Nanoplastic (NP) exposure to the terrestrial water cycle poses an emerging threat to subsurface ecosystems, while the continuous release of NP increases the risk of drinking water contamination.
Fungal communities are a crucial component of terrestrial ecosystems. Traditionally, their presence and functions have been studied in shallow soils as part of the soil microbiome or above ground as decomposers or pathogens. Recent mycobiome screening studies of groundwater wells have revealed the presence of fungal species in deeper aquifers. This confirms the presence of fungi across all compartments of the terrestrial water cycle, highlighting the need to investigate their role in contaminant transport processes.
Fungi have demonstrated the ability to immobilize dissolved organic contaminants, heavy metals, and pharmaceuticals from polluted waters. However, studies examining their effect on NP removal remain limited. Existing research generally lacks the integration of liquid flow dynamics, which is crucial for understanding fungal interactions in natural water systems.
We present a dataset, which shows dynamics of NP-fungi interaction across multiple laboratory scales. Our study compares batch adsorption experiments with transport experiments conducted in inoculated microfluidic chips and transport columns. Carboxylated polystyrene nanoparticles of 100 nm and 250 nm serve as model NPs. Following fungal inoculation in growth media, the experiments are conducted under various ion concentrations of CaCl and flow velocities ranging from 1 m/d and 30 m/d.
Our results indicate scale-dependent modes of NP-fungal interactions. In batch-scale experiments, higher ion concentrations significantly enhance the adsorption efficiency of NPs to fungal hyphae. In contrast, experiments conducted in microfluidic chips and transport columns reveal altered behavior, with notably lower adsorption efficiencies observed.
This suggests that in natural environments, factors such as the spatial distribution of hyphae, ion concentration, flow rates, and consequently reaction times, collectively influence the efficiency of NP removal by fungal communities.
How to cite: Müller, S., Zou, H., Lundqvist, M., Cedervall, T., Mafla Endara, M., and Hammer, E.: Nanoplastic- Fungi interaction – insights from various laboratory scales, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5999, https://doi.org/10.5194/egusphere-egu25-5999, 2025.
The widespread use of plastics has undeniably brought numerous advantages to society, facilitating countless advancements in technology, industry, and daily life. However, the proliferation of plastic debris in various environmental systems has become an escalating concern. Recognizing this pressing issue, our research team at the Civil Engineering Department of the Indian Institute of Technology (IIT) Roorkee has undertaken an experimental investigation to study the transport behavior of microplastics within soil matrices.
Specifically, we focus on coumarin 6 dyed microplastic particles, sized between 35 to 40 microns, as tracers to understand their migration patterns. This study employs vertical soil columns as experimental setups, designed to mimic natural subsurface conditions. Each soil column has a depth of 30.5 cm and is packed with carefully prepared soil types to replicate varying real-world scenarios. By using artificial drip irrigation systems to simulate rainfall or water infiltration, we aim to elucidate the mechanisms by which microplastics are transported through soil systems, potentially leaching into underlying groundwater reservoirs.
The primary objective of the study is to systematically investigate the factors influencing the downward movement of microplastics in different soil types. For this purpose, two types of soil have been used: fluvial sand and gravel soil. The influence of several variables on microplastic transport was examined, including variations in soil pH, organic matter content, drip irrigation intensity. These parameters were chosen because of their potential to alter the physicochemical properties of the soil environment, thereby affecting the mobility of microplastics.
To begin the experiments, vertical soil columns were packed with either fluvial sand or gravel soil. The soil was pre-conditioned to achieve specific pH levels and organic matter contents, ensuring controlled and reproducible conditions across trials. Microplastic particles stained with coumarin 6 dye were introduced at the top of the soil column along with water droplets, mimicking natural infiltration processes under varying drip irrigation intensities.
The effluent from the outlet at the bottom of the soil column was collected at regular intervals to quantify the number of microplastic particles that had traversed the column. These collected samples were then subjected to analysis under a fluorescent microscope, which enabled accurate detection and quantification of microplastic particles.
The study also highlighted the impact of drip irrigation intensity on microplastic migration. Higher flow rates were found to promote greater transport of microplastics, as the increased water velocity reduced the residence time of particles within the soil and minimized opportunities for retention or adsorption. Conversely, lower flow rates allowed for more pronounced interactions between the microplastics and the soil matrix, leading to increased retention.
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How to cite: Khan, M. F. and Ojha, C. P.: Drip Irrigation Promoted Migration of Microplastic Particles Across Vertical Soil Columns., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2391, https://doi.org/10.5194/egusphere-egu25-2391, 2025.
In recent years, microplastics (MPs), have infiltrated diverse environments, including oceans, rivers, lakes, wetlands, groundwater, soils, sediments, air, human tissues, food systems, and even the atmosphere. Among these, groundwater, a critical freshwater source for industrial, agricultural, and domestic applications faces increasing threats from MPs pollution. There is still a knowledge gap in understanding the mechanisms and the pathways governing the transport of MPs in complex groundwater systems, which remains a significant research challenge. Hence, to understand the transport of MPs through the porous media, we have conducted a series of one-dimensional (1D) column transport experiments. To quantify the transport of MPs through the porous media, two types of MPs with different functional groups, polypropylene (PP, C3H6) and polyethylene terephthalate (PET- C10H8O4) of size 100-200 µm are considered for the present study. The experiments are conducted using porous media of IS Grade I (2mm-1mm, d50= 1.5mm) and Grade II (1mm- 0.5mm, d50= 0.75mm) experimental sand. Various flow velocities were used to determine the most vulnerable pore-water velocity on the transport of these contaminants through the porous media. For each case, the experiment is conducted for 10 pore volume and after 10 pore volumes, the sand samples from different depths of the column are taken to determine the number of particles attached to the sand grains. We have observed that, as pore volume increases, the MPs count rises steadily for most samples, indicating enhanced transport through the porous media. This suggests that MPs are progressively mobilized through the porous media as the pore volume expands, with certain volumes contributing more significantly to the overall transport dynamics. Coarser sands (Grade I) with more prominent pores facilitate higher MPs movement, while finer sands (Grade II) reduce transport due to greater retention. Additionally, higher pore-water velocity enhances MP mobility, suggesting that environmental conditions with coarser soil and increased water flow can lead to greater MPs dispersion, impacting its distribution in natural soil-water systems. The findings of this study can play a crucial role in applying indirect site interventions to avoid the spreading of MPs through porous media at polluted sites.
How to cite: Yadav, S., Yadav, P. B. K., and Krause, P. S.: Transport of Microplastics Through Porous Media: Influence of Porosity and Pore-Water Velocity , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18937, https://doi.org/10.5194/egusphere-egu25-18937, 2025.
Ubiquitous microplastics (MP) have emerged as a global environmental concern, recently also in soils. However, limited attention has been given to the behaviour of small-sized MP (< 10 μm) due to the challenges associated with separating and quantifying MP from an exceedingly complex matrix. Here, we show that magnetic labelling of MP greatly increases the efficiency of MP extraction from soil using a magnetic field. Magnetic labelling was achieved by exploiting the glass transition of polystyrene MP sphere. By heating MP (4 µm polystyrene spheres), to induce surface melting in a suspension containing Fe3O4 magnetic nanoparticles (MNS), the MNS were adsorbed onto the MP surface. Subsequent cooling to room temperature, led to fixation of the MNS into the MP surface layer enabling MP extraction using a magnet. Incubating MP and MNS at 90°C for 2.5 h gave the highest MP recovery rate of 92 ± 7% in water. The same MP were then added to a sandy soil suspension to assess and optimize labelling and extraction efficiency of the MP from the soil. The following parameters were optimized: dispersant type, organic matter digestion, and MNS size, concentration, and storage time. Compared to conventional MP detection methods, the MP recovery using magnetic extraction improved from 26% to 94 ± 12%. To the best of our knowledge, this research represents the first successful quantitative extraction of MP < 10 μm from soil and opens new possibilities for fate assessing of small MP and cleaning the environment.
How to cite: Liu, Y., Hu, J., Huang, Y., Krekelbergh, N., Novita Kusumawardani, P., Sleutel, S., Parakhonskiy, B. V., Kollannur Biju, M. S., Hoogenboom, R., De Neve, S., and Skirtach, A.: Magnetic labelling and extraction of micrometer-sized microplastics from soil, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5376, https://doi.org/10.5194/egusphere-egu25-5376, 2025.
Microplastics are ubiquitous and have been detected across all environments. While the focus has been on pollution threats posed by plastic particles e.g. derived from fragmented plastic packaging or tyres – the dominant form of microplastic particles identified in environmental samples tends to be microfibres, shed from textiles. Microfibres are believed to enter the environment mainly via laundering of garments, with soil environments forming an important sink for microfibres due to sewage sludge applications from wastewater treatment plants. There is growing awareness that these microfibres are not only synthetic (plastic) but also originate from natural textiles, such as cotton and wool, which have been largely overlooked from an environmental science perspective. With 100 billion new garments made every year, we know little about the environmental impact during ‘wear-and-use’ and at the ‘end-of-life’ of textile microfibres. Therefore, we need to understand the release of microfibres from natural and synthetic fibres from across the garment life-cycle (from manufacture to end-of-life). We set up an incubation study burying 5 x 5 cm sections of different fabrics in soil, along a gradient of cotton-polyester blends to determine textile biodegradation, microfibre fragmentation and impacts to soil properties. We selected fabrics with contrasting plain dyes (light vs dark colours) to test whether dye quality affected biodegradation rates. Over the course of the short-term incubation, fabric and soil samples were retrieved and analysed for various properties to track changes in fabric samples, microfibres and soils. Here we present some data from the experiment to begin to understand how natural and synthetic fibres biodegrade in soil and their impact on soil properties and soil health.
How to cite: Prendergast-Miller, M., Rogers, A., Mutambo, N., Sheridan, K., and James, A.: Biodegradation of cotton-polyester textiles to understand fate of natural and synthetic microfibres in soil, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7447, https://doi.org/10.5194/egusphere-egu25-7447, 2025.
Microplastics (MPs) in urban areas threaten ecosystems, causing water and soil contamination, as well as health risks. This study examined MPs in road sediments from five functional areas in Daxing District, Beijing, using characterization and risk assessment methods. The abundance of MPs ranged from 2060 to 8680 items/kg, with business areas showing the highest levels, followed by traffic, residential, leisure, and cultural/educational areas. These variations are likely influenced by human activities, urbanization, and traffic volume. MPs were primarily in fragmented forms, with polypropylene (PP) (43%-87%) and polyethylene (PE) (5%-33%) being the most common polymers. Fragmentation characteristics varied, with cultural/educational areas showing the highest α values despite fewer large MPs. Lower λ values (2.80-5.00) suggest a higher potential for MPs to break down, possibly contributing to stormwater pollution. Multiple risk assessments indicate that the presence of polymers like PP and PE contributes to elevated MP risks in both traffic and residential areas. These areas have been identified as "hotspots" with moderate to high pollution risks. Despite frequent street cleaning in traffic areas, contamination persists. In contrast, leisure areas, with lower human activity, have a reduced risk of MP contamination. These findings can inform effective control measures for MP pollution in urban road sediments.
How to cite: Gu, Y., Zhang, X., Liu, J., Deng, J., Zhang, Z., Tan, C., Li, H., and Hu, Y.: Microplastics in Road Sediment of Typical Urban Districts of Beijing: Characteristics and Risk Assessment, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21474, https://doi.org/10.5194/egusphere-egu25-21474, 2025.
Microplastics in rivers originate from various sources and can be transported by river water. During their time in the river, the properties of microplastics may change leading to a temporary deposition and accumulation in the riverbed. In particular, during floodings, stronger flow velocities occur and can remobilize microplastics and sediments, transporting them further downstream and to adjacent floodplains. Floodplains represent dynamic and vegetation-rich environments, where the vegetation increases the floodplains’ roughness, resulting in slower flow velocities during floods and potentially enhance deposition of sediments and microplastics. While previous research has shown that factors such as local topography and flood frequency influence microplastic distribution in floodplains, however, the role of vegetation in microplastic filtering during floods has not been studied.
This study investigates the retention of microplastics and natural sediments by floodplain grassland vegetation during a major river flood. Directly after the flood event in July 2021, we sampled vegetation from a formerly flooded Rhine floodplain north of Cologne, Germany. For comparison we sampled vegetation from an adjacent non-flooded grassland, which was only affected by atmospheric microplastic deposition. After rinsing the deposits from the vegetation, we used ZnCl₂ density separation to extract microplastics, followed by enzymatic-oxidative purification to remove organic material and µ-FPA-FTIR imaging for microplastic analysis.
Our findings show that microplastics from fluvial and atmospheric origin differ in terms of their numbers, shapes, sizes, and polymer types. Concerning the samples from flooded vegetation, higher vegetation biomass was associated with increased deposition of both natural sediments and small microplastics. However, we observed distinct deposition patterns for natural sediments and microplastics. Our results provide valuable insights into the role of floodplain vegetation in the retention, accumulation, and distribution of microplastics at the interface between aquatic and terrestrial ecosystems.
How to cite: Rolf, M., Laermanns, H., Laforsch, C., Löder, M. G. J., and Bogner, C.: The role of floodplain vegetation in filtering microplastics during a major Rhine flood event, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17588, https://doi.org/10.5194/egusphere-egu25-17588, 2025.
Riverbed sediments have been identified as temporary and long-term accumulation sites for microplastic particles (MPs), but the transport and retention mechanisms still need to be better understood. Here we assess the occurrence and spatial distribution of MPs in surface water, riverbed sediments, and groundwater of two German lowland rivers (Teltow Canal and Havel), under prevailing infiltrating conditions. Surface water and groundwater samples were collected at each site on a monthly and three monthly basis over the course of one year, respectively. At each site, three sediment freeze cores up to a depth of 100 cm were taken, and, together with the water samples, analysed by near-infrared spectroscopy (NIR) to infer the number of MPs (Ø > 100 µm), polymer types, and particle sizes.
The number of MPs detected varies considerably between the compartments (with concentrations in the groundwater being approximately one order of magnitude lower than in the river), the sampling sites, and also, but to a much lower extent, over the seasons. MPs were also detected throughout the entire depth of the sandy riverbed sediment, thereby highlighting the retention capacity of the riverbed sediments, but also the partial mobility of MPs from the river through the subsurface into the groundwater. These observations were supported by saturated column experiments with fluorescent polystyrene particles (fPS), which demonstrated that the vast majority of fPS were retained in the upper 20 cm or 15 cm of gravelly or sandy sediments for common filtration rates. However, it was also observed that approximately 0.3% of the introduced MPs, with sizes ranging from 100 µm to 500 µm, were transported throughout the entire column for a high filtration rate.
These results demonstrate that riverbed sediments have the capacity to retain MPs originating from surface water. Furthermore, they indicate that these sediments can also act as potential vectors for the infiltration of small MPs into local groundwater aquifers, especially under prevailing infiltrating conditions.
How to cite: Munz, M., Loui, C., Pittroff, M., and Oswald, S. E.: Occurrence and transport of microplastics across the streambed interface during bank filtration, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15405, https://doi.org/10.5194/egusphere-egu25-15405, 2025.
Plastic nanoparticles, widely used in various consumer products, have become a significant contributor to soil pollution, making it essential to understand their transport in soils, where organic substances are prevalent. This study aimed to investigate the influence of low-molecular-weight organic acids (LMWOAs) on the transport of polystyrene nanoparticles (PS-NPs) through saturated quartz sand. The focus was on seven specific organic acids: three dibasic acids—malonic acid (MA1), malic acid (MA2), and tartaric acid (TA)—and four monobasic acids—formic acid (FA), acetic acid (AA), propanoic acid (PA), and glycolic acid (GA). The effects were evaluated across a range of pH levels (4.0, 5.5, and 7.0) and in the presence of two cations, Na⁺ and Ca²⁺. The results showed that, in the presence of Na+, dibasic acids significantly enhanced the transport of PS-NPs, with TA being the most effective, followed by MA2 and MA1. This enhancement was attributed to the adsorption of LMWOAs onto the PS-NPs and quartz sand, leading to a more negative ζ-potential. This negative shift increased electrostatic repulsion between the particles, reducing their deposition and facilitating transport. The Derjaguin-Landau-Verwey-Overbeek (DLVO) theory further explained that higher pH levels increased the energy barrier, which reduced PS-NPs deposition by stabilizing them in the suspension. In contrast, the monobasic acids—apart from GA—exhibited minimal impact on PS-NP transport. These acids slightly diminished the hydrophilicity of the PS-NPs, as evidenced by a minor increase in the water contact angle, which in turn reduced their mobility. However, GA, with its additional hydroxyl group, acted similarly to dibasic acids, promoting both enhanced hydrophilicity and increased transport of PS-NPs. When Ca2+ was present, the transport enhancement was similar to that observed with Na+. The complexation and bridging effects of Ca2+ with the organic acids and PS-NPs contributed to this effect. Overall, these findings offer valuable insights into the factors influencing the mobility of PS-NPs in soils, which is crucial for understanding their environmental behavior and potential ecological impacts.
How to cite: Lu, T., He, J., and Yang, M.: Impact of Low-Molecular-Weight Organic Acids on the Transport of Polystyrene Nanoplastics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-512, https://doi.org/10.5194/egusphere-egu25-512, 2025.
Biodegradable film mulching has attracted considerable attention as an alternative to conventional plastic film mulching. However, how much of microplastics is being formed during the film degradation and their impact on soil health during long-term use of biodegradable plastic film are not known. We quantified the amounts of microplastics (0.1-5 mm in size) in the topsoil (0-20 cm) of two cotton fields with different mulching cultivations: (1) continuous use of conventional (polyethylene, PE) film for 23 years (Plot 1), and (2) 15 years use of conventional film followed by 8 years of biodegradable (polybutylene adipate-co-terephthalate, PBAT) film (Plot 2). We further assessed the impacts of the microplastics on soil carbon contents and flows. The total amount of microplastics was larger in Plot 2 (8507 particles kg− 1) than in Plot 1 (6767 particles kg− 1). The microplastics (0.1-1 mm) were identified as derived from PBAT and PE in Plot 2; while in Plot 1, the microplastics were identified as PE. Microplastics > 1 mm were exclusively identified as PE in both plots. Soil organic carbon was higher (27 vs. 30 g C kg-1 soil) but dissolved organic carbon (120 vs. 74 mg C kg− 1 soil) and microbial biomass carbon were lower (413 vs. 246 mg C kg− 1 soil) in Plot 2 compared to the Plot 1. Based on 13C natural abundance, we found that in Plot 2, carbon flow was dominated from micro- (<0.25 mm) to macroaggregates (0.25–2 and >2 mm), whereas in Plot 1, carbon flow occurred between large and small macroaggregates, and from micro-to macroaggregates. Thus, long-term application of biodegradable film changed the abundance of microplastics, and organic carbon accumulation compared to conventional polyethylene film mulching.
How to cite: Jiang, R. and Wang, K.: Impact of long-term conventional and biodegradable film mulching on microplastic abundance and soil organic carbon in a cotton field, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1849, https://doi.org/10.5194/egusphere-egu25-1849, 2025.
Soil aggregates play a pivotal role in soil organic carbon dynamics and microbial activity. However, their influence on the pressing issue of microplastic (MP) contamination in soils remains poorly understood. This lack of attention may be attributed to the inherent complexity and heterogeneity of soil, which renders plastic isolation and identification in soil is particularly challenging. This study aims to investigate MPs redistribution among soil aggregate fractions during the process of soil aggregation. Two soil textures (silt loam and sandy loam) were amended with organic matter (OM) to promote aggregation during a two-month incubation period, with 0.1 % microplastics powder added to the soils. A self-made pristine and aged LDPE and PET microplastics (<50 µm) were used in this experiment. Subsequently, physical fractionation were implemented to separate the soils into aggregate fraction (macro-aggregate, micro-aggregates and within associated fractions and silt+clay fractions). Organic matter was removed via oxidation to prevent interference with MP analysis. MPs were subsequently extracted through density separation, filtration, and examined using a Keyence VH-Z500 digital microscope. Unexpectedly, even small amounts of MPs significantly influenced soil aggregation, with effects varying by polymer type, weathering state, and soil texture. LDPE was predominantly retained in the micro-aggregate fractions in both soil textures, except for aged LDPE in loam soil, where over 60% accumulated in the silt+clay fraction. Conversely, PET was primarily retained in the macro-aggregates of silt loam soils and the micro-aggregates of sandy loam soils. Furthermore, the redistribution of MPs during soil aggregation exhibited notable differences, with silt loam soils demonstrating the highest degree of MP redistribution. These findings are relevant as soil aggregates provide different levels of physical protection against degradation and mobility, influencing the bioavailability of microplastics and their potential transfer to other environmental compartments.
How to cite: Kusumawardani, P. N., Amaya, D. P. T., Krekelbergh, N., Liu, Y., Sleutel, S., Skirtach, A., and De Neve, S.: The Re-distribution of Pristine and Aged Microplastics (<50 µm) in Soil Aggregate Fractions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5584, https://doi.org/10.5194/egusphere-egu25-5584, 2025.
Plastics have become an integral part of our lives due to their versatility and durability. Conventional plastics are made from non-renewable resources that are harmful to humans and the environment. They release toxic substances and break down into microparticles. The use of biodegradable plastics, such as polylactic acid (PLA), is a viable alternative to reduce the above-mentioned problematics. This study investigates the long-term (9 months) biodegradability of PLA in soil under laboratory conditions in a closed chamber system. The experiment was set up according to the European standard ISO 17556:2012. The biodegradability percentage of the plastic was calculated by measuring the production of CO2 by microorganisms in the soil on PLA. The percentage biodegradability of the PLA was calculated using soil CO2 emission rates (measured by titration method). PLA was used in net and film forms under two experimental conditions: untreated soil and soil modified with two natural soil amendments (natural zeolites and biochar) to evaluate their potential impacts on PLA decomposition rates and CO2 emissions. Cellulose (100% biodegradable) was used as a positive control. For comparison, PLA degradation was also studied under temperature-controlled composting conditions (58°C) with the same experimental setup. The morphological changes of PLA were analysed using a scanning electron microscope. The results showed different trends over time and significant differences between the treatments, especially concerning the presence of soil amendments, highlighting the complexity of the interactions between PLA and the soil microbial community and physico-chemistry of the substrate.
How to cite: Pignoni, E., Calosi, M., Ferretti, G., Botezatu, C., Alberghini, M., Bertoldo, M., and Coltorti, M.: Long-term biodegradability of Poly-Lactic Acid (PLA) in soil by measuring carbon dioxide evolution in a closed system, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9909, https://doi.org/10.5194/egusphere-egu25-9909, 2025.
Qualifying and quantifying microplastic (MP) pollution in sediments represent a methodological challenge. Most used methods often require sample pretreatments to separate the MP particles of interest from the rest of the sediment. It has been demonstrated that the sampling preparation can influence the analytical results. To overcome these difficulties, Romero-Sarmiento et al. (2022) proposed the use of the pyrolysis and oxidation based-thermal method (a Rock-Eval® device), originally developed to characterize sedimentary organic matter. According to these authors, several parameters calculated from Rock-Eval® analyses, such as Total HC (quantity of hydrocarbons released during pyrolysis) and Tpeak (cracking temperature of plastic polymers), could be used to qualify and quantify microplastics, without sediment pretreatments. However, unpublished preliminary studies have shown that the Tpeak parameter, can vary with catalytic and thermal desorption effects, depending on the nature of the associated mineral and organic matrices. To understand the origin of these effects, we studied matrix effects during the thermal analysis of composite samples. In this study, synthetic mixtures of various mineral matrices, organic materials and pure polymers at different concentrations were analyzed using a Rock-Eval®. As expected, the results show that Total HC varies with the amount of polymer present in the samples. However, Total HC also varies according to the type of the mineral matrix. Indeed, some samples, such as clays and particularly goethite, show retention effects when the mineral matrices are characterized by a high adsorption capacity. Furthermore, for a given polymer, the Tpeak parameter can vary according to the mineral matrix. For example, it seems that some mixtures of polymers and mineral matrices enhance the catalytic cracking of hydrocarbons. While highest expected Tpeak values were obtained for some synthetic blends indicating a delayed release of hydrocarbons. The same mineral matrix can also induce different effects depending on the organic compounds present in the sample. In addition, analyses using natural versus artificial matrices were performed to compare these effects. Obtained results were complemented by scanning electron microscope observations and X-ray diffraction measurements at different temperatures during pyrolysis, to visualize the possible organo-mineral interactions and analyze morphological changes respectively. Understanding these effects of the mineral and organic matrices on the determination of MP concentrations will enable us to refine a more accurate method to quantify the impact of plastic pollution in sediments.
Romero-Sarmiento, M.-F., Ravelojaona, H., Pillot, D., Rohais, S., 2022. Polymer quantification using the Rock-Eval® device for identification of plastics in sediments. Science of The Total Environment 807, 151068. https://doi.org/10.1016/j.scitotenv.2021.151068
How to cite: Ricard, C., Baudin, F., Lieunard, V., Friceau, L., Rohais, S., Copard, Y., Wolfgang, L., and Romero-Sarmiento, M.-F.: Influence of mineral and organic matrices on the thermal characterization of microplastics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10207, https://doi.org/10.5194/egusphere-egu25-10207, 2025.
The presence of NPs in drinking water has raised wide concerns due to their potential impacts on human health. Riverbank filtration (RBF), a natural water treatment process that involves the passage of water through soil, is employed by some Dutch drinking water companies that source water from rivers. Given the emergence of NPs as pollutants, it is essential to understand their transport and removal behavior during riverbank filtration to ensure the safety and quality of drinking water.
The deposition of NPs in porous media is strongly influenced by the physicochemical properties of aquifer grain surfaces. Natural biofilms, consisting of complex communities of bacteria and other microorganisms, typically form on these surfaces and alter their properties. During RBF, biofilm-associated microbial activity leads to rapid oxygen consumption due to the degradation of organic matter, resulting in the formation of localized anoxic and anaerobic zones. However, the impact of this spatial heterogeneity of biofilms on the removal of NPs remains unclear. In this study, we aim to investigate how biofilm spatial heterogeneity influences NP deposition during RBF.
We constructed several long columns (90 cm in length), each composed of ten short columns (9 cm in length, 2 cm in diameter), packed with technical sand (particle size: 0.4–0.6 mm). River water sourced from an RBF site was pumped through the columns at a flow rate of 0.1 mL/min (0.054 m/h) to facilitate biofilm growth over periods of 1, 3, and 6 months. After biofilm formation, columns were segmented into ten short columns to assess NP transport behavior by analyzing breakthrough and retention curves at different biofilm depths. Europium-doped polystyrene NPs (30 mg/L) suspended in synthetic river water with a similar ionic composition to natural river water were used as tracers to evaluate NP transport and retention at an increased flow rate of 0.75 mL/min.
So far, we have obtained breakthrough curves for NP transport in columns with 1- and 3-month biofilms. Preliminary results indicate that site blocking contributed to the concentration- and time-dependent deposition of NPs. The inherent surface roughness of the technical sand created heterogeneous sites that contributed to multi-site NP deposition. Compared to the original sand grains, biofilms exhibited a less negative surface charge, facilitating stronger interaction with NPs. It suggest that biofilms created more favorable heterogeneous sites, enhancing both irreversible and reversible deposition of NPs. The maximum retention capacity of sand grains decreased with depth, with the shallow biofilm layers, which had the highest biomass, greatly enhancing NP retention. Additionally, biofilms grown for 3 months demonstrated a stronger capacity to retain NPs compared to those grown for 1 month.
The remaining experiments are expected to be completed by May next year. This study will enhance the understanding of NP deposition mechanisms during RBF, with a particular focus on the critical role of the spatial heterogeneity of natural biofilms. The findings will provide valuable insights into the potential removal efficiency of NPs in RBF systems, as well as the associated risks of NP exposure in downstream environments and drinking water sources.
How to cite: Xu, Y., van der Hoek, J. P., Liu, G., and Maren Lompe, K.: Biofilm heterogeneity affects the mobility of nanoplastics during riverbank filtration, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10477, https://doi.org/10.5194/egusphere-egu25-10477, 2025.
How to cite: Schneidewind, U., Krause, S., Kelleher, L., Reiss, J., Perkins, D., Barrett, N., and Robertson, A.: Microplastic particles in groundwater systems worldwide, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11153, https://doi.org/10.5194/egusphere-egu25-11153, 2025.
Microplastics (MPs) have emerged as a significant environmental concern, particularly due to their pervasive presence in various ecosystems, including soil and groundwater. These small plastic particles, often resulting from the degradation of larger plastic items, pose serious risks to ecological health and human safety. Their infiltration into groundwater systems is alarming, especially in agricultural practices utilizing mulching techniques, where microplastics can permeate porous media and potentially disrupt soil health and crop productivity. Despite the growing body of research on microplastics, most studies have focused on uniform soil matrices or sediments, neglecting the complexities of layered and heterogeneous aquifer systems. This study investigates the dynamics of polyethylene microplastics within soil column tests, specifically examining their transport behavior through stratified layers of coarse sand and small gravel. We utilized medium-sized microplastics (25 microns) embedded within a layered column consisting of coarse sand (500-1000 microns) and small gravel (4-8 mm), packed uniformly to simulate real-world conditions. Groundwater was injected into the columns at a flow rate of 12 mm per minute for 360 minutes. Water samples were collected at intervals of 5, 10, and 20 minutes for microplastic quantification using fluorescence microscopy after filtration. Post-experiment, sediment layers were sequentially removed every 6 cm to isolate and count microplastics using density separation methods. Results indicated a significantly faster movement of microplastics through gravel compared to sand, with the highest concentrations detected in the outflow from gravel columns. In mixed columns where gravel was positioned below sand, a greater number of microplastic particles were observed compared to when sand was below. This suggests that while gravel facilitates rapid transport, the arrangement of layers plays a critical role in determining the concentration of microplastics in the outflow. Additionally, entrapment of microplastics was most pronounced in the sand layers, while minimal retention occurred in gravel. Notable variations in microplastic counts were observed at the interface between gravel and sand in mixed sediment columns, highlighting the influence of layer interactions on transport dynamics. In conclusion, this study underscores the critical need to consider soil layering when assessing microplastic transport in agricultural settings. The findings reveal that microplastic dynamics are significantly affected by substrate composition and layering, which could have profound implications for groundwater quality and ecosystem health in agricultural landscapes. Further research is essential to explore the long-term effects of microplastic contamination on soil biota and crop systems, as well as to develop effective management strategies to mitigate their impact on environmental health.
Keywords: Microplastics, Soil layering, Transport dynamics, Groundwater contamination
How to cite: Dehbandi, R., Alqrinawi, F., Singh, J., Schneidewind, U., and Krause, S.: Impact of Layering and Heterogeneity on the Transport Dynamics of Microplastics in Soil Columns: Implications for Groundwater Contamination, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15142, https://doi.org/10.5194/egusphere-egu25-15142, 2025.
While there have been advances in understanding the above ground plastic cycle, there is still a substantial lack of understanding the sources and activation mechanisms of plastic pollution affecting the entry, fate, transport, transformation and impact of microplastics into soils, riverbeds, sediment and groundwater aquifers.
We here present the initial outcomes of integrated field and laboratory analytical experimental approaches and mathematical modelling studies to provide mechanistic understanding of the overall magnitude as well as hot spots (and hot moments) of microplastic entry into subsurface ecosystems and their transport and transformation pathways. Our model results highlight that a large proportion (>95%) of all mismanaged plastic waste emitted since the 1950s is temporarily stored in river basins and able to enter subsurface ecosystems in the long-term. Using multi-scale modelling studies in combination with artificial river simulators (flumes) and laboratory column experiments we evidence that hyporheic exchange represents a preferential input mechanism for smaller and lighter microplastics into streambed sediments and underlying groundwater ecosystems. This finding maps directly onto field experimental findings from our global monitoring programmes which identified distinct hotspots of microplastic accumulation. Soil and streambed sediment columns were deployed to explore the controls on microplastic transport once they have entered the subsurface, highlighting that in particular intermittent pulsed hydraulic forcing increases the potential for fast particle transport.
How to cite: Krause, S., Schneidewind, U., Alqrinawi, F., Chen, Z., Fraga, B., Dehbandi, R., Gomez Velez, J., Mecaj, P., Cardoza Pedroza, L., Simon, L., Mermillod Blondin, F., Mourier, B., Volatier, L., Lassabatiere, L., Kelleher, L., Comer-Warner, S., Quinones, Z., Lynch, I., Singh, J., and Yadav, B.: The plastic underground – Exploring the mechanisms controlling the fate and transport of microplastics in the subsurface, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21555, https://doi.org/10.5194/egusphere-egu25-21555, 2025.
Microplastics (MPs) have emerged as contaminants of global concern due to their ubiquity and potential ecological risks. Understanding MP transport, behavior, and fate in soils is crucial for assessing their interactions with soil organisms and for conducting environmental risk assessments. Most studies on MP transport are conducted in laboratory settings, often using soil column experiments. These experiments typically examine MP mobility by assessing the retention of MPs in different soil types under varying flow conditions. To ensure consistent MP application over time or volume, dispersants are frequently added to MP suspensions, particularly when targeting floating or highly hydrophobic MPs. However, dispersants may alter both the behavior of MPs and their interactions with soil particles, potentially introducing biases when attempting to understand natural MP transport—a critical aspect that remains underexplored.
Therefore, this study developed an improved soil column experiment protocol that excludes dispersants while maintaining consistent MP application through a low-liquid-level, continuously stirred suspension. The Coefficient of Variation (< 5%) for this improved experimental design is found to be statistically acceptable.
Based on this improved method, MP transport was investigated in soil column experiments with quartz and natural sandy soil as matrices. Rhodamine B-stained polystyrene (RhB-PS) particles (D90 < 10 µm) were intermittently pumped upward into the columns, with and without the dispersant (0.25% v/v Tween 20). Drainage samples were collected after each RhB-PS application and during intermittent flushing with artificial rainwater. Fluorescence microscopy was used to quantify RhB-PS concentrations in the drainage samples on haematocrit plates.
The analysis of drainage samples revealed that dispersants significantly enhanced MP mobility, allowing more MPs to bypass soil retention. The clay and organic matter in natural sandy soil, through their fine particles and surface charges, may potentially enhance the interaction between microplastics and soil, thereby reducing their movement within the natural sandy soil, regardless of whether dispersants were used. These results suggest that existing transport studies and related models, which are based on dispersant-assisted experiments, may not accurately reflect the natural behavior of MPs in soils.
How to cite: Lu, Y., Rolf, M., Brehm, J., Liu, H., Wagenhofer, J., Khaleel, R., Laermanns, H., Laforsch, C., Nitsche, F., G.J. Löder, M., Gekle, S., and Bogner, C.: Avoiding Bias in Microplastic Transport: Development of an Improved Dispersant-Free Soil Column Experiment Protocol, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18093, https://doi.org/10.5194/egusphere-egu25-18093, 2025.
Microplastics (MPs) are ubiquitous environmental contaminants that not only accumulate in sediments and biota but also act as vectors for toxic substances, facilitating the transport and dispersion of hazardous chemicals within ecosystems. Their environmental impact is exacerbated by their propensity to adsorb pollutants from their surroundings, a process influenced by the physicochemical properties of both the polymers and the contaminants. While MPs typically exhibit limited surface porosity, exposure to natural environmental factors, such as weathering, abrasion, and photo-oxidation, significantly alters their surface characteristics. These transformations result in structural modifications, including the incorporation of oxygen-containing functional groups, sulfhydryl groups, and persistent free radicals. Such alterations lead to the generation of negatively charged surfaces, which enhance the adsorption of metal cations and other pollutants, thereby amplifying their environmental persistence and toxicity.
This study aimed to investigate the distribution of MPs and their interactions between surface water (SW) and groundwater (GW) systems, with a particular focus on understanding how redox potential (ORP), and surface modifications influence their structural transformations, pollutant adsorption mechanisms, and role as carriers of hazardous substances within natural ecosystems. SW and GW samples were collected from various locations across Uttarakhand, India. In-situ parameters, including pH, conductivity, TDS, DO, temperature, salinity, pressure, ORP, turbidity, and alkalinity, were measured using a portable multiparameter probe (HANNA-HI9829-01201). The average concentration of MPs in the GW and SW samples was found to be 34 MPs/L and 29 MPs/L, respectively. In SW, the relationship between MPs and ORP appears less direct but is still influenced by ionic parameters such as conductivity and TDS, reflecting the potential for pollutant adsorption in regions with high redox activity. In GW, MPs exhibit a moderate correlation with ORP and alkalinity, suggesting that redox conditions may play a significant role in their behavior or interaction with other pollutants. Notably, pH and ORP were clustered together in both GW and SW, suggesting a link between acidity/alkalinity and redox conditions driven by shared environmental or geochemical processes. This research provides key insights into MPs' behavior, aiding strategies to combat water pollution and guide policies to protect ecosystems and public health.
Keywords: microplastics; redox; emerging contaminants; transport; interactions.
How to cite: Dogra, K.: Microplastic-Facilitated Transport of Emerging Contaminants in Redox-Active Environments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17448, https://doi.org/10.5194/egusphere-egu25-17448, 2025.
Microplastics (MP) are present in the soil mainly due to the use of agricultural mulch films and sewage sludge as fertilisers. They are small particles of less than 5mm in size, whose presence impacts agricultural productivity by modifying the soil pore structure, affecting its water and nutrient retention properties, and altering the soil water characteristic curve (SWCC). The objective of this study was to investigate the effects of the size and concentration of polypropylene (PP) microplastics on the SWCC of silty sand. The soil comprises of 72.2% sand, 27.7% silt and 0.1% clay. Polypropylene particles of size (0–50 µm and 50–100 µm) were added to the soil at three concentrations (0.1%, 0.2%, and 0.4% w/w) in the range reported in the literature. The SWCC was measured using a pressure-plate assembly designed such that the mass balance of water imbibition and exudation can be verified at all stages. A genetic algorithm from python library (pygad) was employed to fit the observed soil moisture data and estimate the parameters of the Van Genuchten (VG) model. As the pressure increased, the MP of size 50-100 µm showed a significant decrease in the soil water holding capacity up to a pressure of 0.7 bar, beyond which there were no significant differences with the SWCC for the control soil without MP. Increasing MP content decreased the soil water retention capacity. The field capacity decreased by 5.8% at a concentration of 0.4% for larger-sized microplastics. The smaller size MP (0–50 µm) at low concentration of 0.1% did not significantly affect the soil water content, while the accumulation of PP-MP at higher concentrations (0.2% and 0.4%) resulted in a significant decrease in the soil water holding capacity. The differences in microplastic sizes and concentrations led to variations in the SWCC, which was reflected in the variations in the fitted parameters of the VG model. The presence of larger MP may have disrupted the original capillary pore structure and weakened the soil capillarity, contributing to a decline in soil water retention. The small amount of finer MP may have been transported through the soil pores without significantly affecting the water retention properties of the soil. These findings highlight MP potential risk to soil hydraulic properties and its negative impact on plant growth.
How to cite: Gupta, P. and Guha, S.: Effect of Polypropylene Microplastic on Soil Water Characteristic Curve, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6106, https://doi.org/10.5194/egusphere-egu25-6106, 2025.
Research on microplastics (MP) in soils is much complicated due to the lack of dedicated (extraction) methodologies and strong matrix interferences for MP detection, and there is almost no research on the dynamics of the smallest MP in soil. In our research we first compared the possible detection of the smallest MP fraction (1-2 µm) by µ-Raman spectroscopy and fluorescence microscopy in matrices of highly varying complexity. Subsequently, we have demonstrated that it is possible to use fluorescent MP to monitor and measure the rate of the leaching process of small MP in soils under field conditions.
In a first experiment, samples of pure quartz sand, soils with variable texture (sandy loam, silt loam, clay loam) and removal of native soil organic matter (SOM), and a sandy loam soil with native SOM still present were amended with fluorescent polystyrene (PS) microparticles (diameter 1.7 µm) in different concentrations ranging from 0.1 to 0.001%. After mixing and compaction both the Raman spectra and fluorescence microscopy images were obtained. Characteristic PS Raman fingerprint peaks (main peak at 1001 cm-1) were visible in quartz sand (all concentrations) as well as in sandy and silt loam soils without SOM (some concentrations), but not in the other situations, whereas fluorescence microscopy clearly visualized the MPs at all concentrations in all matrices.
In a second experiment, fluorescent PS microparticles were amended under field conditions to a sandy loam soil on a small surface area (circles of ± 0.2 m diameter), to a depth of 3 cm and at a rate of 70 mg kg-1 soil. At regular time intervals, samples were taken up to a depth of maximally 100 cm. The results of the experiment demonstrate the fast process of downward transport of the MP, reaching a depth of 30 cm after only 40 days and subsequently moving further through the vadose zone to get into range of the fluctuating groundwater table. Unambiguous fluorescent MP detection in real soil thus opens up new avenues for monitoring the vertical redistribution of the smallest MP fractions in the soil profile.
How to cite: Krekelbergh, N., Li, J., Kusuwardania, P. N., Liu, Y., Sleutel, S., Parakhonskiy, B., Hoogenboom, R., Skirtach, A., and De Neve, S.: First experimental evidence of fast leaching of small (1.7 µm) microplastics added to soil in field conditions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16631, https://doi.org/10.5194/egusphere-egu25-16631, 2025.
