Per- and polyfluoroalkyl substances (PFAS) have been used extensively in a range of consumer and industrial products since the 1950s, including in fire-fighting foam, given their exceptional interfacial properties and stability. However, concerns related to PFAS (eco)toxicity have only become widely known in the last 25 years. Passage of PFAS regulations and advisories has now proceeded at a much quicker rate than for many groups of anthropogenic chemicals, with the breadth of PFAS subject to regulation continually increasing and deemed acceptable levels continually decreasing. Here, we summarize global surface and groundwater PFAS data (n > 45,000) to quantify the extent to which PFAS water concentrations exceed drinking water advisories and regulations globally (e.g., European Union Directive 2020/2184, US EPA, Health Canda) as well as in the context of the Stockholm Convention for the protection of human health and the environment from persistent organic pollutants.  For example, our analysis suggests that 32% and 16% of sampled groundwater and surface water exceed the threshold of 1.0 for the unitless US PFAS hazard index for drinking water, respectively, when there is no known source of PFAS contamination, with the rate of exceedance increasing when there is a known source. The extent of exceedances for other jurisdictions will be discussed. Further, analysis of PFAS embodied in consumer products suggests that typical methods used to quantify PFAS in surface and groundwater likely underestimate total PFAS concentration.  Given this the future environmental burden posed by PFAS is likely underestimated.

How to cite: O'Carroll, D., Ackerman Grunfeld, D., Gilbert, D., Hou, J., Lee, M., and Kibbey, T.: An Assessment of the Global PFAS Burden to Our Waters, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21370, https://doi.org/10.5194/egusphere-egu24-21370, 2024.

Per- and polyfluoroalkyl substances (PFAS) are persistent organic chemicals. Within the diverse PFAS class with thousands of individual species, the perfluoroalkyl acids (PFAAs) are of environmental concern due to their pronounced stability, prevalent occurrence at contaminated sites globally, and their detrimental health impacts.

On contaminated sites, soil contamination often originates from sources like firefighting foams, industrial waste, or fertiliser from processed waste. This study is closely linked to the “Rastatt case”, where more than 1000 ha agricultural land are contaminated with PFAS due to the application of paper-fiber biosolids, and investigates PFAS immobilization as a strategy to mitigate the risk of groundwater contamination.

The current understanding of the fate and transport of PFAS within the subsurface is limited, largely due to the complex sorption processes and unidentified precursor compounds and transformation rates. The efficacy and long-term stability of PFAS immobilization are crucial parameters for field applications but have not been verified to date. Furthermore, a standardized experimental methodology for testing PFAS immobilization has not been established.

This presentation characterizes PFAS leaching behaviors, examines the efficacy and long-term stability of PFAS immobilization, and assesses the applicability of experimental methods in investigating PFAS immobilization. Mathematical models are employed to characterize various sorption processes.

We found that the complexity of PFAS leaching with rate-limited sorption and biotransformation contribute to long-term leaching. Sorption to air-water-interfaces (AWIs) was highlighted as a potentially dominant retention mechanism under variably-saturated conditions.

The influence of PFAS chain length on the immobilization efficacy was evident. Delayed breakthrough of short-chain PFAAs and prolonged leaching at low rates indicate that PFAS sorption to the immobilization agents is reversible. 

Long-term effects of PFAS immobilization were examined in column experiments with extended durations. The prediction of leaching based on this column data is compromised by indistinct precursor transformation and unaccounted AWI sorption. A thorough examination of PFAS leaching dynamics was achieved through lysimeter experiments, revealing the AWI sorption influence. However, moderate acceleration in PFAS leaching compared to field scenarios constrains long-term predictions.

This presentation sheds light on the benefits and constraints on the application of PFAS immobilization for a large non-point source.

How to cite: Haslauer, C., Bierbaum, T., Kleinknecht, S., and Junginger, T.: Immobilization of Per- and Polyfluoroalkyl Substances (PFAS) – Experimental and Model-based Analysis of Leaching Behavior, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7899, https://doi.org/10.5194/egusphere-egu24-7899, 2024.

PFOS fate and transport in the subsurface are significantly impacted by the spatially and temporally variable hydrochemical conditions found in natural environments, which often exhibit strong ionic strength gradients and pH fluctuations [1,2]. Batch and flow-through column experiments are standard methods for characterizing PFOS adsorption and transport behaviors, and their outcomes are often quantitatively interpreted by defining empirically derived solid-water distribution coefficients (e.g., Langmuir and Freundlich equations) [3]. The limitation of these models is that they are strictly system-dependent and cannot precisely assess PFOS removal under varying water chemistry conditions. Thus, there is a need for mechanistic sorption prediction models able to account for varying electrostatic properties of the surface-solution interface in response to changes in pore water chemistry, and that could be implemented in reactive transport simulators for precisely assessing PFOS migration under dynamic hydrochemical conditions in multicomponent systems [4].

In this work, we initially conducted a comprehensive set of adsorption experiments and IR spectroscopy analyses with varying pH and ionic strength conditions to elucidate PFOS binding behavior on goethite surfaces as a function of solution chemistry. The experimental outcomes were quantitatively interpreted by developing a surface complexation model (CD-MUSIC) built on the results of the adsorption experiments and on the molecular-level understanding acquired through IR spectroscopy. Subsequently, a series of one-dimensional flow-through experiments were conducted in fully saturated goethite-coated silica sand columns by injecting a 2 mg/L PFOS pulse with varying NaCl background electrolyte concentrations and collecting PFOS and pH breakthrough curves at the outlet of the domain. PFOS uptake exhibited a complex behavior that was strongly dependent on solution pH and electrolyte concentration and that originated from the co-existence and speciation of two distinct PFOS-goethite surface complexation mechanisms: (i) a hydrogen-bonded complex (HB) and (ii) a weaker outer-sphere complex involving Na⁺ co-adsorption (OS-Na⁺). The non-trivial dependency of PFOS uptake on solution chemistry significantly impacted its transport behavior. Dynamic ionic strength gradients established during the flow-through experiments led to distinct retardation and transport behaviors which were not observed in the experiments performed with constant ionic strengths [5]. PFOS and pH breakthrough curves were quantitatively described by implementing the developed surface complexation model within the reactive transport simulator PHREEQC-3 coupled with MATLAB through the IPhreeqc module [6,7]. The simulations illuminated the key role of multicomponent transport effects on PFOS mobility and the importance of explicitly accounting for mineral surface charge adjustments in response to changes in water chemistry.

[1] Zhu et al. (2017) Chemosphere 168, 390-398. [2] Blowes et al. (2014) In Treatise on Geochemistry 2nd Edition Vol. 11, pp 131-190. [3] Johnson et al. (2007) J. Chem. Eng. Data 52, 1165-1170. [4] Cogorno and Rolle (2024) Env. Sci. Technol. https://doi.org/10.1021/acs.est.3c09501. [5] Cogorno and Rolle (2024) In prep. [6] Charlton and Parkhurst (2011) Comput. Geosci. 37, 1653-1663. [7] Muniruzzaman and Rolle (2016) Adv. Water Resour. 98, 1-15.

How to cite: Cogorno, J. and Rolle, M.: Impact of variable water chemistry on PFOS-goethite interactions under batch and flow-through conditions: experimental evidence and reactive transport modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10863, https://doi.org/10.5194/egusphere-egu24-10863, 2024.

Background/Objectives: Per- and Polyfluoroalkyl substances (PFASs) are a group of highly recalcitrant, bioaccumulative, and toxic chemicals that are frequently introduced to groundwater through land surface exposure. As a result, the vadose zone has been identified as a significant long-term source zone for PFAS leaching into groundwater. This talk summarizes critical findings regarding PFAS transport in the vadose zone and introduces several emerging topics expected to develop over the next several years.

Approaches/Activities: Early efforts in understanding PFAS Fate & Transport processes focused on their multi-phase retention processes. Specifically, understanding the degree of equilibrium partitioning to the solid phase and the air-water interface have been intensely studied topics. Equilibrium partitioning to solid and air-water interfaces generally increases with increasing molecular volume, with exceptions for very long chain perfluoroalkyl acids (PFAAs), cationic and zwitterionic PFASs, perfluoroalkyl ethers, and PFASs with very large headgroups. Recent research and emerging field data suggest many sites are impacted by non‑ideal, non‑equilibrium processes. Evidence of PFAA generation from precursor transformation, physically driven non-ideal transport, and chemically driven non-idealities have emerged as environmentally relevant topics. A specific list of topics for discussion is presented below:

• Precursor Transformation: Despite the name “forever chemicals”, there are many PFASs known as PFAA precursors. Precursors transform into PFAAs, which are more mobile and can serve as a centurial source of PFAS contamination to underlying aquifers.
• Non-Ideal Transport Mechanisms Can Accelerate PFAS Leaching: Non-Ideal transport can be caused by physically driven non-equilibrium processes. Examples include flow path channelization, immobile water formation, sheet flow, and reduced accessibility of air-water interfaces. It is likely that these mechanisms drive rate-limited desorption from solid-phase materials. Non-Ideal transport appears to be more prevalent at lower saturations.
• Additional Transport Processes: PFAS retention and retardation by the presence of other co-contaminants such as non-aqueous phase liquids (NAPLs) in media are starting to receive more research attention.
• Evidence of Self-Assembly and Chemically Driven Rate-Limited Desorption: Molecular self-assembly refers to the potential of PFASs and other surfactants to form discrete microstructures at liquid interfaces. These thermodynamically stable microstructures may contribute to the consistently elevated PFAS concentrations observed in source zones.

Results/Conclusions: Many considerations are needed when assessing the fate & transport risks for PFASs at a given site. While there is early evidence that equilibrium models can predict long-term mass flux in some locations, these models may not predict large discharges from discrete storm events. Terminal PFAA discharge to groundwater from precursor transformation is of critical importance to understanding the long-term behavior of PFASs in the subsurface. The potential for Non-Ideal transport to accelerate PFAS transport may explain the conundrum of why some long chain PFAAs are found in groundwater systems despite their strong equilibrium retention properties. Another explanation for accelerated transport is the potential for competitive adsorption of mixtures to reduce the equilibrium partitioning potential of substances in mixtures. Additional retention (i.e., adsorption to NAPLs) requires additional study to determine appropriate partitioning parameters. Finally, PFASs may have unique transport and retention mechanisms which may be enhanced by their surfactant properties.

How to cite: Higgins, C., Illangasekare, T., Stults, J., and Guo, B.: Recent Advancements in Mechanistic Understandings of PFAS Fate & Transport in the Vadose Zone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11156, https://doi.org/10.5194/egusphere-egu24-11156, 2024.

Soil Aquifer Treatment (SAT) consists of recharging the effluents of wastewater treatment plants across the soil (possibly reinforced with a reactive layer), unsaturated zone, and aquifer. It has been known since long that a dramatic water quality improvement occurs after soil and aquifer passage. However, the actual contaminant removal mechanisms remain open to discussion. Here, we summarize results observed at a number of sites displaying significant degradation of the most recalcitrant chemical compounds, as well as orders of magnitude reduction of antibiotic resistance and pathogen indicators. We have observed that the most toxic species, with significant partition coefficients, tend to accumulate in biofilms, where microorganisms accumulate. The accumulation of degrading microorganisms at the place where they can be degraded suggest natural selection. Further, a broad range of redox conditions, from aerobic to sulphate reduction (and, thus, a broad diversity of microbial communities), do occur during SAT. Together, these processes ensure a an extremely bioactive environment, which explains the dramatic reduction in toxicity we have observed after relatively modest (some 15 days) residence time in the aquifer. An implication from these observations is that the strict conditions imposed by the EU on SAT must be relaxed.

How to cite: Carrera, J., Rodriguez-Escales, P., Valhondo, C., Martinez-Landa, L., Diaz-Cruz, S., Piña, B., Contreras, A., Quintana, G., and Navarro-Martin, L.: A short review of the processes explaining water quality improvement during Soil Aquifer Treatment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20496, https://doi.org/10.5194/egusphere-egu24-20496, 2024.

Structural dynamics, fluid flow, and reactive transport in permeable media are affected by the presence of and interactions with components of the total mobile inventory (TMI). With the term TMI we take into account the fact that the inventory of mobile substances in natural permeable media extends over an extremely wide range of sizes (spanning five orders of magnitude from the truly dissolved matter in the nanometre range to the large microaggregates and biota, around 250µm) and an almost incomprehensible diversity of proprietary and foreign materials (e.g., organic, inorganic, organo-mineral associations, microaggregates, biota, viruses, MGE, etc.; Lehmann et al. 2021 DOI:10.1016/j.scitotenv.2020.143774). Despite the essential role the larger particles of TMI up to a size of 250µm play for the functions, ecology, and intercompartment exchange in the subsurface and in between the surface and subsurface (Zerfaß et al. 2022 DOI:10.1016/j.watres.2022.118998; Herrman et al. 2023 DOI: 10.1016/j.soilbio.2023.109192), the majority of studies on the subsurface water resources and the biogeochemical cycling are dedicated to the operationally defined dissolved fraction, and, to a lesser extent, to the colloidal sized materials. Larger mobile materials beyond the 2µm size limit are vastly omitted. With increasing size beyond the “magical” 450nm size boundary, however, the understanding of the mechanisms that control the fate of TMI-components gets more demanding. With increasing size, morphology and surface properties control the interactions with the mobile and immobile surfaces and thus the transport behaviour. With increasing size, the effects of gravity on interactions and transport can no longer be neglected (Guhra et al. 2021 DOI: 10.1016/j.jcis.2021.03.153). And with increasing size, the pore-network structure, void-size-distribution, and connectivity constrain the accessibility to fractions of the void space by exclusion. The story does not end here: Interactions of TMI-components with the immobile solid phase change the structure of the void-network (Ritschel et al. 2023, DOI: 10.1016/j.geoderma.2022.116269). And TMI change the properties of the – frequently aqueous fluids in natural systems, e.g., the density, the viscosity, and the surface tension. In sum, fluid dynamics and reactive transport in natural systems like soils, sediments, the vadose and the phreatic zone are rather complex phenomena that are intimately intertwined with the physical and biogeochemical weathering and alteration in the subsurface and pedogenesis at the regolith-atmosphere interface. In view of the growing awareness of the subsurface as a mosaic of habitats and ecosystems (Lehmann and Totsche, 2020 DOI: /10.1016/j.jhydrol.2019.124291; Yan et al. 2020 DOI: 10.1016/j.watres.2019.115341), affected by land-use and climate change, this presentation pleads for a more general and synoptic understanding of fluid flow and reactive transport in natural permeable media and the consequences for their properties, functions and finally life sustaining ecosystem services. Given the power provided by multi-omics in combination with the wide spectrum of (non-invasive) spatio-temporal observational techniques, and the rapid progress in E-science and model-Big-data integration, the reconstruction of the “true” complexity of the subsurface compartments and their development in response to climate and land-use change is possible and allows to define the objectives for ambitious future coordinated research.

How to cite: Totsche, K. U.: Linking the dynamics of the total mobile inventory to the co-evolution of structure and function in the subsurface, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15559, https://doi.org/10.5194/egusphere-egu24-15559, 2024.

The present communication investigated the dynamics (prevalence, seasonality, and removal) of endocrine disruptive chemicals (EDCs) and seven target pharmaceuticals and personal care products (PPCPs) in the Himalayan city of Dehradun in Uttarakhand province of India. Two municipal and two academic institutions WWTPs were selected for wastewater (WW) sampling in the city during spring, summer, and monsoon seasons. The result showed Diclofenac and Caffeine occurrence in all influent samples of the WWTPs indicative of considerable intake in the city. During the study, Caffeine and Acetaminophen concentrations were consistently higher in the sampled WW influents. The total PPCPs concentration in the WWTPs ranged from 1K to 74K ngL^-1 and 22 to 64K ngL^-1in influent and effluents, respectively. Seasonal variations in influent wastewater samples indicated high mean PPCP levels during spring, followed by monsoon and summer seasons. Caffeine showed the highest PPCP concentration (71K ngL^-1) during monsoon and while Ciprofloxacin concentration was high (16K ngL^-1) during the spring season. The study also revealed high correlation between Acetaminophen with Diclofenac (r=+0.77) and Ketoprofen (r=+0.62). In addition, Diclofenac was firmly linked with Ketoprofen (r=+0.89), whereas Ciprofloxacin was strongly linked with Carbamazepine (r=+0.65).

While the estrone showed concentrations at μgL⁻¹ levels in influent concerning ngL⁻¹ levels of triclosan (TCS). The highest global concentration of ~124 μgL⁻¹ is recorded for the estrone during our monitoring period. The tests for Normality showed a non-normal data distribution (p>0.05) for all WW PPCPs samples except for Caffeine influents. PPCP concentration showed a high statistically significant variation between the influent and effluent samples (p<<<0.001), indicating highly decisive evidence for unequal means. The PPCPs treatment rates in the WWTPs ranged from ~69 -100%. In terms of total PPCPs, average removal efficiencies of WWTPs were recorded in the range of 41.66-71.40%. The maximum removal was recorded for Acetaminophen and Ketoprofen, while increased concentrations in the effluents (negative removals) were witnessed for Ciprofloxacin, Carbamazepine, and Caffeine in the WWTPs. The WWTPs have been found to contribute to existing PPCP loads and are channelized toward the disposal sites, posing a severe threat to biodiversity, human health, and the ecological integrity of the region and its downstream. We critically highlighted the limitation of the WWTPs in the treatment, degradation, and assimilation of EDCs leading to several environmental & human health-based threats to one health in the region. This study is vital for setting up baseline data and setting a platform for future research surveillance and control of emerging contaminants (ECs) in ecologically sensitive hilly landscapes.

How to cite: Kumar, M., Silori, R., Madhab Mahapatra, D., and Mahlknecht, J.: Patterns of Prevalence, Seasonality, and Treatment Efficiencies of Endocrine Disruptive Chemicals, Pharmaceuticals, and Personal Care Products in the Wastewaters of the Himalayan City of Dehradun, India, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22435, https://doi.org/10.5194/egusphere-egu24-22435, 2024.

We present the interpretation of the Perfluorooctane sulfonate (PFOS) dataset spread over eighteen years between 2005 to 2023. The data explicitly depicts the essence of i) a growing monitoring network with growing concern i.e. ten to nearly 100 locations; ii) increasing resolution in knowing the chemical closely with advancing technologies i.e. inclusion of branched and linearity of PFOS rather than just ionic form; iii) increasing the diversity of systems being gradually included in the monitoring system to appreciate the environmental interactions, i.e. only groundwater to freshwater to even brackish water systems. This government-supported monitoring data tracks the curve of PFC-related concern for water sectors over the last two decades of the 21st century and thus provides the learnings for the future. The dataset also indicates that knowing a problem is the first step towards taking the right steps towards correcting that given system, as evident by decreasing PFOS concentrations between 2005 (ND to 0.5 µgL⁻¹) to 2023 (ND to 0.012 µgL⁻¹) in the groundwater environment of Yorkshire, UK. However, the data fails to provide confirmatory evidence of PFC pathways linking with surface-groundwater interactions. This work can be an eye-opener for policymakers of developing countries who are so reluctant to acknowledge the lack of regulations, and thus the associated need to monitor of chemicals of emerging concerns like PFAs, thus completely losing the opportunity of establishing stringent guidelines at the right time.

How to cite: Dogra, K., Kumar, M., and Agarwal, V.: Decadal Resolution of ‘Forever Chemical’ of PFOS in the groundwater of Yorkshire County, United Kingdom: The Future of the Past Learnings, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22399, https://doi.org/10.5194/egusphere-egu24-22399, 2024.

The impact of nanoplastics on the co-transport of emerging contaminants is a subject of ongoing debate. Agricultural soils face potential contamination from micro- and nanoplastics through diverse agricultural practices. Various authors argue that the substantial surface area of small particles and their high sorption potential may considerably augment the mobility of numerous contaminants within the critical zone. Concerns have been expressed regarding the role of micro- and nanoplastics as carriers for organic contaminants into deeper soil layers, posing a potential threat to groundwater resources, particularly in agricultural soils where sewage sludge and plant protection products are frequently applied.

In this study, we investigated the correlation between transport and desorption timescales by employing two diffusion models for micro- and nanoplastics ranging from 100 nm to 1 mm. To assess the transport of contaminants bound to these plastics, we examined the diffusion and partitioning coefficients of prominent agrochemicals and additives, along with commonly used polymers like polyethylene and tire material. Our modeling analysis reveals that the desorption rate of most organic contaminants is too rapid for micro- and nanoplastics to serve as effective transport facilitators in soil. Notably, the transport of contaminants facilitated by microplastics was observed to be significant only for highly hydrophobic contaminants under preferential fast-flow conditions.

While micro- and nanoplastics could potentially introduce harmful contaminants into agricultural soils, our study suggests they do not significantly enhance contaminant mobility. Importantly, we found that nanoplastics, in particular, do not promote contaminant relocation under conditions relevant to almost all contaminants of concern.

How to cite: Hofmann, T., Henkel, C., Hueffer, T., and Castan, S.: Why nanoplastics do not enhance the transport of contaminants in the critical zone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6160, https://doi.org/10.5194/egusphere-egu24-6160, 2024.

Microplastic (MP, ⌀ < 5 mm) can be found worldwide. Besides aquatic environments, terrestrial ecosystems are reported to contain large amounts of MP of different origin, polymer type, shape, size, and state of degradation. Furthermore, soil is considered the largest sink of MP in terrestrial ecosystems. Though, little is known about the effects of MP on soil and its interaction with water flow. Since MP is inherently hydrophobic, the transport of MP and the flow of water interact with each other. However, the extent of MP transport in soils and the interactions with water flow remain largely unexplored.

To approach these questions, neutron and x-ray imaging methods were applied. Simultaneous neutron and x-ray CT at the beamline ICON (Paul-Scherrer-Institute) during wetting and drying cycles of a model porous media mixed with MP in different contents were used to monitor MP in different contents (size between 20-75 μm) and water distribution during repeated wetting and drying cycle of a sandy substrate (particle size between 700-1200 μm). Here, the initial MP configuration as well as the configuration after each wetting and drying cycle were captured in three dimensions. During the wetting process, time-series neutron radiographies imaged the water infiltration patterns.

MP reduced water infiltration in soils. High MP contents caused local water reppellency and were by-passed by perculating water. MP impacted the verticle distribution of water, reducing the local soil water content and driving water to deeper soil layers. Significant transport of MP were not visible during the wetting and drying cycles, plausibly because water by-passed the pore space containing MP. Rapid and preferential infiltration into deeper areas of the sample as well as low local volumetric water contents during the course of infiltration are evident. The extent seems to be MP content dependent.

In conclusion, MP-water interactions in soils have a strong impact on water flow and MP transport and fate in soils. Transport processes like advection, which are significant for wettable particles, play only a minor role in transporting low wettability particles like MP under unsaturated conditions. Though, MP seems to be spatially re-configured. This might be due to hydrophobic interactions between water and MP. Hydrophobic MP has an affinity towards adsorbing to the air-water interface rather than being dispersed in water when in contact.

How to cite: Cramer, A., Kaestner, A., Benard, P., Zarebanadkouki, M., Lehmann, P., and Carminati, A.: Water flow and MP transport in sandy soils imaged with neutron radiography and X-ray CT, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1667, https://doi.org/10.5194/egusphere-egu24-1667, 2024.

Biodegradable polymers are considered one of the solutions to the plastic accumulation problem in terrestrial and aquatic systems. It is important to ensure complete degradation since residual micro- and nanoplastics influence soil health and its biota. During biodegradation, microorganisms first colonize the plastic surface, where they then excrete enzymes responsible for the depolymerization. Finally, the mono- and oligomers are utilized by the microorganisms as energy sources (mineralization into CO₂) or for biomass formation. Only by studying the last step the final fate of the anthropogenic pollutant is revealed. Conventionally CO₂ concentrations are measured to monitor microbial activity in samples exposed to plastics in comparison to plastic-free controls. However, this is in no direct relation to the polymer and priming effects or unknown processes due to bacteria adaptation might blur the analysis. Stable isotope labels can be traced from the polymer into ¹³CO₂, D₂O and microbial biomass to overcome those obstacles. While many publications covered ¹³CO₂ monitoring, only Zumstein et al. additionally traced the carbon label into fungal biomass with nanoscale secondary ion mass spectrometry.[1] In our approach, we use deuterium instead of carbon labels due to reduced costs and enhanced availability of labeled compounds. Although we lose the ability to contribute to a closed mass balance, we use non-destructive Raman microspectroscopy to gain additional chemical information on a single cell level. Heavier isotopes lead to a red shift of the according Raman band due to their larger mass. Deuteration of microbial lipids, proteins, DNA, and carbohydrates leads to an extensive shift of C-H vibrations into the Raman-silent region. C-D vibrations can therefore be quickly detected with a facilitated data analysis.

We incubated the environmental bacterium Sphingomonas koreensis with deuterated polylactic acid (dPLA) in an aqueous medium at room temperature under aerobic conditions. After 3 weeks, we observed an additional biomass spectrum for about 50 % of the measured cells besides undeuterated biomass and dPLA particles. After 13 weeks, this spectrum was already recorded for all cells. While the biomass and C‑H str. vibrations clearly indicate microbial biomass, the C-D vibrations of the additional spectra differ from reference deuterated biomass spectra obtained with glucose-d₁₂ and D₂O labeling. After comparing these untypical C-D vibrations to self-obtained and literature reference spectra, they were interpreted to originate from deuterated biomass with strongly deuterated lipids and inhibited labeling of proteins. Now that we can trace deuterium from labeled plastics into microbial biomass, we want to extend the approach to terrestrial environments. Therefore, cell isolation from the soil matrix was successfully adapted from the literature[2] to gain adequate Raman spectra. In ongoing experiments, environmental samples will first be exposed to unlabeled PLA for bacteria adaptation and then used for incubation with dPLA in soil microcosms. 

References:

• Zumstein, M.T., et al., Science Advances, 2018. 4(7): p. eaas9024.
• Eichorst, S.A., et al., FEMS Microbiology Ecology, 2015. 91(10).

Acknowledgments: Deutsche Forschungsgemeinschaft (DFG) Project IV 110/2-2 and International Atomic Energy Agency (IAEA) for funding different parts of the research. Dr. Jürgen Allgaier (FZ Jülich) for providing the deuterated PLA.

How to cite: Müller, K., Elsner, M., and Ivleva, N. P.: Deuterium Labels to Study Biodegradation of Plastics with Raman Spectroscopy , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-227, https://doi.org/10.5194/egusphere-egu24-227, 2024.

How to cite: Yu, Y. and Flury, M.: Transport of Biodegradable Nanoplastics Affected by Weathering and Proteins in Unsaturated Porous Media, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3604, https://doi.org/10.5194/egusphere-egu24-3604, 2024.

Microplastics (MPs), are considered an emerging global pollutant and a significant contributor to environmental pollution. They are defined as plastic particles measuring less than 5 mm which can vary in chemical composition, color, shape, density, size, and other characteristics. MPs generated through urban, industrial, and agricultural activities have the potential to reach the environment, including groundwater. However, despite the significance of groundwater as a vital resource, there is a notable dearth of information regarding the occurrence, transport, and risk of MPs in this environment.

In Slovenia, groundwater resources are the primary source of drinking water for 98% of the population. A considerable number of these resources are affected by different anthropogenic activities that result in contamination by different pollutants, among which MPs are probably included. The present study aimed to investigate the presence of MPs in karst and alluvial aquifers of three different regions of Slovenia. Particular emphasis has been given to the improvement of sampling and detection of MPs in groundwater along with the evaluation of the impact of hydrogeological environment, land use and anthropogenic activities in the recharge zone of each sampling site on the occurrence of MPs in groundwater.

Groundwater samples were collected from a total of 19 locations, 8 were situated in alluvial aquifers and 11 in karst formations. In each location a total of 3 cubic meters of water was sampled using an in-situ filtration system with a filter pore size of 10 - 100 µm. The samples were then analyzed in the laboratory using a digital microscope with a magnification range of 100 - 5000x and stereomicroscope with magnification 12,5 – 100x. The chemical composition of particles was determined using FTIR microscope and ATR-FTIR. The results showed that MPs were present in all sampled sites, with fibers and fragments being the most common observed shapes. The study proves the presence of MPs in both, alluvial and karst aquifers of Slovenia and demonstrates the suitability of an in-situ filtration system for sampling MPs in groundwater.

How to cite: Colmenarejo Calero, E., Kovač Viršek, M., Bizjak, T., and Mali, N.: Microplastics pollution in groundwater: Case study - Slovenia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15458, https://doi.org/10.5194/egusphere-egu24-15458, 2024.

The assessment of nanoparticle NP transformation in the aquatic environment is essential for comprehending the fate of nanoparticles and conducting accurate risk assessments. Nanoparticles encompass a variety of materials, including manufactured nanomaterials, nanoplastics, and natural colloids. Environmental transformation comprises four main routes: dissolution/leaching, abiotic transformation/degradation, biotic transformation/degradation and (hetero-)agglomeration.

The kinetics of heteroagglomeration play a pivotal role in nanoparticle (NP) transport mechanisms in rivers. The parametrization of heteroagglomeration processes between NPs and suspended particulate matter (SPM) was hampered by the variability of SPM floc composition and conformation/size on spatial and temporal scales. Available analytical methods were either unsuitable or required unrealistic high NP concentrations. The SPM used in heteroagglomeration studies was either unrealistically simple (silica particles, clays) or exceptionally unique (specific natural SPM sample).

After a thorough analysis of mechanisms of floc formation and the relevant building blocks of natural, riverine SPM and the successful and reproducible laboratory synthesis of model SPM flocs, we designed a method to determine the heteroagglomeration attachment efficiency α_hetero  under environmentally relevant conditions. This allows well controlled laboratory experiments as well as standardization for risk assessment purposes. The heteroagglomeration attachment efficiency () constitutes the most suitable parametrization of particle-particle interactions. The presented test matrix combines synthetic model SPM flocs with the model freshwater composition suggested in OECD TG 318, both designed to represent agglomeration-relevant characteristics of natural systems. The test matrix was employed in a newly developed stirred-batch method addressing the shortcomings of existing strategies to determine α_hetero. Time-resolved inductively coupled plasma mass spectrometry allowed to work at realistic concentrations of NP (5 ppb) and SPM flocs (20 and 40 ppm).

The approach was evaluated by testing the heteroagglomeration of CeO₂ nanoparticles in four different combinations of SPM and water chemistry.

• Natural flocs in natural water
• Natural flocs in synthetic (TG318) water
• Synthetic flocs in natural water
• Synthetic flocs in synthetic water

The results show the applicability and precision of the invented test system and the synthetic SPM but also reveal some differences between results from natural and synthetic water chemistry which can be explained by the type and quality of the NOM. Calculated transport distances for 50% unassociated NPs reached up to 370 km, what is unexpectedly high.

How to cite: von der Kammer, F., Walch, H., Lehutso, R. F., and Hofmann, T.: Nanoparticle Heteroagglomeration with Natural and Synthetic Suspended Particulate Matter, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8778, https://doi.org/10.5194/egusphere-egu24-8778, 2024.

The cause of non-exponential decreases in colloid concentrations with distance from source was posited to derive from the emergence of fast- and slow- attaching populations from identical individuals (Johnson, 2018).  Fast-attachers were posited to attach according to a rate coefficient corresponding to favorable conditions, whereas the remainder of the population were posited to attach according to a slower rate coefficient.  This talk demonstrates the emergence of fast- and slow- attaching populations in pore network transport experiments under unfavorable conditions.  We explain the segregation into two subpopulations as being driven by colloid-surface repulsion, topological impacts of the flow field (incomplete pore scale mixing), and consequent impacts on the number of interceptions incurred prior to attachment. 

How to cite: Ullauri, L., Johnson, W., Bolster, D., and Al-Zghoul, B.: Experimental Confirmation of Emergence of Fast- and Slow- Attaching Subpopulations from Identical Individuals Produces Non-Exponential Decreases in Colloid Concentrations with Distance from Source under Unfavorable Conditions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13533, https://doi.org/10.5194/egusphere-egu24-13533, 2024.

The importance of nanoscale roughness factors on the fate and transport of colloidal particles has been well emphasized in recent literature; however, most of the works either only used modeling tools or had limitations on unravelling the effect experimentally due to the lack of well-defined systems to solely capture the role of the nanoscale roughness. Therefore, this study aimed to “experimentally” observe the adhesion characteristics of environmental colloidal particles on a surface with nanoscale roughness (NR) factors (i.e., height and fraction) under environmentally relevant solution chemistry conditions. Prior to analyzing the effect of the NR, the solid surface was first fabricated. AFM was employed to confirm the adhesion force between the target material and the uniformly fabricated rough surface, which can influence the contact area. To the best of our knowledge, our study is the first to experimentally quantify the sole effect of the NR with well-controlled NR-surfaces via the adhesion force measurement in aqueous system. The findings are important to verify the role of NR in the interaction of particles with different shapes (i.e., sphere and plateau) and sizes (i.e., 2 μm to 15 μm in length or diameter), which the authors believe will provide new insights to the society on better understanding the role of NR in the interaction of environmental colloidal particles.

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. RS-2022-00166099).

How to cite: Hwang, G. and Kim, H.: Adhesion forces measured between colloids and nanoscale surface roughness in aqueous solution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2071, https://doi.org/10.5194/egusphere-egu24-2071, 2024.

Pesticide use plays a crucial role in achieving high crop yields in the context of a global population growth scenario. However, the extensive application of pesticides has progressively led to the contamination of environmental matrices, particularly soils and groundwater, posing potential risks to human health, flora, and fauna. Nanopesticides can be instrumental in mitigating pesticide pollution, especially for highly soluble and volatile active ingredients. They are formed by nanoparticles (nanocarriers) containing an active ingredient, sometimes shielded by a coating, and dispersed in a colloidal suspension. The nanoformulations proposed in this study utilize low-cost mineral materials (such as montmorillonite, zeolite, kaolin) and food-grade biopolymers to incorporate two distinct herbicides, namely dicamba and S-metolachlor, characterized by high solubility (and thus high migration potentian in the subsoil) and, for dicamba only, moderate volatility.

The efficacy of the newly developed nanoherbicides in terms of reduced mobility in porous media, reduced persistency, and efficacy toward target weeds was assessed in the laboratory against the pure herbicide and commercial formulations containing the same active ingredients. Specifically, the mobility in porous media was tested through column transport experiments under both saturated and unsaturated conditions, using sand and standard soils (representative, respectively, of top soil and aquifers). These tests were conducted at various scales, ranging from small columns (1.6 cm diameter, 10 cm length) to a laboratory lysimeter (30 cm diameter, 70 cm length). Batch degradation tests in soils indicated comparable DT50 values for the nanoformulation and the commercially available product. The efficacy of the nanopesticides was also examined against conventional products in greenhouse settings through dose-response tests on selected sensitive weeds. The greenhouse tests revealed that clay-based nanoformulations do not impede the effectiveness of dicamba against target weeds, showing efficacy comparable to the commercial competitor for both dicamba and S-Metolachlor, although variations were observed depending on the treated species.

Despite the small scale of the tests conducted in the laboratory and greenhouse, these initial results suggest the promising efficacy of the proposed nanoformulation approach in controlling the environmental spread of soluble herbicides without compromising efficacy against target species.

This research was conducted within the Nanograss project, co-funded by the Compagnia di San Paolo Foundation.

Reference

Granetto M., Serpella L., Fogliatto S., Re L., Bianco C., Vidotto F., Tosco T. (2022). Natural clay and biopolymer-based nanopesticides to control the environmental spread of a soluble herbicide. Science of The Total Environment 806(3),151199, https://doi.org/10.1016/j.scitotenv.2021.151199

How to cite: Tosco, T., Granetto, M., Fogliatto, S., and Vidotto, F.: Managing the leaching of water-soluble herbicides in soils using eco-compatible nanocarriers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11500, https://doi.org/10.5194/egusphere-egu24-11500, 2024.