• Detection of plastics in soil systems: methods for sampling, detection, and quantification of plastic pollution in soils
• Distribution and source apportionment: monitoring efforts and source apportionment, spatio-temporal patterns
• Transport dynamics of plastics: transport of plastics and their co-transport with other contaminants from soil to other environmental compartments
• Degradation of plastic in soil: physical and chemical degradation, photodegradation, biodegradation, additive leaching, and the sorption processes of other chemicals
• Impact of plastic on soil ecosystems: physical and chemical interactions between soil and plastic particles, eco-toxicological effects of plastics and/or their leached additives on soil properties, soil health, plant growth and soil fauna
• Economic and policy perspectives: economic drivers for agricultural plastic use, designing solutions, and supporting policies and regulations for reducing and sustainably managing agricultural plastics
Research related to, but not explicitly listed above, may also be considered.
The use of biofertilizer from anaerobic digestion of organic waste in biogas companies provides a valuable nutrient source for agricultural soils and supports the circular economy. However, their use may also contribute to the input of microplastics (MPs) into soils, and data on this topic remains limited. This study investigated the abundance of MPs (<2 mm) in biofertilizers in biofertilizers and estimated their mass input to the Swedish agricultural soils. Samples from three different biogas industries were collected and pretreated using Fenton and enzymatic treatments to remove organic matter and analyzed by optical microscopy and optical photothermal infrared (O-PTIR) spectroscopy. Morphological characteristics were further examined by scanning electron microscopy (SEM). The highest concentration of MPs detected in the samples was 887,840 particles kg⁻¹ (dw). The MPs abundance was moderately positively correlated with the proportion of food waste in the feedstock. Mass estimations were up to 6.19 ± 0.56 mg MPs kg⁻¹ (dw) of biofertilizer. Considering a per-hectare basis, estimated inputs ranged from 0.4 ± 0.06 to 2.0 ± 0.31 g of MPs ha⁻¹ (dw) and a total annual input of 114 ± 17 to 377 ± 126 kg of plastics yr⁻¹ into the soils through biofertilizer application. The predicted environmental concentration (PEC) of MPs in the soil ranged from 1.0 µg MPS kg⁻¹ after one year to 50 µg MPs kg⁻¹ after 50 years, indicating low ecological risk under realistic agricultural conditions. Fragments within the 5–50 µm particle-size range (75%) were the most common type of MPs (98%, n = 2,325). This result suggests consistent fragmentation of MPs across the biogas facilities and biofertilizer production processes. In addition, chemical composition was determined for 71% of the MPs using O-PTIR spectroscopy, among which paint-derived particles (23%) were the most abundant. Therefore, while the amounts of MPs found in biofertilizer in this study are relatively low, its annual applications can serve as a measurable pathway for MPs input to soils, despite their agronomic and environmental benefits. Thus, in the future, MPs monitoring in biofertilizer should be considered.
How to cite: Bertoldi, C., Zanke, M., Pucetaite, M., Hansson, M., Troein, C., and van Praagh, M.: Estimation of microplastics entering agricultural soil through the use of biofertilizers, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3067, https://doi.org/10.5194/egusphere-egu26-3067, 2026.
Current plastic research focuses on particulate water-insoluble polymers such as polyethylene and polystyrene. Synthetic hydrophilic polymers, a class of anthropogenic materials with an annual global production of over 35 Mt, have received little scientific attention. Synthetic hydrophilic polymers are used for the controlled release of agrochemicals and for seed coating. Despite being intentionally added to soil, little is known about their occurrence or fate in soil.
This study aimed to address this knowledge gap by developing and validating a pyrolysis gas chromatography/mass spectrometry (Py-GC/MS) method for identifying and quantifying synthetic hydrophilic polymers in soil. We focused on the most common synthetic hydrophilic polymers: polyacrylic acid (PAA), polyethylene glycol (PEG), polyvinyl alcohol (PVOH) and polyvinyl pyrrolidone (PVP) in agricultural model soil.
The method was validated by measuring one solution containing all four polymers between 1 and 200 µg/mL using pyrolysis gas chromatography/mass spectrometry (Py-GC/MS). Intra-day repeatability was determined by 10-fold measurement of a 150 µg/mL standard. To test polymer recovery from three agricultural model soils (5–47% clay, 1–3% organic carbon), 5 g of soil were spiked with 1 mL of hydrophilic polymer solution (2 mg/mL). Further, three extraction agents were tested: aqueous NH3 solution (pH = 11), aqueous H3PO4 (pH = 3) solution and concentrated sodium pyrophosphate solution (TSPP, 0.1 M, pH = 9). 10 mL of extraction agent were added and agitated for up to 28 days. Samples were taken every seven days, to assess the optimal extraction time and the best possible recovery rate. Non-spiked reference soil was used as a blank. Samples and blanks were measured as duplicates.
Limits of detection (LODs) for PEG, PVOH and PVP were below 1 µg/mL and limits of quantification (LOQs) ranged from 68 to 87 µg/mL. LOD and LOQ for PAA were the highest with 25 µg/ml and 94 µg/mL, respectively. The pyrolysis of PAA and PVOH partly resulted in similar pyrolysis products, challenging the simultaneous and selective quantification of both polymers. The intra-day repeatability was 8–16%. The best recovery rates ranged from 20 to 133% and were achieved with TSPP. While the acidic solution led to recovery rates of 21–115% in soils with 5-16% clay and 1% organic carbon, polymer concentrations in a soil with 47% clay and 2.6% SOM were below LOD. The alkaline solution recovered 5–144% of the polymers. The optimal extraction time varied among soil types. On average, a 14-day extraction yielded the best recoveries with TSPP solution. Blank signals for PVP and PEG were below 10% of the sample spikes. For PVOH and PAA the blank signals were 26–71% and 15–63%, respectively. These results demonstrate the significant challenges of analyzing PVOH and PAA simultaneously, as both polymers produce similar pyrolysis products.
Py-GC/MS is a promising tool for identifying and quantifying synthetic hydrophilic polymers. However, further experiments using complementary analytical methods are required to improve analytical robustness.
How to cite: Plicht, C. and Steinmetz, Z.: Extraction and Quantification of Synthetic Hydrophilic Polymers from Soil with Py-GC/MS, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10808, https://doi.org/10.5194/egusphere-egu26-10808, 2026.
Water-stable soil aggregates (WSAs) are a key to the structural stability of soils. The presence of microplastics (MPs) has been found to affect WSA formation. Additionally, the association of MPs with WSAs may strongly alter the transport behavior of MPs in soils. However, the association of MPs with newly formed WSAs has not yet been investigated as a function of MP and soil properties. In this study, we assessed how polymer composition [polyethylene terephthalate (PET), polylactic acid (PLA)], particle size (small: nominally <63 µm; large: nominally >250 µm), MPs concentration in soil (0.2, 0.5, 1 wt.%) and soil texture (loam, loamy sand) impact WSA formation and MPs-WSA association over a two-week incubation under controlled laboratory conditions. Small PLA fragments reduced WSA formation more strongly and tended to be less associated with WSAs than small PET fragments, potentially due to the slightly greater hydrophobicity of PET. Across all incubations, coarse PLA fragments at 0.2 wt.% showed the largest share of unassociated fragments with approximately 35% of all MPs introduced into the system. The effect of small PLA fragments on WSA formation was concentration-dependent, with reduced aggregation at low and intermediate concentrations but near-control levels at high concentration, despite a higher fraction of unassociated MPs. These non-monotonic effects suggest that MPs affect WSA formation through opposing mechanisms and monotonic concentration–response assumptions may be inappropriate for intra- or extrapolating MP effects on WSA formation. Altering soil texture from loam to loamy sand did not impact the share of unassociated small PET fragments. Collectively, MPs polymer composition, size, and concentration in soil impacted WSA formation and their association with WSAs under the experimental circumstances, showing potential for reduced MPs transport in soils and altered soil structural stability.
How to cite: Rohling, M., Christl, I., and Mitrano, D.: Association of microplastics with water-stable aggregates formed under laboratory conditions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4920, https://doi.org/10.5194/egusphere-egu26-4920, 2026.
Microplastic (MP) contamination in soil ecosystems is a growing concern because MPs can accumulate, interact with soil biota, and have negative impact on soil functioning. Microbial biofilms forming on MP surfaces modify their physicochemical properties, potentially influence the transport and bioavailability of MPs, and possibly contribute to microbial degradation of the particles. While many studies have examined how MPs affect soil organisms, less attention has been given to how soil biota, particularly microbial biofilms, influence MPs in soils. This study investigates bacterial and fungal colonization on polystyrene MPs incubated in two parallel experiments in floodplain soil in the field as well as under controlled laboratory conditions over 4, 8, and 16 weeks. Using scanning electron microscopy and biofilm biomass assays, we observed progressive biofilm formation. We found higher biomass on MPs under laboratory conditions compared to natural incubation after 16 weeks. Metabarcoding analysis (16S rRNA genes for bacteria and ITS genes for fungi) showed that bacterial communities on MPs exhibited distinct dynamics under laboratory and natural conditions, with Acidobacteriota and Proteobacteria dominating and indicating temporal succession in natural conditions. In contrast, fungal communities, dominated by Ascomycota and Basidiomycota, remained more stable in composition across both conditions over time. Genera with known PS degradation potential, such as Pseudomonas, Bacillus, and Penicillium, were also detected, suggesting potential microbial involvement in MP breakdown. Our findings underscore the significance of natural incubations in elucidating MP-microbe interactions in soils, with a particular focus on bacterial and fungal communities. This study also calls for longer-term, polymer-diverse studies to better assess MP fate in soil ecosystems.
How to cite: Khaleel, R., Weig, A., Wagenhofer, J., Rolf, M., Lu, Y., Laermanns, H., Nitsche, F., Lueders, T., Bässler, C., Laforsch, C., Löder, M. G. J., and Bogner, C.: Time-resolved colonization patterns of bacteria and fungi on polystyrene microplastics in floodplain soils, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10997, https://doi.org/10.5194/egusphere-egu26-10997, 2026.
Biodegradable plastics are increasingly promoted as sustainable alternatives to conventional polymers, yet their degradation in soils can mobilize dissolved organic carbon (DOC), alter the stability of soil organic matter (SOM) and generate oligomers and nanoplastic particles with high bioavailability. The release of labile carbon forms from biodegradable microplastics can stimulate microbial activity, weaken mineral protection of organic matter, and enhance CO2 emissions, with effects becoming more pronounced under warmer pedoclimatic conditions. Despite their growing use, the extent to which biodegradable microplastics influence DOC dynamics and priming of native SOM across contrasting soil mineralogies remains poorly constrained. Here, we investigated how biodegradable microplastics affect SOM stability under warming by incubating two contrasting soils, a 2:1 clay-rich Chernozem and a highly weathered Ferralsol dominated by 1:1 clays and Fe/Al oxides, with two biodegradable polymers (polylactic acid, PLA and poly(butylene adipate-co-terephthalate), PBAT) at 22 and 27 ºC. Soil CO2 emissions and priming of native SOM were quantified using stable carbon isotopes (13CO2) measured by cavity ring-down spectroscopy, while changes in DOC quantity and quality were assessed using DOC concentrations and specific ultraviolet absorbance indices (SUVA254, SUVA260, and SUVA280). PBAT induced substantially higher cumulative CO2 emissions than PLA, driven by strong positive priming effects, particularly in the Chernozem, where priming accounted for a large fraction of total CO2-C released at both temperatures. In contrast, PLA showed minor or negligible priming effects. In the Ferralsol, total DOC concentrations were largely unaffected by plastic type, but biodegradable microplastics, especially PLA at 27 ºC, significantly reduced SUVA indices, indicating shifts toward less aromatic and potentially less stable DOM. These contrasting responses reflect differences in mineral protection mechanisms and pH regimes between soils. The contrasting responses of the Chernozem and the Ferralsol demonstrate that soil mineral protection mechanisms fundamentally control how biodegradable microplastics influence soil carbon stability. In the Chernozem, where organic matter stabilization relies primarily on 2:1 clays, cation bridging, and aggregate occlusion under neutral to alkaline pH (7.79), PBAT strongly stimulated microbial activity, resulting in pronounced positive priming and substantial losses of native soil carbon. The absence of concurrent changes in SUVA indices indicates that this destabilization was driven mainly by biological activation of weakly protected carbon pools rather than by disruption of chemically stabilized organomineral associations. In contrast, the Ferralsol, dominated by Fe and Al oxides and characterized by acidic pH (3.98) and strong inner-sphere complexation, showed limited sensitivity in total DOC and CO2 fluxes but exhibited marked, temperature-dependent shifts in DOC quality, particularly under PLA at 27 ºC. Reductions in SUVA indices point to selective alterations in DOC composition, consistent with modified sorption–desorption equilibria or preferential microbial processing of aromatic fractions without large-scale carbon mobilization. These findings indicate that biodegradable microplastics destabilize SOM through distinct pathways depending on mineralogy, either by enhancing microbial priming where mineral protection is weaker, or reshaping DOC composition where physicochemical stabilization dominates, with temperature further modulating these processes.
How to cite: Vezzone, M., Heiling, M., Wang, F., Resch, C., Pucher, R., dos Anjos, R. M., and Dercon, G.: Soil mineralogy and temperature modulate the effects of biodegradable microplastics on dissolved organic carbon in soils, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16614, https://doi.org/10.5194/egusphere-egu26-16614, 2026.
In recent years plastic use in agriculture has led to higher crop yields as well as decreased resources needed to grow crops, such as agrochemicals and irrigation water. However, the complete retrieval of plastics such as mulch films is challenging, leaving plastic fragments in the soil and forming macro-, micro- and nano- plastic residues over time. The sustainability of fully replacing conventional plastics with biodegradable plastics in agriculture is still widely debated due to variable rates of biodegradation which have been observed across various soil and climatic conditions. Understanding which factors control the processes of biodegradation is critical for the development of models to predict the biodegradation of these plastics across various soils.
To this end, we conducted a global meta-analysis of the degradation of biodegradable plastics in agricultural soils. Studies across field, mesocosm and laboratory experimental scales were included to determine which soil, environmental, and polymer parameters are the most impactful on biodegradation rates and how these rates vary across experimental scales. Parameters investigated included but were not limited to temperature, precipitation, land management practices, soil physicochemical properties, polymer surface area, polymer type, and polymer detection methodologies. We found that a large proportion of research on this topic do not report basic soil properties such as soil texture. Despite this shortcoming, we still were able to identify the most relevant soil, environmental, and polymer parameters that affect the biodegradation rates of biodegradable plastics. Results from this meta-analysis will be used in the development of a conceptual process-based fate model to predict the degradation rates and steady-state concentration of biodegradable plastic residues in agricultural soils across various soil types. The development of such model will provide critical information to stakeholders who seek to find alternative biodegradable materials to conventional agricultural plastic products.
How to cite: Severe, E., Börner, T., Som, C., and Nowack, B.: Effects of climate and soil properties on the mineralization and disintegration of biodegradable polymers: A meta-analysis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9108, https://doi.org/10.5194/egusphere-egu26-9108, 2026.
Plastics have become pervasive contaminants in terrestrial environments, notably through compost amendments that introduce large quantities of fragments into agricultural soils. Once in the soil, plastics undergo weathering and degradation, leading to their fragmentation into microplastics (1 µm–5 mm) and nanoplastics (< 1 µm), which can be transported through the soil profile (1). Mobility of nanoplastics is particularly concerning because they can transport adsorbed metals such as lead, titanium and emerging contaminants such as rare earth elements (2,3). While thermal, photo- and mechanical degradation pathways are documented (4,5), the structural transformations induced by soil weathering and their role in generating nanoplastics remain poorly understood.
Here, we investigated polypropylene (PP) macrofragments aged ~30 years in agricultural soils at Meung-sur-Loire (Loiret, France). Using multi-scale synchrotron imaging and diffraction techniques, we characterized the surface alteration layers and assessed their implications for nanoplastic formation.
Synchrotron X-ray fluorescence (s-XRF) shows the heterogeneous distribution of metallic additives containing Ca, Ti, Cr, Mn and Fe, together with surface parallel cracks, trapping soil minerals. Micro-computed tomography (micro-CT) evidences that these surface cracks propagate down to ~150 µm, demonstrating that degradation extends into the interior of the polymer. Rietveld refinement of synchrotron grazing-incidence X-ray diffraction (s-GIXD) reveals that these cracks reflect strong vertical gradients in crystallinity and atomic positions between the altered surface nanolayers and the underlying interior, consistent with surface recrystallization and the development of a deep alteration front. These surface modifications coincide with the formation of large subsurface voids (up to ~300 µm) linked to surface roughening, recording the break-up of the polymer into smaller micro- and nanoplastic fragments. At the nanoscale, synchrotron nano-CT highlights heterogeneous nanoporosity (up to ~2.5 %) in regions enriched in nano-additives, whereas additive-poor regions show < 0.5 % porosity. This spatial correlation demonstrates that metallic additives act as preferential sites that promote localized degradation.
Altogether, this multi-scale structural analysis evidences that soil weathering induces deep structural degradation that is controlled by the distribution of metallic additives. These structural features shed light on the processes controlling the formation and release of potentially harmful nanoplastics in soils.
References
1. Wahl et al., (2024). Journal of Hazardous Materials, 476, 135153.
2. Davranche et al., (2019). Environmental pollution, 249, 940-948.
3. Blancho et al., (2022). Environmental Science: Nano, 9(6), 2094-2103.
4. Cai et al., (2018). Science of the Total Environment, 628, 740-747.
5. He et al., (2018). TrAC Trends in Analytical Chemistry, 109, 163-172.
How to cite: Bollaert, Q., Pécheul, G., Vantelon, D., Vlad, A., Perrin, J., Bihannic, I., Pradas del Real, A., Rivard, C., and Davranche, M.: Plastic Beyond the Surface: Multi-Scale Alteration Mechanisms of Polypropylene in Soils, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11590, https://doi.org/10.5194/egusphere-egu26-11590, 2026.
Microplastics are now widely detected across sediments systems, from soil and riverbeds to estuarine deposits and groundwater-connected aquifers. In soils and saturated sediments, accumulated particles can change pore structure and water-flow pathways, modify aggregation, and persist for decades because of low degradability. Field observations reveal that soils can act as long-term reservoirs that are intermittently remobilized by infiltration events and changing hydraulic gradients. Besides, microplastics can sorb and co-transport hydrophobic organic contaminants, pesticides, and trace metals, and can also leach polymer additives. These risks motivate a hydrological question central to contaminant fate in soils and sediments: how fast and how far can microplastic particles migrate through realistic pore geometries under saturated flow? Answering it requires models that connect pore structure to transport behaviours such as breakthrough curves over representative sediment volumes, while remaining computationally feasible for heterogeneous natural media.
We develop a fast, memory-efficient, purely geometry-driven pore-network framework that predicts microplastic transport in water-saturated sediments using only reconstructed pore-space geometry, without solving the Stokes field or performing particle-resolved tracking. At the pore scale, we derive a flux-weighted transit-time distribution for one-in-one-out pore cells and obtain a near-universal decay close to t-3. For pores with multiple inlets and outlets, we partition each pore into one-in–one-out subdomains using an optimal-transport allocation that minimizes viscous energy dissipation, yielding physically consistent weights and a mechanistic pore-scale transit-time model. We then propagate these statistics through the network via flux-weighted random walks and compute macroscopic breakthrough curves by convolving the inlet signal with the predicted transit-time distribution.
Benchmarks against direct NS equations simulation of lattice Boltzmann method and immersed boundary methods on identical micro-CT geometries and against microplstic trnasport through quartz-sediment column experiments show that the model captures arrival times, tailing, and non-Fickian spreading, while reducing runtime and memory demands by orders of magnitude compared with direct simulations. By requiring only geometry, the approach scales to representative sediment volumes relevant to hyporheic zones and shallow aquifers, providing a practical tool to predict microplastic migration and associated contaminant risks in soil-sediment environments.
Fig. Stokes flow through a quartz column (left) and a comparison of breakthrough curves of direct simulation and our PNM method (right).
How to cite: Liu, H. and Gekle, S.: Geometry-Driven Prediction of Microplastic Transport in Saturated Sediments: Fast and Memory-Efficient Pore-Scale Modeling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13225, https://doi.org/10.5194/egusphere-egu26-13225, 2026.
Root zones of agricultural soils are particularly vulnerable to microplastic accumulation due to high rates of inputs from agriculture-specific sources, including fertilizers and plastic mulch films. As microplastics degrade very slowly, any removal of microplastics from the root zone within agriculturally relevant timescales of several months or years likely requires mechanical means, such as hydrologically driven leaching and erosion. However, the potential for microplastic leaching appears to be low. Plastic mulch, a major contributor to microplastics in agricultural soils, is used to help retain soil moisture. Plastic mulch is thus often used in dryland agriculture, where leaching may be minimal due to similar mean water inputs (precipitation, irrigation) and outputs (evapotranspiration) at the soil surface. To gain new insight into this critical issue on agricultural soil sustainability, we conducted several studies on microplastic leaching and erosion in agricultural soils.
Firstly, we performed a column experiment with microplastics added to disturbed and undisturbed soil columns, subject to multiple irrigation-drying cycles. Results show that microplastics were highly immobile both in the soil matrices and fractures. The overall subsurface transport behavior of microplastics appeared to be primarily diffusive, meaning that remediating microplastic polluted soils by forced leaching may not be feasible.
Secondly, our pore-scale/fracture-scale hydrodynamic modelling study suggests that the trajectories of microplastics in soils are highly sensitive to fluctuations in water fluxes, spatial heterogeneities in soil properties, and the physical properties of microplastic particles (which change over time due to weathering), because most microplastics have near-neutral density in water. Collectively, the chaotic trajectories of numerous microplastics may partly explain the primarily diffusive transport observed in the column experiment. Furthermore, the model shows that particles with near-neutral density are especially likely to be trapped in low-flow parts of the soil where particles are unlikely to be remobilized by fluid flow. This may explain the low mobility of microplastics in our column experiment despite the large mean pore-water velocities (20 cm·h-1) during irrigation.
Thirdly, from another ongoing experimental study, we find that because of the minimal downwards leaching of microplastics, microplastics are susceptible to overland transport during runoff-erosion events. Preliminary results suggest that the subsurface and overland transport mobility and behavior of microplastic film debris from agricultural mulch are highly distinct from that of microplastic fragments from other sources such as fertilizer.
Therefore, microplastics are prone to accumulate in the shallow layers of agricultural soils, whether at the source location, or off-site due to overland transport. Nevertheless, this transport and accumulation is very sensitive to microplastic type and physical properties.
How to cite: Tang, D. and Yang, X.: Mechanisms of microplastic accumulation in the root zones of agricultural soils, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13305, https://doi.org/10.5194/egusphere-egu26-13305, 2026.
Nanoplastics (NPs) have been shown to be taken up by plants, raising concerns about their transfer into food webs and potential risks to human health. However, most existing studies have been conducted in hydroponic systems, which hardly represent realistic soil conditions and/or used fluorescent NPs, that do not allow for exact quantification. To quantify NP uptake and translocation by different crops under environmentally realistic conditions, 14C-labelled polystyrene NPs (~25 nm) were applied to intact soil monoliths at an environmental realistic concentration of 0.03% in the topsoil (0–10 cm). Winter barley (Hordeum vulgare) and lettuce (Lactuca sativa) were grown in spiked and unspiked monoliths; and plant samples were collected after five and nine weeks. Radioactivity in plants was quantified using liquid scintillation counting, additionally NP leaching through the soil columns was assessed.
After five weeks, lettuce had taken up an average of 8.9 µg NP g-1 dry matter (DM), while winter barley accumulated 1.5 µg NP g-1 DM, corresponding to approximately 0.02‰ and 0.004‰ of the applied NP, respectively. After nine weeks, lettuce accumulated on average 2.5 µg NP g-1 DM and barley 2.0 µg NP g-1 DM, corresponding to 0.026‰ and 0.014‰ of the applied NP, respectively. Detectable radioactivity in the soil percolates further indicating NP transport through the soil profile.
These findings demonstrate that NPs can be taken up and translocated by plants under realistic soil conditions and accumulate in edible tissues, highlighting a potential pathway for entry into the food chain.
How to cite: Groß, M., Braun, M., Zhang, H.-J., Amelung, W., Adamczyk, S., Borchard, N., Bosker, T., Huang, Z., Miao, A.-J., Nizzetto, L., Hurley, R., Ji, R., Velmala, S., Zantis, L., and Pütz, T.: Nanoplastics are taken up by lettuce and barley under realistic soil condition, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18604, https://doi.org/10.5194/egusphere-egu26-18604, 2026.
Microplastic (MP) contamination in agricultural soils is increasingly linked to low-density plastics originating from plasticulture (e.g., mulching) and from MP-contaminated organic fertilisers such as compost and sewage sludge. Although these entry pathways are well documented, robust quantification of MP in soil remains challenging and time-consuming. Established microscopic–spectroscopic approaches (µ-Raman, µ-FTIR) are highly effective in aquatic matrices but require intensive soil sample preparation because soil organic matter (SOM) interferes with polymer identification. Many soil protocols rely on density separation with high-density salt solutions (e.g., ZnCl₂) and chemical oxidation to remove SOM with hazardous and corrosive reagents that can modify MP in relevant ecotoxicological parameters like size, shape, and surface properties. Additionally, MP surface quantification is still rarely integrated into routine analysis, despite its relevance to toxicity. To address these limitations, this study developed and rigorously evaluated a hazard-free workflow for MP detection and surface property quantification in contaminated agricultural soils without the need for SOM removal. The key advance is automated MP detection in the presence of SOM, while enabling 3D surface property quantification by surface roughness-related descriptors. The workflow combines (i) sample preparation for 25 g soil (<2 mm fraction) using physical dispersion, density separation with ultrapure water, and freezing-based extraction technique, with (ii) high-resolution 3D Laser Scanning Confocal Microscopy (3D LSM; Keyence VK-X1000, Japan) and (iii) machine-learning-based data analysis using a supervised Random Forest classifier with respecting optical, laser and height values. The 3D LSM scans a 25 mm diameter filter with a minimum pixel size of 2.7 µm and a height resolution of 4 µm. The Random Forest classifiers enable reliable identification even when soil contact modifies the apparent colour of MP particles and avoid watershed segmentation in the postprocessing. The workflow outputs MP particle counts alongside detailed size distributions, 3D shape, and quantification of surface properties. Performance was evaluated using three agricultural topsoils spanning contrasting textures (sand, loam, silt) spiked with representative polymers: transparent polypropylene, transparent low-density polyethylene (LDPE), and black LDPE particles across three size fractions <53 µm, 53-100 µm, and 100-250 µm, plus fibres (1000 µm length). The method reliably detected both transparent and black MP ≥53 µm in soils with low particulate organic matter content, achieving a mean recovery rate of 80% ± 28%. Transparent MPs were robust against low particulate organic matter, whereas black MPs and fibres were more sensitive. MPs <53 µm were consistently underestimated, regardless of SOM presence or soil texture, indicating current limitations driven by physical dispersion during sample preparation and size-dependent background correction. Four parallel samples (4 x 25 g; 100 g total soil) can be processed within three days, from preparation to analysis, enabling rapid throughput without the use of hazardous substances. As density separation is performed with ultrapure water, the workflow is currently most suitable for low-density polymers. Overall, this hazard-free 3D LSM–Random Forest workflow provides a scalable and automated tool for screening and characterising low-density MPs in agricultural soils, generating quantitative datasets that support ecotoxicology-relevant assessments and complement existing laboratory approaches.
How to cite: Scheiterlein, T. and Fiener, P.: Microplastics detection in agricultural soil combining 3D Laser Scanning Confocal Microscopy with machine learning, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5293, https://doi.org/10.5194/egusphere-egu26-5293, 2026.
Introduction
Biking as a form of transportation and leisure activity in natural environments has the potential to introduce MPs directly into ecosystems, often with shorter pathways than cars. While tire wear particles (TWP) from cars are known to be a major source of microplastics (MP), little is known about bicycle tire abrasion quantities. Our first study delivered the first real-life usage abrasion data of mountain bike tires with 3.6 grams per 100 kilometres (front and rear tire combined). This second study quantifies microplastic abrasion from different bicycle tire types (road, gravel, cross country, trail, downhill) in real-life usage and tries to identify influential parameters on abrasion rates (bike, rider, environment).
Methods
We measured the weight loss of bike tires to quantify abrasion throughout their lifecycle. Over 90 subjects tracked their routes via GPS ridden with provided tires to calculate weight loss with distance. This follows a similar approach tested for quantifying tire abrasion of motorized vehicles.
Results
We found an average abrasion rate from 0.4 (road bike, front tire) to 3.6 grams (downhill mountain bike, rear tire) per 100 kilometres and tire. At every measurement point for all tire sets the rate was higher for the rear compared to the front tire. These values are comparatively low to abrasion rates between 11 up to 95 grams per 100 kilometres from motorized vehicles.
Discussion
Overall, the method of gravimetrically measuring weight loss proved to be an effective way to quantitatively assess the microplastic abrasion emitted by bike tires. Tire abrasion quantities of different tire types could be explained by tire attributes (e.g. different compounds, contact area and ridden tire pressure). Different abrasion quantities of individual tires of the same type could be explained by rider and bike attributes (e.g. system weight, riding style, suspension travel) and environmental attributes (e.g. surface type, incline/decline, surface moisture, temperature).
Outlook
We aim to detect potential intervention points in use and production to reduce MP abrasion from bicycles. By calculating the influence of different parameters (bike, rider and environment) we will try to model the load and spatial distribution of bicycle tire-based MPs in the environment. Our research can deliver valuable insights for a better understanding of the global MP cycle.
How to cite: Sommer, F., Audorff, V., and Steinbauer, M.: Quantifying the abrasion of microplastics from bicycle tires into the environment, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7266, https://doi.org/10.5194/egusphere-egu26-7266, 2026.
The widespread emissions of tire and road wear particles (TRWP) as particulate pollutants, originated from tire abrasion on roads, represent a potential threat to the soil ecosystems. TRWP can accumulate in roadside soils over time and are suspected to have hazardous effects through released toxic additives and metals, demonstrating the urgent need for implementable analytical methods allowing the quantification of TRWP in soils. Up to now, there is a lack of reliable “real-world” TRWP data in roadside agricultural soils. Furthermore, previous research on TRWP in soils reported mass-based concentration, which does not include necessary information on TRWP shape and size distribution. We have determined the TRWP concentrations in 75 topsoil samples from agricultural fields adjacent to roads (1 and 5 m distance) in the Rhine-Main metropolitan area (Hesse, Germany). The sampling locations are close to federal highways, state roads and country roads covering a wide range of daily traffic volumes. TRWP were extracted from soil matrix via combined density separation method that uses high- (NaI, ρ = 1.8 g cm-3) and low (NaCl, ρ = 1.1 g cm-3) density solutions as well as subsequent sample purification via Urea/Thiourea treatment and Fenton reaction. The particle-based identification of TRWP was based on their characteristic black color, accessed by optical microscopy and subsequent image analysis using a machine learning approach. This method allows full TRWP quantification and single particle characterization including systematic information on particle size and morphology. The particle-based data can be further used to perform TRWP mass-estimations using 3D particle data derived from microscopy z-stacking and assumed particle densities. Our method shows a mean recovery of 85% with a detection limit of 30 µm and no blank contamination. So far, our preliminary results show higher TRWP concentrations in locations closer to the road and decreasing concentrations with increasing distances from the road. We detected TRWP concentrations (particles per kg) exhibiting mean values of 90,000 p kg-1 for 1 m distance and 1,000 p kg-1 for 5 m distance. Furthermore, estimated TRWP masses for both distances show mean values of 100 mg kg-1 & 0.2 mg kg-1, respectively. At this stage, we can conclude that there is no dilution of TRWP quantities by agricultural tillage practices and TRWP concentrations are within comparable range to roadside soils.
How to cite: Bornemann, J., Nitzsche, K. N., Foetisch, A., Bigalke, M., and Weber, C. J.: Particle-based quantification of tire and road wear particles in roadside agricultural soils, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7931, https://doi.org/10.5194/egusphere-egu26-7931, 2026.
Soils are recognized as major sinks of microplastics (MPs), yet their mobility under field-relevant conditions remain poorly understood. Most studies investigating water-driven vertical transport of MPs have employed simplified experimental setups with repacked soils or artificial homogeneous porous media. However, natural soils are structurally heterogeneous and contain macropore networks that can serve preferential transport pathways, even for larger MPs. Incorporating key soil physical controls on transport is therefore crucial for improving the applicability of experimental findings to natural soil systems.
This study examined the vertical transport of MPs in undisturbed soil with an intact macropore system. Intact soil cores (11 cm height, 9 cm diameter) were collected from a clay loam agricultural topsoil. Soil pore architecture, including pore connectivity, tortuosity, and pore size distribution, was characterised using X-ray computed tomography (CT). To further facilitate interpretation of the MP transport experiments, we carried out non-reactive tracer experiments at constant water flow rate. Metal-doped polyethylene terephthalate (PET; 63–125 µm) fragments were subsequently introduced to the soil surface, and the cores were subjected to intermittent rainfall simulations at 5 mm day-1 under near-saturated conditions. MP transport was quantified by measuring the metal tracer in leachates and soil cores at different depths using ICP-MS.
By linking MP transport to soil pore architecture, this work aims to unravel the role of the soil pore structure in determining MP mobility in soils. We expect transport depth and rate of MPs are likely governed by pore-network geometry, such as connectivity, continuity and pore-to-MP size ratios. Thereby, this work contributes to a more field-realistic assessment of MP transport process and a step towards improving long-term predictions of MP exposure in soils.
How to cite: Yun, J., Mareile Heinze, W., Larsbo, M., M. Mitrano, D., and Cornelis, G.: Rainfall-Induced Transport of Microplastics in Soils Depends on Soil Pore Structure, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7966, https://doi.org/10.5194/egusphere-egu26-7966, 2026.
Floodplains are increasingly recognised as important sinks for microplastics (MPs) at the interface between terrestrial and aquatic systems, yet their role in the long-term retention, redistribution, and vertical transport of MPs in soils remains poorly understood. While rivers are known pathways for microplastics to marine environments, floodplain soils may act as intermediate storage compartments where hydrological dynamics, sediment properties, and biological activity jointly control plastic fate.
Here, we investigate the spatial and vertical distribution of microplastics in floodplain soils along the Rhine River, combining field observations, depth-resolved soil analyses, and hydrodynamic flood modelling. Soil profiles were sampled across multiple transects spanning contrasting floodplain topographies and flooding frequencies. Microplastic abundance and mass concentrations were quantified using FTIR spectroscopy and pyrolysis GC/MS. To assess controls on vertical redistribution, top soils and one selected soil profile were studied, supported by physico-chemical analyses and dating. In parallel, a hydrodynamic flood model was used to relate observed microplastic patterns to flood frequency and inundation dynamics.
Our results reveal pronounced spatial heterogeneity in MP distribution across floodplains. Highest concentrations consistently occur in topographic depressions characterised by frequent inundation and enhanced sediment deposition. Vertically, microplastics are predominantly enriched in upper soil horizons but are also detected at depth, indicating downward transport beyond simple surface accumulation. Associations with finer-grained horizons suggest a role of soil physical structure in regulating retention, while deviations from this pattern point to the modifying influence of biological activity and soil mixing processes.
These findings highlight floodplains as dynamic and heterogeneous microplastic sinks, where hydrological connectivity, local topography, and soil properties interact to control transport and long-term fate.
How to cite: Bogner, C., Rolf, M., Laermanns, H., Seidel, P., Gröbner, M., Riedesel, S., Holzinger, A., Kienzler, L., Horn, J., Kernchen, S., Möller, J. N., Dierkes, G., Pohl, C., Feldhaar, H., Laforsch, C., and Löder, M. G. j.: Spatial heterogeneity and vertical redistribution of microplastics in floodplain soils, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18180, https://doi.org/10.5194/egusphere-egu26-18180, 2026.
Pyrite is a naturally occurring soil mineral that can be used as a reactive material in Fenton process for the treatment of groundwater and wastewater treatment plant effluent containing various micropollutants and microorganisms. However, microplastics enter into domestic wastewater and natural systems through some anthropogenic activities, and may interact with soil minerals in subsurface environment. In this study, batch experiments were conducted to determine the role of microplastics on simultaneous degradation of antibiotics and bacterial inactivation in groundwater and secondary wastewater treatment plant effluents with Fenton process using pyrite as the catalyst. Our results indicate that the removal of antibiotics and bacterial inactivation from water is driven by a combined effect of adsorption, followed by oxidative degradation/inactivation on pyrite surface. However, the presence of microplastics in water adversely affects the degradation of antibiotics and bacterial inactivation with pyrite-based Fenton process since they interact with pyrite surface through hydrophobic bonding, thereby reducing the catalytic activity of pyrite for an effective Fenton operation.
Note: This study was partly funded by a research grant from Canakkale Onsekiz Mart University under a grant number of FDK-2025-5103.
How to cite: Kantar, C. and Can Gulacar, S.: Effect of microplastics on simultaneous degradation of antibiotics and bacterial inactivation in groundwater and secondary wastewater treatment plant effluents with Fenton process using pyrite as the catalyst , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9381, https://doi.org/10.5194/egusphere-egu26-9381, 2026.
Plastic pollution and its degradation into microplastics (MPs) represent a critical environmental challenge. Initially studied in aquatic ecosystems, MPs are now recognized as ubiquitous emerging contaminants, detected in atmosphere, water, soils, compost and soft tissues of living organisms. This widespread occurrence raises increasing concern about their environmental fate and potential impacts on ecosystems and human health, particularly in terrestrial matrices such as compost and agricultural soils. Our goal was to develop and evaluate a method for extracting and determination MPs in these complex matrices, given their significance for agricultural sustainability. A methodology was developed based on reported techniques, adapted to overcome the inherent heterogeneity of the samples. The protocol included physical separation and analysis. Characterization involved Fourier-transform infrared spectroscopy (FTIR) for polymer identification, optical microscopy for morphometric analysis, and statistical methods to compare samples. Extraction was performed via sequential density fractionation (NaCl: 1.2 g·mL⁻¹; ZnCl₂: 1.6 g·mL⁻¹; NaI: 1.8 g·mL⁻¹) and oxidative digestion with H₂O₂, followed by filtration and stereomicroscope counting. We analysed three compost samples with different C/N ratios and one reference sample, four paddy soil samples from surface and subsurface horizons, flood sediment, soil amended with pelleted compost, and an undisturbed forest soil as a negative control. Process blanks and air controls (with/without air conditioning) were included to assess laboratory air quality. Results confirmed the presence of MPs in all samples, with maximum extraction in the intermediate-density solution (1.6 g·mL⁻¹). In compost, concentrations ranged from 1,793 to 8,736 microparticles per kilogram (MP kg⁻¹). In soils, surface horizons contained higher MP abundance (≥ 5 × 10³ MP kg⁻¹) than subsurface horizons (≤ 10³ MP kg⁻¹), with amended soils and sediment showing intermediate levels. Statistical analysis revealed significant differences between samples and a positive association between MP abundance and organic matter content. Air controls indicated airborne contamination, exacerbated by air conditioning use. Although FTIR could not conclusively identify polymers due to fouling, detailed analysis of particle shape, size, and colour was achieved via spectroscopic microscopy. MPs in the reference compost were attributed to cross-contamination, highlighting the challenge of avoiding it. In summary, the method successfully extracted MPs, showing a predominance of mid-density plastics isolated with ZnCl₂. Our findings also emphasize the need for strict anti-contamination measures, especially in non-specialized labs. This preliminary study underscores the urgency of developing efficient and reproducible protocols for accurate polymer identification and confirms MP pollution as a priority issue in compost and agricultural soil research.
How to cite: Boluda Hernández, R., Young, J., Ruíz-Pérez, G., Alejos-Campo, A., Roca-Pérez, L., Andreu-Sánchez, Ó., and Fernández-Gómez, E.: Development of an extraction and determination method for microplastics in compost and soil matrices, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10672, https://doi.org/10.5194/egusphere-egu26-10672, 2026.
Microplastics (< 5 mm) are ubiquitous environmental pollutants. The extensive accumulation of microplastics in marine and terrestrial ecosystems has become a critical global issue, driven by their ecotoxicological impacts and persistence. The knowledge about its occurrence, especially in the agricultural ecosystem, remains limited, which makes environmental assessments and the development of mitigation strategies difficult.
This study aims at assessing the background levels of microplastics in German soils to elucidate the influence of site characteristics and land-use practices on their spatial distribution. To this end, soil was sampled from 400 cropland and 200 pasture sites in Germany. The samples were characterized for soil type, soil organic carbon (SOC), and pH. Polyethylene (PE), polypropylene (PP), and polystyrene contents are quantified using solvent-based pyrolysis GC/MS. An oxidative digestion with hydrogen peroxide (H2O2) was used to reduce SOC in the samples. Microplastics was density-separated from the soil matrix using a saturated NaCl solution.
To validate the method, a recovery test was performed, as the samples contained varying SOC (0.7–39.0%). The recovery experiments were conducted on the following soil types: a clay soil (2.4% SOC), a sandy loam (1.7% SOC), a sandy silt (12.5% SOC), and a quartz sand. Recoveries varied with respect to polymer and soil type. Higher polymer spikes (25 µg/g) yielded higher recoveries (12.5 – 88.0 %) than lower concentrations (5 µg/g, 0 – 48.9 %). The highest recovery rate was 88% for PS with quartz sand. Among the polymers tested, PE showed the highest recovery, whereas PP exhibited the lowest. Recovery experiments with different soil types are crucial in microplastic research to ensure accurate quantification, as varying soil properties can significantly affect the efficiency and reliability of the extraction process.
First results from 52 out of the 600 soil samples indicate that concentrations are overall low and near the analytical detection limits (0,5 – 3 mg kg⁻¹). Average PE levels were 3.4 ± 0.3 mg kg⁻¹ in arable soils and 10 ± 20 mg kg⁻¹ in grasslands. PP concentrations were comparable in both land-use types, ranging from 2.0 to 2.1 mg kg⁻¹. PS levels in both land-use types were below the limit of detection. The values determined must be considered in relation to their SOC content, which may interfere with polymer quantification. Differences in microplastic types could also be attributed to the different site factors depending on land use and potentially driven by atmospheric deposition or littering.
These findings are preliminary and based on a subset of the sampled sites. Data collection and analysis are ongoing and will be extended to the full set of the 600 sites. The data generated in this project will help to develop a geoinformatics-based assessment framework for classifying microplastic pollution in the German agricultural landscape and to derive recommendations for mitigating microplastic inputs.
How to cite: Placzek, S., Heinze, W. M., Bloem, E., and Steinmetz, Z.: Microplastic background levels in German soils: The influence of site-specific characteristics and land-use practices, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18812, https://doi.org/10.5194/egusphere-egu26-18812, 2026.
The advantages of plastic products in modern agriculture are well-documented. Greenhouse films and tunnels enable temperature control, while ground coverings, like films and nonwovens, are used to regulate evaporation, soil temperature, weeds and pests. These applications help to save water and agrochemicals, increase crop yields and extend the growing season. However, the use of plastics in agricultural fields also poses risks, such as the release and accumulation of persistent (micro)plastics in the environment. This could have negative effects on soil physics, biogeochemistry, microorganisms, plants and animals. The cross-border project AgriRePlas aims to evaluate the current use of plastics in agriculture, their potential leakage pathways and the management of used materials. By bringing together stakeholders along the entire value chain, including growers, plastic producers and manufacturers, retailers, as well as collection and recycling companies, the project plans to develop measures to improve plastic use and minimize environmental impacts in three agricultural sectors. In close collaboration with public administrations, growers’ associations, agricultural schools, research centers and academic partners, AgriRePlas will promote multiple-use and deposit-refund systems, particularly for packaging. Recycling rates of used agricultural plastics will be increased through improved information, coordination of logistics and optimization of material quality and quantity. Plastic products currently used in agricultural production are screened for applications with a high risk of loss and leakage. Wherever appropriate, biodegradable alternatives are being identified. Existing biodegradable products are tested in real-world field trials together with farmers and accompanied by scientific monitoring. Complementary studies will examine plastic contamination from conventional products and the behavior, degradation and effects of biodegradable alternatives in soil, with particular consideration of regional climatic and conditions. Information and knowledge transfer play a central role in the project, aiming to strengthen plastic literacy among consortium members and stakeholders. All generated data and results will be made publicly available in German, French and English to support practitioners and policymakers in the Upper Rhine region and beyond.
How to cite: Steinmetz, Z., Neff, J., Eckerle, V., Rupp, A.-S., Berning, A., Buchmann, C., Mougenot, J., Weber, M., and Lott, C.: Reducing the Plastic Footprint in Agriculture: The Cross-Border Project AgriRePlas as a Case Study in the Upper Rhine Valley, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17899, https://doi.org/10.5194/egusphere-egu26-17899, 2026.
Global plastic production now exceeds 400 million tons per year and continues to increase, despite plastics being ubiquitous and pervasive in every environmental compartment. Soils are increasingly recognized as major sinks for macro-, micro- and nanoplastics. The presence of plastic in soils can affect their quality and impair ecosystem services. Yet, degradation pathways in soils remain insufficiently constrained, limiting our ability to predict plastic persistence and associated risks. Manufactured plastics contain complex organic and inorganic additive packages (e.g. pigments, fillers, stabilizers, flame retardants, and catalyst residues), which may leach, transform or fragment during aging. Copper (Cu)-bearing pigments, widely used in green and blue plastics, offer an opportunity to couple elemental and isotopic information to track additive mobilization during degradation.
Here, we investigate temporal changes in elemental composition and copper isotope ratios (δ⁶⁵Cu) during a controlled laboratory degradation experiment in plastic-contaminated soil systems. Three common polymers - polyethylene (PE), polypropylene (PP) and polyvinyl chloride (PVC) - were cut into 1 x 1 cm pieces. For each polymer, 400 mg were exposed to two conditions over 1 to 24 weeks (1, 2, 4, 8 and 24 weeks): (i) agitation in a soil suspension prepared with ultrapure water (soil:water 1:1) and (ii) incubation in water-saturated soil under static conditions. Triplicates and controls were prepared for each condition and duration.
Following microwave digestion, major and trace element concentrations were determined by ICP-MS. Copper was purified by chromatographic separation, and δ⁶⁵Cu was measured by MC-ICP-MS on plastics recovered at each time point. Under static conditions, δ⁶⁵Cu remained unchanged for all polymers during the 24 weeks. Under agitation, PE showed no significant δ⁶⁵Cu shift, whereas PVC and PP displayed a slight decrease during the first two weeks, followed by an increase at 4, 8 and 24 weeks. In contrast, most major and trace element concentrations remained stable over the 24-week experiment in both conditions.
Overall, our results show that Cu isotopes can capture subtle, time-dependent processes during plastic aging in soils that are not apparent from bulk elemental concentrations alone, providing an additional tracer dimension for assessing the fate and behaviour of plastics in terrestrial environments. Ongoing experiments extending to 40 weeks and future comparisons with field-collected plastics from contaminated sites will further test and scale up this approach.
How to cite: Le Corre, M., Pierson-Wickmann, A.-C., Gueguen, B., Pattier, M., Davranche, M., and Dia, A.: Tracing Plastic Degradation in Soils Using Copper Isotopes: Novel Insights from Laboratory Experiments, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18104, https://doi.org/10.5194/egusphere-egu26-18104, 2026.
The agricultural application of digestate (D) derived by the anaerobic treatment of organic waste can contribute to the microplastics (MPs) accumulation in soils. MPs represent an emerging environmental concern because of their high persistence and their documented effects on terrestrial and aquatic ecosystems, as well as their capacity to interact with co-occurring contaminants such as pesticides and antibiotics, with consequences for ecosystem functioning. A deeper investigation of the interplay among MPs, digestate, and xenobiotics is therefore essential to clarify their dynamics in soils, as well as to assess potential long-term environmental impacts.
The 3IMPACT(*) project evaluated soil health, as well as sorption and persistence of xenobiotic compounds (seven antibiotics and one herbicide), under the concurrent presence of D and a mixture of MPs (namely, polyethylene, polystyrene, polypropylene, and polylactic acid), each at real case dose. Laboratory experiments were conducted on two Italian soils (S) treated with MPs (S+MPs), and soils amended with D contaminated with MPs (S+D+MPs) to study xenobiotics mobility and persistence, microbial composition and functionality, and organic matter dynamics.
The results showed that the incorporation of MPs into D-amended soils impaired organic matter turnover, reduced microbial respiration, and suppressed key enzymatic activities, including dehydrogenase, β-glucosidase, urease, and fluorescein diacetate hydrolysis. MPs prolonged the half-life of herbicide Foramsulfuron, whereas D reduced it by 10% in both soils. The herbicide adsorption increased in the presence of MPs and D, following the order (S) < (S+MPs) < (S+D+MPs). Soil dehydrogenase, β-glucosidase, and urease were stimulated by Foramsulfuron, MPs, and D, likely due to the addition of carbon and energy sources for soil microorganisms. Effects varied depending on soil type, exposure time, and interactions among treatments. MPs also prolonged the half lives of Gamithromicin, Tiamulin and Tilmicosin, while had no significant effect on other studied antibiotics. Adsorption coefficients of Gamithromicin, Lincomicin, Marbofloxacin, Oxytetracyclin, Tiamulin increased in soils amended with D but decreased for Florfenicol and Tilmicosin. MPs had no significant effects on adsorption coefficients.
Summarising, MPs contamination in soils amended with digestate exhibited significant alteration of microbiota activity. As a trend, the effect of digestate on xenobiotics adsorption within soils was higher than the effect of MPs, likely due to the additional digestate surface available for adsorption. Additionally, we hypothesized that the increased persistence of xenobiotics in soils observed in the presence of MPs can be associated to changes in microbiota composition, which is currently under study.
(*) 3IMPACT project (2022M24ASJ) is within the PRIN 2022 call (D.D. 104/2022 MUR) funded by the European Union - Next Generation EU, Mission 4, Component 2, CUP J53D23010170006.
How to cite: Bacci, L., Buscaroli, E., Diquattro, S., Montegiove, N., Braschi, I., Ciurli, A., Luise, D., Castaldi, P., Pinna, M. V., and Pezzolla, D.: Dynamics of microplastics in soils amended with digestate: interactions with pesticides and antibiotics - Project 3Impact, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19083, https://doi.org/10.5194/egusphere-egu26-19083, 2026.
Microplastics (MPs) have become ubiquitous in terrestrial ecosystems, while the responses of biogeochemical cycles in forest soils to MPs remain poorly understood. This study aimed to explore the potential disturbances of MPs on soil carbon and nitrogen cycling and their associations with soil chemical properties under different MP input treatments in a global warming trend.
Surface soil samples (0-10 cm) were collected from a subtropical forest in Hong Kong and incubated with four MP types (PE, PP, PLA, and PBAT), three concentrations (0% as controls, 1%, and 5%), and two temperatures (20℃ and 30℃) for three months. Key chemical properties (e.g., total carbon (TC), total nitrogen (TN), soil organic carbon (SOC), dissolved total carbon (DTC), nitrate nitrogen (NO3-N), ammonium nitrogen (NH4-N), etc.) and cumulative greenhouse gas emissions (CO2, CH4) were measured. After that, three-way ANOVA was used to analyse the main and interactive effects of MP types, concentrations, and temperatures on soil properties, while Spearman’s correlation analysis was applied to explore the associations between soil properties. Also, redundancy analysis (RDA) was used to understand the synergistic relationships of soil property changes defined by key driving factors.
Preliminary RDA analysis revealed that temperature and concentration jointly explained approximately one-third of the total variation in soil chemical properties, with temperature being the dominant driver. However, MP types alone did not significantly structure the overall property matrix, three-way ANOVA revealed significant interactive effects. It indicated that MP types could interact with either temperature or concentration to significantly affect key processes such as NO3-N content and cumulative CO2 emission. Spearman’ s correlation analysis also illustrated that these interactions were triggered by a temperature-dependent shift in carbon-nitrogen coupling. At 20 ℃, cumulative CO2 emission was strongly negatively correlated with NO3-N, whereas at 30℃ it became positively linked with NH4-N and DTC, suggesting a shift toward a more rapid, tightly coupled mineralization pathway under warmer conditions. Notably, the temperature sensitivity (Q10) of soil respiration was altered by MP addition, certain polymers (e.g., PBAT) exhibited higher Q10 values than the control, indicating an amplified respiratory response to warming.
In conclusion, the combination of different statistical analysis methods suggests that MPs may disturb the key carbon and nitrogen cycling of subtropical forest soil not merely by changing the content of soil properties, but also by modifying the system’ s temperature sensitivity and by differentially occurring certain metabolic pathways at specific temperatures. This work aligns with the SSS7 focus on anthropogenic influences on soil systems and supports further research on MP-microbe-climate feedbacks.
How to cite: Gong, L. and Lai, Y. F. D.: Interactive Effects of Microplastic Pollution and Global Warming on Soil Carbon and Nitrogen Dynamics in Subtropical Forests, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17241, https://doi.org/10.5194/egusphere-egu26-17241, 2026.
