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Research Interests: Geology, Carbon Dioxide, Tectonics, Seismology, Radon monitoring studies for geological exploration, and 10 moreTransport Phenomena in Porous Media, Borehole Geophysics, Radon, Borehole, FRONTIERS, Porous Medium, Earthquake Precursors, Archaeology of Natural Places, dozen, and earthquakes precursors
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Summary The relationship between the density, temperature and viscosity of hypersaline solutions, both natural and synthetic, is explored. An empirical equation of the density–viscosity relationship as a function of temperature was... more
Summary The relationship between the density, temperature and viscosity of hypersaline solutions, both natural and synthetic, is explored. An empirical equation of the density–viscosity relationship as a function of temperature was developed for the Dead Sea brine and its dilutions. The viscosity levels of the Dead Sea brine (density of 1.24 ⋅ 10 3 kg/m 3 ; viscosity of 3.6 mPa s at 20 °C) and of the more extremely saline natural brine (density of 1.37 ⋅ 10 3 kg/m 3 ) were found to be ∼3 and ∼10 times greater than that of fresh water, respectively. The combined effect of the above changes in viscosity and density on the hydraulic conductivity is reduction by a factor of 3–7. The chemical composition significantly affects the viscosity of brines with similar densities, whereby solutions with a higher Mg/Na ratio have higher viscosity. This explains the extremely high viscosity of the Dead Sea and related Mg-rich brines in comparison with the much lower values of NaCl and KCl brines with similar density. Possible impacts of the results include reduced settling velocity of grains in hypersaline viscous brines and changing hydraulic dynamics at the freshwater–saltwater and the vicinity of sinkholes.
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We introduce a calibration procedure for a non‐penetrating TDR probe. The measured dielectric permittivity is a volume average of the soil and the measurement apparatus. We experimentally calibrated the TDR probe for various soils.
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Research Interests: Environmental Engineering, Civil Engineering, Environmental Science, Geology, Materials Science, and 15 moreHydrology, Water resources, Applied Economics, Keywords, Soil moisture, Porous Media, Porous media equation, Soil retention water, Surface Area, Porous Medium, Light Transmission, Physics based Modeling, Instruments and Techniques, Area Under the Curve, and Unsaturated Zone
Research Interests: Chemistry, Water, Environmental Monitoring, Medicine, Multidisciplinary, and 15 moreIsrael, Volatile Organic Compounds, Ground Water, Water Table, Aquifers, Interface, AQUIFER, Fresh water, Water Movements, Tetrachloroethylene, Geologic Sediments, Volatile organic compound, Volatilization, Chloroform, and Ethyl chloride
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Research Interests: Chemistry, Kinetics, Carbon, Groundwater, Environmental Chemistry, and 14 moreMedicine, Multidisciplinary, Environmental science and technology, Israel, Forensic Sciences, Computer Simulation, Carbon Isotopes, Motion, Chlorine, Trichloroethylene, Tetrachloroethylene, Silicon Dioxide, Environmental, and Isotope Labeling
Enzyme-substrate microbial water tests, originally developed for efficiency gains in laboratory settings, are potentially useful for on-site analysis in remote settings. This is especially relevant in developing countries where water... more
Enzyme-substrate microbial water tests, originally developed for efficiency gains in laboratory settings, are potentially useful for on-site analysis in remote settings. This is especially relevant in developing countries where water quality is a pressing concern and qualified laboratories are rare. We investigated one such method, Colisure, first for sensitivity to incubation temperatures in order to explore alternative incubation techniques appropriate for remote areas, and then in a remote community of Zambia for detection of total coliforms and Escherichia coli in drinking-water samples. We sampled and analyzed 352 water samples from source, transport containers and point-of-use from 164 random households. Both internal validity (96-100%) and laboratory trials (zero false negatives or positives at incubation between 30 and 40 °C) established reliability under field conditions. We therefore recommend the use of this and other enzyme-based methods for remote applications. We also found that most water samples from wells accessing groundwater were free of E. coli whereas most samples from surface sources were fecally contaminated. We further found very low awareness among the population of the high levels of recontamination in household storage containers, suggesting the need for monitoring and treatment beyond the water source itself.
Research Interests: Environmental Science, Inorganic Chemistry, Africa, Biotechnology, Developing Countries, and 15 moreEcology, Environmental Monitoring, Environmental science and technology, Diarrhea, Humans, Escherichia coli, Ground Water Analysis, Glucuronidase, Enterobacteriaceae, Hygiene, Cost Benefit Analysis, Incubation Temperatures, Field conditions, Efficiency gains, and Family Characteristics
Relations are presented that describe the behavior of water with high salt concentrations in variably saturated porous media for isothermal systems. Equations were derived using classic equilibrium thermodynamics of closed systems.... more
Relations are presented that describe the behavior of water with high salt concentrations in variably saturated porous media for isothermal systems. Equations were derived using classic equilibrium thermodynamics of closed systems. Resulting corrections for vapor pressure, liquid pressure, and Darcy coefficients are presented, and an extension of the relations to non-isothermal systems is proposed. Next, the governing equations obtained using
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Soil aquifer treatment (SAT) is an established and sustainable wastewater treatment approach for water reuse that has been gaining increased attention in various countries around the world. Increasing volumes of domestic wastewater and... more
Soil aquifer treatment (SAT) is an established and sustainable wastewater treatment approach for water reuse that has been gaining increased attention in various countries around the world. Increasing volumes of domestic wastewater and escalating real estate prices around urban areas emphasize the urgent need to maximize the treatment efficiency by revisiting the SAT setup. In this study, a novel approach was examined to increase biodegradation rates and improve the quality of SAT topsoil effluent. Experiments with midscale, custom-made columns were carried out with sand collected from an operational SAT and a highly permeable natural material with high internal porosity, tuff, which was maturated (i.e., buried in the SAT infiltration basin) for 3 months. The filtration efficiency, biodegradation rates of organic material, microbial diversity, and outflow quality were compared between the operational SAT sand and the tuff using state-of-the-art approaches. The results of this study ...
. Soil aquifer treatment (SAT) is a tertiary process for wastewater treatment where the wastewater infiltrates through a thick vadose zone for purification and storage in the underneath aquifer. SAT infiltration basins are typically... more
. Soil aquifer treatment (SAT) is a tertiary process for wastewater treatment where the wastewater infiltrates through a thick vadose zone for purification and storage in the underneath aquifer. SAT infiltration basins are typically flooded intermittently, while maintaining a fixed ratio between the wetting and the drying stages. However, infiltration basins exhibit different physical and chemical properties, limiting the generalization of SAT operation to attain optimal efficiency. Since frequent sampling of the soil pore water to verify the SAT’s biodegradation efficiency can be arduous, continuous monitoring of the SAT vadose zone’s physico-chemical conditions is required. In this study, redox potential (Eh) was continuously monitored, together with other variables such as water content (θ), soil temperature, and gaseous oxygen (O2), at multiple depths of a SAT vadose zone throughout the year and while the system was constrained to different operational modes. Hydrological models were calibrated and validated to water content observations, and they illustrated the seasonal changes in water infiltration. Furthermore, it was shown that under long wetting stages during winter, there was a reduction in the SAT’s drainage capabilities. The Eh observations, under long wetting stages, demonstrated larger variability and very negative values as ambient temperature increased. Assembling the daily Eh observations illustrated that a wetting stage should cease after about 30 hours, once suboxic conditions are established. A drying stage’s optimal duration should be 36 hours, according to the Eh and O2 observations during summer and winter. Ultimately, the study shows that the length of wetting and drying stages should be defined separately, rather than by adhering to the wetting/drying ratio.
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The reuse of greywater and other wastewaters are important considerations for effectivewater management strategies. It is also imperative that the potential for detrimentalenvironmental effects be investigated. As part of ongoing research... more
The reuse of greywater and other wastewaters are important considerations for effectivewater management strategies. It is also imperative that the potential for detrimentalenvironmental effects be investigated. As part of ongoing research into the reuse ofgreywater and oil-rich agro-wastewaters, the potential impact of oil and grease (O&G)to soils irrigated with greywater (GW) was studied. Greywater streams were sampledand analyzed for O&G content. Along with the greywater, soil profile samples werecollected from garden soils irrigated with these waters. The goal was to determine theO&G content of these GW streams, verify ifeO&G was accumulating in the soil profiles,and investigate the effect O&G can have on water movement through O&Gcontaminated soils.Untreated kitchen GW averaged 200 mg/L O&G, over an order of magnitude more thanother GW streams. GW-irrigated soils showed O&G accumulation of up to 200 mg/kgwithin the first 20-cm of depth. GW with low O&G concentration (
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Gas diffusion is a fundamental transport process in porous media. However, to date, there is no method for experimentally estimating the gas diffusion coefficient of coarse porous media. A modified method is proposed here and was... more
Gas diffusion is a fundamental transport process in porous media. However, to date, there is no method for experimentally estimating the gas diffusion coefficient of coarse porous media. A modified method is proposed here and was validated against sand media. The method was tested using particle sizes ranging between 1 and 4 cm: ?10−3 cm2 < intrinsic permeability < ?10−2 cm2. Laboratory experiments were conducted in large horizontal columns filled with different homogeneous spherical particles inside a climate-controlled laboratory under isothermal (± <0.2°C) and windless conditions. Diffusion coefficients were similar for particles sizes of 1 and 2 cm, which indicates that pure diffusion governs gas transport. Above 2 cm, diffusion coefficients were higher, suggesting an enhanced gas transport, most likely initiated by small, local advective components. Because the enhanced transport can be modeled by the diffusion equation using a larger diffusion coefficient, it is associated with the enhanced diffusion concept.
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The dependency of radon emanation on soil texture was investigated using the closed chamber method. Ground phosphate rock with a large specific surface area was analyzed, and the presence of inner pores, as well as a high degree of... more
The dependency of radon emanation on soil texture was investigated using the closed chamber method. Ground phosphate rock with a large specific surface area was analyzed, and the presence of inner pores, as well as a high degree of roughness and heterogeneity in the phosphate particles, was found. The average radon emanation of the dry phosphate was 0.145 ± 0.016. The emanation coefficient was highest (0.169 ± 0.019) for the smallest particles (<25 μm), decreasing to a constant value (0.091 ± 0.014) for the larger particles (>210 μm). The reduction rate followed an inverse power law. As expected, a linear dependence between the emanation coefficient and the specific surface area was found, being lower than predicted for the large specific surface area. This was most likely due to an increase in the embedding effect of radon atoms in adjacent grains separated by micropores. Results indicate that knowledge of grain radium distribution is crucial to making accurate emanation pred...
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In field applications, mostly in porous media, transport of stabilized nano zerovalent iron particles (nZVI) has never exceeded a few meters in range. In the present study, the transport of Carbo-Iron Colloids (CIC), a composite material... more
In field applications, mostly in porous media, transport of stabilized nano zerovalent iron particles (nZVI) has never exceeded a few meters in range. In the present study, the transport of Carbo-Iron Colloids (CIC), a composite material of activated carbon as a carrier for nZVI stabilized by carboxymethyl cellulose (CMC), was tested under field conditions. The field site lies within a fractured chalk aquitard characterized by moderately saline (∼13 mS) groundwater. A forced gradient tracer test was conducted where one borehole was pumped at a rate of 8 L/min and CMC-stabilized CIC was introduced at an injection borehole 47 m up-gradient. Two CIC-CMC field applications were conducted: one used high 100% wt CMC (40 g/L) and a second used lower 9% wt loading (∼2.7 g/L). Iodide was injected as a conservative tracer with the CIC-CMC in both cases. The ratio between the CIC-CMC and iodide recovery was 76% and 45% in the high and low CMC loading experiments, respectively. During the low C...
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In the context of geological disposal of radioactive waste, one of the controlling mechanisms for radionuclide migration through subsurface strata is sorption to mobile colloidal bentonite particles. Such particles may erode from the... more
In the context of geological disposal of radioactive waste, one of the controlling mechanisms for radionuclide migration through subsurface strata is sorption to mobile colloidal bentonite particles. Such particles may erode from the repository backfill or bentonite buffer and yield measurable (0.01-0.1 g/L) concentrations in natural groundwater. The extent of sorption is influenced by colloid concentration, ionic strength, radionuclide concentration, and the presence of competing metals. Uranium (VI) and cesium sorption to bentonite colloids was investigated both separately and together in low ionic strength (2.20 mM) artificial rainwater (ARW) and high ionic strength (169 mM) artificial groundwater (AGW; representative of a fractured carbonate rock aquitard). Sorption experiments were conducted as a factor of colloid concentration, initial metal concentration and opposing metal presence. It was shown that both U(VI) and Cs sorption were significantly reduced in AGW in comparison t...
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ABSTRACT The identification of perchlorate on Mars by the Phoenix mission (Hecht et al. 2009 Science vol 325, 64) encouraged those who favored the Atacama Desert as an analog. However, in the Atacama, nitrate predominates wherever... more
ABSTRACT The identification of perchlorate on Mars by the Phoenix mission (Hecht et al. 2009 Science vol 325, 64) encouraged those who favored the Atacama Desert as an analog. However, in the Atacama, nitrate predominates wherever perchlorate is found and the extreme aridity is unlike the Phoenix landing site, where there is ice. In Israel, the site of a former ammonium perchlorate factory was investigated because of environmental concerns about perchlorate in both groundwater and the unsaturated zone but it is also a valuable Mars analog. The unsaturated zone comprises 40 m of sands with sandy clay and clay-rich layers in which bacteria with perchlorate reducing capability had been detected. Microbial perchlorate reduction occurs under anaerobic conditions, not those expected in the unsaturated zone, and the process needs water and an electron donor (e.g. trace organic matter). Chlorine stable isotope analyses quantitatively characterize both partially reduced perchlorate and the resultant chloride product. Our analyses show varying extents of perchlorate reduction in the unsaturated zone, up to 10%, but not correlated with depth, clay content, or water content. We assume that the reduction is occurring in microenvironments in a generally aerobic system but the precise source of the electron donor is still enigmatic; organic coatings on clays would be one possibility. This site, despite having been modified by human activity, is a valuable analog for possible microbial processes on Mars. The microbial activity has given another example of the persistence of life in an extreme environment where nutrients are extremely limited. Although not analogous in terms of Mars temperatures, this site offers the potential for new understanding of life processes (and new challenges for Mars exploration).
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ABSTRACT Widespread perchlorate contamination was found in the vadose zone near a plant that manufactures ammonium perchlorate above the coastal aquifer of Israel in Ramat Hasharon. As part of the plant&#39;s operations, untreated... more
ABSTRACT Widespread perchlorate contamination was found in the vadose zone near a plant that manufactures ammonium perchlorate above the coastal aquifer of Israel in Ramat Hasharon. As part of the plant&#39;s operations, untreated industrial wastewater was disposed of for over 30 years in unlined wastewater ponds and nearby washes, causing contamination of the unsaturated zone (up to 2200 mg kg-1 sediment at a depth of 20 m) and the groundwater below it (up to 300 mg L-1). In this study, we examined the potential for microbial metabolism of perchlorate reduction in the contaminated deep vadose zone profile by native microbial communities. Microbial reduction of perchlorate was found in three of the four sediment samples taken from different depths. The sediments taken from 1 m (shallowest) and 35 m (deepest- close to the water table) showed the fastest degradation rates, while the sediment taken from 15 m showed the slowest rate. No perchlorate reduction was observed in the sediment taken from 20 m, where perchlorate concentrations were highest. These results were correlated to the viable microorganism counts in the profile. In experiments in which the effect of nitrate was examined, the lag time for perchlorate degradation was found to be inversely correlated to the initial nitrate concentration, while the perchlorate-reduction rates were faster in treatments with higher initial nitrate concentrations. We found no perchlorate degradation as long as nitrate was present in the system: perchlorate reduction was initiated only after all of the nitrate had been reduced. Nitrate-reduction rates were correlated to the initial nitrate concentrations and no lag period was observed. Nitrite was temporarily accumulated during nitrate reduction and was totally reduced, like nitrate, after 4 days. Count of viable microbial communities as well as PCR analysis of the chlorite dismutase gene in the native microbial population exposed to high concentrations of perchlorate (10,000-20,000 mg L-1) showed no toxicity effect on the microorganisms, and even promotion of the perchlorate-reducing bacteria. Natural organic matter (NOM) in sediments taken from ground surface could be used as carbon and energy sources for perchlorate-reducing bacteria. The average perchlorate-reduction rate using NOM as the carbon source was 0.45 mg day-1, whereas when acetate was used as the carbon source, it was 7.2 mg day-1.
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ABSTRACT Evaporation from surface-exposed fractures (ESEF) was investigated experimentally. Surface-exposed fractures can act as major conduits of flow from land surface to underlying aquifers. This role is intensified for low-... more
ABSTRACT Evaporation from surface-exposed fractures (ESEF) was investigated experimentally. Surface-exposed fractures can act as major conduits of flow from land surface to underlying aquifers. This role is intensified for low- permeability matrix and deep vadose zone. ESEF can cause salt accumulation (SA) at and near the fracture surface and within the fracture aperture, drawing solution from the vadose zone towards the fracture walls. Surface waters which penetrate and flow through these fractures during flood or intensive rain events can dissolve the accumulated salt and carry it downwards towards underlying groundwater. In this laboratory study, artificial fractures were formed by placing two rock blocks, 50x50x20 cm, with 1 cm between them, mimicking a large-aperture fracture. Pore solution in the rocks was held under low tension, and flux was continuously monitored. The system was constructed in a way that loss of pore solution could occur only via evaporation from the two fracture surfaces. All measurements were taken under controlled ambient temperatures ranging between 9 and 25°C. It was found that decreasing the ambient atmospheric temperature, while the bottom of the rock blocks were kept at constant temperature of 23°C, increases the evaporation from the fracture surfaces by up to three folds. It is concluded that moist air convection is the controlling mechanism for ESEF rates. Long-term effects of SA on EFEF rates were also studied, where evaporation rates began decreasing after approximately 100 gram of salt per square meter of fracture surface had accumulated. Furthermore, ESEF decreased by ~50% compared to its initial value after approximately 160 gram per square meter had accumulated.
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Migration of colloids may facilitate the transport of radionuclides leaked from near surface waste sites and geological repositories. Intrinsic colloids are favorably formed by precipitation with carbonates in bicarbonate-rich... more
Migration of colloids may facilitate the transport of radionuclides leaked from near surface waste sites and geological repositories. Intrinsic colloids are favorably formed by precipitation with carbonates in bicarbonate-rich environments, and their migration may be enhanced through fractured bedrock. The mobility of Ce(III) as an intrinsic colloid was studied in an artificial rainwater solution through a natural discrete chalk fracture. The results indicate that at variable injection concentrations (between 1 and 30 mg/L), nearly all of the recovered Ce takes the form of an intrinsic colloid of &amp;amp;amp;amp;amp;amp;amp;amp;gt;0.45 μm diameter, including in those experiments in which the inlet solution was first filtered via 0.45 μm. In all experiments, these intrinsic colloids reached their maximum relative concentrations prior to that of the Br conservative tracer. Total Ce recovery from experiments using 0.45 μm filtered inlet solutions was only about 0.1%, and colloids of &amp;amp;amp;amp;amp;amp;amp;amp;gt;0.45 μm constituted the majority of recovered Ce. About 1% of Ce was recovered when colloids of &amp;amp;amp;amp;amp;amp;amp;amp;gt;0.45 μm were injected, indicating the enhanced mobility and recovery of Ce in the presence of bicarbonate.
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