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-364, https://doi.org/10.5194/egusphere-egu24-364, 2024.

Mulch films are widely used in modern agriculture due to their many benefits, including extension of the growing season, control on weeds, and saving irrigation water. Biodegradable mulch films (BDMs) — films containing one or more polymer(s) that can be fully metabolically utilized by soil microorganisms to form CO₂ and microbial biomass — are considered a viable substitute to conventionally used, environmentally persistent polyethylene films that accumulate in soils over time if not completely removed after harvest. The European Norm for BDMs (EN 17033:2018) stipulates laboratory incubations at 20-28°C to test biodegradation of BDMs for certification. However, to comprehend and predict the fate of BDMs in situ in field soils, it is crucial to understand how temperatures (and variations thereof in the field) affect biodegradation dynamics. Research on this subject is currently limited. In the work presented here, we systematically assess the effect of temperature on the biodegradation dynamics of three commercially available BDMs which are mainly composed of the biodegradable polyesters poly(butylene adipate-co-terephthalate) (PBAT) and polylactic acid (PLA). Laboratory soil incubations were conducted at four environmentally relevant temperatures (i.e., 5, 15, 25, and 35°C) across three different agricultural soils over a two-year period. The biodegradation extents were monitored by quantifying residual PBAT and PLA in the soils at five specific timepoints by Soxhlet extraction of the polymers from the soils combined with polymer quantification using proton nuclear magnetic resonance spectroscopy analysis (¹H-NMR). The results show that the biodegradation of both PBAT and PLA is substantially affected by temperature, with a general trend of higher temperatures leading to increased biodegradation rates and extents. In the case of PLA, increasing temperature consistently increased biodegradation across all tested soils and BDMs. PBAT exhibited similar trends, except for one soil, in which the highest temperature (35°C) did not result in the highest PBAT biodegradation extents. The differences between PLA and PBAT likely reflect their distinct primary hydrolysis pathways — enzymatic hydrolysis for PBAT and abiotic hydrolysis for PLA — as well as differences in the presence and activity of polymer-specific microbial degraders between the soils. The results of modeling efforts will be presented that aim to further clarify the temperature effects on biodegradation rates and assess the extent to which these dynamics can be captured by temperature-reactivity relationships, such as the Arrhenius rate law. The results of this work will provide a basis towards predicting the effects of temperature on in situ field biodegradation rates, using laboratory incubations at temperatures of 20-28°C (as specified by the European Norm for BDMs (EN 17033:2018)) as a basis.

How to cite: Wille, F. and Sander, M.: Assessing the Effect of Temperature on the Biodegradation Dynamics of Biodegradable Mulch Films in Laboratory Soil Incubations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17809, https://doi.org/10.5194/egusphere-egu24-17809, 2024.

Microplastic (MP) contamination of agricultural soils is a growing concern. Synthetic textiles shed MP fibres throughout their lifecycle, which can end up in agricultural soils through the application of urban by-products as soil amendment. MP fibres can affect soil structure and have potentially adverse effects on soil organisms in high concentrations. Polyesters, such as polyethylene terephthalate (PET), are highly resistant to biodegradation and thus very persistent in soils. Understanding the fate and transport behaviour of MP fibres in soils is therefore essential for estimating long-term exposure levels and the potential effects of MP fibres on soil health. Fibres are considered less mobile in soil porewater compared to other particle shapes, but earthworms potentially displace or ingest and excrete fibres, even those within the millimetre size range. Hence, MP fibres may be prone to biologically driven transport despite their relatively large length.

We therefore investigated whether earthworm burrowing causes vertical transport of relatively large MP fibres in soil. We measured the redistribution of MP fibres in laboratory-based process-studies introducing anecic earthworms (Lumbricus terrestris) to soil columns (30 cm depth) spiked with PET MP fibres of 1.3±0.7 mm length. The MP fibres were spiked to an upper surface layer of soil and doped with a metal tracer to facilitate detection with inductively-coupled plasma mass-spectrometry after acid extraction. MP fibre transport was monitored over a total of 4 weeks in different depth segments of the soil columns. We further analyzed the size distribution of MP fibres for the different depths using a visual microscope. At the end of the experiment, MP fibres were detectable in all depth segments, highlighting the transport potential of MP fibres by larger earthworms, such as L. terrestris. We also observed that the depth-dependent decline for MP fibres was stronger in comparison to previous studies with smaller particles proposedly because these are ingested more easily. Accordingly, we expect a relative enrichment of smaller MP fibres in the deeper soil layers. We conclude that biologically driven transport may overall be influenced, but less dependent, on particle length than other transport processes such as advective transport in soil pores. In the field, MP fibres will be exposed to bioturbation processes for much longer times than in this current study, likely resulting in a successive downward transport of even larger fibres depending on the local soil conditions and earthworm activity.

How to cite: Heinze, W. M., Mitrano, D. M., and Cornelis, G.: Earthworms transport microplastic fibres in soils, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18087, https://doi.org/10.5194/egusphere-egu24-18087, 2024.

Transport of microplastics (MPs) in terrestrial compartments has been a growing body of research in recent years, however many of these soil models do not include the realistic role that soil organisms play in terrestrial MP movement. Here, we explore, for the first time, MP transport capabilities of multiple soil species from various ecological niches to investigate complex community structure’s interaction with MPs. Soil column mesocosms were incubated for 18 weeks with 250mg LLDPE (300-600µm) placed on soil surface and introduced were communities of naturally sourced earthworms from single and combined ecological niches (anecic, epigeic and endogeic) along with further integration of the three major ecological niches of collembola (epedaphic, hemiedaphic and euedaphic). Infiltration was performed bi-weekly to simulate intermittent rainfall events and to investigate leaching potential of microplastics through the soil columns with and without the influence of organisms. Throughout the experiment MPs were counted from leachate collected every two weeks and at the end the columns were separated into 11 layers to analyze the distribution of MPs. The presence of anecic, deep burrowing, earthworms significantly increased transport of MPs through the column into the leachate, yet there was an additive effect of leached MPs with all three types of earthworms present together and an even more so when collembola were present with anecic and all earthworms together. Thus, complex community structure increases vertical transport of MPs. At the end of the experiment significantly more MPs were still present at the soil surface of treatments with no organisms and only collembola present, treatments with earthworms present had much less MPs at soil surface and more integration of MPs in each soil layer throughout the entirety of the column. This study highlights the importance of factoring in realistic communities of soil inhabitants as a driver for intensified MP movement and needs to be considered in MP transport modeling.

How to cite: Quigley, E. and Briones, M. J.: Leaching of Soil Microplastics Through Meso- and Macrofuanal Community Transport (manuscript introduction), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18929, https://doi.org/10.5194/egusphere-egu24-18929, 2024.

Column experiments are used to study infiltration and transport behavior of microplastics (MP) in aquifers. The transport behavior of various MP polymer types, including PET, POM, PMMA, and PS, which differ in size (0.8 – 3 mm), density (1.03 – 1.42 g/cm³), and shape, has been examined. The MP particles were added to the inflow of columns containing different gravel compositions, having both unimodal (d₅₀ = 12, 6.5, 2.5, 1.2 mm) and bimodal distribution (d₅₀ = 10, 6, 3.5 mm), and also of columns filled with sand (d₅₀ = 0.031 and 0.065 mm). To introduce MP particles into the sediment, a novel approach involving melting frozen MP particles embedded in ice layers was employed. This method naturally replicated the infiltration process while minimizing blockages or particle losses in the circuit's pipes and connectors. After infiltration at defined flow rates for three days, MP particles have been separated from sediment layers of 3 cm thickness manually or using density separation. The depth where they were identified is defined as infiltration depth. Micro computed tomography (Micro-CT) was applied to visualize sediment pores and throats where MP passed through. Results for infiltration in different gravel textures showed as expected that smaller MP are transported to a greater depth. Lighter MP were also found in deeper layers due to its shape. Concerning shape effects, flat circular discs showed a higher potential to be found at greater infiltration depth, compared to spheres, fibers and pellets. Concerning the size ratio between MP and sediment grains bimodal sediment reveals to hinder the infiltration of MP due to its lower pore size, which is consistent with results from the Micro-CT pore measurement. Initial results from sand column experiments will be analyzed to explore the size ratio range between sediments and MP under saturated conditions, highlighting the differences in MP behavior between sand and gravel. The findings enhance our understanding of MP transport mechanisms in aquifer sediments and infiltration basins and offer insights for groundwater and sediment MP contamination mitigation.

How to cite: Ding, J. and Grischek, T.: Laboratory Experiments on the Transport of Microplastic Particles in Gravel and Sand Sediments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3856, https://doi.org/10.5194/egusphere-egu24-3856, 2024.

Agricultural soils receive substantial inputs of microplastic pollution from a range of different sources. The degradation and fragmentation of mulching films during and after use is expected to represent an important source of microplastic particles to soils, backed up by emerging evidence from monitoring activities. Yet, the transport and fate of these particles after they enter soil environments remains a persistent knowledge gap. This is important as soils may effectively retain these particles – resulting in increasing pollution with successive inputs – or particles may be mobilised from soils, contaminating other environments such as groundwater or surface waters. The processes that control retention versus export of particles have been poorly constrained and are expected to be complex. Chemical additives are routinely added to plastic mulching films to bestow a range of specific material properties. The extent to which these chemicals may leach out of particles in soil environments, and their potential to be transformed or mobilised in soils following release is not well known.

This study tracked the vertical transport of microplastic fragments derived from two relevant mulching films and associated chemical additives within soils: one biodegradable mulching film and one conventional plastic mulching film. The study specifically investigated the influence of factors expected to exert a control on particle/chemical fate: bioturbation and soil water inputs. The experiment was conducted in the CLIMECS (CLImatic Manipulation of ECosystem Samples) facility at Vrije Universiteit Amsterdam, which comprises 40 soil columns that simulate ecosystems – with soil, vegetation, and fauna – and are individually controlled for different environmental conditions. The two types of microplastic fragments were added to the upper layer (10 cm) of soil columns (total length: 40 cm) to represent a contaminated plough layer. Different treatments consisted of high and low microplastic concentrations, high and low watering regimes, and the presence and absence of earthworms. The columns were maintained for a period of twelve weeks. Microplastic and chemical additives content was measured in six different depths within each core at the end of the three months, to assess the extent of vertical transport. The results from this study reveal important insights on the mobility of mulching film fragments within soil systems and elucidate some of the important controls on particle movement. This provides crucial context related to the exposure of soil environments to soil microplastic and chemical additive pollution derived from mulching film use.

How to cite: Hurley, R., Consolaro, C., van Loon, S., Tsagkaris, A., Dvorakova, D., de Jeu, L., J. Zantis, L., A.M. van Gestel, C., and Nizzetto, L.: Vertical transport of microplastics from agricultural mulching films and associated chemical additives in soil ecosystems , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16962, https://doi.org/10.5194/egusphere-egu24-16962, 2024.

The transport of microplastics within and across terrestrial ecosystems is a critical factor controlling plastic pollution in the environment. However, our understanding of these transport processes remains extremely limited. Particular uncertainty surrounds how the changes driven by aging of plastics, for example in surface roughness or hydrophobicity, affect polymer transport.  In this study we compare the rate of transportation of pristine and aged polystyrene microplastics in a simulated rainfall event providing the first empirical data describing these processes. Additionally, we quantified the proportion of both aged and pristine microplastics incorporated into soil aggregates after several wet-dry cycles and the influence wet-dry cycles had on microplastic mobilization. The results from this study will provide critical insights into the influence of polymer age on microplastic mobility and retention in terrestrial environments.  

How to cite: Severe, E., Phan Le, Q. N., Maqbool, A., Surridge, B., Halsall, C., Gómez, J. A., and Quinton, J.: Influence of polymer age and soil aggregation on microplastic transport in soil erosion events, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10940, https://doi.org/10.5194/egusphere-egu24-10940, 2024.

Soil is polluted with plastic waste from macro to submicron level, and research has intensified on the fate and transport of plastic with more focused particulate plastic, including fibers (<5mm). Yet, our understanding of macroplastic (>5mm) occurrence and behavior has remained comparatively elusive, mainly due to a lack of tracing mechanism. This study utilized magnetically tagged soil movement and provided a comparison with a method for tracing macroplastic pieces labeled with a physically adhesive passive radiofrequency identification transponder used as an innovative and efficient approach. A field study following best practice approaches of soil tillage was carried out to determine the displacement of macroplastic during the non-inversion chisel and inversion disk tillage process to understand the fate of macroplastic in arable land. All the experiments were performed at plain topography to eliminate the downslope and drift effect, while tillage depth (0.15 m) and speed (4.5 km h^-1) were kept constant during the tillage process. The results indicate that non-inversion tillage has a significantly more protracted macroplastic transport displacement compared to inversion tillage by a factor of 2.4.  The mean displacement of macroplastic by tillage erosion is 0.36 ± 0.25 m chisel and 0.15 ± 0.13 m disk tillage per pass. However, inversion tillage caused substantially more fragmentation of macroplastic. In general, both tillage implements drove the burial of surface macroplastic into the plow layer.  This highlights that soil can act as a long-term sink for macro and microplastic and would expect less plastic to be transported into the atmosphere and aquatic system from arable land.

This project gets financing from the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement number 955334.

How to cite: Maqbool, A., Guzman, G., Fiener, P., Wilken, F., Soriano, M.-A., and Gomez, J. A.: A field experiment on macroplastic redistribution and fragmentation by soil tillage , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4033, https://doi.org/10.5194/egusphere-egu24-4033, 2024.

Post-Brexit agricultural policy has generated an extensive range of new instruments to improve the sustainability of UK farming. However, none of these proposed policies deal with plastic pollution on UK farmlands. In this article, we use the UK's evolving policy context regarding farming payments to propose a monetary incentive whose environmental policy target is to change or reduce the use of -potentially harmful- agricultural plastics. We conducted a Discrete Choice Experiment among a sample of northern England farmers in which they considered two hypothetical Sustainable Farming Incentive (SFI) contract alternatives plus an opt-out alternative. The proposed SFI contracts include five attributes, including the contract length, the SFI payment, and three agricultural plastic-reducing actions: i) reduce the use of polymer-coated fertilizers, ii) reduce the use of plastic mulch film, and iii) reduce the use of silage films made only of virgin plastics. These actions can be accomplished at a lower, medium, and high level of compromise, and the payment varies with them. As agricultural plastics are essential for farm productivity, farmers are not asked to completely eliminate their use but replace them with more sustainable alternatives. Moreover, we used a within-farmers design to test the effect of a stringent enforcement strategy on their participation and willingness to accept SFI. We hypothesize relevant trade-offs between the contract's compromise level, the monetary payment offered, and farm and farmer-specific variables such as farm size, farming activities, and plastic and microplastic pollution awareness, among many others. Likewise, stringent enforcement may lead to a reduction in the stated participation and an increase in the monetary compensation needed to perform the indicated activities. This research may help develop incentive-compatible agricultural policies to reduce the usage of harmful agricultural plastics and improve our understanding of key factors explaining farmers’ adherence to new agri-environmental schemes in the UK.

How to cite: Barrientos, M., Aftab, A., and Scarpa, R.: Farmers’ preferences for reducing agricultural plastics: A discrete choice experiment among UK farmers., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9723, https://doi.org/10.5194/egusphere-egu24-9723, 2024.

In Europe, about 50 million tons of plastic are produced per year out of which ca 40% is processed into packaging (Plastic Europe, 2022). Packaging often ends up in landfill or in the environment after only a short or single use. Unfortunately, recycling is often inadequate, contributing to only about 10% of the European demand for plastic being met by recycled plastics (Plastics Europe, 2022). Large amounts of plastic end up in the oceans, accumulating as "garbage patches" and washing up on shores. However, the amounts of plastics that end up in soils is not precisely known. Scientific studies have concluded that 4 to 32 times as much plastic ends up in soils as in water bodies (Horton et al., 2017). In addition, little is known about what types of plastics enter the soil environment, and in what proportions.

The Soil Plastic App allows citizens to input observations of visible plastics and their characteristics, with a strong focus on agricultural plastics, on soils and enable to monitor the change of plastics in soils. The App runs on the citizen science Spotteron Platform and is available for iOS, Android and as a web application. This way, observations can be entered anywhere on the globe and anytime. Since December 2022, citizens have already made over 22.000 plastic observations in the SoilPlastic App. The first set of validated Austrian citizen observations between beginning of April 2023 and end of July 2023 resulted in ca 6000 observations, as part of the Austrian Citizen Science Award Project Bunter Boden. This presentation will present the first results from Austria and discuss the potential of SoilPlastic App in observing change of plastics in soils.

How to cite: Sandén, T., Miloczki, J., Götzinger, S., Hummer, P., Milewski, A., Spiegel, H., and Guggiari Dworatzek, M. S.: The potential of participatory citizen science in observing change in plastics in soils, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21237, https://doi.org/10.5194/egusphere-egu24-21237, 2024.