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.

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 (K_d) 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 K_d (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 K_d (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.

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 (K_d) 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. K_d 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.