Orals: Thu, 1 May | Room 2.44
Nanoremediation involves the injection of reactive nanomaterials into the subsurface to promote the in situ degradation of pollutants. This technique is emerging as a promising alternative to conventional remediation methods, such as Pump & Treat, Permeable Reactive Barriers, aiir sparging, etc. Due to their nanoscale size, iron-based nanoparticles—such as zero-valent iron (nZVI) and iron oxides—exhibit high reactivity and can create reactive zones capable of treating a wide range of contaminants near their source. However, despite their efficacy in laboratory-scale degradation tests, the application of iron-based micro- and nanoparticles at the field scale remains challenging. Specifically, zero-valent iron particles tend to have limited mobility due to agglomeration caused by magnetic interactions, whereas iron oxides can be overly mobile, leading to the unintended dispersion of reactive material and bypassing the contamination zones.
This presentation will address two key approaches to overcome these limitations. First, we explore the use of green biopolymers to achieve both kinetic and electrosteric stabilization of zero-valent iron nanoparticles, enabling the formulation of highly stable and injectable nanofluids. Second, we introduce a patented strategy for tuning the mobility of iron oxides to precisely target contamination sources while minimizing their dispersion in the subsurface. These approaches are optimized using a hybrid experimental and modeling framework, with upscaled models serving as valuable tools for the design of field-scale applications.
Finally, we will present an innovative and patented in situ synthesis process that overcomes the mobility issues associated with conventional nanoremediation by generating nanoparticles directly within the contaminated zone thanks to the reaction of liquid precursors injected in the target area. This novel approach represents a significant step forward in enhancing the efficiency and feasibility of nanoremediation for groundwater treatment.
How to cite: Sethi, R., Bianco, C., and Tosco, T.: Advanced Nanoremediation: Stabilization and Transport Control of Iron Nanoparticles for Contaminant Treatment, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7315, https://doi.org/10.5194/egusphere-egu25-7315, 2025.
Over the past several decades, the focus of colloid transport in groundwater has expanded from pathogens and radionuclide-bearing clays to include engineered nanomaterials and most recently micro- and nano-plastics. For all of these and other colloid types, the following variances from expectations of Colloid Filtration Theory (CFT) have been well-demonstrated under unfavorable conditions where a repulsive barrier exists in colloid-surface interactions: a) extended tailing of low concentrations in breakthrough-elution concentration histories (BTEC) following initial elution; b) retention profiles (RP) that are non-exponential (multiexponential or nonmonotonic). We present recent experiments and simulations demonstrating that these variances from CFT arise from variations in interception history among the attached colloids. Specifically, we show that the fraction of the colloid population that attaches after a single interception is the majority under favorable conditions whereas it is the minority under unfavorable conditions. We show that colloid concentrations decrease exponentially only for colloids that attach after a single interception, whereas colloids that attach following multiple interceptions assume gamma distributions down gradient from the source with maxima at transport distances that increase with interception order. We show that all these distributions are governed by the collector and attachment efficiencies ( and ). The well-observed non exponential RPs result from superposition of the RPs for single- and multiple- interception attachers, wherein decreases or increases in or with interception order yields multiexponential or nonmonotonic RPs, respectively. Extended tailing in BTECs reflects colloids that eluted after many repeated interceptions without attachment. We speculate on the origin of changes in or with interception order. We emphasize that these variances reflect a fundamental aspect of transport under unfavorable conditions, i.e., the stochastics of attachment to nanoscale heterogeneity, as they arise in the absence of variations in colloid size, surface properties, and density, as well as in the absence of straining and detachment.
How to cite: Johnson, W., Bolster, D., Ullauri, L., Al-Zghoul, B., and Volponi, S.: Interception History: A Paradigm Shift for Particle Transport in Porous Media, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14606, https://doi.org/10.5194/egusphere-egu25-14606, 2025.
Predicting the transport and fate of nanoparticles in the subsurface requires understanding of their interactions with collector surfaces. We report here on the effect of the less-studied hydrophobic interactions, which are relevant to the fate of hydrophobic nano-colloids (i.e., nanoplastics) and their attachment onto solid-water (SWI) and air-water interfaces (AWI) in groundwater. Using a model nanoplastic (charge-stabilized, ethyl cellulose nanoparticles) and a model porous medium (regular array of collectors in a pore network etched on glass), we demonstrate the dominance of hydrophobic attraction over electrostatic repulsion when an otherwise hydrophilic glass surface is rendered hydrophobic via coating with octadecyltrichlorosilane (OTS). An empirical model of hydrophobic interactions between dissimilar surfaces (Yoon et al., 1997), informed by contact angle measurements, explains the irreversible attachment of ethyl cellulose nanoparticles on OTS-coated glass surfaces, which is confirmed by atomic force microscopy. The same model explains the irreversible attachment of the model nanoplastic on AWIs, which is revealed by fluorescence microscopy. Transport experiments in microfluidic pore networks etched on glass further demonstrate the irreversible attachment of ethyl cellulose nanoparticles on hydrophobic collector surfaces (SWI or AWI) even in the absence of salt. These findings provide novel insights into the mechanisms affecting the transport and fate of nano-colloids in subsurface aquatic environments and lend further support to the conclusion that contact angle can serve to quantify the magnitude of hydrophobic interactions between nanoparticles and collector surfaces.
How to cite: Rahham, Y. and Ioannidis, M. A.: Hydrophobic Interactions Drive the Attachment of a Model Nanoplastic on Hydrophobic Collector Surfaces, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12697, https://doi.org/10.5194/egusphere-egu25-12697, 2025.
Microplastics (MPs), ubiquitous in terrestrial environments, are usually covered by an eco-corona (EC) under natural conditions. When mistakenly ingested by soil organisms, MPs could harm their development, reproduction, and survival rates. The EC, a natural layer on MP surfaces, contains organic matter like carbohydrates, proteins, DNA, and compounds like humic and fulvic acids. It strongly influences the transport and behaviour of MPs, by altering their surface properties, thereby affecting their adsorption efficiency. While limited research on EC formation on MP in aquatic environments exists, our understanding of typical ECs in soils is limited. Therefore, the present study aims to evaluate the identification, formation, and variation of EC on MPs in floodplain soils, and the physico-chemical changes induced on MP surfaces under different incubation conditions. Polystyrene MPs (600-1000 microns) were incubated with soil samples in cylindrical chambers (mesh size 500 microns) for 4, 8, and 16 weeks in both field (Northern floodplains in Cologne, Germany) and laboratory settings. Laboratory-incubated samples were controlled for temperature and moisture, while the field incubations were left to natural conditions. Additional soil parameters including pH, CN content, grain size, and elemental composition were also measured. After each incubation period, MPs were extracted manually and were analyzed, employing 16S-V4 and ITS1 for metabarcoding and sequencing for attached ECs (bacteria and fungi), ATR-FTIR spectroscopy for polymer-level analysis, and the SEM imaging for visual inspection along with EDS for identifying potential heavy metal attachments on MPs. While the degree of change in the lab samples stayed low, the DNA results in the field samples demonstrated that various bacterial communities formed on MP surfaces during the incubation periods. This communal change could be attributed to the variation in the environmental condition of the incubations. Both incubation settings resulted in intricate fungal structures on MP surfaces, which were also visible during SEM imaging. Potential attachments of heavy metals like Ti, Mn, Zr, Th, and Ag were also identified on incubated MP surfaces. Our findings help uncover the influence of soil organisms on environmental MPs and clarify the formation of EC in soil ecosystems, providing insights into the ecological impacts of MPs.
How to cite: Khaleel, R., Rolf, M., Wagenhofer, J., Lu, Y., Laermanns, H., Weig, A., Nitsche, F., Schott, M., Laforsch, C., Löder, M., and Bogner, C.: Understanding the formation and influence of soil-typical eco-coronas on microplastics through laboratory and field incubation experiments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3952, https://doi.org/10.5194/egusphere-egu25-3952, 2025.
Terrestrial soils are an environmental compartment in which microplastics are known to accumulate. Compared to the surface water of global oceans, soils contain more microplastics, however they are less well studied to date. In particular, the applications of wastewater and corresponding sludge as fertilizers are a major source of microplastics to agricultural soil, as they include washing machine effluent which is often concentrated in polyester fibres. Other relevant microplastic sources include plastic mulching, netting, greenhouses, plastic drainage pipes, and atmospheric deposition. The characteristics and transfer dynamics of microplastics between different environmental compartments including soil in the same agricultural watershed are not well understood. Additionally, very limited information is known on the stock of microplastics in soils. In this work, a long-term French research site, the Orgeval watershed (104 km2), was sampled for soil. This watershed, located slightly beyond the extremities of the Eastern Parisian suburbs, is composed largely of intensive cereal crops and minimal urban zones. Nine locations within the watershed were composite sampled at the soil surface including locations both upstream and at the watershed outlet. These soil samples were derived from various land use areas including agricultural zones such as tilled or undisturbed agricultural fields, greenhouses, and drainage canal riverbanks, plus soil in forested areas and an urban green space. Of these land use types, greenhouse soils demonstrated the highest concentrations of microplastics in surface soils up to 11,200 MPs/kg, where polyethylene and polypropylene made up the majority of the polymers identified. In comparison, forest soils contained far fewer microplastics up to a concentration of 880 MPs/kg. Soil cores were also collected from two of these sites down to a depth of 60 cm, the typical maximum tilling depth used in this watershed. The most noticeable concentration decrease was observed between soil samples collected at the soil surface versus a further 20 cm below it. This study helps better understand the sources of microplastics as well as their fate in agricultural soils.
How to cite: Smyth, K., Dourneau, L., Kedzierski, M., Tassin, B., and Dris, R.: Influences of land use and depth profile on the characteristics of microplastics in agricultural soils, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10646, https://doi.org/10.5194/egusphere-egu25-10646, 2025.
The presence of Microplastics (MPs) and microfibers (MFs) in coastal environments is a significant environmental concern. MPs, defined as particles between 1 μm and 5 mm, and MFs, elongated fibers with a length-to-width ratio between 3:1 and 5:1, persist in sedimentary systems due to their durability and resistance to degradation. The physical and chemical properties of these particles, such as particle size, shape, surface roughness, and degree of alteration, influence their transport, deposition, and interactions with the environment. These characteristics also affect their fate and bioavailability for marine organisms. Building on a novel green protocol developed by Rossi et al. (2024) [1] for identifying MPs and MFs in marine sediments, this study investigates the morphodepositional dynamics of these pollutants along the Vesuvian Coast, southern Italy. The research utilizes a combination of stereomicroscopy for particle morphology, scanning electron microscopy (SEM) for detailed structural analysis, and granulometric and grain morphoscopic methods for characterization.
A key innovation of this study is the development of an eco-friendly protocol that combines optical microscopy and statistical analysis, eliminating the need for traditional methods such as chemical digestion and density separation. This approach provides a more sustainable and precise method for particle identification and analysis. Results revealed a predominance of MFs over MPs across all sites, with significant spatial variability in their characteristics. MFs near the shoreline were longer (mean length of 1,437 μm) and less weathered compared to those found further inland, where smaller, more degraded particles were present due to prolonged exposure to environmental stressors. MPs were primarily angular fragments closely associated with sediment grains, while fibrous MPs adhered to or coiled around the grains, influencing their movement during littoral drift. Pollution levels varied significantly across the study sites. San Giovanni a Teduccio beach, adjacent to industrial facilities and wastewater outlets, exhibited the highest levels of contamination, while beaches further south, such as Torre del Greco, showed lower levels, reflecting the role of longshore currents in dispersing pollutants.
The statistical and morphodepositional analysis applied in this study provides a deeper understanding of the environmental processes that govern the distribution and alteration of MPs and MFs in coastal systems. These insights can help improve strategies for pollution management and the preservation of marine ecosystems. The innovative protocol developed in this research offers a valuable tool for future studies of MPs and MFs, contributing to more sustainable environmental monitoring practices.
Reference:
[1] Rossi, M., et al. "A new green protocol for the identification of microplastics and microfibers in marine sediments, a case study from the Vesuvian Coast, Southern Italy", 2024. Journal of Hazardous Materials, 477(7), 135272. URL: https://doi.org/10.1016/j.jhazmat.2024.135272
How to cite: D'Aniello, M., Donadio, C., Lämmle, L., Arienzo, M., Ferrara, L., Vedi, V., and Rossi, M.: Morphodepositional Insights into Microplastics and Microfibers in Beach Sediments of the Vesuvian Coast, Southern Italy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1065, https://doi.org/10.5194/egusphere-egu25-1065, 2025.
Microplastics impact marine and terrestrial ecology as vectors of chemical pollution and are widespread contaminants in beach sediment. Wind tunnel studies suggest that microplastics are more easily transported by wind than mineral sand grains, and hence coastal dunes ought to be relatively enriched as a local accumulation sink of microplastics blown in from the beach, relative to the sub-tidal marine environment.
To test this hypothesis, concentrations and polymer assemblage of sand-sized microplastics in surface sediment were compared between intertidal beach and coastal dune samples at two different UK coasts (Wales and SE England), using FT-IR microscopy.
Results show no differences in polymer composition, diversity, or abundance between beach (marine) and dune (aeolian) sediments. Average concentrations reached 100s of MPs/kg and their composition was dominated by rayon and polyester fibres. The lack of expected microplastics enrichment of the coastal dunes by preferential aeolian transport from the adjacent beach is attributed to the severe supply-limitation of these particles at the sediment surface interface, compared with the transport-limited movement of the wind-blown mineral sand.
How to cite: Baas, A. C. and Ormane, R.: Aeolian transport of microplastics from the sub-tidal beach surface into coastal dunes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8903, https://doi.org/10.5194/egusphere-egu25-8903, 2025.
There has been a rapid increase in the number of studies on both trash and microplastics in recent years, with little data standardization. However, as data is being produced by a wide range of practitioners with differing study goals, researchers adhering to a single data standard may not be realistic. Post-hoc data harmonization is a pathway that transforms non-standardized data from prior studies into harmonized, comparable databases. Harmonization, however, is hindered by the vast number of categorical descriptors used to describe trash and microplastics (thousands or more), making manual harmonization efforts labor intensive. Additionally, non-semantic data misalignment also exists as different studies measure plastic occurrence via different metrics (particle count, mass, volume, etc.) and evaluate differing size ranges that must be rescaled to make meaningful comparisons between concentrations. We created Microplastics and Trash Cleaning and Harmonization (MaTCH), an AI automated algorithm utilizing manually developed databases that describe relationships between categorical descriptors of trash and microplastic particles. MaTCH also integrates other data harmonization techniques to address non-semantic issues of misalignment. All steps are combined into a single algorithm that can harmonize datasets from studies using various nomenclature, study methods, data formats, and reporting metrics. MaTCH is available as an open-source web tool for the research community to rapidly and accurately leverage existing data from trash and microplastic studies to better perform meta-analyses and make more meaningful assessments of data trends. By providing MaTCH as a live web-tool, we are able to include data from new and emerging studies to improve algorithm performance and keep up with the rapid pace of discovery. In a field as labor intensive as plastics research, we believe this may greatly expedite future discovery.
How to cite: Hapich, H., Cowger, W., and Gray, A. B.: Microplastics and Trash Cleaning and Harmonization (MaTCH): Semantic Data Ingestion and Harmonization Using Artificial Intelligence, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13062, https://doi.org/10.5194/egusphere-egu25-13062, 2025.
Numerous studies have shown the potential risk that nanoplastic (NP) represents for the living organisms in the different ecosystems. However, the amount and characteristics of NP present in the environment are still unknown in its full extent. Even if several methods have already managed to quantify or characterize environmental NP, none, to our best knowledge, could yet provide a single particle complete characterisation over the full nanoscale range combined with a high sample throughput.
The present work tackles the challenge of NP full characterisation in soil by testing an innovative combination and alignment of µ Raman spectroscopy (RS), scanning electron microscopy coupled with energy dispersive x-ray spectroscopy (SEM/EDX), pyrolysis gas chromatography mass spectrometry (Py-GC/MS) and artificial intelligence (AI). The aim is to use the RS data to train an AI model that can automatically recognise NP in environmental samples using SEM/EDX data. The SEM data used to classify the particles include textural features extracted from the 2D images, elemental composition given by the EDX spectrum and the particle behaviour under the electron beam. Particles shape/size transformation when being exposed to high voltage has already been used for microplastic identification but still need to be tested for NP.
First, NP down to 500 nm are identified using RS in samples of increasing complexity, starting with pure NP, mixed NP, spiked media and, finally, environmental samples. Secondly, the suitability of NP behaviour under electron beam to identify plastic material in complex matrices with SEM is tested on the identified NP. Then, the dataset acquired with RS and SEM/EDX on NP is divided into a training and testing set to build a convolutional neural network (CNN) allowing the differentiation between NP and non-NP particles present in a sample. Finally, textural features, elemental composition and behaviour under the beam data are acquired for all particles down to 50 nm in the different samples. The total mass of each polymer present in the sample is extrapolated and then cross-validated by performing a Py-GC/MS analysis on the same sample. Monte Carlo simulations are then used to model the error of the extrapolation based on data provided by the RS and SEM data. The aim of this model is then to allow the identification and characterisation of <500 nm NP present in a sample using SEM/EDX data and AI.
In case of success, this model would provide for the first time a full characterisation of environmental NP with a high sample throughput. This methods combination could then provide a more accurate assessment of the NP pollution in the environment.
How to cite: Foetisch, A., Weber, C., Stricker, K., and Bigalke, M.: Overcome the obstacle of NP analysis – a concept of chemical/microscopic methods combined with artificial intelligence, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16022, https://doi.org/10.5194/egusphere-egu25-16022, 2025.
Graphene Oxide (GO) is a two-dimensional carbon nanomaterial that has witnessed rapid increase in industrial production in the last decade and is likely to reach the subsurface through disposal of e-waste. Recent laboratory studies have also suggested that GO nanoparticles (GONPs) may also be used for insitu remediation of groundwater contaminated with toxic organic compounds and with the increasing GO production GONPs are expected to reach subsurface formations. The objective of this study is to understand the adsorption of graphene oxide nanoparticles (GONPs) onto quartz sand in pH range of 5.5 to 9 at 25 °C. Effects of natural organic matter in the form of Humic acid (HA) and Fulvic acid (FA) were also studied. Batch sorption experiments were conducted under varying concentrations of GO and quartz sand. Amongst several elutant studied for desorption and recovery of adsorbed GONPs from the quartz sand, deionized water was the most effective. The equilibrium attachment of GONPs onto quartz sand was analyzed using Linear, Langmuir, Freundlich, and Temkin adsorption isotherm models. Based on the Bayesian Information Criterion (BIC), the Langmuir isotherm provided the best fit to the adsorption data in the presence and absence of organic matter. The experimental results suggested that adsorption of GONP is affected by pH and presence of organic content. The highest adsorption capacity of 0.175 mg/g was observed at pH 6, while the lowest adsorption capacity of 0.0256 mg/g was recorded at pH 9. The maximum adsorption capacity of GO onto quartz sand at pH 8 showed no variation in the presence of FA or HA at a concentration of 12 mg/L. However, at higher concentrations of FA and HA, the adsorption of GONPs onto quartz sand increased in the presence of Humic Acid (HA) but decreased in the presence of Fulvic Acid (FA). Therefore, the remediation strategies need to consider the effects of pH and organic matter on the transport of GONPs in the subsurface. Significant desorption with the deionized water also suggests potential for mobilization of the adsorbed GONPs to the aquifer.
How to cite: Padmanabhan, S., Guha, S., and Ojha, R.: Effect of Physicochemical Parameters on Sorption of Graphene Oxide Nanoparticles in Porous Media, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9188, https://doi.org/10.5194/egusphere-egu25-9188, 2025.
PFAS-LEACH is a comprehensive decision support platform developed at the University of Arizona that has the capability to quantify source attenuation, spatial mass distribution, and long-term mass discharge of PFAS from the vadose zone to groundwater at PFAS-impacted sites. It includes a suite of four tiers of models spanning from a full-process 3D numerical simulator to analytical solutions implemented in Excel to simple dilution-attenuation calculations. These models account for the various PFAS-specific fate and transport processes in soil and groundwater. This presentation will describe the specific processes represented in each of the model Tiers and will discuss how the different model Tiers can be used to answer practical questions such as characterizing source strengths and risks of groundwater contamination, and derivation of soil screening levels. Illustrative examples of model applications will be presented. As a decision support platform, PFAS-LEACH can improve risk assessment and long-term site management, and will be useful for developing remedial action objectives and for evaluating anticipated impacts of different site remediation approaches at different PFAS-impacted sites.
How to cite: Guo, B., Zeng, J., Brusseau, M., Smith, J., and Ma, M.: PFAS-LEACH: A Comprehensive Decision Support Platform for Modeling PFAS Leaching in Source Zones, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2928, https://doi.org/10.5194/egusphere-egu25-2928, 2025.
Understanding how per- and poly-fluoroalkyl substances (PFAS) are transported in soil and groundwater is critical to site characterization, monitoring, risk assessment, and remediation planning. This includes an understanding of PFAS retention and release associated with adsorption to air-water interfaces, which is particularly important for transport through the vadose zone. Many previous laboratory studies have focused on individual PFAS with experiments conducted over a narrow range of concentrations and pore-water velocities. However, the effects of PFAS mixtures, concentrations and velocities are important to extend our understanding, and the application of numerical models, to realistic site conditions.
In this study, a series of laboratory experiments was conducted using one-dimensional sand-packed columns (40 cm × 5 cm dia.). Trapped air bubbles were emplaced in the sand (quasi-saturated conditions) by sequential drainage and imbibition. Similar to fluctuations in the water table, this emplacement technique was used to create immobile air-water interfaces that are uniformly distributed throughout the column and are readily accessible to flowing water. Each experiment included separate injections of non-reactive tracer (NaCl) and PFAS solutions through both water-saturated and quasi-saturated columns. A clean, low organic carbon sand was used to eliminate solid-phase sorption (verified through comparison of non-reactive tracer and PFAS breakthrough in the water-saturated columns) and to isolate the effect of air-water interfaces. Experiments were conducted using single-component solutions of PFOS over a range of concentrations (2 to 1000 μg/L) and pore-water velocities (0.8 to 2.6 cm/day). Experiments were also conducted using diluted aqueous film-forming foam (AFFF) solutions containing PFOS.
The results showed that PFOS breakthrough was significantly delayed in the presence of trapped air bubbles, and that breakthrough varied considerably with concentration and velocity. Greater retardation occurred generally at lower PFAS concentrations and slower velocities. However, the change in retardation due to a change in velocity was sensitive to concentration, with greater changes occurring for lower concentrations. PFOS breakthrough was also affected by the presence of other PFAS and surface active components in AFFF, with PFOS in the diluted AFFF arriving earlier than expected for an equivalent concentration of PFOS alone. Mixture effects were also observed in the breakthrough of other PFAS in AFFF, particularly concentration overshoot (effluent concentration temporarily greater than the influent concentration) of some less surface active PFAS. The results highlight the need for more comprehensive models of PFAS transport that incorporate non-ideal and competitive behaviour to capture processes occurring in complex field scenarios.
How to cite: Mumford, K., Barnes-James, J., Patch, D., and Weber, K.: PFAS adsorption to air-water interfaces: Effects of velocity and PFAS concentration, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14104, https://doi.org/10.5194/egusphere-egu25-14104, 2025.
Per- and polyfluoroalkyl substances (PFASs) have received increasing attention in the last two decades due to the gathered knowledge about their risks to the environment and human health. The processes that contribute to the transport of PFASs contamination in the environment from the source to groundwater need to be better understood to implement effective mitigation strategies reducing the risk of the most common pathway of PFASs exposure to humans, drinking PFASs-contaminated tap water. Previous studies have already pointed out sorption of PFASs to soil surfaces as well as to the air-water interface (AWI) under unsaturated conditions. Additionally, it is known that physical heterogeneities, such as macropores in soils originating, for example, from earthworms or decayed roots, have an impact on the retention and transport of solutes. The relatively rapid preferential flow through the macropore channels interacts with the slow flow and diffusion in the soil matrix, affecting the chemical breakthrough. This influence of these macroscopic physical heterogeneities and the related hydrodynamics on the transport of PFASs in soil has not been fully elucidated, requiring controlled laboratory studies.
Our study aims to fill this scientific gap using column experiments where breakthrough curves (BTCs) from homogenously packed porous media are compared with those including artificial macropores. In preliminary experiments we were able to prove the primary hypothesis that the macropore configurations, defined by the diameter and length, affect the BTCs. It is expected that PFASs transport in sand under unsaturated experiences retardation caused by sorption only to the AWI, meaning that the sorption of PFASs is only controlled by the water saturation. Modeling the experimental BTCs helps to validate our conceptual model – derived from the column experiments - of the interactions of PFASs sorption and release from the double domain media (sand vs macropore).
This work presents the preliminary data and findings to test our hypothesis on the effect of macropore configuration on PFASs BTCs and provides a basis for further work with field-collected undisturbed soil containing macropores in a natural configuration.
How to cite: Fries, E., Singha, K., Illangasekare, T., and Higgins, C.: How Macroporous Soil Heterogeneities Influence the Transport and Retention of PFASs in the Vadose Zone: A Controlled Laboratory Study, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13522, https://doi.org/10.5194/egusphere-egu25-13522, 2025.
Per- and polyfluoroalkyl substances (PFAS) are emerging pollutants of global environmental concern due to their persistence, widespread occurrence, and toxicity. Accurate PFAS sorption data in soils is essential for assessing their fate and transport in the environment; however, current prediction models often lack precision and broader applicability. To address this limitation, we present PFASorptionML, an advanced machine learning (ML)-based tool designed to predict the solid-liquid distribution coefficients (Kd) of 49 PFAS compounds with diverse chemical structures, including ionizable PFAS with environmentally relevant acid dissociation constants (pKa), in soils.
We developed an extensive literature-based sorption dataset comprising 1,274 Kd (PFAS) entries across 47 peer-reviewed studies. This dataset enabled a critical evaluation of the effects of PFAS chain length and functional groups on sorption behavior. This dataset was used to train the ML model, which integrates PFAS-specific properties—such as molecular weight, hydrophobicity, and charge density—with soil-specific properties, including pH, organic carbon content, texture, and cation exchange capacity. Before training the model, gaps in soil property data were addressed using advanced imputation techniques (e.g., K-nearest neighbor), ensuring data completeness and reliability. Sensitivity analysis revealed the dominant role of hydrophobic interactions and the minor contribution of electrostatic interactions in PFAS sorption, highlighting the importance of incorporating these factors into environmental modeling.
Beyond its predictive capabilities, PFASorptionML represents a significant advancement in PFAS modeling for environmental scenarios. It enables the generation of high-resolution European Kd (PFAS) maps by integrating soil property repositories (e.g., LUCAS EU dataset), thereby upscaling laboratory findings to European conditions. Furthermore, PFASorptionML offers a free-to-use online platform for practitioners, supporting risk assessment, groundwater management, and the development of effective remediation strategies for PFAS-contaminated sites.
How to cite: Ershadi, A., Fabregat-Palau, J., Finkel, M., Rigol, A., Vidal, M., and Grathwohl, P.: Modeling PFAS sorption in soils using machine learning, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3098, https://doi.org/10.5194/egusphere-egu25-3098, 2025.
PFAS contamination from soil additives like biosolids or compost poses a long-term risk to human health and the environment. Remediation is essential for sustainable long-term land-use. Managing PFAS leaching from soil to groundwater is challenging due to their persistence, complex behavior, and the large volume of soil involved. Immobilization techniques have shown promise for in-situ PFAS remediation, but their application is site-specific, and few studies detail the methods or assess their long-term effectiveness.
This study investigates the role of activated carbon in immobilizing a PFAS source within the vadose zone of an agricultural field in Rastatt, southern Germany, which is contaminated by paper-sludge biosolids applied between 1999 and 2008. The treatment applied powdered activated carbon, which was mixed in-situ into a 50 cm soil layer located between 50 and 100 cm below the surface, with subsoil and topsoil layers acting as coverage. The primary objective is to mitigate PFAS leaching into the groundwater and to monitor this effect over 2 years. Site characterization included hydrological assessments and PFAS profiling through soil and soil pore water sampling and depth-specific analysis. Field monitoring involved installing groundwater monitoring wells and suction lysimeters in different locations in the treated and reference parcels.
Our site characterization confirmed aged contamination with long-chain PFAS and precursors, but no short-chain compounds, across the 6 m soil profile from the surface to the groundwater. Polyfluoroalkyl phosphate esters (PAPs) were the most abundant precursors. Over 95% of the PFAS contamination or nearly 1 mg/kg was concentrated in the topsoil (0-30 cm), with PAPs contributing 75% of the total. Some precursors were detected in deeper soil layers, including the capillary fringe, suggesting more complex leaching patterns than previously understood.
Preliminary field results after one year monitoring revealed mixed outcomes: (i) total PFAS concentrations in soil pore water below the treated layer was reduced by 93%, with reductions for most individual substances ranging from 49% to 100%; (ii) concentrations of key substances of concern, as outlined in German groundwater guidelines (LAWA 2017), were reduced to levels considered safe for human health; (iii) while substances like PFPrA and PFTrA were no longer detected, others such as PFDA, PFUnDA, PFOS, and FOSA showed slightly increased concentrations. Over the same period, groundwater contamination levels were stabilizing or declining.
The field monitoring is ongoing, but the initial findings highlight the potential of immobilization techniques using activated carbon and in-situ implementation to reduce PFAS leaching. The study emphasizes the need for detailed analyses, comprehensive field trials, and long-term monitoring to improve understanding and application of these methods. This approach could be adapted for other contaminated sites, such as areas affected by fire-fighting foam.
How to cite: Nguyen, H., Junginger, T., Lange, F. T., Löffler, N., Kleinknecht, S., and Haslauer, C.: Field Application of Activated Carbon for PFAS Immobilization in Agricultural Soil, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11862, https://doi.org/10.5194/egusphere-egu25-11862, 2025.
Injection of colloidal activated carbon (CAC) into the subsurface is an innovative low-cost technology for remediation of legacy and emerging contaminants. It is typically used as a permeable barrier for removing contaminants via sorption and/or followed by microbial/chemical degradation. In addition, CAC has also been used as a catalyst for oxidative degradation of organic contaminants as well as a carrier for subsurface delivery of nano zerovalent iron. A growing application of CAC in the subsurface is its use for sorption and plume control of per-/polyfluorinated alkyl substances (PFAS). With a growing suite of remediation technologies for PFAS, CAC offers the advantage of not producing unknown and/or toxic intermediates while limiting further spread of PFAS in the subsurface. The performance of CAC largely depends on its ability to transport to and deposit at the desired location in the contaminated aquifer under environmentally relevant groundwater conditions. Two such conditions of utmost interest are: (1) injection of CAC with or without downgradient injection of CaCl₂ which restricts CAC mobility by aggregation and (2) multiple injections of CAC in the event of breakthrough of sorbed contaminants. Under these conditions, variations in CaCl₂ concentrations over time are expected due to its potential post-injection downstream migration as well as potential changes in hydraulic conductivity from repeated CAC injections. Thus, it is critical to understand how these conditions impact retention, release, and remobilization of not only the CAC but also of the sorbed contaminants. Our study has examined the effects of input CAC concentration, transient changes in CaCl₂ concentration, and multiple injections of CAC on its transport and deposition in 1-D saturated sand columns. The breakthrough curves and retention profiles generated for the CAC in this study are primary inputs for 1-D transport models which are necessary for prediction of CAC mobility in groundwater.
How to cite: Ndubueze, E., Boparai, H., and Sleep, B.: Transport and Deposition of Colloidal Activated Carbon (CAC) in Saturated Sand Columns: Impacts of input CAC concentration, transient ionic strength, and multiple CAC injections, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14017, https://doi.org/10.5194/egusphere-egu25-14017, 2025.
Understanding the accumulation and behavior of per- and polyfluoroalkyl substances (PFASs) in subsurface environments is crucial for effective environmental management. This study investigates the distribution and sorption dynamics of PFASs in Swedish offshore sediments, with a particular focus on the Bothnian Gulf in the northern Baltic Sea, where elevated PFAS concentrations were observed, reaching up to 33 μg kg⁻¹ in the Bothnian Sea and 27 μg kg⁻¹ in the Bothnian Bay for ∑PFASs. Through sediment sampling, sorption batch experiments, and partitioning analyses, the role of sediment properties from different regions in PFAS fate and transport was examined. Sediment-pore water partitioning coefficients (Kd) were particularly high in some regions, particularly for long-chain PFASs in the Baltic Proper. However, contrary to initial expectations, sediments in the Bothnian Gulf did not exhibit consistently higher sorption capacity despite their elevated PFAS levels, suggesting distinct, unidentified PFAS sources in this region. Kd values varied across locations, with the highest values observed in the southern Baltic Sea, specifically the Baltic Proper and the Southern Baltic, where the organic carbon content was also highest, ranging from 2.2% in the North Sea to 12.7% in the Baltic Proper. While organic carbon strongly influenced PFAS sorption, no consistent trends fully explained the disparities between the northern and southern Baltic regions. The elevated PFAS concentrations in the northern Baltic Sea, despite the estimated limited sorption capacity, highlight the need for further comprehensive source identification and monitoring, particularly of tributary inputs and transboundary influences, to address regional contamination. This study underscores the criticality of integrating source characterization with fate and transport studies, to effectively manage and tackle PFASs in soil-groundwater systems.
How to cite: Niarchos, G., Ruin, E., and Ahrens, L.: Per- and polyfluoroalkyl substances in Baltic sediments: Role of sediment-pore water partitioning on their distribution and fate , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10675, https://doi.org/10.5194/egusphere-egu25-10675, 2025.
The widespread contamination of the environment by fluorinated compounds, particularly those categorized as per- and polyfluoroalkyl substances (PFAS), has emerged as a pressing global issue. These substances have well-documented adverse effects on human health, biodiversity, and overall ecosystem stability. Recent scientific investigations have identified PFAS-class chemicals in pesticide formulations, including within the active ingredients of these products. Considering the wide range of health effects associated with PFAS exposure, it is critical to investigate how the presence of carbon-fluorine bonds within pesticide ingredients contributes to their environmental persistence and toxicity. Therefore, this study aims to unravel the interactions among PFAS and pesticides, in particular, offering insights into their combined effects on the ecosystem and organismal health. Surface water (SW) and groundwater (GW) samples were collected from various sites across Yorkshire County, England, in 2023. The concentrations of total PFAS and pesticides in SW ranged from <0.00009 to 0.0531 μg L-1 and <0.0001 to 0.04 μg L-1, respectively. Among PFAS and pesticide compounds analyzed, perfluorooctane sulfonic acid (PFOS), Endrin, and Permethrin exhibited the highest concentrations in SW. Conversely, GW samples demonstrated relatively lower concentrations of all compounds, except Atrazine, Endosulfan, and Aldicarb, which were detected at elevated levels. Correlation analysis revealed moderate to weak relationships between PFAS and pesticides, with comparatively stronger correlations observed between DDT and perfluorooctanoic acid (PFOA), perfluorooctanoic acid (PFPeA), and perfluorohexanoic acid (PFHxA). These correlations likely stem from the inherent persistence, mobility, and water solubility of these substances. Furthermore, strong correlations among pesticides such as Endosulfan, DDT, Aldrin, and Malathion were identified, likely reflecting shared chemical behaviors and historical usage patterns in pest control practices. Therefore, the result from this study constitutes a pioneering exploration of the potential interactions between PFAS and pesticides, underscoring the critical need for further research to assess their toxicity comprehensively.
Keywords: PFAS; pesticides; interactions; UK; groundwater; PFOS; toxicity; surface water.
How to cite: Kumar, M., Dogra, K., Lalwani, D., and Agarwal, V.: Interpreting the unheeded inherent connections between micropollutants: PFAS and Pesticides, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14572, https://doi.org/10.5194/egusphere-egu25-14572, 2025.
Organotin (OT) compounds are essential in various industrial applications, but they pose significant risks to both the environment and human health. The toxicity and transport dynamics of OTs depend on their specific chemical forms— i.e., the type and number of organic substituents—resulting in distinct toxicity profiles and varying affinities for environmental colloids. These colloids-species interactions collectively influence the mobility, bioavailability, and health impacts of OTs. To date, however, most studies addressed speciation and colloidal characterization separately; thus, the data on the combined determinations of the organometallic species in association with their carrier colloidal fractions remain largely elusive. Here, we present a comprehensive account of method development, application, and validation to quantitatively characterize the adsorption dynamics of 10 different OT species on natural colloidal particles (<500 nm). Our approach utilizes asymmetrical flow field-flow fractionation (AF4) coupled with inductively coupled plasma time-of-flight mass spectrometry (ICP-ToF-MS), achieving detection limits for Sn-equivalent concentrations as low as 6.0 ng/L. The method effectively separates free OT species from those bound to colloids, facilitates the fractionation of particles ranging from a few nm up to 500 nm, and enables the determination of fraction-specific OT interactions. This unique dataset offers comparative insights into the interactions of 10 OT species, representing a significant advancement in understanding species-colloid interactions. Our findings have important implications for assessing the distribution and mobility patterns of toxic organometallic species in surface waters, groundwater, sediments, and soils. The approach can be applied to an array of organometallics species (e.g., organolead, organomercury), generating essential experimental data that are critical for informed risk assessments and the improvement of regulatory frameworks.
How to cite: Azimzada, A. and Meermann, B.: AF4/ICP-ToF-MS for the investigation of species-specific adsorption of organometallic contaminants on natural colloidal particles, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10240, https://doi.org/10.5194/egusphere-egu25-10240, 2025.
Managed aquifer recharge (MAR) is a vital water management strategy that infiltrates surface water or wastewater effluent into aquifers through soil and sediment. However, this process can introduce pharmaceutically active compounds (PhACs) and their metabolites, posing environmental risks. This study investigates the transport behavior of four selected PhACs—caffeine, carbamazepine, diclofenac, and ibuprofen—under neutral pH conditions using column experiments in both unsaturated and saturated porous media. PhACs and a tracer solution were introduced into the system, and experimental results were simulated using the CXTFIT model to determine retardation and degradation factors. Experimental findings indicate high mobility for carbamazepine and ibuprofen across both unsaturated and saturated conditions. Ibuprofen behaved similarly to the tracer with a retardation factor of ~1 and negligible degradation, while carbamazepine showed slight retardation and tailing effects showing higher persistence in the water. Diclofenac significantly degrades in saturated media (44% recovery) but increases release under unsaturated conditions (98% recovery). This indicates the release of diclofenac through the vadose zone but can undergo degradation and retardation in aquifers. Caffeine displayed high retardation and degradation under both conditions independent of the moisture content during transport. These findings highlight the differential transport of PhACs during MAR showing contaminant release to the groundwater, emphasizing the need for effective management practices to mitigate contamination risks and ensure groundwater quality.
How to cite: Dibyanshu, D. and Scheytt, T.: Tracing Contaminants: Assessing the Release of Trace Compounds via Managed Aquifer Recharge, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11480, https://doi.org/10.5194/egusphere-egu25-11480, 2025.
Posters on site: Thu, 1 May, 10:45–12:30 | Hall A
Microplastic concentration is increasing in the terrestrial environments from primary to secondary sources, leading to concern about their impact on soil-plant water uptake and subsurface water storage. However, the impact of microplastic at the pore-scale level remains elusive, making it difficult to explain the in-silico behavior of soil water. Physical models can potentially identify microplastic's implications for capillary and film water content and conductivity than mathematical modeling. The effect of microplastics on capillary and film water content and flow is investigated by considering the polymer type [polybutylene adipate terephthalate (PBAT), low-density polyethylene (LDPE), polyethylene terephthalate (PET), polystyrene (PS), and polypropylene (PP)], as well as concentrations (2, 5, 6, and 8 % w.w), soil compaction (1.06 to 1.50 g.cm-3), and different textures. The PDI (Peter-Durner-Iden) model system allows for a clear partitioning between capillary and film water content and capillary and film conductivity. The PDI model is calibrated and evaluated based on root means square errors for measured soil water retention curves (SWRC) and hydraulic conductivity curves (HCC) in saturated to dry moisture ranges with and without microplastic treatments. Results showed that the fitted physical parameters of soil without microplastics differ from the soil with microplastics. Capillary and film-dominated water content phases shifted, requiring less or more suction potential (m) depending upon the microplastic effect. However, the capillary and film-dominated conductivity phase decreases with microplastic inputs compared to without microplastics. Microplastic's impact on shifting film water content and conductivity-dominated phase may hinder the root's water uptake and biofilm formation in soil. Likewise, microplastic’s impact on capillary water content and conductivity-dominated phase can influence the vertical distribution of water fluxes and prolong the evaporation process on the soil surface. These changes occurred at concentrations exceeding those currently reported in terrestrial environments; thus, their interpretation should be cautiously approached.
This research was conducted within the SOPLAS project, financed by the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie (GA 955334).
How to cite: Maqbool, A., Soriano, M. A., and Alfsonso Gomez, J.: Modelling the effect of microplastics on soil capillary and film water content and flow , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-706, https://doi.org/10.5194/egusphere-egu25-706, 2025.
The attraction between a hydrophobic particle and a hydrophobic surface may be strong enough for irreversible attachment to take place, even under conditions of strong electrostatic repulsion (so called “unfavorable” attachment conditions). This fact has fundamental implications for the transport and retention of hydrophobic nano-colloids (i.e., nanoplastics) in subsurface aquatic environments, where hydrophobic surfaces and interfaces are ubiquitous. Inclusion of hydrophobic attraction in extended DLVO calculations of the total interaction potential between hydrophobic negatively charged ethyl cellulose nanoparticles (a model nanoplastic) and (i) glass surfaces rendered hydrophobic via treatment with octadecyltrichlorosilane (OTS) or (ii) naturally hydrophobic air-water interfaces, indicate the absence of a barrier to attachment and support an expectation of irreversible attachment. We present here a series of experiments in saturated and unsaturated 2D (pore networks etched on glass) and 3D (columns packed with glass beads) porous media which confirm this expectation. The ability of a continuum model accounting for advection, dispersion and irreversible attachment to describe the breakthrough curves is also tested. The results advance the ability to describe the fate of hydrophobic nano-colloids in porous media for a variety of applications.
How to cite: Ioannidis, M., Rahham, Y., Moraglio, N., Granetto, M., Tosco, T., and Sethi, R.: Hydrophobic Interaction Effects on the Transport of a Model Nanoplastic in 2D and 3D Porous Media, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14864, https://doi.org/10.5194/egusphere-egu25-14864, 2025.
Soils are considered the largest sink of microplastic (MP) particles in terrestrial ecosystems. However, there is little knowledge on the implications of MP on soil functions. In particular, we lack understanding of conditions under which MP are transported through porous media and, if they are deposited, how they affect soil hydraulic properties. Since MP generally exhibits a high degree of hydrophobicity, we hypothesize that MP enhances soil water repellency. Depending on the distribution of MP, we expect localized restrictions in water flow, with water preferentially bypassing MP-rich areas, resulting in a limited impact of water flow on the transport of MP.
To quantify the effect of MP on water flow, we applied simultaneous neutron and X-ray imaging methods at the beamline ICON (Paul-Scherrer-Institute) to porous media samples (sand, 0.7-1.2 mm) mixed with MP (PET, 20-75 µm) during repeated wetting and drying cycles. Samples were wetted by drip irrigation at 3.93 mm min-1 create unsaturated flow conditions. The distribution of water and MP was captured in three dimensions before and at the end of each wetting and drying cycle (neutron combined with X-ray tomography). During wetting, time-series neutron radiography was used to image water infiltration patterns. The employed MP contents reflect static contact angles of 30° (0.00 % MP, control), 60° (0.35 % MP), 90° (1.05 % MP) and >90° (2.10 % MP).
Analysis of the acquired images indicates that MP significantly altered infiltration patterns. In particular, high local MP contents caused local water repellency and were bypassed by water flow, with MP remaining in air filled pores. This resulted in rapid and preferential water percolation towards the bottom of the samples and in lower average water saturation behind the wetting front. Analysis of the wetting fronts during infiltration revealed an increasing infiltration speed with an increase in overall MP content. Significant vertical transport of MP was not evident during wetting and drying cycles. Instead, a rather horizontal re-distribution of MP was visible.
We conclude that the presence of MP in soils can have severe effects on local water flow with feedbacks on MP transport, as MP is bypassed by water during infiltration. Low water contents in microregions might also limit MP degradation due to reductions in hydrolysis, prevented coating of MP surfaces and delayed colonization by microorganisms.
How to cite: Cramer, A., Benard, P., Kaestner, A., Zarebanadkouki, M., Lehmann, P., and Carminati, A.: Interaction of unsaturated water flow and microplastic transport in a sandy soil imaged with neutron and X-ray CT, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15453, https://doi.org/10.5194/egusphere-egu25-15453, 2025.
In agriculture, biodegradable plastic mulch has gained significant attention due to its in-situ degradability and satisfying agronomic performance. However, these mulches do not degrade instantaneously; instead, they fragment into micro- and nanoplastics, which can persist in soils or migrate off-site via surface runoff or subsurface water flow. Here, we studied the stability and mobility of biodegradable nanoplastics made from a polybutylene adipate co-terephthalate (PBAT) mulch in both pristine and weathered forms under various environmental conditions. Stability was assessed with aggregation kinetics in NaCl and CaCl2 solutions, and mobility was evaluated under unsaturated flow conditions in sand columns. Additionally, we examined the effects of proteins, i.e., negatively charged bovine serum albumin (BSA) and positively charged lysozyme (LSZ), on the stability and mobility of PBAT nanoplastics. Results show that pristine PBAT nanoplastics exhibited greater aggregation in CaCl2 compared to NaCl, with critical coagulation concentrations of 20 mM in CaCl2 and 325 mM in NaCl. In contrast, weathered PBAT nanoplastics remained stable in both NaCl and CaCl2 solutions. Unsaturated column experiments revealed high mobility for both pristine and weathered PBAT nanoplastics, consistent with their high stability observed under low ionic strength conditions (i.e., 10 mM NaCl). Protein interactions affected stability and mobility: both BSA and LSZ promoted aggregation of pristine PBAT nanoplastics, with LSZ having a more pronounced effect. Correspondingly, LSZ reduced the mobility of pristine PBAT nanoplastics due to its destabilizing effect. Our findings suggest that biodegradable nanoplastics derived from plastic mulch are stable and mobile under environmental conditions, posing potential risks of migration within and beyond agricultural systems.
How to cite: Yu, Y. and Flury, M.: Stability and Mobility of Biodegradable Nanoplastics in the Subsurface, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3326, https://doi.org/10.5194/egusphere-egu25-3326, 2025.
Microplastics (MPs, diameter < 5mm) are pervasive, persistent environmental contaminants. MPs enter agricultural soil via direct sources, such as plastic mulches and irrigation pipes, as well as indirect sources, including compost and sewage sludge. Once in soil, MPs can be incorporated into soil aggregates, altering soil structure and hydro-physical properties (e.g., bulk density, aggregate stability, water retention curve). These changes could potentially limit or enhance the transport of MPs in soil as well as their detachment and transport with runoff and erosion. Despite their significance, research on MPs transport on agricultural fields via runoff and erosion remains limited, and detailed empirical data is missing.
This study aims to investigate the dynamics of MPs transport on agricultural slopes during natural rainfall events, focusing on quantifying lateral MPs transport with runoff and erosion, assessing MPs enrichment or depletion in eroded sediment, exploring the preferential flow patterns of MPs (whether free or sediment-bound), and comparing transport behaviors of various MPs polymer types. To achieve this, we will construct three enclosed soil flumes (22 m long and 2 m wide) in hilly south-Limburg, the Netherlands. From April to October 2025, we will use ISCO automatic samplers, attached at the outlet of the soil flumes, to capture runoff and eroded sediment at six-minute intervals. For each rainfall event, the runoff and eroded sediment will be continuously collected and quantified. Additionally, MPs in runoff water and eroded sediment will be extracted and analyzed respectively using μ-FTIR to determine the MPs polymer types and particle numbers.
This project is currently in the initial stages, and we anticipate installing the soil flumes in April 2025, followed by collecting and analyzing the data as described, with results expected to be available at the beginning of 2026. The expected findings aim to bridge the gap in empirical data regarding MPs' lateral transport in agricultural slopes during natural rainfall events. We will use this dataset to incorporate MPs as a pollutant in erosion models, enabling the estimation of their transport under various scenarios. The project will also provide insights into the potential for agricultural soils to act as sources or sinks of MPs pollution.
How to cite: Liu, Q., van Schaik, L., and Baartman, J.: Microplastic Lateral Transport in Agricultural Slopes: A Field-Based Approach , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9184, https://doi.org/10.5194/egusphere-egu25-9184, 2025.
Hydrothermal Carbonization (HTC) has emerged as a promising technology for treating biosolids. Recently, HTC has gained significant attention in mitigating Microplastic contamination [1]. This study investigates the impact of HTC on the morphology and distribution of Microplastics in biosolids by using scanning electron microscopy (SEM) as a key analytical tool. Biosolid samples were subjected to HTC at three different temperatures: 200, 210, and 220 °C and autogenous pressure to assess the structural transformations of Microplastic. Polymer particles were extracted by 15% H2O2 chemical digestion, separated by density using saturated CaCl2 solution and filtered by anodic alumina membrane microfilters. It has been proven that the HTC process causes significant morphological alterations in Microplastics, which are dependent on the severity of the HTC process parameters [1]. Based on previous research, higher temperatures (>220 °C) promote the decomposition and embrittlement of Microplastics the most, reducing particle size and affecting their chemical composition [2]. In this study, the SEM analysis was applied to assess morphological changes, as it can be used to evaluate Microplastic transformations under hydrothermal conditions [3]. After that, the interaction between Microplastics and biosolid matrices during HTC was explored, highlighting the encapsulation and immobilisation of residual particles in hydrochars. This study contributes to the understanding of Microplastic behaviour under hydrothermal conditions and supports the adoption of HTC as an innovative solution for the management of sewage sludge.
Acknowledgements: This research project was supported by the programme "Excellence Initiative – Research University" for the AGH University of Krakow, Poland. The research was partially supported by Research Subsidy AGH 16.16.210.476.
References:
[1] Prus, Z., Wilk, M. Microplastics in Sewage Sludge: Worldwide Presence in Biosolids, Environmental Impact, Identification Methods and Possible Routes of Degradation, Including the Hydrothermal Carbonization Process. Energies 2024, 17, 4219. https://doi.org/10.3390/en17174219
[2] Xu, Z., Bai, X. Microplastic Degradation in Sewage Sludge by Hydrothermal Carbonization: Efficiency and Mechanisms. Chemosphere 2022, 297, 134203. https://doi.org/10.1016/j.chemosphere.2022.134203
[3] Akaniro, I. R., Zhang, R., Tsang, C. H. M., Wang, P., Yang, Z., & Zhao, J. Exploring the potential of hydrothermal treatment for microplastics removal in digestate. ACS Sustainable Chemistry & Engineering 2024, 12, 38, 14187–14199. https://doi.org/10.1021/acssuschemeng.4c04124
How to cite: Prus, Z., Szkadłubowicz, K., Mikusińska, J., Berniak, K., Stachewicz, U., Chwiej, J., Styszko, K., and Wilk, M.: Transformations of Microplastics in Biosolids Through Hydrothermal Carbonization: A Morphological SEM Study, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13264, https://doi.org/10.5194/egusphere-egu25-13264, 2025.
Understanding the processes that give rise to hydrodynamic dispersion of nanoparticles in porous media is important not only for assessing the risk from their accidental release in subsurface environments, but also for the design of nanoremediation strategies. Pore network models offer distinct advantages over continuum models, including the ability to account for the distribution of pore-scale velocities, as well as other phenomena that occur at the pore scale and are dependent on the interaction between nanoparticles and the local geometry of the pore space (hindered diffusion, size exclusion, etc.). Adopting a Eulerian approach, we formulate here a pore network model in OpenPNM, and present simulations of nanoparticle transport in a fully-saturated column packed with spherical beads. The pore network which is extracted from a voxel image of the simulated sphere pack is found to accurately represent the permeability, tortuosity and capillary properties of a real column of glass beads. The resulting pore network model is used to investigate an aspect of nanoparticle transport that has so far received limited attention, namely the possible effect of nanoparticle size on dispersivity. To this end, the longitudinal dispersion coefficient is determined by simulating transient advection and diffusion in the pore network, introducing either a pulse or step-change injection, and then fitting analytical solutions to the resulting elution curve. It is found that nanoparticle size influences the dispersion coefficient or the effective particle velocity only when the ratio of particle to bead (solid grain) size is sufficiently high (greater than about 0.01). Under such conditions, the nanoparticles experience an earlier breakthrough due to the velocity profile exclusion. Hindered diffusion is found to play a significant role only when the Peclet number is less than 10. In the absence of such effects, the simulations provide a priori predictions of the longitudinal dispersion coefficient in agreement with a large body of literature data.
How to cite: Ioannidis, M., Dauphinais, S., Mansourieh, A., and Gostick, J.: Pore Network Modeling of Nanoparticle Dispersion in Porous Media, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14384, https://doi.org/10.5194/egusphere-egu25-14384, 2025.
The migration of aggregating nanoparticles in water-saturated, homogeneous porous media with one-dimensional uniform flow was conceptualized through a novel numerical model. Nanoparticles were assumed to be found suspended in the aqueous phase or attached reversibly and/or irreversibly to the solid matrix. The Smoluchowski population balance equation was used to model the process of particle aggregation and was coupled with the advection-dispersion-attachment equation to form a nonlinear transport model. Employing an efficient and precise solver for the population balance equation, coupled with an iterative solver for linear or nonlinear attachment equations, significantly reduced computational time, while maintaining its accuracy. The new numerical model was successfully applied to nanoparticle transport experimental data available in the literature. Conventional colloid transport models may prove to be inadequate in scenarios of high ionic strength where aggregation becomes a dominant process. The proposed model demonstrated exceptional performance under high ionic strength conditions, capturing various physical processes related to nanoparticle transport, including the particle-size-dependent dispersion. Neglecting the aggregation process and relying solely on conventional colloidal transport models, could potentially yield inaccurate results.
How to cite: Chrysikopoulos, C. V. and Katzourakis, V. E.: Transport of aggregating nanoparticle in porous media: Novel Mathematical Modeling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3225, https://doi.org/10.5194/egusphere-egu25-3225, 2025.
A conceptual mathematical model was designed to simulate the transport behavior of migrating nanoparticles in homogeneous, water-saturated, one-dimensional porous media. The model accounts for nanoparticle collisions that lead to aggregation and considers nanoparticles as either reversibly or irreversibly attached to the solid matrix of the porous medium or suspended in the aqueous phase. These attached particles can influence further deposition by promoting or hindering it, leading to either ripening or blocking phenomena. The aggregation process is described using the Smoluchowski Population Balance Equation (PBE), which is coupled with the advection-dispersion-attachment equation (ADA), resulting in a system of partial differential equations governing nanoparticle migration in porous media. An efficient finite volume solver was utilized to solve the PBE, optimizing computational efficiency by reducing the number of equations while maintaining accuracy. The model was validated against experimental nanoparticle transport data available in the literature and successfully simulated experimental data exhibiting nonlinear attachment behaviors, such as ripening and blocking, demonstrating its ability to capture the multiple physical mechanisms governing nanoparticle transport
How to cite: Katzourakis, V. and Chrysikopoulos, C.: Modeling and Experimental Validation of Aggregating Nanoparticle Transport with Nonlinear Attachment, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5313, https://doi.org/10.5194/egusphere-egu25-5313, 2025.
Copper nanoparticles (Cu-NPs) were evaluated as a potential control agent against both sensitive and fludioxonil-resistant isolates of Alternaria alternata in vitro and in vivo. Five highly fludioxonil-resistant, spontaneous mutants of A. alternata, were acquired from wild-type strains after selection on media containing fludioxonil. Mutations in the coding region of the AaHK1 gene leading to premature termination of the protein in resistant isolates were identified by sequencing. Notably, these resistance mutations did not adversely affect mycelial growth or virulence; however, fludioxonil-resistant isolates demonstrated increased sensitivity to osmotic stress and reduced conidia production compared to wild-type strains. Cu-NPs exhibited a superior fungitoxic effect against both wild-type and resistant isolates, outperforming the reference Cu(OH)2-containing fungicide. The combination of Cu-NPs with fludioxonil or iprodione resulted in a significant synergistic effect, that could be associated with an enhanced fungicide bioavailability. The fungitoxic mechanism of Cu-NPs was not solely attributable to copper ion release, as evidenced by the synergistic interaction with EDTA, a strong chelating agent, and the distinct lack of correlation with Cu(OH)2. The synergistic activity observed between Cu-NPs and EDTA may be attributed to a reduction in nanoparticle size due to the chelating agent's capping effect. Additionally, ATP-dependent ion efflux may play a role in the fungitoxicity of Cu-NPs against A. alternata, supported by the additive effects observed with fluazinam, an oxidative phosphorylation uncoupler. Collectively, these findings indicate that Cu-NPs represent a viable, alternative fungicide against A. alternata and offer a promising strategy for mitigating resistance when used in combination with fludioxonil or iprodione, ultimately reducing environmental impacts associated with synthetic fungicides.
This study was co-financed by the European Regional Development Fund of the European Union and Greek national funds through the Rural Development Program (RDP/ΠΑΑ) 2014 – 2020, under the call "Cooperation for environmental projects, environmental practices and actions for climate change" (project code: Μ16SΥΝ2-00354).
How to cite: Malandrakis, A., Kavroulakis, N., Tsiouri, O., Papadopoulou, K., Papadakis, S., Katzourakis, V., and Chrysikopoulos, C.: Copper nanoparticles combined with fungicides: an eco-compatible anti-resistance tool against Alternaria alternata, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1623, https://doi.org/10.5194/egusphere-egu25-1623, 2025.
The development of novel per- and polyfluoroalkyl (PFAS) remediation techniques is critical for the removal of contaminants from soil and water at sites impacted by aqueous film-forming foam (AFFF). This study is the first to explore the feasibility of flushing PFAS with a rhamnolipid biosurfactant solution using column testing and soil from an AFFF-contaminated site. Soil is flushed by tap water alone and a 0.005% rhamnolipid solution. PFAS concentrations in eluate and mass balances are compared for each test. In the first 12 pore volumes, 91% of the total perfluorooctane sulfonic acid (PFOS) flushed by the rhamnolipid solution was removed, while only 64% of PFOS was flushed in that time by tap water alone. Phosphate leached from soil and PFOS measured in the same eluate had similar concentration patterns, suggesting competitive sorption occurs with negatively charged phosphate, PFOS, and the anionic biosurfactant rhamnolipid. A one-dimensional groundwater transport model confirmed that PFOS retardation (R-values) was lower with the rhamnolipid solution (9.76) than with tap water as the eluent (22.3 ± 0.9). The flushing tests and model both confirm that there is no significant difference in flushing PFAS with a biosurfactant for PFAS compounds other than PFOS. The decreased retardation and the faster elution of PFOS by the rhamnolipid solution indicate that it is more efficient at removing PFOS from soil than water alone.
How to cite: Hibben, S., Zech, A., and van Leeuwen, J.: Biosurfactant-induced PFAS leaching from aqueous film-forming foam (AFFF) impacted soil, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5119, https://doi.org/10.5194/egusphere-egu25-5119, 2025.
Per- and polyfluoroalkyl substances (PFAS) constitute an increasing problem for water resources and aquatic ecosystems globally. PFAS are extremely persistent, many are also mobile in water and can transport long distances in the groundwater. Highly contaminated source zones for PFAS exist all over the world in connection to firefighting training areas of rescue services and airports. Modelling tools to predict the subsurface transport of PFAS are important both for understanding the transport, assess risk and design of remediation measures such as in-situ stabilization using sorbents.
PFAS have several properties that distinguish them from many other pollutants. For PFAS reactive transport modelling, several challenges and development needs therefore exist. PFAS are surface-active substances and are attracted to interfaces between air and water, which affects retention in the unsaturated zone. Hundreds of PFAS with different transport properties may be present in typical PFAS-pollution source zones. Many of these substances can be partially degradable (so-called precursors) and break down until a perfluorinated substance is formed. This typically increases mobility, and can be critical for how quickly PFAS leach from the unsaturated zone to groundwater. The different PFAS can also compete for sorption sites, which may increase the mobility of some PFAS and therefore affect both the risks associated with PFAS transport and the efficacy of remediation strategies such as sorbent amendments.
In two recently started research projects, we aim to test and develop practically useful models for subsurface PFAS transport from source zone to recipient. In modelling tools such as GMS/MODFLOW, we have added capability in the transport module to account for competition effects during sorption and we are currently investigating how degradation of precursors coupled to the leaching of PFAS from the unsaturated zone and should best be included in the modelling.
How to cite: Fagerlund, F., Earon, R., Berggren Kleja, D., Zúniga Ekenberg, A., and Das, M.: Modelling the transport of per- and polyfluoroalkyl substances (PFAS) from source zones to recipients – challenges and model developments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11492, https://doi.org/10.5194/egusphere-egu25-11492, 2025.
PFAS are emerging contaminants that have been widespread in the environment. A growing body of site investigations suggests that PFAS have accumulated significantly in soils at contamination sites, threatening to contaminate the groundwater underneath. Quantifying PFAS leaching in soils and mass discharge to groundwater is therefore critical for characterizing, managing, and mitigating long-term contamination risks.
Many PFAS are surfactants that adsorb at air–water and solid–water interfaces, which leads to complex retention of PFAS in soils. Soils have abundant air-water interfaces (AWI), which generally consist of two types: one is associated with the bulk water between soil grains (i.e., bulk AWI) and the other arises from the thin water films covering the soil grains. The latter contributes to over 90% of AWIs in soils under many field-relevant wetting conditions. This talk will discuss two unique complexities introduced by thin water films for PFAS fate and transport in soils: 1) slow mass transfer along the thin water films affects the accessibility of the water films and the film-associated AWI by PFAS; and 2) the interactions between the solid surface and air-water interface change the chemical potential and adsorption capacity of PFAS at the air-water interface. Both phenomena can substantially modify the overall retention and transport behavior of PFAS in soils, which have important implications for quantifying the risks of PFAS contamination to groundwater at the field scale.
How to cite: Guo, B., Chen, S., and Zhang, W.: Thin water films in controlling PFAS fate and transport in soils: Interfacial processes, pore-scale modeling, and upscaling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5223, https://doi.org/10.5194/egusphere-egu25-5223, 2025.
Per- and polyfluoroalkyl substances (PFAS) are contaminants of emerging concern, as they are persistent, ubiquitous, and toxic. They pose a threat to both human health and the environment, therefore efficient remediation strategies are urgently needed. One possible remediation technology to treat contaminated soil is thermal desorption. However, the chemical processes and potential transformation products created during thermal desorption have not been fully assessed. Especially precursor substances, that transform to persistent PFAS substances in the environment, are of interest.
This study investigates the thermal desorption and transformation of PFAS. We developed an experimental stand, where sand and soil, artificially contaminated with various PFAS substances, is heated by a heating rod in a stainless-steel column. The maximum temperature reached in the column is 450 °C. We hypothesize that during this experiment the PFAS will desorb from the sand and enter the gas phase. Further, we assume that chemical transformation processes will occur, leading to products with shorter chain lenghts. To understand the fate of the PFAS substances, we analyze the gas phase and the concentration of PFAS in the sand before and after the heat application. We use target and non-target approaches to identify transformed products. Furthermore, the decomposition of PFAS is examined by measuring the produced fluoride ions.
Initial experiments with short-chain (PFBA) and long-chain (PFOA, PFOS) PFAS showed that thermal desorption of the substances is taking place in the regions of the column where the boiling temperatures of the individual compounds were exceeded. No transformation products have been found using target analysis to date, however we expect more transformation processes with the next round of experiments, where two precursor substances will be tested. Based on these first results and the coming experiments we expect to enhance our understanding of the chemical processes taking place during thermal desorption. With this knowledge, it will be possible to make well informed decisions and improve the application of thermal desorption remediation strategies for PFAS contaminated soils.
How to cite: Burkhardt, A., Junginger, T., Schüßler, M., Zwiener, C., Heilemann, S., and Haslauer, C.: Investigation of the transformation products formed during thermal desorption of PFAS, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3705, https://doi.org/10.5194/egusphere-egu25-3705, 2025.
Per- and polyfluoroalkyl substances (PFAS) are chemical compounds containing carbon-fluorine bonds of high toxicity related with several concerning effects to human health and to the environment. Since PFAS are widely used in everyday life with numerous industrial uses as well as in fire training sites, airports and military areas, these substances have already penetrated to the soil and the aquatic environment. PFAS movement in surface water, soil and groundwater is a field of high interest during the last few years among the scientific community with much recent research focusing on PFAS movement, sorption and travel time through modeling. The aim of the present work is to examine the movement of Perfluorobutanesulfonic acid (PFBS) in the subsurface through numerical modeling. Different hydraulic models were utilized to simulate water and solute movement in the unsaturated zone and the groundwater. More specifically, HYDRUS 1-D and PHREEQC codes for unsaturated zone flow and MODFLOW 6 code for groundwater flow were implemented. The proposed framework was applied in Kifissos basin, Athens, Greece. The unsaturated zone flow model was constructed for a pilot area where Kifissos riverbed is natural (not channelized). To conceptualize the unsaturated zone column under the natural riverbed in the pilot site, several lithostratigraphic data were employed. Sensor data of the river stage were utilized for model inflow. Mass transport within the unsaturated zone was simulated using Hydrus 1D code for the convection and dispersion of chemical species in the liquid phase of the unsaturated zone. PFBS initial concentration was obtained from a grab sampling campaign. Reactive sorption onto the solid phase and adsorption onto the air-Air-Water Interface (AWI) of the unsaturated zone is simulated with PHREEQC 3, given the initial concentrations from Hydrus-1D mass transport simulation. For the simulation of air-water interfacial adsorption the predefined mathematical rate expressions have been scripted into RATES data block of PHREEQC 3. A regional groundwater model was constructed for the case study. The model includes two convertible (phreatic) aquifer layers. The complex lithology of Athens was configured through hydraulic properties zonation. Groundwater flow model performance was validated with existing measurements. Further discretization was applied to model grid at the vicinity of the pilot area. The Groundwater Transport Process (GWT) of MODFLOW 6 was utilized to simulate advection and dispersion processes. Mobile Storage Transfer (MST) Package was utilized to simulate solute storage, sorption, and decay on the mobile domain. Finally, the coupling of the unsaturated flow and solute transport results was accomplished through Mass Source Loading package (SRC). The coupling of several subsurface hydrological models revealed that PFBS can be characterized as threatening substance for groundwater due to its mobility, the minimal sorption at the AWI and the competitive displacement from solid surfaces with the introduction of longer-chain PFAS. Groundwater numerical modeling suggested that PFBS plume movement and concentration is affected by regional groundwater flow and sorption processes.
Acknowledgements: This reasearch is part of the project UPWATER (Understanding groundwater Pollution to protect and enhance WATERquality) that has received funding from the European Union under grant agreement No 101081807
How to cite: Perdikaki, M., Chrysanthopoulos, E., Lacorte, S., Markantonis, K., Dafnos, I., Samios, S., and Kallioras, A.: Coupled hydrological modelling for PFBS movement into the subsurface, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17993, https://doi.org/10.5194/egusphere-egu25-17993, 2025.
Per- and polyfluoroalkyl substances (PFAS) have become a major environmental concern due to their widespread presence in ecosystems, even in remote and pristine areas. These substances, resulting from extensive use and improper disposal practices, pose a threat to the environment and drinking water sources. Effective remediation strategies are critical to mitigate PFAS contamination, particularly in soils. One promising technique for PFAS remediation is the stabilization of PFAS in the subsurface using colloidal activated carbon (CAC). However, a deeper understanding of this approach is essential for its optimization. Additionally, the transport behaviour of PFAS in soil and groundwater is complex due to the diverse mobility properties of individual PFAS compounds and various sorption mechanisms. This study investigates the influence of different sorption isotherms on model predictions of PFAS transport in CAC-treated soil columns, with a focus on both equilibrium and kinetic sorption processes. A one-dimensional numerical model, developed using MODFLOW and MT3DMS, simulates a column experiment to assess PFAS transport dynamics and compare model predictions to experimental observations. The results indicate that accounting for non-equilibrium sorption processes is needed to match the observed asymmetric breakthrough curves and pronounced tailing of PFAS in the leaching experiments. This suggests that kinetic sorption plays a significant role for PFAS transport in CAC-amended soil and highlights the importance of considering kinetic sorption in the modelling and remediation of PFAS contamination in soils.
How to cite: Das, M. and Fagerlund, F.: Modelling investigation of the sorption dynamics of per-and polyfluoroalkyl substances (PFAS) in activated carbon amended soil columns , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12523, https://doi.org/10.5194/egusphere-egu25-12523, 2025.
Nitrification inhibitors (NI) and urease inhibitors (UI) are substances which are useful to delay nitrification in soil. This delay can have several advantages: nitrate leaching reduction, longer availability of ammonium for plants and slower conversion of urea to ammonia. But everything comes with a price. The release of artificial substances can have negative impacts on the environment such as observed with PFAS or some pesticides and their transformation products. Therefore, it is crucial to know their environmental fate before using it on a large scale.
To learn about the fate of NI and UI, we conducted two soil column studies. In the first study, we applied three fertilizers with different inhibitors on two different topsoils at a concentration of 15 g/m²: ENTEC 26 (3,4-dimethylpyrazole phosphate [DMPP]), ENSIN PLUS (Dicyandiamide [DCD] and 4-amino-1,2,4-triazole [ATC]), Alzon Neo-N (reaction mass of N-((5-Methyl-1H-pyrazol-1-yl)methyl)acetamide, N-((3-Methyl-1H-pyrazol-1-yl)methyl)acetamide [MPA] and N-(2-nitrophenyl)phosphoric triamide [2-NPT]. In the second study we applied the same inhibitors without fertilizer on two different subsoils.
Both studies were conducted under two different temperatures to learn about its impact on transformation rates. In the first study, mass balances after 40 weeks showed that 0.36-1.26% DMPP, 0.03-0.22% DCD and 4.09-9.22% ATC were recovered from soils and cumulated percolates. Temperature effects were especially visible for the less transformed ATC, but with differences between both soils. In one soil, more ATC dissipated at 20 °C than at 10 °C, in the second soil it was the other way around. There are several possible explanations for those temperature differences such as different soil properties influencing adsorption and formation of non-extractable residues, the composition of microorganisms and their available nutrients.
No masses of MPA and 2-NPT were detected in either soil or percolate, indicating complete transformation. These results are consistent with reported DT50 values in the literature, implying that both substances undergo 50% biotransformation in soil within less than 10 days. 1,2,4-Triazole masses in one of the soil and related percolate increased with a factor of 4-14, compared to background concentrations which were analyzed at the beginning of study. These results will be compared with those gained by the second study, in which the subsoils are less adsorptive.
How to cite: Weidemann, E. and Gassmann, M.: Veni, inhibui, disparui - The Journey of Nitrification and Urease Inhibitors in Soil, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1647, https://doi.org/10.5194/egusphere-egu25-1647, 2025.
Arsenic (As) contamination threatens public health as it migrates from soil surface to groundwater through the vadose zone. The attenuation factor (AF), defined as the ratio of initial As concentration to maximum concentration reaching the groundwater, quantifies As retention in vadose zone. While the U.S. Environmental Protection Agency recommends a default AF value of 1, this approach overlooks site-specific attenuation capacity of soils, potentially overestimating contamination. To improve As risk assessment, tailored datasets of AF for As that consider local soil variability are essential. The transport of As in vadose zone is often modeled by the Mobile-Immobile Model (MIM), which effectively accounts for the mass transfer within the stagnant water regime in the vadose zone. However, the lack of site-specific datasets for MIM-based transport parameters and the overlook of wet-dry cycle effects hinder accurately applying attenuation factor to As risk assessments. This study aimed to: (1) develop regression models to predict MIM-based solute transport parameters and As remobilization under repeated wet-dry cycles using soil properties, and (2) integrate these models into a comprehensive framework to estimate AF values for soils in South Korea.
First, we compiled 129 published data points, covering diverse soil textures, bulk densities, and MIM-based solute transport parameters such as mobile water content, dispersivity, and mass transfer coefficients. This dataset was used to train Random Forest (RF) regression models, where soil texture and bulk density served as input variables, and MIM-based solute transport parameters were the outputs. Second, we conducted experiments using 22 soil columns with varying organic matter content, iron content, particle size distribution, and bulk density to assess the influence of soil heterogeneity on As remobilization under repeated wet-dry cycles. Initial As concentrations in soil and As concentrations in leachate after the first wet-dry cycle were measured. A new parameter, Re, was introduced as the ratio of As concentration in leachate to the initial As concentration in soil. A separate RF model was developed to predict Re, using soil properties as input variables. Model performance was evaluated with the coefficient of determination (R²) to assess predictive accuracy. The outputs from these RF models, MIM-based solute transport parameters and Re were integrated to estimate site-specific AF values.
The RF models demonstrated excellent performance, with R² values exceeding 0.9, in predicting both MIM-based solute transport parameters and Re. Soil properties from 28 sites across South Korea were collected, encompassing diverse characteristics such as variations in texture, organic matter content, iron content, and vadose zone depths. Using the developed models, MIM-based solute transport parameters and Re values for these 28 sites were estimated. Subsequently, site-specific AF values were calculated, ranging from 4.26 to 26.07. This variability highlights the significant influence of heterogeneous soil properties on As attenuation in vadose zone. These findings underscore limitations of using the default AF value of 1 and validate the importance of site-specific analyses for accurate As risk assessments. The proposed methodology provides practical tools for estimating AF values for arsenic and enhancing risk assessments globally, particularly in areas vulnerable to As contamination.
How to cite: Tran, T. H. H., Kim, S. H., Chung, J., and Lee, S.: Site-Specific Attenuation Factor Estimation for Arsenic in Vadose Zone: A Data-Driven Framework Incorporating Soil Properties and Wet-Dry Cycles, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14253, https://doi.org/10.5194/egusphere-egu25-14253, 2025.
