Displays

Diverse processes such as bioremediation, biofertilization, and microbial drug delivery
rely on bacterial migration in porous media. However, how pore-scale confinement alters
bacterial motility is unknown due to the inherent heterogeneity in porous media. As a
result, models of migration are limited and often employ ad hoc assumptions.
We aim to determine the impact of pore confinement in the spreading dynamics of two
populations of motile metal reducing bacteria by directly visualizing individual Acidovorax
and Pelosinus in an unconfined liquid medium and in a microfluidic chip containing regular
placed pillars. We observe that the length of runs of the two species differs from the
unconfined and confined medium. Results show that bacteria in the confined medium
display a systematic shorter jumps due to grain obstacles when compared to the open
porous medium. Close inspection of the trajectories reveals that cells are intermittently
and transiently trapped, which produces superdiffusive motion at early and subdiffusion
behavior at late times, as they navigate through the confined pore space. While in the open
medium, we observe a linearly increasing variance with respect to time for Acidovorax, and
for Pelosinus the variance increases at a much faster rate showing super diffusive behavior
at early times. At late times, the rate of growth in spreading increases for Acidovorax while
it reduces for Pelosinus. We finally discuss that the paradigm of run-and-tumble motility
is dramatically altered in the confined porous medium and its practical applications of
these effects on large-scale transport.

How to cite: Perez, L. J., Sund, N. L., Parashar, R., Plymale, A. E., Hu, D., and Scheibe, T. D.: Influence of pore geometry on motility and trapping of metal reducing bacteria, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4226, https://doi.org/10.5194/egusphere-egu2020-4226, 2020.

Excessive fecal indicator bacteria concentration leads to swimming advisories that are very common to freshwater beaches. To evaluate the concentration and interaction of indicator bacteria in beach sand and water and to examine the factors that affect bacteria concentration, a study was undertaken at Bradford beach, Milwaukee county on the shore of Lake Michigan. In this research, results from monitoring of E. coli and Enterococci in sand and water from Lake Michigan beach were presented. Bacteria counts were obtained using the IDEXX Most Probable Number (MPN) method. An attempt was made to establish a direct ratio of bacteria counts between the two most common eluents used to detach bacteria from sand, i.e., deionized water (DI) and phosphate buffered saline (PBS). The beach sand bacteria count was analyzed using the EPA CANARY event detection software to identify the onset of periods of anomalous water quality. Analysis of beach sand from this study show that for E. coli, it may be possible to establish a relationship between the results generated using two eluents. Results from the model indicates that sand can be a better potential reservoir for indicator bacteria survival than water as a source. The results also show that CANARY may be useful as an early warning system for monitoring beach contamination and may help to identify any abnormal condition very quickly. Also, in this study, the factors that contributed to the high concentration of bacteria resulting in abnormal water quality events are examined which are the impact of Algae in beach water sample and the rainfall effect during the overall month of sampling duration. CANARY software can best indicate the impact of the presence of Algae on bacteria concentration. The analysis of rainfall effect on bacteria concentration was done using statistical software by determining the significance (p-value) between the seasonal mean concentration of E. coli and the mean concentration of E. coli during the sampling duration and from the analyses it is evaluated that rainfall does affect the bacteria concentration. Moreover, the correlation coefficient indicates greater impact of rainfall event on bacteria concentration relative to the presence of Algae level. Regression analysis was also done to estimate the best model that describes the relation between E. coli and water temperature resulting in weak negative linear relationship between the variables.

How to cite: Li, J., Bevers, B., Nafsin, N., and Liao, Q.: Monitoring of E. coli and Enterococci in Lake Michigan Beach Sand , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2459, https://doi.org/10.5194/egusphere-egu2020-2459, 2020.

Most ocean microplastic concentration data come from manta net trawling. Net trawling has a low sample rate that may be underestimating the true plastic concentrations. Plastic concentrations are also not well sampled outside the North Atlantic and North Pacific gyres. Ocean circulation models have been used to estimate the transport of plastics in the ocean and model predictions of their accumulation in ocean gyres have been validated to some degree by net trawl data. However, concentrations of plastic debris in close proximity can vary by orders of magnitude in the span of days, suggesting the presence of complex transport mechanisms and spatiotemporal variability that net trawl sampling and global circulation models may be unable to adequately resolve.

Attempts have been made to use spaceborne remote sensing methods to detect areas of high oceanic plastic concentrations. Methods based on hyperspectral imaging are being successfully explored, but their coverage and timeliness are limited. An alternate approach is presented here which provides more global, time resolved, coverage. Spaceborne radar measurements of ocean surface roughness are used to infer the reduction in responsiveness to wind-driven roughening caused by microplastics and surfactant tracers. On a global scale over long time periods, the reduction correlates strongly with the mass density of microplastics near the surface measured by net trawl campaigns and predicted by ocean circulation models. On a global scale on shorter time scales, time lapse images derived from the radar observations reveal seasonal changes in the microplastic mass density which appear to be related to seasonal ocean circulation patterns. On smaller spatial and temporal scales, time lapse images reveal episodic bursts of microplastic outflow from major river discharges into the sea.

How to cite: Ruf, C. and Evans, M.: Detection and Dynamic Imaging of Ocean Microplastics from Space, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3120, https://doi.org/10.5194/egusphere-egu2020-3120, 2020.

The rapid aggregation/sedimentation and decreased transport of nanoscale zero-valent iron (nZVI) particles limit their application in groundwater remediation. To decrease the aggregation/sedimentation and increase the transport of nZVI, sodium alginate (a neutral polysaccharide) and bentonite (one type of ubiquitous clay) were employed to modify nZVI. Different techniques were utilized to characterize the modified nZVI. We found that modification with either sodium alginate or bentonite could disperse the nZVI and shifted their zeta potentials from positive to negative. Comparing with the bare nZVI, the sedimentation rates of modified nZVI either by sodium alginate or bentonite are greatly decreased and their transport are significantly increased. The transport of modified nZVI can be greatly increased by increasing flow rate. Furthermore, Cr(VI) can be efficiently removed by the modified nZVI (both sodium alginate and bentonite modified nZVI). Comparing with bare nZVI, the two types of modified nZVI contain lower toxicities to Escherichia coli. The results of this study indicate that both sodium alginate and bentonite can be employed as potential stabilizers to disperse nZVI and improve their application feasibility for in situ groundwater remediation.

How to cite: Zhang, M., Yi, K., Zhang, X., Han, P., Liu, W., and Tong, M.: Modification of Zero Valent Iron Nanoparticles by Sodium Alginate and Bentonite: Enhanced Transport, Effective Hexavalent Chromium Removal and Reduced Bacterial Toxicity, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2342, https://doi.org/10.5194/egusphere-egu2020-2342, 2020.

Recent research discovered that airborne microplastics pollution can reach very remote areas. However, analysis of nanoplastics in environmental samples remains challenging, mostly due to technical and methodological issues. A new method for chemical characterisation of nanoplastics based on TD-PTR-MS has been recently introduced. The detection limit of <1ng allowed for the first time the analysis of nanoplastics deposited on the snow in the pristine Alps. In this work, we analysed daily samples of surface snow close to the Sonnblick Observatory, Austria (3106 m altitude) in the period from 2017-02-07 to 2017-03-19, using our new method. The results showed a positive detection for various types of nanoplastics, and the most common type found was Polyethylene terephthalate (PET). We will present our results on the to-date longest daily record of nanoplastics deposition in high altitude regions and further discuss optimisations of TD-PTR-MS method for nanoplastics detection and quantification.

How to cite: Materic, D., Ludewig, E., Cristescu, S. M., Röckmann, T., and Holzinger, R.: Deposition of nanoplastics in high-altitude Alpine snow, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9072, https://doi.org/10.5194/egusphere-egu2020-9072, 2020.

The use of pesticides in agriculture has numerous advantages but also significant environmental drawbacks; The uncontrolled or excessive use of agrochemicals has progressively contributed to the contamination of environmental matrices, and in particular of soils and groundwater. To contribute solving these issues, an eco-compatible nano-formulation was recently developed by the authors to help controlling the environmental dispersion of Dicamba, a herbicide widely used to control broadleaf weeds; Dicamba is highly soluble and moderately volatile, but is less toxic and persistent compared to other competing herbicides. The proposed nano-formulation was developed using eco-compatible, low-cost materials, including natural clays an biopolymers, with the aim to reduce Dicamba volatilization (thus reducing dispersion in air, and consequently potential impacts on both workers and neighboring crops) and solubility (thus reducing infiltration during and after application, and consequently uncontrolled dispersion in the subsoil).  In this work, the results of laboratory and greenhouse tests are discussed, comparing the efficacy of the nano-formulation against the pure herbicide compound and a commercial Dicamba-based product, in terms of volatilization, mobility in porous media (both saturated and unsaturated) and efficacy in weed control. The column tests results are modeled using colloid transport software (namely MNMs and Hydrus) and used for the development of a preliminary field-scale model of herbicide application and dispersion in the subsoil. The work was developed in the framework of the project Nanograss, co-funded by Compagnia di San Paolo Foundation.

How to cite: Tosco, T., Granetto, M., Re, L., Audino, A., Serpella, L., Fogliatto, S., and Vidotto, F.: A novel nano-formulation to reduce the environmental dispersion of herbicides, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18817, https://doi.org/10.5194/egusphere-egu2020-18817, 2020.

The sulfidation and aging of silver nanoparticles (Ag-NPs) with natural organic matter (NOM) are major transformation processes along their pathway in wastewater treatment plants and surface waters. Although porous media, such as soils or riverbank filtration systems, appear to be a sink for disposed Ag-NPs, the impacts of biological interfaces, the presence of NOM in the aquatic phase, and of variable water saturation on the transport and retention of Ag-NPs are still not fully understood.

We have performed two laboratory studies to examine the mobility of Ag-NPs in porous media under different conditions. At first, we investigated the mobility of citrate-coated Ag-NPs in sand obtained from an artificial riverbank filtration system comparing pristine and pond-water aged sediments as well as different flow velocities. Second, we investigated how the sulfidation of Ag-NPs (S-Ag-NPs) and the presence of NOM in the aquatic phase can change the transport characteristics in saturated and unsaturated sand at different transport velocities. Flow experiments inside an X-ray microtomograph enabled to study the impact of phase distribution (solid, water, air) and their interfaces on the retention of Ag-NPs.

Our experimental results show that the mobility of Ag-NPs in porous media is affected by the presence of biological components, the sulfidation of particles and, when unsaturated, the additional air phase. In saturated riverbank filtration systems, naturally occurring biological aging processes on sediments enhanced the efficiency of the system to retain citrate-coated NPs. The sulfidation of Ag-NPs to S-Ag-NPs decreased the mobility in porous media while the NP-aging with NOM re-established mobility to some extent. In unsaturated sand, the retardation of NOM aged S-Ag-NPs was strongly increased by decreasing water content, i.e. the propagation of an air phase, and decreasing flow velocity.

How to cite: Leuther, F., Degenkolb, L., Köhne, J. M., Metreveli, G., Klitzke, S., and Vogel, H.-J.: Mobility of silver nanoparticles in porous media: The impact of biological interface, water saturation, and nanoparticle aging, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6630, https://doi.org/10.5194/egusphere-egu2020-6630, 2020.

Natural colloids may act as carriers of contaminants and enhance the transport of strongly-sorbing pollutants toward surface waters and groundwater. Field investigations on colloid transport remain rare. This is of high importance for the hilly central Sichuan in the upper reaches of the Yangtze River, which is characterized by thin (mostly <60 cm) purple soil cover and underlying finely fractured mudrock and impermeable sandstone. In Jieliu catchment of Yanting, colloid dynamics in surface and subsurface flows for two sloping (6°) farmland plots (24 m² and 1500 m²) as well as in stream flows at two weirs (3 ha and 35 ha) were monitored based on individual rain events to identify the major factors governing colloid transport. Daily monitoring of fracture flow from the 1500 m² plot and biweekly monitoring of three lowland shallow wells was also conducted simultaneously throughout a whole year to identify the source of colloids in groundwater.

Results show that colloid concentration in the surface runoff was 1-2 orders of magnitude higher than that in the subsurface flows (i.e., the interflow from the soil-mudrock interface and fracture flow from the mudrock-sandstone interface). The lowest colloid concentration was observed in the interflow, probably as a result of pore-scale colloid straining. The rainfall intensity and its temporal variation govern colloid dynamics in both surface runoff and subsurface flows. Analyses of δ¹³C and mineral composition, organic matter and carbonate content in groundwater colloids and the upper geological samples can be used combinedly to identify the sources of groundwater colloids. By using the δ¹³C tracking technique, it was found that the suspended fine sediment export via stream flow during rain events at the catchment outlet came mainly from the sloping farmland, while the deposited fine sediment on stream bed derived from multiple sources including paddy field (55.3%), woodland (29.7%) and sloping farmland (15.0%).

How to cite: Tang, X., Zhang, W., and Xian, Q.: Dynamics and source identification of colloids in surface and subsurface waters, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10562, https://doi.org/10.5194/egusphere-egu2020-10562, 2020.

A thorough knowledge of the interaction energy between a hollow particle (HP) and a surface or between two HPs is critical to the optimization of HP-based products and assessing the environmental risks of HPs and HP-associated pollutants. The van der Waals (vdW) energy between a HP and a surface is often calculated by subtracting the vdW energies of the inner and outer HP geometries. In this study, we show that this subtraction method is only valid when the interior and exterior fluids are the same, for example, for water-filled HPs (WHPs) dispersed in an aqueous solution. Expressions were developed to calculate the vdW energies for HPs whose interiors were filled with air (AHPs). The vdW energies were then calculated between a planar surface and a spherical or cylindrical WHP and AHP, and between WHPs or AHPs. The vdW attraction between a surface and a WHP was decreased at large separation distances compared to solid particles, and this reduced the depth of the secondary minimum. In contrast, the vdW attraction for AHPs and a surface was significantly reduced at all separation distances, and even became repulsive for thin shells, and this inhibited both primary and secondary minimum interactions. The vdW attraction between WHPs decreased with increasing shell thicknesses, and this reduced aggregation in both primary and secondary minima. In contrast, aggregation of AHPs was increased in both minima with decreasing shell thicknesses because of an increase in vdW attraction. Our theoretical calculations show the evolution of vdW and total interaction energies for HPs with different interior fluids and shell thicknesses. These results help explain various experimental observations such as inhibited attachment and favorable aggregation for AHPs (e.g., carbon nanotubes) and favorable bubble coalescence.

How to cite: Shen, C.: Interaction between air filled hollow particles and surface in water, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11915, https://doi.org/10.5194/egusphere-egu2020-11915, 2020.

This study was to investigate the effect of different manure colloids on the stability and transport of TiO₂ NPs. Manure was used in fields as a common organic fertilizer. Different manure colloids were selected to study their effects on the aggregation and transport of nTiO₂ at neutral pH conditions. The absorbance and particle size of the nTiO₂ suspension at a certain ionic strength and manure colloid concentration were measured to determine the stability and aggregation of the nTiO₂ particles at pH 7. Column experiments were performed to examine colloidal transport in quartz sand under water condition similar to those used in stability tests. The interaction energy among the nTiO₂ particles and between nTiO₂ particle and quartz sand were calculated using the classical DLVO theory to elucidate the underlying mechanisms involved at pH 7. The results showed that manure colloids can promote the dispersion and transport of TiO₂ NPs under different conditions. 

How to cite: Shang, J. and Yan, C.: Effect of manure colloid on stability and transport of titanium dioxide , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12759, https://doi.org/10.5194/egusphere-egu2020-12759, 2020.

Phytophthora cactorum, is an economically important plant pathogen causing sever damage on a wide range of crops, fruits, and ornamental plants. P. cactorum's infective potential and its spatial dissemination relies on rapid and copious production of asexual zoospores. However, little is known about P. cactorum zoospore transport behavior in porous media, impeding the development of effective technology in controlling  infection and disease spreading. In this study, we investigated the transport and retention of P. cactorum zoospores in sand columns at three levels of water saturation (100%, 65%, 48%). Both motile and encysted zoospores were studied as well as carboxylate-modified polystyrene microspheres with the same size as the zoospores (10 um). We hypothesized that (1) motile zoospores are more readily transported than polystyrene microspheres under the same conditions, implying the minor role of size (straining) and the critical role of zoospore motility in controlling zoospore transport; (2) the higher mobility of motile zoospores compared to that of encysted zoospores is caused by the lack of sticky chemicals and the existence of flagella on the surface of motile zoospores; and (3) transport of motile and encysted zoospores, as well as of polystyrene microspheres is enhanced as column saturation increases.

How to cite: Flury, M. and Yu, Y.: Transport of Phytophthora cactorum Zoospores in Unsaturated Sand Columns, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1500, https://doi.org/10.5194/egusphere-egu2020-1500, 2019.

Nowadays engineered silver nanoparticles (AgNP) are being widely used for a multitude of purposes. At certain times during their life-cycle they might enter soils and freshwater resources and thus recent research has focused on their transport and fate in soils and the vadose zone as well as the saturated zone. AgNP retention in the subsurface depends on a multitude of parameters including the type and shape of the sediments through the nanoparticles are exposed to, the chemical composition of pore and groundwater acting as background solution or the type and quantity of soil organic matter present. One aspect that has received little attention so far is their transport behaviour in the presence of nutrients.

Here we study PVP-AgNP transport and retention in saturated columns containing silicate-dominated aquifer material that is also exposed to orthophosphate (NaH₂PO₄) or myo-inositol hexakisphosphate (IP6) via the background solution. In particular, we compare PVP-AgNP transport behaviour for different pH (6 and 4.5) in the background solution, for different mass concentrations of sediments <63 µm in the columns (0 and 2%) and in the presence/absence of soil organic matter (SOM). Experimental data were modelled using HYDRUS 1D.

Results of our experiments show that PVP-AgNP exhibit a higher mobility through the columns in the presence of phosphate as the latter can block attachment sites otherwise available to the nanoparticles. In the presence of SOM this mobility is even higher than in the absence of SOM as SOM and phosphate anions are both negatively charged and potentially bound to the same attachment sites. PVP-AgNP mobility also increased for both P-species when an increase in pH occurred but this increase was more pronounced in columns with orthophosphate. Results further show that PVP-AgNP are more mobile in columns with IP6 than orthophosphate in the absence of sediments <63 µm at pH 4.5. However, while for columns with material < 63 µm the overall AgNP mobility is decreased due to an overall increase in sediment surface area, AgNP are more mobile in the presence of orthophosphate as IP6 is more strongly bound to iron and aluminium oxides found in higher abundance in the fine sediments.   

How to cite: Adrian, Y., Schneidewind, U., Bradford, S., Simunek, J., Klumpp, E., and Azzam, R.: Transport and retention of engineered silver nanoparticles in the presence of phosphorus, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11094, https://doi.org/10.5194/egusphere-egu2020-11094, 2020.

Pathways for the physical disintegration of biochar (BC) and the release of water dispersible BC colloids (WDBC) have received much attention due to their unique impacts on carbon loss and contaminant. However, the current understanding of the mechanisms involved in WDBC formation and associated influencing factors is rather limited. This study systematically explored the formation and colloidal stability of WDBC in various solutions. Results showed that the WDBC yield decreased in the order BC400 (400℃)> BC700 (℃)> BC200(200℃) at a solution ionic strength (IS) ≤ 1 mM （NaCl）. With the exception of BC200, increasing IS (0.1–20 mM NaCl) and decreasing pH (3.0–10.0) significantly inhibited WDBC yield. Release and sedimentation dominated the WDBC formation processes with the former being more susceptible to solution chemistry. The test results of 22 soil solutions showed that the yields of WDBC from BC400 were considerable, while the yield of WDBC from BC700 could be neglected. Principal component analysis showed that the yield of WDBC in soil solutions was closely related to the contents of dissolved organic carbon, Fe and Al ions of soil solutions. WDBC had high colloidal stability and could stabilize well in natural surface waters and soil solutions. These findings represent new knowledge regarding the physical decomposition and the fate of BC in the environment.

How to cite: Fang, J.: Formation and stability of water dispersible biochar colloids in soil-water systems, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3197, https://doi.org/10.5194/egusphere-egu2020-3197, 2020.

Nano-scale volcanic ash particles (nanotephra) are produced during explosive volcanic eruptions. They can travel laterally above the tropopause for thousands of kilometers before returning to Earth’s surface. Within a short time, they will aggregate, settle, and end up in sedimentary sinks, such as lakes and oceans, and might be used as a tephrochronological age marker. These ultra-distal tephra deposits can be highly diluted by geogenic or biogenic background sedimentation. Consequently, the identification of nanotephra in these environmental archives poses an immense analytical challenge. A new generation of time-of-flight mass spectrometers (TOF-MS) can deliver particle specific multi-element information providing the analytical prerequisite to tease out a signal of trace amounts of nanotephra among a majority of background nanoparticles.

Here, we present the first single-particle geochemical data of Eyjafjallajökull nanotephra, Iceland. The sub-micron particles were separated from bulk reference ash collected close to the eruption site and measured in a single-particle inductively coupled plasma TOF-MS. We tested their identification based on trace element heterogeneities in a mixture of tephra and sediment from Millstätter Lake, Austria, serving as a model archive deposition. We are developing this method to identify the source eruption of nanotephra deposited in lake sediment and thereby allow for better dating of the corresponding layer.

How to cite: Schüürman, J., Tepe, N., Daxer, C., Huang, J.-J. S., Strasser, M., von der Kammer, F., and Hofmann, T.: Nanotephra in environmental archives – method development for single-particle multi-element fingerprinting in tephrochronology, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9062, https://doi.org/10.5194/egusphere-egu2020-9062, 2020.

Recently, global annual plastics production has reached a record of 359 million tonnes and in Europe nearly 62 million tonnes, with only a small portion (6-26%) being recycled. Plastic debris released into the environment are categorized, according to size, as macroplastics (> 5mm), microplastics (0.1μm - 5mm) and nanoplastics (< 0.1μm). Microplastics are now recognized as an emerging pollutant due to their abundance in natural environments, and because of growing concerns, the United Nations Environment Programme (UNEP) has included it in the list of top 10 environmental problems.

Additionally, microplastics have a tendency to act as a vector for other contaminants such as pathogens, organic pollutants and heavy metals due to strong dispersion and diffusion mechanisms. The majority of ongoing research on microplastics has primarily focussed on marine systems, but land surface contamination may also be important due to observed release rates that are approximately 20 times higher, in comparison to oceans. Nevertheless, only a few studies have addressed the presence of microplastics in soil and groundwater.

A research gap exists regarding the physical and chemical mechanisms that govern microplastic transport and retention in groundwater. Therefore, a study is being conducted to investigate the distribution, fate and transport of microplastics through groundwater. The overall aim is to improve the understanding of the transport mechanisms of these emerging pollutants and if they enhance the mobility of microbial communities. This research has two main objectives: firstly, to simulate the transport behaviour of various kinds of microplastics (different types, shapes, sizes, and surface morphology), secondly, to analyse the microplastics as potential vectors for microorganisms.

The key factors that are affecting the transport of different sized microplastics will be addressed. Additionally, the co-transport of microorganisms with microplastics during their movement within soil and groundwater will also be considered.

How to cite: Ameen, A., Stevenson, M., and Blaschke, A. P.: Microplastics: Are they really a threat to groundwater systems?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9069, https://doi.org/10.5194/egusphere-egu2020-9069, 2020.

As an environmentally friendly material, biochar has been widely used to remediate soil/water contaminants such as heavy metals and organic pollutants. The addition of biochar or modified biochar to porous media might affect the retention of plastic particles and thus influence their fate in natural environment. In this study, both biochar and magnetic biochar (Fe₃O₄-biochar) were synthesized via a facile precipitation method at room temperature. To determine the significance of biochar and Fe₃O₄-biochar amendment on the transport and deposition behaviors of plastic particles, the breakthrough curves and retained profiles of three different sized plastic particles (0.02 μm nano-plastic particles, and 0.2 μm and 2 μm micro-plastic particles) in quartz sand were compared with those obtained in quartz sand either with biochar or Fe₃O₄-biochar amendment in both 5 mM and 25 mM NaCl solutions. The results show that for all three different sized plastic particles under both examined solution conditions, the addition of biochar and Fe₃O₄-biochar in quartz sand decreases the transport and increases the retention of plastic particles in porous media. Fe₃O₄-biochar more effectively inhibits the transport of plastic particles than biochar. We found that the addition of biochar/Fe₃O₄-biochar could change the suspension property and increase the adsorption capacity of porous media (due to the increase of porous media surface roughness and negatively decrease the zeta potentials of porous media), contributing to the enhanced deposition of plastic particles. Moreover, we found that negligible amount of biochar and Fe₃O₄-biochar (<1%) were released from the columns following the plastic particle transport when the columns were eluted with very low ionic strength solution at high flow rate (to simulate a sudden rainstorm). Similarly, small amount of plastic particles were detached from the porous media under this extreme condition (16.5% for quartz sand, 14.6% for quartz sand with biochar amendment, and 7.5% for quartz sand with Fe₃O₄-biochar amendment). We found that over 74% of the Fe₃O₄-biochar can be recovered from the porous media after the retention of plastic particles by using a magnet and 87% plastic particles could be desorbed from Fe₃O₄-biochar by dispersing the Fe₃O₄-biochar into 10 mM NaOH solution. In addition, we found that the amendment of unsaturated porous media with biochar/Fe₃O₄-biochar also decreased the transport of plastic particles. When biochar/Fe₃O₄-biochar were added into porous media as one layer of permeable barrier near to column inlet, the decreased transport of plastic particles could be also obtained. The results of this study indicate that magnetic biochar can be potentially applied to immobilize plastic particles in terrestrial ecosystems such as in soil or groundwater.

How to cite: Tong, M., He, L., and Rong, H.: Transport Behaviors of Plastic Particles in Saturated Quartz Sand without and with Biochar/Fe3O4-Biochar Amendment , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21117, https://doi.org/10.5194/egusphere-egu2020-21117, 2020.

The occurrence of microplastics in the environment has become a major research interest in the last years. Aside from the marine environment, microplastic particles in various amounts, forms and compositions have now also been identified in freshwater bodies, groundwater, soils and interfaces connecting these compartments such as the hyporheic zone. Their transport and fate in these compartments has thus become the focus of recent field and laboratory studies.

Here we present first results from mesocosm studies performed at the Environmental Change Outdoor Laboratory (ECOLAB) facility of the University of Birmingham, UK. In a series of experiments conducted in recirculating flumes (12 setups in total, flume dimensions are 200 by 42 by 15 cm) we studied the behaviour of polyamide fragments and fibers in two different types of sediments and under different flow conditions. Polyamide fragments (diameter < 600 μm) were obtained from crushing larger pellets using a ball mill and liquid nitrogen while fibers (Flock Depot, Germany, fiber length of 500 μm, 1.7 dtex) were obtained commercially. Sand and gravel of known particle diameter ranges were used to represent natural sediments. Flow experiments were conducted over several days in duplicate by injecting a known concentration of microplastic particles into the flumes and taking samples (20 mL) at three flume locations at predefined intervals. Target particles were stained with Nile red before injection for better visibility and further analyzed using a stereomicroscope after filtering. First results show significant differences in fiber and fragment particle concentrations suspended in the water column/retained in the sediments as well as between different fragment sizes.

Further studies are planned as to the long-term behaviour of these microplastics in freshwater sediments experiencing biofilm growth as well as regarding possible chemical additives. The information generated with these flume experiments improves our understanding of microplastic distribution and immobilization at the sediment-water interface.

How to cite: Schneidewind, U., Nel, H., Kukkola, A., Sambrook Smith, G., Lynch, I., and Krause, S.: Transport of polyamide microplastics at the sediment-water interface – First results from mesocosm studies, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11514, https://doi.org/10.5194/egusphere-egu2020-11514, 2020.

Riverine colloids are important carriers of macronutrients, trace metals and pollutants into marine waters. These carriers span in size from molecules over colloidal, to particulate matter. Our current understanding of the different riverine carrier phases and how they respond to salinity relies on indirect assessments based on size separation. Thus a division between iron (Fe)-rich and organic carbon (OC)-rich colloids has been made, where the former are predominantly found in the larger size fractions and the latter in the smaller fractions. While these applications have significantly improved our knowledge of the physical partitioning of the two main fractions, those phases are likely to overlap in size. To gain a more comprehensive understanding of Fe and OC colloids in boreal rivers and their fate at higher salinities, X-ray absorbance spectroscopy (XAS) and dynamic light scattering (DLS) were used to explore both Fe speciation and colloidal characteristics such as size and surface charge. The presence of two Fe phases in the river waters - Fe-organic matter (OM) complexes and Fe(oxy)hydroxides - were confirmed by XAS. Further, the DLS measurements, combined with filtration, identified three different particle size distributions. Fe (oxy)hydroxides were observed both as nanoparticles (10-40 nm) with positive surface charge, and larger aggregates with OM interactions (300-900 nm). An intermediate (100-200 nm) and negatively charged distribution was inferred to contain Fe-OM complexes. After increasing salinity, the smallest Fe (oxy)hydroxide nanoparticles were no longer detected in suspension. Unexpectedly, both the intermediate and largest size distributions were still detected in suspension at high salinity. The collective results from XAS and DLS suggest that Fe (oxy)hydroxides and Fe-OM complexes are both found across the wide size range studied, and that colloidal size does not necessarily reflect neither Fe speciation nor stability towards salinity induced aggregation. From this it follows that the fate of riverine nutrients, trace elements and pollutants depend largely on the carrier phase to which they are associated and not solely on the size.

How to cite: Herzog, S. D., Gentile, L., Olsson, U., Persson, P., and Kritzberg, E.: Characterization of natural riverine colloids and their fate at increased salinity, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20034, https://doi.org/10.5194/egusphere-egu2020-20034, 2020.

An important fundamental block in the geochemical studies is the evaluation of the equilibrium distribution of metals in water and the influence of environmental conditions on the spetiation. It is important to understand the difference between the behavior of nanoparticles, dissolved particles, colloid particles, and suspended particles. The research deals with study and assess of geochemical processes of metal speciation in Arctic lake in the zone of metallurgical waste and other areas, where natural processes prevail. Consecutive and parallel membrane filtration methods were used to compare of the results of water analysis in the Imandra lake. The membrane pore sizes were: 8 µm, 1.2 µm, 0.45 µm, 0.2 µm. The following filterates characteristics were used: (microfiltration-based) mechanical suspension and oxidized contaminants (>8 μm, 1.2 μm, 0.45 μm, 0.2 μm, 0.1 μm); and (ultrafiltration-based) colloid, bacteria, viruses, etc (less than 0.1 μm).

Industrial effluents lead to the formation of higher concentrations of elements (Ni, Cu, Pb) in their labile forms as were found. In the wastewater-mixing zone, the concentrations of most elements are evenly distributed in depth. In areas that are more distant, there was a significant increase in the concentration of elements in the near-bottom horizon in comparison with the surface waters (Fe by more than 3 times). The obtained results showed that numerous elements had diverse distribution by speciation in the point located closer to the source of wastewaters. This indicates a significant influence of adsorption process on the system balance by such elements as Fe, Cu, and rare earth elements.

The impact of the regional geochemical and anthropogenic speciation and the possible influence of the climatic factor on the metals speciation were showed.   The authors did not have data on the metals speciation in the chosen points for the whole period of monitoring from 1980 until present. However, ElementPhasMigration (certificate 2017662509, Dinu M.I.) software was used to calculate the shares of labile and non-labile metal speciation during the years of the highest pollution (beginning of the 1990s) and during the current period of the ecosystem restoration.    

The software used mathematic modeling of chemical reactions happening in the natural waters and was based on the main laws of analytical and physical chemistry: material balance equation, equilibrium constant, equations of electrical neutrality, equations of proton balance, and competing reactions.

On the one hand, the initial data comprised a significant number of physicochemical parameters of the environment (more than 10 metal ions, рН, content of organic and non-organic anions, etc.). On the other hand, it included diverse mathematical tools for consecutive calculation of acidity constant of organic acids, conditional constants of complexes stability, the share of strong and weak acids in the system, etc. The software solved the tasks on the evaluation of the metal speciation depending on the physical and chemical parameters of the environment and provided the data on the balance speciation of a wide spectrum of elements in the system. The final stage of the calculations included the results verification with the field data.      Financing RFS 18-77-00018

How to cite: Dinu, M.: Metals speciation in Arctic lake under pollution impact (1980-2019): in-situ measurements, experimental estimates, model calculations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5905, https://doi.org/10.5194/egusphere-egu2020-5905, 2020.

A   novel   mathematical   model   was   developed   to   describe   the   transport   of nanoparticles in water saturated, homogeneous porous media with uniform flow. The model accounts for the simultaneous migration and aggregation of nanoparticles. The nanoparticles can  be found suspended  in the  aqueous phase  or attached  reversibly and/or   irreversibly   onto   the   solid   matrix.   The  Derjaguin-Landau-Verwey-Overbeek (DLVO)  theory   was   used   to   account   for   possible   repulsive   interactions   between aggregates allowing for both reaction-limited aggregation (RLA), and diffusion-limited aggregation (DLA) cases to be considered.   The governing coupled partial differential equations were solved initially by employing adaptive operator splitting methods, which decoupled   the   reactive   transport   and   aggregation   into   distinct   physical   processes. Subsequently, the resulting equations were treated individually with proper use of either a finite difference scheme or a specialized ordinary differential equations solver. The results from various model simulations showed that the transport of nanoparticles inporous media is substantially different than the transport of conventional biocolloids. In particular,   aggregation   was   shown   to   either   decrease   or   increase   nano particle attachment   onto   the   solid   matrix   and   to   yield  either  early   or  retarded  breakthrough. Finally,   useful   conclusions   were   drawn   regarding   the   particle   distribution   density   at various points in time and space.

How to cite: Katzourakis, V. and Chrysikopoulos, C.: Transport of aggregating nanoparticles in porous media, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1899, https://doi.org/10.5194/egusphere-egu2020-1899, 2020.

The potential of copper nanoparticles (Cu-NPs) alone or in combination with conventional fungicides against sensitive and resistant to fungicides Botrytis cinerea isolates was assessed in vitro and in vivo. DNA sequencing revealed the E198A resistance mutation in the β-tubulin gene in three B. cinerea isolates highly resistant to benzimidazoles (BEN-R), thiophanare methyl (TM), and the G143A mutation in the cytb gene in four isolates highly resistant to the QoI pyraclostrobin (PYR-R). Cu-NPs could effectively control sensitive and resistant isolates. A synergistic effect between Cu-NPs and TM both in vitro and in vivo was observed in the case of benzimidazole sensitive   isolates while an additive effect was observed in BEN-R isolates. The above observed synergistic action could be attributed to increased TM availability in the target site as indicated by the positive correlation observed between TM and TM+Cu-NPs treatments. A positive cross sensitivity and antagonistic action between Cu-NPs and NaCl suggested that copper ions contribute in the fungitoxic action of Cu-NPs, at least partly, since no correlation between Cu(OH)₂ and Cu-NPs sensitivity was found. The co-application of Cu-NPs with the oxidative phosphorylation inhibitor fluazinam (FM) resulted in a synergistic action  in all isolates regardless resistance phenotype, indicating a ATP-dependent mechanism of toxic action of Cu-NPs. Cu-NPs combined with conventional fungicides can aid in the design and implementation of eco friendly, sustainable management strategies by reducing fungicide use and combating resistance against B. cinerea.

How to cite: Malandrakis, A., Kavroulakis, N., and Chrysikopoulos, C.: Cu-NPs combating fungicide resistance: effectiveness and synergy against B. cinerea, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1929, https://doi.org/10.5194/egusphere-egu2020-1929, 2020.

Colloid-sized clay particles are in great abundance in the unsaturated or vadose zone and are capable of binding a variety of contaminants, which in turn either facilitate or hinder their migration in the subsurface. Also, FA has relatively strong affinity for kaolinite colloid particles (Fountouli et al., 2019). This study examines the effects of two representative colloid-sized clay particles (kaolinite, montmorillonite) on the transport of formaldehyde (FA) in unsaturated porous media. Transport experiments were performed in columns packed with quartz sand, under unsaturated conditions. The transport of FA was examined with and without the presence of suspended clay particles under various flow rates and various levels of saturation. DLVO interaction energies and the capillary potential energy associated with colloid retention at air-water and solid-water interfaces were calculated. The experimental results clearly suggested that the presence of suspended clay particles hindered the transport of FA in unsaturated packed columns. Moreover, as expected, it was shown that clay particle retention in the packed column increased with decreasing level of water saturation.

Reference

Fountouli, T.V., C.V. Chrysikopoulos, and I.K. Tsanis, Effect of salinity on formaldehyde interaction with quartz sand and kaolinite colloid particles: batch and column experiments. Environmental Earth Sciences 78, 152, 2019.

How to cite: Fountouli, T. V. and Chrysikopoulos, C. V.: Transport of formaldehyde in water unsaturated laboratory columns packed with quartz sand: Effect of colloid-sized clay particles., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7203, https://doi.org/10.5194/egusphere-egu2020-7203, 2020.

Titanium dioxide (TiO₂) is one of the most frequently employed nanoparticles (NPs) in consumer products. The rapid development of nanotechnology has led to the inevitable introduction of NPs in the natural environment, which subsequently may reach underground formations. Also, kaolinite is one of the most common minerals, which can be found in the subsurface. Numerous experimental and theoretical studies have shown that kaolinite clay particles can impact on the transport behavior of colloids, biocolloids (bacteria, viruses) and engineered nanoparticles. Therefore, the aim of this study is to examine the interaction of kaolinite (KGa-1b) particles with suspended TiO₂ NPs in the presence of quartz sand.Static and dynamic batch experiments were performed with three different TiO₂ concentrations (50, 100, 200 mg/L) and four different ionic strength values ​​(1, 25, 50, 100 mM). All of the experiments were conducted at room temperature (22 °C) and pH=7.The experimental results clearly suggested that TiO₂ attachment onto KGa-1b particles was slightly enhanced with increasing TiO₂ concentrations,but significantly increased with increasing ionic strength. Consequently, the presence of suspended KGa-1b particles can retard the TiO₂ transport in water saturated porous media.

How to cite: Chrysikopoulos, C. V. and Fasouletou, D.: Interaction of titanium dioxide nanoparticles with kaolinite clay particles in the presence of quartz sand, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20815, https://doi.org/10.5194/egusphere-egu2020-20815, 2020.