Ciliates are abundant unicellular organisms capable of resisting high concentrations of metal ions in the environment caused by various anthropogenic activities. Understanding the cellular pathways ...involved in resistance to and detoxification of elements is required to predict the impact of ciliates on environmental element cycles. Here, we investigated the so far unknown process of tolerance, cellular uptake and bioaccumulation of the emerging rare earth element gadolinium (Gd) in the common ciliate Tetrahymena pyriformis. Gd treatment results in the intracellular formation and excretion of biogenic Gd-containing particles. This cellular process effectively removes dissolved Gd from the organic growth medium by 53.37% within 72 h. Based on light and electron microscopic observations, we postulate a detoxification pathway: Cells take up toxic Gd
ions from the medium by endocytosis, process them into stable Gd-containing particles within food vacuoles, and exocytose them. Stable biogenic particles can be isolated, which are relatively homogeneous and have a diameter of about 3 µm. They consist of the elements Gd, C, O, P, Na, Mg, K, and Ca. These findings broaden the view of metal ion accumulation by protists and are of relevance to understand environmental elemental cycles and may inspire approaches for metal recovery or bioremediation.
A pilot injection test with guar gum stabilized microscale zerovalent iron (mZVI) particles was performed at test site V (Belgium) where different chlorinated aliphatic hydrocarbons (CAHs) were ...present as pollutants in the subsurface. One hundred kilograms of 56μm-diameter mZVI (~70gL−1) was suspended in 1.5m3 of guar gum (~7gL−1) solution and injected into the test area. In order to deliver the guar gum stabilized mZVI slurry, one direct push bottom-up injection (Geoprobe) was performed with injections at 5 depths between 10.5 and 8.5m bgs. The direct push technique was preferred above others (e.g. injection at low flow rate via screened wells) because of the limited hydraulic conductivity of the aquifer, and to the large size of the mZVI particles. A final heterogeneous distribution of the mZVI in the porous medium was observed explicable by preferential flow paths created during the high pressure injection. The maximum observed delivery distance was 2.5m. A significant decrease in 1,1,1-TCA concentrations was observed in close vicinity of spots where the highest concentration of mZVI was observed. Carbon stable isotope analysis (CSIA) yielded information on the success of the abiotic degradation of 1,1,1-TCA and indicated a heterogeneous spatio-temporal pattern of degradation. Finally, the obtained results show that mZVI slurries stabilized by guar gum can be prepared at pilot scale and directly injected into low permeable aquifers, indicating a significant removal of 1,1,1-TCA.
•mZVI slurries stabilized with guar gum (GG) can be prepared at pilot scale.•Highly concentrated GG-mZVI slurries can be injected via direct push technique.•A heterogeneous distribution of the GG stabilized mZVI was observed.•Abiotic degradation of 1,1,1-TCA was proven 1m from injection at 4.5m bgs.
Humic acid-coated goethite nanoparticles (HA-GoeNPs) have been recently proposed as an effective reagent for the in situ nanoremediation of contaminated aquifers. However, the effective dosage of ...these particles has been studied only at laboratory scale to date. This study investigates the possibility of using HA-GoeNPs in remediation of real field sites by mimicking the injection and transport of HA-GoeNPs under realistic conditions. To this purpose, a three-dimensional (3D) transport experiment was conducted in a large-scale container representing a heterogeneous unconfined aquifer. Monitoring data, including particle size distribution, total iron (Fetot) content and turbidity measurements, revealed a good subsurface mobility of the HA-GoeNP suspension, especially within the higher permeability zones. A radius of influence of 2 m was achieved, proving that HA-GoeNPs delivery is feasible for aquifer restoration. A flow and transport model of the container was built using the numerical code Micro and Nanoparticle transport Model in 3D geometries (MNM3D) to predict the particle behavior during the experiment. The agreement between modeling and experimental results validated the capability of the model to reproduce the HA-GoeNP transport in a 3D heterogeneous aquifer. Such result confirms MNM3D as a valuable tool to support the design of field-scale applications of goethite-based nanoremediation.
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•Development of innovative, rapid, non-destructive measurement system for nZVI particles in sand-packed columns.•In-depth explanation of measurement system characteristics including ...the data manipulation.•Method validation according to several guidelines in disciplinary areas.•Evaluation of linearity, sensitivity, and precision as well as reliability and long-term stability of measurement system.•Study of system influence by dispersants and chemical solutes often used to formulate nZVI injection solutions.•Relevance of system for advancing groundwater-remediation experimental research on nZVI transport and reactivity.
The purpose of this work was to develop and validate a rapid, non-destructive, real-time measurement system for nanoscale zero-valent iron (nZVI) particles determination in sand-packed columns. This aims to provide an approach to analyse for nZVI particle transport and nZVI induced contaminant degradation reactions in 1-dimensional aquifer experiments. The inductive measurement system (IMS) was developed and tested by measuring columns filled with varying portions of nZVI and sandy aquifer material. Method validation was conducted for this innovative approach in accordance with several guidelines in disciplinary areas. The linearity of ZVI concentration and measurement signal was confirmed. Calibration curves were determined to be linear over the range of 0.11–53.50 g/L for nZVI NANOFER STAR, 0.10–81.67 g/L for nZVI BASF 1, 0.12–58.26 g/L for nZVI Carbo-Iron, 0.12–69.70 g/L for nZVI NANOFER 25DS ORM, 0.12–50.69 g/L for nZVI NANOFER 25DS, and 0.21–1613.39 g/L for nZVI Höganäs 1* (dry). This method was determined to be sensitive in nZVI, accurate (101.63 % within-run recovery, 101.85 % between-run recovery covering 76 days), and precise (0.46 % repeatability RSD, 0.85 % intermediate precision RSD covering 76 days). LOQ was determined ranging from 0.10 to 0.21 g/L for nZVI used in experiments and regression through origins was selected as the calibration model. Quality control processes were performed to assure the reliability of the results and the long-term stability. Additional data processing steps allowed to compensate for measurement deviations resulting from different liquid phase compositions, e.g. dispersants used for nZVI suspensions. This method is now successfully validated in single-laboratory conditions.
The evaluation of PFAS immobilization performance in laboratory experiments, especially the long-term stability, is a challenge. To contribute to the development of adequate experimental procedures, ...the impact of experimental conditions on the leaching behavior was studied. Three experiments on different scales were compared: batch, saturated column, and variably saturated laboratory lysimeter experiments. The Infinite Sink (IS) test – a batch test with repeated sampling – was applied for PFAS for the first time. Soil from an agricultural field amended with paper-fiber biosolids polluted with various perfluoroalkyl acids (PFAAs; 655 μg/kg ∑18PFAAs) and polyfluorinated precursors (1.4 mg/kg ∑18precursors) was used as the primary material (N-1). Two types of PFAS immobilization agents were tested: treatment with activated carbon-based additives (soil mixtures: R-1 and R-2), and solidification with cement and bentonite (R-3). In all experiments, a chain-length dependent immobilization efficacy is observed. In R-3, the leaching of short-chain PFAAs was enhanced relative to N-1. In column and lysimeter experiments with R-1 and R-2, delayed breakthrough of short-chain PFAAs (C4) occurred (> 90 days; in column experiments at liquid-to-solid ratio (LS) > 30 L/kg) with similar temporal leaching rates suggesting that leaching in these cases was a kinetically controlled process. Observed differences between column and lysimeter experiments may be attributed to varying saturation conditions. In IS experiments, PFAS desorption from N-1, R-1, and R-2 is higher than in the column experiments (N-1: +44 %; R-1: +280 %; R-2: +162 %), desorption of short-chain PFAS occurred predominantly in the initial phase (< 14 days). Our findings demonstrate that sufficient operating times are essential in percolation experiments, e.g., in column experiments >100 days and LS > 30 L/kg. IS experiments may provide a faster estimate for nonpermanent immobilization. The comparison of experimental data from various experiments is beneficial to evaluate PFAS immobilization and to interpret leaching characteristics.
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•Chain-length dependent immobilization efficacy observed in all experiments•Long-term percolation experiments show delayed breakthrough of short-chain PFAS.•Kinetic processes affect immobilization efficacy in percolation experiments.•Long experiments with various conditions are essential to evaluate immobilization.•IS (batch) tests may provide a quick estimate for nonpermanent immobilization.
Surfactant-enhanced in-situ chemical oxidation (S-ISCO) is an emerging innovative remediation technology for the treatment of dense non-aqueous phase liquids (DNAPLs). S-ISCO combines the ...solubilization of contaminants by means of surfactants with the chemical oxidation by an oxidizing agent, thus, potentially increasing the efficiency of the state-of-the-art ISCO technique. Scientific investigations are needed to enable the technology transfer for potential field applications based on the development of a remediation design under well-defined boundary conditions.
For this purpose, experimental upscaling analyses were performed using the special infrastructure of the research facility for subsurface remediation (VEGAS). Batch tests showed that oxidation of the selected surfactant E-Mulse 3® (EM3) by activated persulfate (Na-PS) reduced the solubilization of the model contaminants 1,4-DCB, naphthalene, and PCE. As a consequence, the processes of contaminant solubilization and degradation were temporally and spatially separated in the developed remediation design.
A proof of concept was provided by performing an S-ISCO medium-scale experiment (100 cm length, 70 cm height, 12.5 cm width), with 1,2-DCB as model DNAPL contaminant to be treated. A groundwater circulation well (GCW) was used to inject a 60 g/L Na-PS solution and to effectively mix the reagents. Sampling of the experiment's outflow and the soil material after treatment showed that neither rebound effects nor residual mass loadings on the soil material could be detected after termination of the S-ISCO treatment.
To further evaluate the S-ISCO remediation design under field-like conditions, a large-scale S-ISCO experiment was conducted (6 m length, 3 m height, 1 m width), allowing for an extensive sampling campaign to monitor relevant processes. An efficient contaminant removal from the former source zone could be reached by surfactant solubilization, decreasing contaminant levels from initially over 2000 mg/L 1,2-DCB to final concentrations below 5 mg/L 1,2-DCB. The heterogeneously distributed contaminant degradation, implemented by a three-filter GCW, was attributed to density-induced migration processes that impeded an optimal reaction zone. A density-dependent numerical transport could qualitatively match the observations. By comparing different simulation scenarios, an adapted operation of the GCW was established that provides for a more efficient distribution of the density-influenced oxidant injection.
•The contaminant solubilization potential of the studied surfactant is affected by sodium persulfate oxidation.•Separating the processes of contaminant solubilization and degradation contributes to the S-ISCO remediation efficacy.•Effective mixing of solubilized contaminant and oxidizing agent by using a groundwater circulation well.•Experimental upscaling to field-like conditions showed that density effects influence the distribution of S-ISCO reagents.•Numerical simulation scenarios propose an optimized S-ISCO process design that considers these density effects.
Site characterisation can be conducted more effectively and flexibly using field screening tools. The availability of the measured data in the field allows a dynamic adaptation of the measuring grid ...to the results. Compared to the conventional procedure, this approach is not only time- and cost-saving, but also leads to a better identification of the quantity and the heterogeneous distribution of the contaminants in the subsurface. To allow such a procedure, sensor-based field screening tools have been developed at VEGAS. These measurement systems are suitable for in situ and on-site measurement of organic contaminants such as mineral oil, organic solvents and PAH. The devices are capable of measuring VOC in soil gas in the unsaturated zone, dissolved organic contaminants in groundwater and NAPL in the saturated and unsaturated zones. Sensors are suitable for most of these purposes because of their fast response, which is necessary for on-line monitoring. Different sensor principles are taken into consideration for the detection of different contaminants that are typically found at brownfield sites. The sensor systems are integrated into conventional drilling tools to enable a flexible site exploration without groundwater wells. Various field applications show that the tools are robust, easy to apply and allow cost-effective measurements.
The injection of colloidal nano sized zero valent iron (nZVI) into a contaminated aquifer is a promising new in-situ groundwater remediation technique. An inductive sensor is presented to directly ...detect and measure the concentration of nZVI in the subsurface. The method is based on the inductive measurement of magnetic material properties of nZVI within an alternating magnetic field. The change of magnetic flux density generated by one coil is determined by measuring an induced voltage in a second coil. Numerical simulations with the finite element software COMSOL Multiphysics were performed to optimize the sensor design. Furthermore, these components were used to analyze the possible measuring range, taking into account the accuracy of the measuring device to be used. Since the susceptibility of nZVI in the aquifer is very small, it is necessary to use a background measurement to improve the sensitivity of the measurement system. Finally, the measuring concept was experimentally verified.
Consumer cameras, particularly onboard smartphones and UAVs, are now commonly used as scientific instruments. However, their data processing pipelines are not optimized for quantitative radiometry ...and their calibration is more complex than that of scientific cameras. The lack of a standardized calibration methodology limits the interoperability between devices and, in the ever-changing market, ultimately the lifespan of projects using them. We present a standardized methodology and database (SPECTACLE) for spectral and radiometric calibrations of consumer cameras, including linearity, bias variations, read-out noise, dark current, ISO speed and gain, flat-field, and RGB spectral response. This includes golden standard ground-truth methods and do-it-yourself methods suitable for non-experts. Applying this methodology to seven popular cameras, we found high linearity in RAW but not JPEG data, inter-pixel gain variations >400% correlated with large-scale bias and read-out noise patterns, non-trivial ISO speed normalization functions, flat-field correction factors varying by up to 2.79 over the field of view, and both similarities and differences in spectral response. Moreover, these results differed wildly between camera models, highlighting the importance of standardization and a centralized database.
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