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ABSTRACT The removal of heavy metal ions from wastewater often necessitates the use of ion exchange resins. Current methods for assessing ion exchange efficiency are indirect and destructive. Some heavy metal ions, such as Cu2+ and Ni2+, are paramagnetic and influence the NMR relaxation times of water protons. NMR relaxometry can therefore be utilized to track the removal of these ions by ion exchange resins. In this study, we use relaxometry to monitor in situ the loading with Ni2+ and Cu2+ of Amberlite IR120 and Dowex Marathon MSC resins, with the resin column inserted into a low‐field NMR device. The multiexponential transverse relaxation curves were fitted using a biexponential model. Before and during the loading of the resin, the water with the slowest relaxation corresponds to treated water (free of Ni2+ or Cu2+) flowing between the resin beads. After saturation, the slowest fraction corresponds to the untreated solution (containing Ni2+ or Cu2+) flowing between the resin beads saturated with paramagnetic ions. The evolution with time of the transverse relaxation rate and the amplitude of the slowly relaxing water fraction shows a clear transition, occurring later at the bottom of the resin bed compared with the middle and top. This is interpreted as an indication of the saturation of the studied zone with paramagnetic ions, confirmed by the quantification of Ni2+ or Cu2+ in the effluent using AES spectroscopy. This proof‐of‐concept study demonstrates that NMR relaxometry can be used in situ to monitor the loading of a resin bed with paramagnetic ions. [ABSTRACT FROM AUTHOR]

This study investigated the efficacy of biochar as a soil amendment for enhancing soil physicochemical properties and solute transport dynamics, with implications for agricultural sustainability and environmental stewardship. Batch laboratory experiments and column studies were conducted to assess the effects of biochar application on soil parameters and solute transport under saturated conditions. The saturation soil extraction approach was employed in batch leaching tests, while column experiments replicated subsurface conditions. Transport modeling using CXTFIT 2.1 elucidated solute dispersion dynamics in biochar-amended soils. Batch experiments revealed significant alterations in soil pH, electrical conductivity, and nutrient release following biochar addition. Biochar exhibited adsorption capacity for fluoride ions and released dissolved organic carbon, highlighting its potential for soil carbon sequestration and microbial activity. Column studies demonstrated enhanced solute dispersion and increased microbial activity in biochar-amended soils, as evidenced by changes in breakthrough curves and degradation rates of nitrate. Indeed, nitrate first-order degradation coefficients were 9.08E-06 for the column with only sandy soil, 3.09E-05 and 1.47E-04 for the columns with minimum and maximum doses of biochar respectively. Biochar application significantly influenced soil physicochemical properties and solute transport dynamics, with potential implications for nutrient management and contaminant attenuation in agricultural systems. Despite limitations in laboratory-scale experiments, this research provides valuable insights into biochar-soil interactions. It underscores the need for further investigation under field conditions to validate findings and optimize biochar management practices for sustainable soil and environmental management. Highlights: The release of solutes following biochar application highlights the complex chemical biochar-soil interactions. Biochar application increased nitrate degradation coefficient in both minimum and maximum treatment. Biochar alters soil pore structure, leading to more extensive solute spreading. [ABSTRACT FROM AUTHOR]

Salinization of reservoir will affect domestic water, agricultural irrigation and sustainable utilization of water. Previous research focused on the salt release of sediment. There are few researches on the influence of groundwater on salinization of reservoir. This study took Beidagang Reservoir in Tianjin as the research area and conducted the indoor column experiment using reservoir water at different sampling points. This study analyzed the vertical dynamic change law of TDS, Cl- and hydrogeochemical changes to reveal the mechanism of salinization of reservoir. The results show that TDS and Cl- went through three periods: the resting periods, the rising periods and the dynamic equilibrium periods. In the first week after the injection of groundwater, there are no significant changes in TDS and Cl- concentration. After one week, it went through the rapid rising period about 30 days and reached the dynamic equilibrium period at a later stage. There was a concentration gradient in the vertical direction with the highest concentration of TDS and Cl- in the bottom layer. There was a diffusion boundary layer and the concentration in the boundary layer changes more than that outside the boundary layer. The TDS concentrations at 10cm depth are 13.59 ρ0 and 4.52 ρ0, and those at 30cm depth are 6.82 ρ0 and 1.97 ρ0. The release fluxes of TDS and Cl- went through three stages: fluctuation stage(1~14 d), rising stage (15~44 d) and descent stage(45~106 d). The ions ratio indicated that hydrochemical component derived from evaporite, carbonate rock and sulfate minerals. [ABSTRACT FROM AUTHOR]

The distribution coefficient (Kd) of radionuclides is a crucial parameter in assessing the safety of high-level radioactive waste (HLW) geological repository. It is determined in the laboratory through batch and column experiments. However, differences in obtained Kd values from distinct experiments have not been thoroughly assessed and compared. This study evaluated strontium (Sr) sorption on different granite materials using static batch and dynamic experiments (column and core-flooding experiments). The results from batch sorption experiments showed higher Sr sorption on granite under acidic and strongly alkaline conditions, low solid–liquid ratios, and low ionic strength. In column experiments, a two-site sorption model was used to simulate Sr transport in crushed granite and mixed pure minerals. The sorption of Sr on crushed granite exhibited a higher affinity than that of mixed pure minerals. The dual-porosity transport model was employed to investigate Sr transport behavior in fractured granite in the core-flooding experiment. Kd obtained from batch sorption experiments are four to twenty times higher than those from column experiments, and two to three orders of magnitude higher than that from a core-flooding experiment. The results of this study provide valuable insights into safety assessment for the HLW geological repository. [ABSTRACT FROM AUTHOR]

Linear alkylbenzene sulfonate (LAS), a widely used anionic surfactant, is present in wastewater and can be discharged, causing environmental damage. When biodegradation is negligible, adsorption and desorption reactions play an important role, depending on the media characteristics (organic matter and clays) and hydrodynamic parameters. Previously published laboratory column data are modelled with PHREEQC (version 2.18) in three scenarios of LAS input: spill (LAS pulse), continuous discharge (LAS adsorption step) and remediation (LAS desorption step). The distribution coefficients (0.1–4.9 × 10−3 L/g) in the sand columns are lower than those determined in this paper from batch tests and in columns of 25% and 50% agricultural soil mixtures (1–70 × 10−3 L/g). Considering the Freundlich constant parameters from the modelling, the results are similar to the distribution coefficients, but the linear isotherms are more consistent throughout. The mass transfer coefficient from the sand columns is lower than the agricultural soil columns (20–40 h−1), indicating longer elution times for the heavier homologues and a higher percentage of agricultural soil. For lighter homologues, fast migration could cause contamination of aquifers. The great persistence of LAS in the environment necessitates the development of mitigation strategies using reactive transport models, which predict longer times for the remediation of LAS homologues. [ABSTRACT FROM AUTHOR]

A pumice–maghemite (P-maghemite) composite was developed using the chemical coprecipitation method with a 20% iron loading ratio by weight. The characterization of the composite using SEM and XRD indicated the effective loading and dispersion of nanoparticles on the surface of the developed base materials. Thereafter, in situ sequestration experiments were conducted in the laboratory for an arsenic-polluted aquifer system using two well-integrated permeable reactive barrier (PRB) modules filled with the developed composite. A vertical fixed-bed column setup was used for the columnar PRB, whereas a sand tank experimental setup was employed for the well-screen-integrated PRB; both PRB systems were fed by a synthetic solution representing the arsenic-contaminated groundwater. More than 99% arsenic removal was observed in the columnar PRB, with an average effluent concentration of 4 μg/L at the end of the experiment, which is well below the acceptable limit of drinking water for arsenic (<10 μg/L). Removal of arsenic by the 4-cm-wide well-screen-integrated PRB from 652 μg/L to less than 20 μg/L shows a great potential of the developed composite for arsenic remediation at slower groundwater flow rates. A maximum arsenic removal of 99% was attained at the start of the experiment, which decreased to 97% after 1 month of PRB operation. The effluent concentration of all other major ions also was reduced considerably in the PRB modules. The hydraulic conductivity of the developed media was reduced by 35% in the columnar PRB and by approximately 20% in the well-screen-integrated PRB. The high arsenic removal efficiency in continuous flow-through remediation systems indicates the applicability of the developed PRB system in in situ remediation of arsenic-contaminated groundwater. [ABSTRACT FROM AUTHOR]

Soil salinisation is a pervasive form of land degradation posing a significant threat to the global environment. Saline soil, covering roughly 10% of the total land area, represents a crucial reserve of land resources. The use of super absorbent polymer (SAP) impacts capillary water movement through the soil because of its exceptional water absorption and retention capabilities. SAP is expected to influence the intricate water‐salt migration processes and their redistribution within soil. This study employed soil column experiments to investigate the impacts of varying SAP dosages (A), heights (B) and thicknesses (C) on soil water and salt transport in the Tianjin Binhai New Area, China. The main findings showed that: (1) average capillary water rise rate decreased with SAP dosage increase. The groundwater recharge trend in time was like that of capillary water rise height; (2) SAP usage increased water and salt content on the application layer and reduced surface soil salt accumulation; (3) the best SAP combination for application was 1.1% SAP at 17–18 cm from the groundwater level. This study provides basic effective SAP application strategies for preventing soil salinisation. [ABSTRACT FROM AUTHOR]

In small populations and scattered communities, wastewater treatment through vegetation filters (VFs), a nature-based solution, has proved to be feasible, especially for nutrient and organic matter removal. However, the presence of pharmaceuticals in wastewater and their potential to infiltrate through the vadose zone and reach groundwater is a drawback in the evaluation of VF performances. Soil amended with readily labile carbon sources, such as woodchips, enhances microbial activity and sorption processes, which could improve pharmaceutical attenuation in VFs. The present study aims to assess if woodchip amendments to a VF's soil are able to abate concentrations of selected pharmaceuticals in the infiltrating water by quantitatively describing the occurring processes through reactive transport modelling. Thus, a column experiment using soil collected from an operating VF and poplar woodchips was conducted, alongside a column containing only soil used as reference. The pharmaceuticals acetaminophen, naproxen, atenolol, caffeine, carbamazepine, ketoprofen and sulfamethoxazole were applied daily to the column inlet, mimicking a real irrigation pattern and periodically measured in the effluent. Ketoprofen was the only injected pharmaceutical that reached the column outlet of both systems within the experimental timeframe. The absence of acetaminophen, atenolol, caffeine, carbamazepine, naproxen and sulfamethoxazole in both column outlets indicates that they were attenuated even without woodchips. However, the presence of 10,11-epoxy carbamazepine and atenolol acid as transformation products (TPs) suggests that incomplete degradation also occurs and that the effect of the amendment on the infiltration of TPs is compound-specific. Modelling allowed us to generate breakthrough curves of ketoprofen in both columns and to obtain transport parameters during infiltration. Woodchip-amended columns exhibited Kd and μw values from one to two orders of magnitude higher compared to soil column. This augmentation of sorption and biodegradation processes significantly enhanced the removal of ketoprofen to over 96%. [ABSTRACT FROM AUTHOR]

Abstract Riverbed sediments have recently been found to be an important reservoir for microplastics. But the hydrogeological factors that control the abundance of microplastics are complex and conceptual frameworks priorising the parameters affecting their transport and retention during deep riverbed filtration are still missing. In this study a series of saturated column experiments was conducted to investigate the vertical distribution patterns of secondary polystyrene fragments (100–2000 μm) in dependence on their particle size, grain size of the sediment, seepage velocity and duration of infiltration flow. The columns with a length of 50 cm were operated with flow velocities between 1.8 m d−1 and 27 m d−1. Invasive samples obtained after the experiments were density separated and then depth profiles of microplastic concentrations were retrieved using fluorescence imaging analysis. Most polystyrene particles were retained in the upper 20 cm and 15 cm of the medium gravel and coarse sand sediments, respectively. Through the high particle retention riverbed sediments can act as a temporary sink or long term retention site for the transport of microplastic particles (MPPs) from streams to oceans. A small fraction of particles ranging from 100 to 500 μm in size was observed down to infiltration depths of 50 cm suggesting that MPPs at the pore scale have the potential to be advectively transferred via hyporheic exchange or induced bank filtration into coarse riverbed sediments and alluvial aquifers. MPP abundance over column depth follows an exponential relationship with a filter coefficient that was found to depend significantly on the flow rate, MPP and sediment grain size, as indicated by multiple linear regression (R2 = 0.92). The experimentally derived empirical relation allows to estimate particle abundances of initially negatively buoyant MPP in riverbed sediments by surface water infiltration.

Riverbed sediments have recently been found to be an important reservoir for microplastics. But the hydrogeological factors that control the abundance of microplastics are complex and conceptual frameworks priorising the parameters affecting their transport and retention during deep riverbed filtration are still missing. In this study a series of saturated column experiments was conducted to investigate the vertical distribution patterns of secondary polystyrene fragments (100–2000 μm) in dependence on their particle size, grain size of the sediment, seepage velocity and duration of infiltration flow. The columns with a length of 50 cm were operated with flow velocities between 1.8 m d−1 and 27 m d−1. Invasive samples obtained after the experiments were density separated and then depth profiles of microplastic concentrations were retrieved using fluorescence imaging analysis. Most polystyrene particles were retained in the upper 20 cm and 15 cm of the medium gravel and coarse sand sediments, respectively. Through the high particle retention riverbed sediments can act as a temporary sink or long term retention site for the transport of microplastic particles (MPPs) from streams to oceans. A small fraction of particles ranging from 100 to 500 μm in size was observed down to infiltration depths of 50 cm suggesting that MPPs at the pore scale have the potential to be advectively transferred via hyporheic exchange or induced bank filtration into coarse riverbed sediments and alluvial aquifers. MPP abundance over column depth follows an exponential relationship with a filter coefficient that was found to depend significantly on the flow rate, MPP and sediment grain size, as indicated by multiple linear regression (R2 = 0.92). The experimentally derived empirical relation allows to estimate particle abundances of initially negatively buoyant MPP in riverbed sediments by surface water infiltration. [ABSTRACT FROM AUTHOR]

In this study, the characteristics and transport of oxygen-doped graphitic carbon nitride (OgCN) were investigated in comparison with multi-walled carbon nanotube (MWCNT), and the transport of OgCN was evaluated under various conditions. OgCN was superior to MWCNT in transport within a quartz sand layer with less attachment and more detachment than MWCNT, which is attributable to more diverse and abundant functional groups, charges, defects, and amorphous graphitic structures. OgCN transport was well described by a one-dimensional advection–dispersion–retention model. The coefficients of retention (Smax), attachment (ka), and detachment (kd) calculated by the model were not always well-correlated with OgCN concentration and the grain size of the medium, suggesting that the OgCN transport was affected by various factors such as attachment, detachment, and pore size. However, it was clearly and significantly inhibited by ionic strength, via improved aggregation of OgCN. It is believed that the results of this study contribute to establish proper sub-surface injection strategies of carbonaceous materials for in situ chemical oxidation. [ABSTRACT FROM AUTHOR]

In the present study, biochar prepared from green wastes was investigated about the effects of pyrolysis environment on its characteristics and purposively employed to remove As(III) in column-based treatments. Characterization analyses were performed to investigate the insightful of the biochar prepared from corncob and sugarcane biomasses under comparatively lower temperatures (350, and 450 °C), and retention times (1 h) in locally made furnace and named CCB@350, CCB@450, and SCB@350 and SCB@450, respectively. In addition, a conventional method (CM) was used for biochar preparation from the same feedstocks and named CMCCB and CMSCB, respectively. The idea was to adopt resource efficient pyrolysis methods to synthesize biochar for multiple applications. Biochar characterizations demonstrated that lower temperature was found sufficient to prepare biochar from the green wastes and met all the characteristics including clear pore size and structure (i.e., 2.301 µm pore size in CCB@350), elemental compositions (> 76 At% of carbon), presence of large number of functional groups and thermally super stable (> 20% residual mass). Column-based experiments found variations in the adsorption capacity for As(III) in different samples. However, biochar prepared from sugarcane biomass possessed good As(III) adsorption capacity (> 92%) for lower arsenic concentration. Thus, it was concluded that biochar synthesized at low pyrolysis temperatures was found appealing with good mineralogical, morphological, elemental, and thermal characteristics and possessed acceptable adsorption capacity for low arsenic contaminated water and the pyrolysis method can be optimized as a resource efficient technology. [ABSTRACT FROM AUTHOR]

Linear alkylbenzene sulfonate (LAS), a widely used anionic surfactant, is present in wastewater and can be discharged, causing environmental damage. When biodegradation is negligible, adsorption and desorption reactions play an important role, depending on the media characteristics (organic matter and clays) and hydrodynamic parameters. Previously published laboratory column data are modelled with PHREEQC (version 2.18) in three scenarios of LAS input: spill (LAS pulse), continuous discharge (LAS adsorption step) and remediation (LAS desorption step). The distribution coefficients (0.1–4.9 × 10−3 L/g) in the sand columns are lower than those determined in this paper from batch tests and in columns of 25% and 50% agricultural soil mixtures (1–70 × 10−3 L/g). Considering the Freundlich constant parameters from the modelling, the results are similar to the distribution coefficients, but the linear isotherms are more consistent throughout. The mass transfer coefficient from the sand columns is lower than the agricultural soil columns (20–40 h−1), indicating longer elution times for the heavier homologues and a higher percentage of agricultural soil. For lighter homologues, fast migration could cause contamination of aquifers. The great persistence of LAS in the environment necessitates the development of mitigation strategies using reactive transport models, which predict longer times for the remediation of LAS homologues.

Riparian zones are one of the most complex redox‐dynamic systems, where sequential redox zones of dissolved oxygen, nitrate, manganese dioxide, ferric hydroxide and sulfate reduction commonly form. River stage dynamics and microbes are two key controls on nutrient transformation in the riparian zone. Microbial growth, on one hand, increases the biogeochemical reaction rate by altering the microbial population. On the other hand, decreases the permeability of the media due to clogging effects, thereby increasing the residence time of solutes. However, previous studies have often concentrated on steady‐state flow systems and overlooked the impacts of river stage fluctuations and dynamic microbial growth on redox zonation. In this study, we investigated the interactions among river fluctuations, nutrient supplies, microbial metabolisms, and sediment physical properties in a dynamic riparian system. A column experiment was conducted, and a one‐dimensional modeling framework that coupled flow, reactive solute transport, dynamic microbial growth and bioclogging processes was developed to study the spatiotemporal evolution of redox zonation in response to river stage fluctuations and microbial growth. Our results showed that two redox zonation patterns, including a typical sequence and an interlaced sequence, could form in the dynamic riparian zone. Increasing exogenous dissolved organic carbon concentration facilitates the occurrence of anomalous sequence redox zonation. Modeling results also indicated that ignoring microbial growth leads to a significant difference in the spatiotemporal characterization of the redox zonation, especially for a more permeable sediment. Our results implicate the occurrence of more complicated redox zonation in a dynamic riparian system than previously reported. Key Points: Two redox zonation patterns including a normal sequence and an anomalous sequence can form in a dynamic riparian zoneVariations in exogenous dissolved organic carbon (DOC) concentration and distributions of solid‐phase terminal electron acceptors jointly control the anomalous sequence redox zonationRedox zonation in high‐permeable media is more sensitive to external DOC than that in low‐permeable media [ABSTRACT FROM AUTHOR]

Many people in rural areas use freshwater, including irrigation water for domestic purposes. The pervious mortar filter (PMF) is a modification of mortar and pervious concrete, designed as an alternative water filter to improve the natural water quality for domestic use. According to its physical characteristics (pore structure and geometry), pervious mortar can be a filter to reduce several types of pollutants in the water. On the other hand, based on its chemical characteristics, pervious mortar can be dissolved if passed by certain types of water for an extended period, called leaching. This study aims to determine the leachability of pervious mortar filters by identifying the influent and effluent concentration of calcium ion (Ca2+), hardness, pH, and total dissolved solids (TDS) in two types of water sources, i.e., pure water and irrigation water. This study analyzes the leachability of the filter by the filter column experiment method. The leaching is analyzed by the water's pH, TDS, calcium ion (Ca2+), and hardness concentration before and after the water is filtered by PMF. The filtered water for each specimen was 50 liters (L). 50 L of pure water showed increased pH, TDS values, Ca2+ concentration, and hardness in the effluent. The increase in pH, TDS, Ca2+, and hardness concentration in the effluent with irrigation water was less than the increase of the same parameter in PMF through pure water. [ABSTRACT FROM AUTHOR]

In small populations and scattered communities, wastewater treatment through vegetation filters (VFs), a nature-based solution, has proved to be feasible, especially for nutrient and organic matter removal. However, the presence of pharmaceuticals in wastewater and their potential to infiltrate through the vadose zone and reach groundwater is a drawback in the evaluation of VF performances. Soil amended with readily labile carbon sources, such as woodchips, enhances microbial activity and sorption processes, which could improve pharmaceutical attenuation in VFs. The present study aims to assess if woodchip amendments to a VF’s soil are able to abate concentrations of selected pharmaceuticals in the infiltrating water by quantitatively describing the occurring processes through reactive transport modelling. Thus, a column experiment using soil collected from an operating VF and poplar woodchips was conducted, alongside a column containing only soil used as reference. The pharmaceuticals acetaminophen, naproxen, atenolol, caffeine, carbamazepine, ketoprofen and sulfamethoxazole were applied daily to the column inlet, mimicking a real irrigation pattern and periodically measured in the effluent. Ketoprofen was the only injected pharmaceutical that reached the column outlet of both systems within the experimental timeframe. The absence of acetaminophen, atenolol, caffeine, carbamazepine, naproxen and sulfamethoxazole in both column outlets indicates that they were attenuated even without woodchips. However, the presence of 10,11-epoxy carbamazepine and atenolol acid as transformation products (TPs) suggests that incomplete degradation also occurs and that the effect of the amendment on the infiltration of TPs is compound-specific. Modelling allowed us to generate breakthrough curves of ketoprofen in both columns and to obtain transport parameters during infiltration. Woodchip-amended columns exhibited Kd and μw values from one to two orders of magnitude higher compared to soil column. This augmentation of sorption and biodegradation processes significantly enhanced the removal of ketoprofen to over 96%.

The understanding of the mechanical properties of sensitive marine clay subgrade stabilized with cement is vital for the safe, economical, and durable design of road structures. As the curing temperature affects the cement hydration progress, it is necessary to investigate the influence of the temperature on the evolution of the mechanical properties of cement-reinforced marine clay in road construction. A column testing and relevant monitoring program were performed to study the effect of various curing temperatures (2 °C, 22 °C, and 40 °C) on the mechanical properties' development of cement-reinforced clay within 28 days. After these cement clay samples were cured for a specific time (1, 3, 7, and 28 days), they were subjected to two mechanical tests (i.e., California Bearing Ratio (CBR) test and uniaxial compressive strength (UCS) test). The findings reveal that a higher curing temperature accelerates cement hydration and self-desiccation. Consequently, the UCS and CBR values increase with curing temperature and the strength might vary by more times, especially for early age (≤7 days) samples. The results of this study contribute to a deeper understanding of the influence of temperature on the mechanical properties of the cement-reinforced clay and thus provide practical guidance with regards to road construction in the field. [ABSTRACT FROM AUTHOR]

Soil column experiments in both saturated and unsaturated conditions are widely used for practical and theoretical research in a variety of domains, including the assessment of transport models, the fate and transport of pesticides, explosives, microorganisms, heavy metals, and non-aqueous phase liquids. And the application of models associated with experiments has grown in popularity, owing mostly to their predictive capacity. This paper discusses the complex interactions between saturated/unsaturated porous media and the mechanisms of contaminant migration in column experiments, with an emphasis on the relevant environmental factors affecting the migration of various types of contaminants in column experiments and an analytical summary of the mechanisms affecting contaminant migration factors. The modeling of contaminant transport in unsaturated and saturated groundwater zones is integrated and presented, and research on the coupling of related models with other modeling algorithms is presented. The assessment of regional-scale pollutant transport models is integrated with other assessment models and algorithms to arrive at the appropriate groundwater management options. • Environmental factors and mechanisms in column experiments are summarized. • Effects of saturated/unsaturated media and colloids are summarized. • Presence of colloidal and air-water interfaces plays an important role. • Source and sink transport mechanisms of pollution are given and summarized. [ABSTRACT FROM AUTHOR]

In this study, the characteristics and transport of oxygen-doped graphitic carbon nitride (OgCN) were investigated in comparison with multi-walled carbon nanotube (MWCNT), and the transport of OgCN was evaluated under various conditions. OgCN was superior to MWCNT in transport within a quartz sand layer with less attachment and more detachment than MWCNT, which is attributable to more diverse and abundant functional groups, charges, defects, and amorphous graphitic structures. OgCN transport was well described by a one-dimensional advection–dispersion–retention model. The coefficients of retention (Smax), attachment (ka), and detachment (kd) calculated by the model were not always well-correlated with OgCN concentration and the grain size of the medium, suggesting that the OgCN transport was affected by various factors such as attachment, detachment, and pore size. However, it was clearly and significantly inhibited by ionic strength, via improved aggregation of OgCN. It is believed that the results of this study contribute to establish proper sub-surface injection strategies of carbonaceous materials for in situ chemical oxidation.

The effects of stormwater discharges on receiving aquatic environments and the need for their purification were highlighted by an EU court in May 2020. The ruling stated the need for removal of dissolved pollutants, which justifies field studies for development of far-reaching methods for runoff treatment. In this study, a standard sand was used as medium for road runoff filtration and removal of dissolved and particle-bound (

Engineering soil substrate using a porous composite constructed by a block-structured design (BSD), offers an innovative water-saving approach for high-cash crops in arid regions. We report modeling and experimental studies of the effects of two geometries: a single block (1L) and two stacked blocks (2L) BSD designs on evaporative losses and water distributions in laboratory column experiments involving wetting and evaporation cycles. A reasonable agreement between water content measurements and numerical simulations (HYDRUS 2D/3D code) is demonstrated (7.2E-2

Sand filtration is a low-cost and easy solution for household wastewater treatment in areas lacking a centralized sewage system. However, there are only a few studies about the treatment efficiencies of nutrients and enteric microorganisms and their removal or filter mass reuse potential. Sand columns with different phosphorus adsorbents, gypsum, biotite, and peat were tested in laboratory-scale filters at 4 °C to assess their performance in variable conditions and their possibility to increase the efficiency of sand filters. The columns were fed with real municipal wastewater with variable wastewater flow and phosphate load at different stages of the experiments. Phosphate and total nitrogen concentrations were low in the effluent of all columns, and they were mostly rather similar. Waste gypsum was found to greatly increase the conductivity of the effluent. The numbers of enteric microorganisms in the effluents were low, and the used filter masses achieved good hygienic quality after the tests. Phosphate, ammonium, and nitrate concentrations were low in the used masses, evidently since the columns had operated only for 21–30 weeks. Sand filtration proved to be an effective method for wastewater treatment, but changing conditions should be considered when designing these filters. The masses have reuse potential as soil improvement. [ABSTRACT FROM AUTHOR]

Riverbank filtration (RBF) is an important part of the surface water–groundwater cycle, and it intercepts and retains many pollutants in rivers. However, RBF affects the biogeochemical process which enables aquifer sediments to release iron (Fe) and manganese (Mn). In this study, column experiments were performed to investigate the effects of ammonium ions and organic matter on Fe and Mn release from anaerobic RBF sediments. In addition, high-throughput sequencing technology was used to characterize the microbial community. The results showed that the ammonium ions (NH4+) and organic matter (COD) in groundwater promote the release of Fe and Mn from aquifer sediments. The trends of Fe and Mn release were similar during the leaching process. The maximum concentrations of Fe and Mn were 0.32 and 40 μg/L, respectively. The structural diversity and abundance of the microbial communities in the groundwater were closely related to the Fe/Mn content. Actinobacteriota, Proteobacteria, Acidobacteriota, Bacteroidota, and Chloroflexi were the dominant phyla, while Rhodococcus, Ochrobactrum, and Pseudarthrobacter were the dominant genera. These functional microbes are actively involved in the biogeochemical cycling of Fe, Mn, and N. In summary, contaminants and the microbial-community structure have dual effects on the release of Fe and Mn from RBF aquifers. [ABSTRACT FROM AUTHOR]

The direct deposition of polyethyleneimine (PEI), a weak polycation with a large content of amino groups, onto sand fractions with different sizes (F70, F100, F200, and F355), resulted in versatile core-shell sorbents for water cleaning. Herein, PEI and the weak polyanion poly(acrylic acid) (PAA) were directly precipitated as an nonstoichiometric polyelectrolyte complex ([PEI]:[PAA] = 2:1) onto a sand surface followed by cross-linking with glutaraldehyde (GA) at three molar ratios ([CHO]:[amine] = 1:10; 1:5; 1:1 = r). Non-crosslinked polyelectrolyte chains were washed out in strongly basic (pH 14) and acidic (pH 0) media. The sand/PEI-GA composites were evaluated to determine the organic shell stability using swelling experiments and X-ray photoelectron spectroscopy. The sorbed/desorbed amount of two model pollutants (copper ions and bromocresol green) in column experiments depended on the sand fraction size and cross-linking degree of the PEI shell. The maximum recorded values, after five loading/release cycles of pollutant species onto F70/PEI-GAr, F100/PEI-GAr, F200/PEI-GAr, and F355/PEI-GAr, were situated between the 0.7–5.5 mg Cu2+/mL column and 3.7–15 mg BCG/mL column. Sand/PEI-GAr composites could act as promising sorbents, low-cost and eco-friendly, which could be applied for water purification procedures. [ABSTRACT FROM AUTHOR]

The riparian zone is a typical groundwater-surface water interaction zone, and there are few research reports on the behavior of arsenic in this interaction zone under different hydrodynamic conditions. In this study, the river sand samples from the riparian zone are collected to carry out indoor column experiments, the influence of different hydrodynamic factors (including flow velocity and particle size) on the migration of arsenic in the river sand are analyzed, and related models are established. The results show that (1) at a flow rate of 0.5 mL/min, the adsorption rate of the river sand on As(V) and the time required to reach an equilibrium state are both faster than those on As(III), and the smaller the particle size, the more obvious the phenomenon; at a flow rate of 1.0 mL/min, the adsorption rate of the river sand with different particle sizes on As(V) increases with the increasinng particle size, but there is no significant difference in the adsorption of As(III). (2) In a packed column filled with sand of the same particle size, the adsorption capacity of the river sand for As(III) and As(V) decreases with the increasing flow velocity. (3) Under the conditions of different flow rates and particle sizes, the migration processes of As(III) and As(V) in the sand column are more in line with the Thomas model, and the fitting R2 are higher than those of the Yoon-Nelson and Adams-Bohart models under the same conditions. Among them, at low flow rates, the Thomas model fitting R2 (≥0.94) to the migration processes of As(III) and As(V) in the particle size of 0.15−0.25 mm are significantly better than that of the larger particle size of 1.00−2.00 mm. At high flow rates, the model has little difference in fitting R2 to the migration process of arsenic in different particle sizes.

Temperature is an important factor affecting the leaching of contaminants from waste deposits, especially in the Nordic region where temperature change is more drastic than other areas. In this study, the impact of temperature variation in the leaching of sulphate, Co, Fe, Mn, Ni and Zn from the Ballangen tailings deposit, northern Norway, was investigated using a column leaching experiment. Unoxidized tailings were fed into four columns, which were subsequently put into four wine fridges set at 5, 10, 14 and 18 °C, respectively. The columns were filled with 600 mL of deionized water from the top every second week. Leachate was collected at the bottom and tested for pH, conductivity and concentrations of , Co, Fe, Mn, Ni and Zn. The saturation index for ferrihydrite and the activity of Fe2+ in the leachate were calculated with PHREEQC. The results showed that the conductivity and leachate concentrations of , Co, Fe, Mn and Ni were highest at 14 and 18 °C, and lowest at 5 °C, which showed high tailings oxidation and subsequent leaching of contaminants at higher temperatures. X-ray photoelectron spectroscopic (XPS) analysis of the residual material confirmed the oxidation of sulphides and leaching of many elements. Ferrihydrite was supersaturated in the leachate from the 14 and 18 °C columns, which showed the oxidation of pyrrhotite and olivine and the precipitation of ferrihydrite. The cumulative mass of Zn leached out was highest at 10 °C, which might be the threshold temperature for the leaching of Zn. HIGHLIGHTS Temperature is an important factor in the leaching of contaminants from the tailings deposit.; High oxidation and leaching of contaminants from tailings were observed at a higher temperature.; 10 °C is suggested to be the threshold temperature for the leaching of Zn.;

This study investigated heavy metal(HM) soil pollution and evaluated the risk and sources at a legacy tailings pond's area in Meizhou, China. Result shows that HM accumulation in soil, particularly Cd, Pb, and Zn, were serious. Zn and Cd in tailing soil and all studied elements in field soil had a significant release potential. Four HM sources were identified by positive matrix factorization (PMF) model: cinder and vehicle emissions (11.3%), natural sources (16.3%), tailings pond and human activities (32.8%), tailings pond (39.7%). The soil was severely polluted with Cd, Pb, and Zn, which posed a high potential environmental risk near surrounding area. Column leaching tests showed that large quantities of HMs were released from the tailings soil during simulated rainfall with different pH. This study indicates that the study area has been severely polluted and continues to have a great risk of HM pollution under natural conditions. [ABSTRACT FROM AUTHOR]

Although riverbank filtration (RBF) has been widely applied in China, the managers do not pay enough attention to the inevitable clogging issues during continuous RBF operation. The RBF site, which is located near the Lalin River, northeastern China, was selected as the study area, and the laboratory column experiments were used to simulate the RBF process and further investigate the physical and chemical clogging. The removal of turbidity (59.4–95.1%), COD (21.9–71.7%), NH4+ (10.9–39.4%), Fe (18.5–64.8%), and Mn (19.8–71.7%) demonstrated the water quality improvement by RBF. Whereas, the significant decrease in permeability (39.6–88.2%) also indicated that the clogging issues could not be ignored during RBF. Among them, the physical clogging-dominated area, chemical clogging-dominated area, and the transition zone were located at 0–12.5%, 37.5–100%, and 12.5–37.5% of the infiltration pathway, respectively. Moreover, the concentration of suspended particle materials, mean size of riverbed sediments, and aquifer media are the major impact factors for physical clogging; the precipitation of soluble constituents and redox reaction and other hydrochemical processes were the major impact factors for chemical clogging. The conclusion of this study can contribute to managers alleviating the clogging issues and improving the effectiveness of the sustainable operation in the local RBF system. [ABSTRACT FROM AUTHOR]

Low mobility and solubility reduce the availability of traditional phosphorus (P) fertilizer in red acidic soil. Hydroxyapatite (HAP), especially nano-hydroxyapatite (n-HAP), may be more efficient than P fertilizer because of its nanoparticle characteristics. Camellia oleifera (C. oleifera) is an edible oil tree whose productivity is greatly affected by P fertilizer. During this study, we investigated the migration of different particle sizes of HAP (20 nm, 200 nm, and 80 μm) and their effects on the seedling growth of C. oleifera cultivar Huashuo (HS) cuttings. A column experiment showed that the efflux ratio was negatively correlated with particle size in red acidic soil. The leaching results revealed that the contents of total P and available P in the 20-nm treatment were significantly higher than those in the 200-nm and 80-μm treatments in the deep soil (10–15 cm or 15–20 cm), whereas the application of 20-nm n-HAP caused 13.43% wastage of available P. During the container experiments, 200-nm and 20-nm HAP significantly promoted the growth of the seedlings in terms of seedling height, stem diameter, and biomass. The available P contents in the rhizosphere and nonrhizosphere soils were negatively correlated with the HAP particle sizes. In conclusion, the migration of HAP is inversely correlated with particle size, and HAP improves the P bioavailability in red acidic soil. In summary, 200-nm HAP was the best P fertilizer for the seedlings of HS among the three particle sizes. This study offers preliminary results indicating that 200-nm HAP might be a better P fertilizer compared with other two HAP particle sizes for use in future C. oleifera orchards.

【Background】 Heavy saline coastal soil is a valuable land resource but its high salt content and sticky texture, along with its high sodium adsorption ratio and shallow groundwater table, makes it difficult to remediate. Previous studies had shown that the pH of coastal saline soil increased during its remediation, which could alter physical, chemical and microbiological properties of the soil for crops to grow. Common methods to alleviate these side effects include application of organic fertilizers, desulfurized gypsum, biochar and other additives. But they are expensive and not applicable to large-scale soil remediation. As such, more efficient methods are needed. 【Objective】 The aim of this paper is to present a simple and low-cost, yet green and efficient method to control soil pH in remediating heavy saline coastal soils by acidifying the drip irrigation water. 【Method】 The experiment was conducted in laboratory columns. It consisted of five treatments with the irrigation water pH controlled at 6 (S1), 6.5(S2), 7(S3), 7.5(S4) respectively. Without acidification (pH 8.2~8.5) was taken as the control (CK). In each treatment, we measured spatiotemporal variation in electrical conductivity of the saturated soil paste (EC), and its associated pH after the soil was leached by 60 mm, 120 mm, 180 mm and 240 mm of water respectively. 【Result】 Desalination occurred in the soil below the emitter first and it then expanded gradually; soil salinity decreased logarithmically with the amount of irrigation water. In all treatments, the temporal changes in salt leaching pattern and leaching rate were similar, while the change in soil pH differed. After 240 mm of water was applied, the average soil pH in 0~55 cm of soil under S1—S5 treatment was 7.73, 7.78, 7.86, 7.92, 7.92, respectively. Soil pH in the non-saline area (

The application of rock powder on agricultural land to ameliorate soils and remove carbon dioxide (CO2) from the air by chemical weathering is still subject to many uncertainties. To elucidate the effects of grain size distribution and soil partial pressure of carbon dioxide (pCO2) levels on CO2 uptake rates, two simple column experiments were designed and filled nearly daily with an amount of water that simulates humid tropical conditions, which prevail in areas known for being hotspots of weathering. Multiple materials (dunite, basanite, agricultural oxisol, a combination of the latter two, and loess) were compared under ambient and 100% CO2 atmosphere. In a second series, single material columns (dunite) were filled with three different grain size distributions. Total alkalinity, pH, major ions, and dissolved silica were determined in the outflow water of the columns for about 300 days. Under ambient atmospheric conditions, the CO2 consumption was the lowest in the oxisol column, with 100 t CO2 km−2 year−1, while dunite and basanite showed similar consumption rates (around 220 t CO2 km−2 year−1). The values are comparable to high literature values for ultramafic lithologies. Interestingly, the mixture of basanite and oxisol has a much higher consumption rate (around 430 t CO2 km−2 year−1) than the basanite alone. The weathering fluxes under saturated CO2 conditions are about four times higher in all columns, except the dunite column, where fluxes are increased by a factor of more than eleven. Grain size distribution differences also play a role, with the highest grain surface area normalized weathering rates observed in the columns with coarser grains, which at first seems counterintuitive. Our findings point to some important issues to be considered in future experiments and a potential rollout of EW as a carbon dioxide removal method. Only in theory do small grain sizes of the spread-material yield higher CO2 drawdown potentials than coarser material. The hydrologic conditions, which determine the residence times in the pore space, i.e., the time available for weathering reactions, can be more important than small grain size. Saturated-CO2 column results provide an upper limit for weathering rates under elevated CO2.

Per-and poly fluoroalkyl substances (PFAS) from aqueous film forming foam (AFFF) used at firefighting training facilities (FTF) contaminate waterbodies and pose a threat to human health and the environment worldwide . In this study, leaching of PFAS from historically AFFF contaminated field soil has been investigated under saturated conditions using up-flow columns for four soil samples with varying PFAS concentrations to quantify the long-term release potential of the source zone. PFOS was the most abundant PFAS present in the soils (84–98% of ΣPFAS12), varying from 358 to 1097 µg/kg and the total organic carbon (TOC) content varied from 0.73 to 2.0%. The experiment was run until a liquid to solid (L/S) ratio of 10 was reached (equivalent to 80 pore volumes or approximately 100 years of natural infiltration at the sampled field site). Results show a general trend of decreasing concentrations of short chain PFAS with increasing leaching volume. However, PFOS concentrations initially increased by 45–87% in three samples with relatively low TOC (0.7, 1.0 and 1.4%), before being reduced. In the 2.0% TOC soil PFOS concentrations continued to increase throughout the experiment. The residual PFOS content in the four soil samples showed no correlation with TOC content in the soil. Up to 50% of the initial PFOS content was retained in the soil with the lowest TOC content (0.7%), whereas all PFOS was removed in the soil with a TOC content of 1.4%. It is hypothesized that DOC present in the eluates originates from other non-fluorinated components present in AFFF that can facilitate PFAS leaching.

[Display omitted] • Mechanism of KBBC/PS system for mining water treatment under different pH conditions was studied. • Direct electron transfer process contributed under acidic and neutral conditions. • Various active species contributed under alkaline conditions. • Continuous flow experiments prove the potential applicability of KBBC/PS process. The challenges of remediating polluted water in mine areas are exacerbated by low emission dispersion and long-lasting pollution, particularly the significant fluctuations in pH value. Notably, the treatment of flotation reagent polluted water with variable pH scenarios remains a challenge. In this study, metal-free biochar-based materials (KBBC)/persulfate system was used for flotation reagent contaminated wastewater treatment with a wide pH range. Regarding the intrinsic nature of the biochar-based materials, ball milling enhanced the degree of graphitization, while introducing a hard template of KCl increased the proportion of carbonyl functional groups on their surface, thereby facilitating persulfate activation. Experimental findings revealed that the KBBC/PS system displayed efficient degradation of aniline aerofloat (AAF) as a representative flotation reagent across a wide pH range (pH = 3.6–10.4 with buffer). Investigations on the mechanism indicated that, under acidic and neutral conditions, superoxide radicals and direct electron transfer processes constituted primary pathways for pollutant degradation. Meanwhile, various active species contributed under alkaline conditions with increased involvement of free radicals (•OH and SO 4 •−) and singlet oxygen. Furthermore, continuous flow experiments were set up to prove the potential applicability of the KBBC/PS process. This study not only deepens the understanding of persulfate activation by metal-free carbon-based materials across a wide pH range but also expands their potential applications in mine-polluted water purification. [ABSTRACT FROM AUTHOR]

CQDs-doped TiO 2 (C-TiO 2) has drawn increased attention in recent because of its excellent catalytic performance. Understanding the transport of C-TiO 2 in porous media is necessary for evaluating the environmental process of this new nanomaterial. Column experiments were used in this study to investigate ionic strength (IS), dissolved organic matter (DOM) and sand grain size on the transport of C-TiO 2. The mobility of C-TiO 2 was inhibited by the increased IS and decreased sand grain size, but was promoted by the increased DOM concentration. The promotion efficiency of DOM ranked as humic acid (HA) > alginate (Alg) > bovine serum albumin (BSA), which was in the same order as their ability to change surface charges. The micromodels of pore network were prepared via 3D printing to further reveal the deposition mechanisms and spatial/temporal distribution of C-TiO 2 in porous space. C-TiO 2 mainly attached to the upstream region of collectors because of interception. The collector ripening was observed after long-time deposition. The existence of DOM caused visible decrease of C-TiO 2 deposition in the pore network. HA caused the most remarkable reduce of deposition in the three types of DOM, which was consistent with the column experiment results. This research is helpful to predict the transport of C-TiO 2 in natural porous media. [Display omitted] [ABSTRACT FROM AUTHOR]

Copyright of Hydrogeology & Engineering Geology / Shuiwendizhi Gongchengdizhi is the property of Hydrogeology & Engineering Geology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Electric arc furnace (EAF) slag aggregate, a waste by-product of the steel industry, exhibited a high potential for phosphorus (P) removal and had attracted considerable attention. The main objectives of this study were to evaluate the performance of using EAF slag aggregate as an adsorbent for P removal and identify its P removal capacity. A series of batch tests showed that P removal capacity of EAF slag increases gradually with the increase of pH with a range of 2–10, while the highest P removal capacity (1.94 mg/g) can be obtained at pH 12. The adsorption kinetics of P on EAF slag can be described by pseudo-second-order kinetic equations. Isothermal adsorption simulations showed that the best fitted model was the Freundlich model with a correlation coefficient of 0.9825. A continuous flow column experiment feeding a synthetic influent containing 15 mg P/L was operated for 60 days and the P removal efficiency was greater than 95% with a P removal capacity of 1.6 mg P/g slag. The results obtained in this study showed that EAF slag could act as an efficient adsorbent for P removal. Calcium phosphate precipitation depends on the release of Ca2+ and OH− by the dissolution of calcium oxide in EAF slag was found to be the dominant removal mechanism for P removal. [ABSTRACT FROM AUTHOR]

Riverbank filtration (RBF) is an important part of the surface water–groundwater cycle, and it intercepts and retains many pollutants in rivers. However, RBF affects the biogeochemical process which enables aquifer sediments to release iron (Fe) and manganese (Mn). In this study, column experiments were performed to investigate the effects of ammonium ions and organic matter on Fe and Mn release from anaerobic RBF sediments. In addition, high-throughput sequencing technology was used to characterize the microbial community. The results showed that the ammonium ions (NH4+) and organic matter (COD) in groundwater promote the release of Fe and Mn from aquifer sediments. The trends of Fe and Mn release were similar during the leaching process. The maximum concentrations of Fe and Mn were 0.32 and 40 μg/L, respectively. The structural diversity and abundance of the microbial communities in the groundwater were closely related to the Fe/Mn content. Actinobacteriota, Proteobacteria, Acidobacteriota, Bacteroidota, and Chloroflexi were the dominant phyla, while Rhodococcus, Ochrobactrum, and Pseudarthrobacter were the dominant genera. These functional microbes are actively involved in the biogeochemical cycling of Fe, Mn, and N. In summary, contaminants and the microbial-community structure have dual effects on the release of Fe and Mn from RBF aquifers.

The direct deposition of polyethyleneimine (PEI), a weak polycation with a large content of amino groups, onto sand fractions with different sizes (F70, F100, F200, and F355), resulted in versatile core-shell sorbents for water cleaning. Herein, PEI and the weak polyanion poly(acrylic acid) (PAA) were directly precipitated as an nonstoichiometric polyelectrolyte complex ([PEI]:[PAA] = 2:1) onto a sand surface followed by cross-linking with glutaraldehyde (GA) at three molar ratios ([CHO]:[amine] = 1:10; 1:5; 1:1 = r). Non-crosslinked polyelectrolyte chains were washed out in strongly basic (pH 14) and acidic (pH 0) media. The sand/PEI-GA composites were evaluated to determine the organic shell stability using swelling experiments and X-ray photoelectron spectroscopy. The sorbed/desorbed amount of two model pollutants (copper ions and bromocresol green) in column experiments depended on the sand fraction size and cross-linking degree of the PEI shell. The maximum recorded values, after five loading/release cycles of pollutant species onto F70/PEI-GAr, F100/PEI-GAr, F200/PEI-GAr, and F355/PEI-GAr, were situated between the 0.7–5.5 mg Cu2+/mL column and 3.7–15 mg BCG/mL column. Sand/PEI-GAr composites could act as promising sorbents, low-cost and eco-friendly, which could be applied for water purification procedures.

To explore the effects of modified pomace on copper migration via the soil on the banks of the rivers in northern Sichuan and Chongqing, fruit pomace (P) and ethylene diamine tetra-acetic acid (EDTA) modified P (EP) were evenly added (1% mass ratio) to the soil samples of Guanyuan, Nanbu, Jialing, and Hechuan from the Jialing River; Mianyang and Suining from the Fu River; and Guangan and Dazhou from the Qu River. The geochemical characteristics and migration rules of copper in different amended soils were simulated by column experiment. Results showed that the permeation time of copper in each soil column was categorized as EP-amended > P-amended > original soil, and the permeation time of amended soil samples at different locations was Jialing > Suining > Mianyang > Guangan > Dazhou > Nanbu > Guanyuan > Hechuan. Meanwhile, the average flow rate of copper in each soil column showed a reverse trend with the permeation time. Copper in exchangeable, carbonate, and iron–manganese oxide forms decreased with the increase of vertical depth in the soil column, among which the most evident decreases appeared in the carbonate-bonding form. The copper accumulation in different locations presented a trend of Jialing > Suining > Mianyang > Guangan > Dazhou > Nanbu > Guangyuan > Hechuan, and the copper content under the same soil showed EP-amended > P-amended > original soil. The copper proportion of the carbonate form was the highest in each soil sample, followed by the exchangeable form. The proportions of iron-manganese oxide and organic matter forms were relatively small. A significant correlation was observed between the cation exchange capacity and the copper content in exchangeable and carbonate forms. Moreover, total organic carbon and copper contents were negatively correlated.

Chromite ore processing residues (COPR) are real environmental threats, leading to CrO42-, i.e., Cr (VI) leaching into groundwater. It is of serious concern as Cr (VI) is proven to be carcinogenic. Here we emphasize the application of novel and eco-friendly chitin functionalized iron-enriched hydroxyapatite nanocomposite (HAP-Fe0-Ct) in the remediation of Cr (VI)-contaminated groundwater samples collected from Khan Chandpur, India, where the level of Cr (VI) is found to be 11.7 mg/L in a complex aqueous matrix having 793 mg/L of total dissolved solids. Chitin functionality in the composite has resulted in positive zeta potential at circum-neutral pH, favoring electrostatic attraction of chromate ions and resulting in its bulk surface transport. The HAP-Fe0-Ct showed faster kinetics of removal with efficiency (qm = 13.9 ± 0.46 mg/g) for Cr (VI). The composite has shown sorption equilibrium and 100% removal of Cr (VI) within 3 h of interaction time in groundwater samples. No Cr (VI) leaching in the acid wash process at pH 3.5 also suggests chromium's strong chemisorption onto nanocomposite. During the interaction in aqueous solutions, the reduced iron (Fe0) on the nanocomposite becomes oxidized, suggesting the probable simultaneous reduction of Cr (VI) and its co-precipitation. Continuous column extraction of chromate ions was also efficient in both spiked solutions (39.7 ± 0.04 mg/g) and COPR contaminated water (13.2 ± 0.09 mg/g). Reusability up to three cycles with almost complete Cr (VI) removal may be attributed to surface protonation, new binding sites generation, and electron transfer from Fe0 core through defects. The study concludes that HAP-Fe0-Ct could be utilized for continuous Cr (VI) removal from COPR contaminated complex groundwater matrices. [ABSTRACT FROM AUTHOR]

• PANI nanowires-coated PP filter was used for Cr(VI) adsorption at near neutral pHs. • PANI-PP filter exhibited 40% higher Cr(VI) removal ability than PANI powder. • Cr(VI) removal was mainly driven by reduction and Cr(III) adsorption/precipitation. • ~105% Cr(VI) removal efficiency was achieved after electro-chemical regeneration. • PANI-PP filter can be a feasible adsorbent for Cr(VI) remediation of drinking water. Limited work was done about remediation of Cr(VI))-contaminated water at near neutral pHs (6-8), such as drinking water resources. Polyaniline nanowires-coated polypropylene filter (PANI-PP filter) was fabricated for easy recollection and reuse of spent adsorbents. The physicochemical properties of PANI nanowires were characterized by SEM, FTIR, BET, and XPS. The effect of solution pH, contact time, and Cr(VI) concentration on Cr(VI) reduction and total Cr removal are investigated with batch and column adsorption experiments. The PP filter provided micro-sized fiber for PANI deposition, and the deposited PANI nanowires exhibited higher surface area and Cr(VI) removal ability than the PANI powders formed in synthetic solution. At near neutral pHs, Cr(VI) removal by PANI-PP filter was attributed to the Cr(VI) adsorption by the amine groups, Cr(VI) reduction to Cr(III), and subsequent Cr(III) adsorption/precipitation on the PANI nanowires, and the maximum removal capacity of Cr(VI) and total Cr were in the range of 55.7 to 113.8 mg/g PANI. The Cr(VI) reduction was accompanied with the oxidation of amine groups to imine groups of PANI. The electro-chemical regeneration promoted the reduction of imine groups back to amine groups, and after 10 regeneration cycles, around 105% Cr(VI) removal efficiency was still achieved. [Display omitted] [ABSTRACT FROM AUTHOR]

Radioactive strontium (90Sr) is considered as one of the most dangerous radionuclides due to its high biochemical toxicity. For the efficient and selective separation of Sr from acidic environments, a novel functional adsorbent CEPA@SBA-15-APTES was prepared in this work through the phosphorylation of amino-modified mesoporous silica with organic content of approximately 20 wt%. CEPA@SBA-15-APTES was characterized by TEM, SEM, EDS, TG-DSC, BET, FTIR, and XPS techniques, revealing its characteristics of an ordered hexagonal lattice-like structure and rich functional groups. The experimental results demonstrated that the adsorbent exhibited good adsorption capacity for Sr over a wide acidity range (i.e., from 10−10 M to 4 M HNO 3). The adsorption equilibriums of Sr by CEPA@SBA-15-APTES in 10−6 M and 3 M HNO 3 solutions were reached within 30 and 5 min, respectively, and the adsorption capacities at 318 K were 112.6 and 71.8 mg/g, respectively. Furthermore, by combining the experimental and characterization results, we found that the adsorption mechanism consisted of ion exchange between Sr(II) and H+ (in P-OH) in the 10−6 M HNO 3 solution and coordination between the Sr(II) and oxygen-containing (C O and P = O) functional groups in the 3 M HNO 3 solution. [Display omitted] • A novel porous CEPA@SBA-15-ATES adsorbent was prepared by phosphonating amino-modified mesoporous silica. • The adsorbent exhibited good adsorption selectivity for strontium in both low and high concentration nitric acid media. • The adsorption equilibriums of strontium in 10−6 M and 3 M HNO 3 media reached within 30 min and 5 min respectively. • The adsorption mechanisms of strontium were ion exchange in 10−6 M HNO 3 solution and coordination in 3 M HNO 3 solution. [ABSTRACT FROM AUTHOR]

Column leaching tests become methodology important for assessing the risk of release of pollutants from soil into groundwater. In this present study column leaching test were applied on soil samples taken directly in the vicinity of Kenadsa coking plant (Algeria) in order to evaluate the mobility of copper and their potential environmental risks. These samples have been lixiviated in laboratory column in water-saturated condition at room temperature. All leachates have been collected by fraction and analyzed from copper and dissolved organic carbon. The percentages leached in column with water are very low (< 1%). The concentrations of copper in the resulting leachates do not present a toxicological hazard. The effect of dissolved organic carbon on copper leaching was also investigated in this study; the results of column leaching showed that the mobility of copper in these contaminated soil samples is associated with the mobility of dissolved organic carbon.

The aim of the study was to prepare a novel adsorbent by chemical modification of hazelnut shells and evaluate its potential for the nitrate removal from model solutions and real wastewater. The characterization of the novel adsorbent, i.e., modified hazelnut shell (MHS) was performed. The adsorbent characterization included the analysis of elemental composition and the surface characteristics analysis by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The adsorption experiments (batch technique) were performed to investigate the effects of adsorbent concentration, contact time, initial nitrate concentration, and solution pH. The nitrate removal efficiency increased with the increase in MHS concentration and decreased with the initial nitrate concentration. MHS was found to be effective in nitrate removal over a wide pH range (from 2 to 10), and the highest amount of nitrate adsorbed was 25.79 mg g−1 in a model nitrate solution. Depending on the aqueous medium (model solutions or real wastewater samples), it was shown that both Langmuir and Freundlich adsorption isotherm models can be used to interpret the adsorption process. It was found that the kinetics are well described by a pseudo-second order model and the nitrate adsorption process can be controlled by chemisorption. The intraparticle diffusion model has been used to identify an adsorption-controlled process by diffusion mechanisms. Adsorption/desorption experiments in column confirmed that MHS could be successfully used in multiple cycles (at least three), indicating the potential of MHS as an alternative to costly commercial adsorbents for the removal of nitrates from wastewater.

• Poly(ethylene glycol) polymers are stable, mobile, and reactive in porous media. • We investigated the novel tracer in columns filled with quartz, goethite, and illite. • Adsorption of polymers to silicate surfaces is governed by Langmuir-type isotherms. • Transport was predicted independently with striking agreement to observation. A prominent fraction of mobile organic matter in natural aqueous soil solutions is formed by molecules in sizes that seamlessly exceed the lower end of what is defined as a colloid. The hydrodynamics and the functional diversity of these molecules result in a transport behavior that is fundamentally different from smaller compounds. However, there is a lack of "reactive tracers" that allow for the study of colloidal transport phenomena appropriately. We hypothesize that tailor-made and well-defined synthetic polymers can overcome this limitation. We prepared and characterized the hydrodynamic properties of water-soluble poly(ethylene glycol)s (PEG) and studied their adsorption to mixtures of quartz, illite, and goethite in batch and column experiments. We used this information to independently predict the transport of PEG with striking agreement to the observed mean breakthrough times in all porous media. As PEG transport can be comprehensively and quantitatively reconstructed, we conclude that functionalized PEGs are promising candidates to be used as tailorable and non-toxic tracers available in the size range of natural organic (macro-)molecules. [ABSTRACT FROM AUTHOR]

Copyright of Environmental Science & Technology (10036504) is the property of Editorial Board of Environmental Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Purpose: Heavy metal/metalloid pollution in sewage-irrigated soils (SIS) is one of the major environmental issues in China. Mobility of heavy metals/metalloids in the contaminated soils and their potential threats to groundwater are needed to be understood. This study investigated impacts of organic matter, solution pH, and water level on forms and migration of heavy metals/metalloids (As, Cr, Cu, Pb, and Cd) in the contaminated soils from a typical sewage-irrigated area in the North China Plain (NCP). Materials and methods: Based on extensive field measurements, two sewage-irrigated sites and a non-sewage-irrigated site were selected in the study area. Soil samples were collected every 10 cm in a profile (no more than 1 m) from each site. The release and mobility of heavy metals/metalloids in the SIS were investigated using column experiments with two leaching stages (stage I: low water level; stage II: high water level). Deionized water, synthesized acid rain, and poultry manure extractant were used as influents for different columns to stimulate leaching of rainfall, acid rain, and compost leachate, respectively. Soil samples before and after leaching were subjected to sequential extraction for 7 target phases, evaluating the impacts of three leaching conditions on forms of heavy metals/metalloids in soils at different depths. Results and discussion: Results revealed that more As and Cu were mobilized in the column with a compost leachate as the influent than the columns with organic matter-free influents, resulting from reductive dissolution, complexation, and desorption. Cr and Pb concentrations were higher in effluents from the column with low pH influent (acid rain) than those from near-neutral pH influents (rainfall and compost leachate). Proton-promoted desorption and dissolution of very amorphous Fe oxides was the major cause for mobilized Cr and Pb in porewater. Moreover, decrease in dissolved oxygen (DO) was observed with the increase in water level in the column, triggering microbial respiration of Fe/Mn oxide reductions in the presence of bioactive dissolved organic matter, which elevated concentrations of porewater heavy metals/metalloids. Conclusions: This study suggested that sewage irrigation significantly increased heavy metal/metalloid contents associated with labile and bioavailable fractions in the SIS, and both the compost leachate and low pH solution should enhance the mobility of heavy metals/metalloids in the SIS and potentially contaminate groundwater. [ABSTRACT FROM AUTHOR]