Actual Groundwater Research Articles

Physical modeling of organics-contaminated groundwater remediation by ozone micro-nano-bubbles enhanced oxidation

Ozone micro-nano-bubbles (MNBs) enhanced oxidation is a promising in-situ remediation technology for organics-contaminated groundwater. The transport behavior of MNBs and contaminant removal effect in actual groundwater scene is not yet comprehensively understood, although one-dimensional column experiments and batch tests were conducted to investigate the migration of MNBs and contaminant degradation in previous studies. Here, a novel two-dimensional (2D) physical modeling facility was developed, which can characterize the tempo-spatial distribution of MNBs and contaminant in groundwater. The facility was used to explore the migration of MNBs under different hydraulic gradients and the removal of methyl orange, a representative organic pollutant, using ozone MNBs. The experimental results show that groundwater flow velocity has a significant influence on the migration behavior of MNBs. A model including groundwater flow, MNBs transport, and dissolved gas transport can well capture the migration and distribution of MNBs under different hydraulic gradients. The longitudinal and transverse dispersivities of the MNBs were calculated to be 1.14 cm and 0.18 cm, respectively. MNBs are able to migrate with groundwater flow to long distances and exhibit strong dispersion in the lateral and longitudinal directions. The increase in hydraulic gradient greatly enhances the transport of MNBs in groundwater and relieves the deposited MNBs on the surface of porous media. At a hydraulic gradient increasing from 0.033 to 0.1, the range of influence of MNBs increased from about 80 cm × 40 cm to 140 cm × 39 cm after 36 h of injection of oxygen MNBs water. The methyl orange in groundwater is effectively removed by ozone MNBs enhanced oxidation, showing the remarkable remediation ability of ozone MNBs. The area of influence and pollutant removal of the ozone MNBs expanded with injection, and the area of influence was approximately 48 cm × 30 cm after 48 h of treatment. We also discuss the effect of groundwater matrix on ozone MNB migration and degradation of contaminants. The 2D model tests illustrate the mechanism of MNB migration and indicate that ozone MNBs enhanced oxidation technology has great potential in the remediation of organics-contaminated groundwater.

Evaluation of Groundwater Resources in the Middle and Lower Reaches of Songhua River Based on SWAT Model

The SWAT model primarily investigates sources of water pollution and conducts ecological assessments of surface water in contemporary hydrology and water resources research. To date, there have been limited accomplishments in the study of groundwater resources in China. The MODFLOW model currently primarily simulates groundwater levels and the migration of water quality, depending on the hydrological surface water data in the relevant area. This study aims to investigate the groundwater distribution characteristics of the middle and lower reaches of the Songhua River, a significant agricultural and grain production region in China. The research focuses on the middle and lower reaches of the Songhua River basin in Northeast China and employed the SWAT distributed hydrological model to simulate runoff. The monthly recorded runoff at Tongjiang Station in Jiamusi City was utilized to calibrate the model parameters. Consequently, the MODFLOW model was introduced to compare and assess the simulation outcomes of the SWAT model, ultimately ascertaining the distribution characteristics of shallow groundwater, groundwater recharge, recoverable volume, and groundwater levels in the Songhua River Basin. The findings indicate that: (1) The SWAT model demonstrates efficacy in the study region, achieving R2 and NS values of 0.81 and 0.76, respectively, thereby fulfilling the fundamental criteria for scientific research. The MODFLOW model exhibits strong performance in the study region, achieving a periodic R2 of 0.98 and a verification R2 of 0.97, with the discrepancy between simulated and actual groundwater levels confined to 0.6 m, thereby satisfying the criteria for scientific research. (2) In 2011, 2014, and 2016, the groundwater recharge in the middle and lower sections of the Songhua River was 24.33 × 108 m3, 30.79 × 108 m3, and 32.25 × 108 m3, respectively, aligning closely with the SWAT simulation results, while the average annual groundwater level depth was 8.17 m. (3) In the research area, groundwater recharging occurs primarily by atmospheric precipitation, while drainage predominantly transpires via groundwater as base flow, constituting 81.46%. Secondly, the recharge of shallow groundwater to deep aquifers is around 7.14%, with a minimal share attributed to vadose zone loss, constituting merely 2.1%. (4) From 2010 to 2016, the average groundwater runoff modulus of the middle and lower reaches of the Songhua River basin was 1.005 L/(s·km²), with a total recharge of 216.58 × 108 m3 and a total recoverable amount of 105.11 × 108 m3. The mean yearly supply was 25.11 × 108 m3. The total groundwater recharge was 26.54 × 108 m3 in the driest year (2011) and 33.25 × 108 m3 in the year of most ample water (2016).

Ecologically friendly remediation of groundwater sulfamethoxazole contamination: Biologically synergistic degradation by thermally modified activated carbon-activated peracetic acid in porous media

This study examines the efficacy and environmental impact of peracetic acid (PAA) activated by thermally modified activated carbon (AC600) for degrading antibiotics in actual groundwater. Laboratory-scale experiments evaluated the system's effects on contaminant degradation, ecological balance, and substance cycling in the hyporheic zone. Our findings demonstrated the effectiveness of the AC600/PAA system in removing sulfamethoxazole (SMX) from groundwater porous media. Additionally, the AC600/PAA system synergistically interacted with the in-situ microbiota of the hyporheic zone, producing more fragmented degradation products without increasing mixed toxicity. Bacterial abundance increased post-reaction, with notable alterations in the bacterial community and enhanced bacterial metabolism. Key genera such as Lysobacter thrived in the treated environment, playing critical roles in microbiota modification and SMX degradation. The pH remained stable before and after the reaction, while dissolved organic carbon content increased. Overall, our results highlight the promising potential of PAA activation by carbonaceous materials as a low-impact, ecologically friendly technology for in-situ remediation of organic pollutants in groundwater, characterized by high compatibility and biosynthesis.

In situ evolution of electrocatalysts for enhanced electrochemical nitrate reduction under realistic conditions

Electrochemical nitrate reduction to ammonia (ENRA) is gaining attention for its potential in water remediation and sustainable ammonia production, offering a greener alternative to the energy-intensive Haber-Bosch process. Current research on ENRA is dedicated to enhancing ammonia selectively and productivity with sophisticated catalysts. However, the performance of ENRA and the change of catalytic activity in more complicated solutions (i.e., nitrate-polluted groundwater) are poorly understood. Here we first explored the influence of Ca2+ and bicarbonate on ENRA using commercial cathodes. We found that the catalytic activity of used Ni or Cu foam cathodes significantly outperforms their pristine ones due to the in situ evolution of new catalytic species on used cathodes during ENRA. In contrast, the nitrate conversion performance with nonactive Ti or Sn cathode is less affected by Ca2+ or bicarbonate because of their original poor activity. In addition, the coexistence of Ca2+ and bicarbonate inhibits nitrate conversion by forming scales (CaCO3) on the in situ-formed active sites. Likewise, ENRA is prone to fast performance deterioration in treating actual groundwater over continuous flow operation due to the presence of hardness ions and possible organic substances that quickly block the active sites toward nitrate reduction. Our work suggests that more work is required to ensure the long-term stability of ENRA in treating natural nitrate-polluted water bodies and to leverage the environmental relevance of ENRA in more realistic conditions.

Mineralization and stabilization of toxic Pb2+ ions using CMC loaded S/P co-doped biochar composite

Creating more stable chemical precipitates containing lead using biochar composite represents a significant and promising strategy for the treatment of lead contamination. Biochar, a porous and carbonaceous material, was fabricated by pyrolyzing plant biomasses (i.e., soybean straw) under anoxic conditions. In this research, a high capacity of adsorbent called carboxymethyl cellulose-loaded sulfur-phosphorus co-doped biochar composite was prepared, and the optimal lead adsorption parameters and mechanism were also investigated. The experimental results showed that CMC@SP2BC exhibited excellent Pb2+ removal capacity, reaching 829.3 mg/g maximum adsorption under optimum conditions (dosage 0.5 g/L, temperature 308 K, initial pH 5, initial lead concentration 2000 mg/L), which was in agreement with the Langmuir and second-order kinetic models. Moreover, the sequential extraction results indicated that the predominant passivation mechanism for Pb was chemical precipitation, followed by ion exchange, complexation, and physical adsorption. In addition, structural characterization revealed that the passivated lead was mainly in the form of minerals such as PbSO4, Pb3(PO4)2, Pb5(PO4)3OH, and Pb5(PO4)3Cl, which was also further confirmed by PHREEQC model simulation at different pH value and Pb2+ concentrations. Finally, Pb2+ was effectively removed from actual ground water by CMC@SP2BC to achieve Class I and Class II ground water standard. The current work offers an efficient solution for immobilizing Pb2+, which has enormous promise for stabilizing heavy metals.

Effect of the Fe0/PMS advanced oxidation system on the removal of aromatic organic compounds

The aromatic organic compounds present in groundwater environments have low contents, high toxicity, long half-lives and stable chemical properties, which increase the difficulty of degradation under natural conditions. In this study, an zero-valent iron activated peroxymonosulfate system (Fe0/PMS) was constructed to remove common aromatic organic compounds in groundwater. The results showed that at an initial pH of 7.0, Fe0=0.3 g/L, PMS= 0.5 mM, and initial concentration of organic matter (C0) =0.1 mM, the removal efficiency of the seven aromatic organic compounds by the Fe0/PMS system reached more than 70 %, which shows good removal ability. Alcohol quenching tests and liquid chromatography time-of-flight mass spectrometry tests showed that the main active oxygen species in the system were SO4•─ and OH•, which could efficiently degrade aromatic organic compounds through electrophilic substitution, hydroxylation, carbonylation and decarboxylation reactions and reduce the biological toxicity of organic compounds in wastewater to a certain extent. In the long-term dynamic reaction process, the removal rate of aromatic organic compounds in actual groundwater by the Fe0/PMS system can be maintained above 75 %, and the complex structure can be effectively destroyed. This research can provide a theoretical basis for the efficient treatment of aromatic organic compounds in groundwater.

Land use hierarchical mapping for delineation of groundwater potential zones in the Ba river basin using satellite imagery and GIS technology

Abstract The evaluation of groundwater potential is crucial for the best use and replenishment of groundwater resources, as well as for the appropriate growth and administration of a region. To study groundwater potential, it is necessary to analyze the factors that directly affect this resource. In addition to the criteria that contribute to the formation of groundwater, such as rainfall, land cover, geology, slope, etc., land use types and their infiltration capacity are also the main factors affecting the groundwater prospect. In recent years, remote sensing and geographic information systems (GIS) have emerged as the most important technologies in the field of groundwater research, which aid in determining groundwater potential. This paper presents a method to generate the land use hierarchical map based on the level of impact on the formation of groundwater in the Ba river basin using GIS technology and remote sensing. According to the classification result, the three classes of groundwater potential zones including “low”, “moderate”, “high” occupy 1.51%, 77.43%, and 21.06% of the study area respectively. The findings can be validated with the actual groundwater level at some locations that are evenly distributed throughout the basin. The obtained results indicate that there is an agreement between groundwater potential levels at each actual location and those depicted on the land use hierarchical map. The methodology utilized in this study is reliable, accurate and can be used to generate hierarchical maps of additional parameters. This paper will be a useful document for groundwater potential zoning in the study area

Carbon-modified bentonite ion-exchange electrode in rocking-chair capacitive deionization with superior desalination capacity and high stability

Conventional carbon electrodes possess low desalination capacity and poor cycling stability, while faraday electrode materials are not economical with limited resource for capacitive deionization (CDI) technology. Therefore, exploring new type of electrode materials with high desalination capacity, low cost and excellent cycle stability is highly desirable. Bentonite (Bent) is an excellent ion-exchange material, with high natural abundance, super stability, but it has low conductivity. In this paper, a nitrogen-doped carbon modified Bent (NC@Bent) was prepared by in-situ polymerization of dopamine on the surface of Bent followed by carbonization. The N,C-modified thin layer on Bent improved the conductivity, boosting the charge transportation and ion diffusion. The NC@Bent was used as ion-adsorption electrode, exhibiting excellent electro-adsorption behavior. In a rocking-chair CDI (RCDI) cell, it delivered an extraordinary desalination capacity of 82 mg g−1 and super cycling stability with 90 % capacity retention in 50 cycles. Finally, the total dissolved salts in the actual groundwater were effectively reduced by using the current RCDI cell, meeting the WHO recommendation for drinking water. In consideration of the unique feature of low-cost and non-toxicity of Bent, this ion-exchange electrode material (NC@Bent) has much potential for drinking-water purification.

Phytic acid-functionalized polyamidoxime/alginate hydrogel for targeted uranium extraction from acidic wastewater

Efficient removal of uranium from radioactive wastewater is crucial for both environmental protection and sustainable development of nuclear energy. However, selectively extracting uranium from acidic wastewater remains a significant challenge. Here we present a phytic acid-functionalized polyamidoxime/alginate hydrogel (PAG) via a facile one-step hydrothermal reaction. The PAG, leveraging the robust binding affinity of phytic acid and the selective coordination of amidoxime for U(VI), exhibited high efficiency and selectivity in adsorbing U(VI) from acidic uranium-containing wastewater. At pH 2.50, U(VI) adsorption equilibrium was achieved within 60 min, showcasing a maximum theoretical adsorption capacity of 218.34 mg/g. Additionally, the PAG demonstrated excellent reusability, maintaining a uranium removal rate exceeding 90 % over five adsorption-desorption cycles. Remarkably, the as-synthesized PAG removed 94.1 % of U(VI) from actual acidic uranium-contaminated groundwater with excellent anti-interference performance, reducing U(VI) concentration from 272.0 μg/L to 16.1 μg/L and making it meet the WHO drinking water standards (30 μg/L). The adsorption mechanism was elucidated through XPS and DFT calculation, revealing that the uranyl ion primarily coordinated with phosphate and amidoxime groups on phytic acid and polyamidoxime, respectively. These findings underscore the promising potential of PAG hydrogel for addressing acidic uranium-containing wastewater from uranium mining and metallurgy.

Geospatial technique for the delineation of groundwater potential zones using multi-criteria-based AHP and MIF methods

ABSTRACT In the recent past, the growing climate change and transformation of the green cover into urban areas have posed a threat to natural water supply, which will have a direct impact on water demand for emerging cities such as Nava Raipur. As a result, the increasing demand coupled with the reduced availability of surface water prompts scientific investigation into groundwater availability and its sustainable management as an alternative. The study attempted to determine groundwater potential zones using the analytic hierarchy process (AHP) and multi-influencing factor (MIF) techniques. Twelve contextually significant regulating environmental factors were selected, and their significance and influences on decision-making approaches models have been attempted to determine through the sensitivity analysis. The final GWPZ map obtained, from a combination of thematic layers, was verified using the receiver operating curve (ROC) and the area under curve (AUC) with discharge (yield) records taken from 21 bore wells. According to the ROC curve's AUC estimation, MIF can explain 82.9% of the actual groundwater situation in the region, and for AHP, an AUC value of 0.751 is relatively low. This indicates that the MIF model is the most appropriate to accurately define potential groundwater zones for emerging cities like Nava Raipur.

Simultaneous Degradation, Dehalogenation, and Detoxification of Halogenated Antibiotics by Carbon Dioxide Radical Anions

Despite the extensive application of advanced oxidation processes (AOPs) in water treatment, the efficiency of AOPs in eliminating various emerging contaminants such as halogenated antibiotics is constrained by a number of factors. Halogen moieties exhibit strong resistance to oxidative radicals, affecting the dehalogenation and detoxification efficiencies. To address these limitations of AOPs, advanced reduction processes (ARPs) have been proposed. Herein, a novel nucleophilic reductant—namely, the carbon dioxide radical anion (CO2−)—is introduced for the simultaneous degradation, dehalogenation, and detoxification of florfenicol (FF), a typical halogenated antibiotic. The results demonstrate that FF is completely eliminated by CO2−, with approximately 100% of Cl− and 46% of F− released after 120 min of treatment. Simultaneous detoxification is observed, which exhibits a linear response to the release of free inorganic halogen ions (R2 = 0.97, p < 0.01). The formation of halogen-free products is the primary reason for the superior detoxification performance of this method, in comparison with conventional hydroxyl-radical-based AOPs. Products identification and density functional theory (DFT) calculations reveal the underlying dehalogenation mechanism, in which the chlorine moiety of FF is more susceptible than other moieties to nucleophilic attack by CO2−. Moreover, CO2−-based ARPs exhibit superior dehalogenation efficiencies (> 75%) in degrading a series of halogenated antibiotics, including chloramphenicol (CAP), thiamphenicol (THA), diclofenac (DLF), triclosan (TCS), and ciprofloxacin (CIP). The system shows high tolerance to the pH of the solution and the presence of natural water constituents, and demonstrates an excellent degradation performance in actual groundwater, indicating the strong application potential of CO2−-based ARPs in real life. Overall, this study elucidates the feasibility of CO2− for the simultaneous degradation, dehalogenation, and detoxification of halogenated antibiotics and provides a promising method for their regulation during water or wastewater treatment.

Ascorbic acid enhanced the circulation between Fe(II) and Fe(III) in peroxymonosulfate system for fluoranthene degradation.

In this research, ascorbic acid (AA) was used to enhance Fe(II)/Fe(III)-activated permonosulfate (PMS) systems for the degradation of fluoranthene (FLT). AA enhanced the production of ROS in both PMS/Fe(II) and PMS/Fe(III) systems through chelation and reduction and thus improved the degradation performance of FLT. The optimal molar ratio in PMS/Fe(II)/AA/FLT and PMS/Fe(III)/AA/FLT processes were 2/2/4/1 and 5/10/5/1, respectively. In addition, the experimental results on the effect of FLT degradation under different groundwater matrixes indicated that PMS/Fe(III)/AA system was more adaptable to different water quality conditions than the PMS/Fe(II)/AA system. SO4·- was the major reactive oxygen species (ROS) responsible for FLT removal through the probe and scavenging tests in both systems. Furthermore, the degradation intermediates of FLT were analyzed using gas chromatograph-mass spectrometry (GC-MS), and the probable degradation pathways of FLT degradation were proposed. In addition, the removal of FLT was also tested in actual groundwater and the results showed that by increasing the dose and pre-adjusting the solution pH, 88.8 and 100% of the FLT was removed for PMS/Fe(II)/AA and PMS/Fe(III)/AA systems. The above experimental results demonstrated that PMS/Fe(II)/AA and PMS/Fe(III)/AA processes have a great perspective in practice for the rehabilitation of FLT-polluted groundwater.

Uncertainties in physical and tracer methods in actual groundwater recharge estimation in the thick loess deposits of China

Groundwater recharge (GR) can be estimated with physical, tracer techniques and numerical modelling; however, the uncertainties in these methods have not been fully interpreted. This study selected six methods for actual GR estimation in the saturated zones with different data requirements and method assumptions, including two physical methods (i.e., water table fluctuation WTF and Darcy's law DL) and four tracer techniques (i.e., chloride mass balance CMB, tritium renewal rate TRR, chlorofluorocarbons CFC and 14C dating method CBD). Taking the loess tablelands of China as an example study area, we first analyzed the uncertainties in these methods and then recommended the appropriate methods for GR estimation in regions with thick vadose zones. Overall, the recharge rates from WTF, CMB and CFC (88 ± 24, 98 ± 33 and 53 ± 9 mm/year) were much greater than those from DL, TRR and CBD (10 ± 3, 14 ± 3 and 7 ± 5 mm/year). The differences in estimated GR are closely related to the method parameters, assumptions and temporal scales. Specifically, the model parameters (e.g., specific yield, hydraulic conductivity) exhibit large ranges due to spatiotemporal heterogeneity, and the physical methods are more sensitive to hydrogeological parameters compared with the tracer techniques. The uncertainties related to model assumptions originate from the simplified water/solute movement processes. The lag effect of the thick vadose zone largely limits WTF and TRR, but contributes to CMB. Ignoring the mixing and dispersion effect may overestimate recharge by 36–48 % for CFC, and the heterogeneity of the aquifer reduces the potential of CBD for recharge estimation. Overall, CMB is considered as the most optimal method for estimating GR in the thick loess deposits. This study deepens the understanding of the uncertainties in GR assessment methods in regions with thick vadose zones.

Remediation of groundwater polluted with lindane production wastes by conductive-diamond electrochemical oxidation

This work studies the remediation of groundwater saturated with dense non-aqueous phase liquid (DNAPL) from lindane production wastes by electrochemical oxidation. DNAPL-saturated groundwater contains up to 26 chlorinated organic compounds (COCs), including different isomers of hexachlorocyclohexane (HCH). To do this, polluted groundwater was electrolysed using boron-doped diamond (BDD) and stainless steel (SS) as anode and cathode, respectively, and the influence of the current density on COCs removal was evaluated in the range from 5 to 50 mA cm−2. Results show that current densities higher than 25 mA cm−2 lead to the complete removal and mineralisation of all COCs identified in groundwater. The higher the current density, the higher the COCs removal rate. At lower current densities (5 mA cm−2), chlorobenzenes were completely removed, and degradations above 90 % were reached for COCs with more than five chlorine atoms in their molecules. The use of BDD anodes promotes the electrochemical generation of powerful reactive species, such as persulfate, hypochlorite or hydroxyl radicals, that contribute to the degradation and mineralisation of COCs. The applied current density also influences the generation of these species. Finally, no acute toxicity towards Vibrio fischeri was observed for the treated groundwater after the electrochemical oxidation performed at 5 and 10 mA cm−2. These findings demonstrate that electrochemical oxidation with BDD anodes at moderate current densities is a promising alternative for the remediation of actual groundwater contaminated with DNAPLs.

Hydrological effects of the conversion of tropical montane forest to agricultural land in the central Andes of Peru

AbstractAgricultural expansion is one of the main causes of deforestation of tropical montane forests in the central Andes of Peru. The hydrological impacts of converting forests to cropland are well known; however, an issue that is not entirely clear is related to the hydrological effects that can result from the conversion of montane forests to agroforestry systems and the recovery of the hydrological functions of montane forests after a disturbance. In this study, we compare the hydrological processes of different land covers previously modified by agricultural expansion, in order to determine the impact of the conversion of tropical montane forest to agricultural land on the ecosystem service of water provision and regulation. To achieve this, we establish study plots in four land cover types located in the central Andes of Peru (mature montane forest (BMC), natural regenerating secondary forest (BMR), coffee agroforestry systems (AF), and cropland (C)), for the purpose of measuring the vegetation structure and soil properties in them, and subsequently carry out a soil water balance in each plot to calculate the actual evapotranspiration, surface runoff, and groundwater recharge. The results revealed the following percentages (based on precipitation) for the hydrological components in the four land cover types: annual actual evapotranspiration—BMR (41.2%), AF (40.4%), BMC (40.0%), and C (38.0%); annual surface runoff—C (16.1%), BMC (8.3%), BMR (5.2%), and AF (4.6%); and annual groundwater recharge—AF (43.0%), BMR (41.6%), C (34.0%), and BMC (31.7%). Furthermore, the study also examined the relationship between vegetation structure and the hydrological components across the four land cover types. The findings indicated that the reduction of thicker and taller trees could increase surface runoff generation, whereas the presence of thinner and shorter trees could facilitate groundwater recharge. These results shed light on the complex interactions between land cover types, vegetation structure, and hydrological processes, emphasizing the importance of considering these factors in water resource management and land use planning.

Tracing the contributions of different nitrate sources associated with submarine groundwater discharge in coastal seawaters off Jeju Island, Korea

We measured the concentrations of dissolved inorganic nutrients and the dual isotopic composition of nitrate (δ15N-NO3− and δ18O-NO3−) in coastal waters off Jeju, a volcanic island in Korea, to trace its main sources. Sampling of seawater and fresh groundwater was conducted in four different coastal areas of Jeju Island: Haengwon (HW), Pyoseon (PS), Ilgwa (IG), and Sagye (SG) in May 2020 and 2021. The significant negative correlations between NO3− and salinity in the four areas indicate that the main source of NO3− is fresh submarine groundwater discharge (FSGD), with the extrapolated fresh groundwater endmember values ranging from 170 to 300 μM (δ15N-NO3−: 4.1–10.8 and δ18O-NO3−: 1.7–6.4). The actual sources of SGD-driven NO3− in these coastal waters were determined using a bi-plot diagram (δ15N-NO3− vs. δ18O-NO3−) and a Bayesian stable isotope mixing model (MixSIAR). The results showed that, besides the background contribution from open-ocean waters, the main sources of NO3− in HW were fertilizer (69 ± 5%) and manure and sewage (24 ± 7%) and those in PS, IG, and SG were manure and sewage (PS: 53 ± 11%, IG: 57 ± 12%, SG: 63 ± 13%) and fertilizer (PS: 27 ± 8%, IG: 24 ± 5%, SG: 22 ± 5%). Our extrapolation approach for NO3− dual isotopes provides a better way to evaluate the main sources of NO3− in coastal waters off volcanic islands where SGD-driven NO3− is significant, but its actual source groundwater cannot be located.

Prediction of ground water quality in western regions of Tamilnadu using LSTM network

Assessing and safeguarding groundwater quality is critical for sustaining life in water-scarce regions like western Tamil Nadu. The motivation behind this study stems from the pressing need to address water quality challenges in a region grappling with scarcity. Despite existing efforts, a notable research gap exists in predictive tools that comprehensively capture the nuanced temporal variations and trends in groundwater quality. This is where the LSTM network steps in, showcasing exceptional accuracy in short-term predictions and discerning long-term trends. This research uses Long Short-Term Memory (LSTM) networks, a variant of recurrent neural networks, to predict groundwater quality in South Indian Regions, especially in Tamil Nadu. Extensive data, encompassing parameters such as pH, dissolved oxygen, turbidity, and various chemical constituents, were gathered over an extended timeframe. The LSTM model was then trained on this historical dataset, factoring in temporal dependencies and seasonality inherent in groundwater quality data. The validation process rigorously tests the LSTM model against actual groundwater quality measurements. The results were impressive, as the model demonstrated a remarkable ability to unravel the complex variations in groundwater quality.

An Inversion Study of Reservoir Colluvial Landslide Permeability Coefficient by Combining Physical Model and Data-Driven Models

The saturated permeability coefficient (ks) is a key parameter for evaluating the seepage and stability of reservoir colluvial landslides. However, ks values obtained from traditional experimental methods are often characterized by large variations and low representativeness. As a result, there are significant deviations from actual observations when used in seepage field calculations for reservoir landslide analysis. This study proposes an intelligent inversion method that combines a physical model and a data-driven model for reservoir landslide ks based on actual groundwater level (GWL) monitoring data. This method combines Latin Hypercube Sampling (LHS), unsaturated flow finite element (FE) analysis, particle swarm optimization algorithm (PSO), and kernel extreme learning machine model (KELM). Taking the Hongyanzi landslide in Sichuan Province, China, as the research object, the GWL of the landslide under different ks was first obtained by LHS and transient seepage FE analysis. Then, a nonlinear functional relationship between ks and the landslide GWL was fitted based on the PSO-KELM model. Finally, the optimal landslide ks was obtained by minimizing the root-mean-squared error between the predicted and actual GWL using the PSO. A global sensitivity analysis was also conducted on the ks of different rock and soil layers to reveal their control rules on the calculation of landslide GWL. The research results demonstrate the feasibility of the proposed method and provide valuable information for similar landslides in practice.

Lanthanum Cerate Microspheres for Efficient Fluoride Removal from Wastewater.

The performance of lanthanum cerate microspheres (LCM) at removing fluoride was analyzed in batch experiments after they were synthesized via the hydrothermal strategy. The ball-shaped microsphere morphology of LCM is confirmed by SEM and TEM. The synthesized LCM adsorbent showed excellent adsorption capacity in the pH range 3.0-7.0, with the optimal pH range being 3.5-4.5. The Langmuir adsorption model was more appropriate than the Freundlich model for describing the adsorption isotherm. The LCM adsorbent exhibited a significantly higher Langmuir adsorption capacity of 104.83 mg/g at pH 4.0, surpassing that of any other reported adsorbent. We investigated the adsorption of fluoride under a variety of conditions, including the presence of distinct anions. Furthermore, testing the adsorbent in actual groundwater demonstrated its high effectiveness in removing fluoride. Different useful analytical techniques were used for measurements and to learn and deduce the adsorption mechanism.

The long-term effect of Fe3O4 in activating persulfate to degrade refractory organic contaminants for groundwater remediation

Highly reactive metal-based materials for persulfate activation have been intensively studied for treatment of groundwater contaminants. However, the long-term efficacy of the readily available metal-oxide additives, which can be more important for groundwater remediation practice, has received minimal attention. In this study, the results of preliminary experiments demonstrated that Fe3O4 was superior to seven metal oxides (MnO, Fe2O3, MnO2, CuO, Cu2O, CoO, NiO) and zero-valent iron for activating persulfate to degrade 1,2-dichloropropane. Experiments were then conducted to examine the long-term effects of Fe3O4-activated persulfate degradation of four contaminants, i.e., 1,2-dichloropropane, 1,1,2-trichloroethane, 1,4-dioxane, and methyl tert-butyl ether (MTBE). The system achieved complete removal of the contaminants in approximately 72 h, which was contrasted to a removal efficiency less than 35 % in the absence of Fe3O4. Highly efficient use of persulfate for contaminant degradation was observed with insignificant production of soluble Fe before depletion of the contaminants. Production of sulfate radical (SO4•−) and hydroxyl radical (HO•) via surface reactions was likely the process responsible for the degradation. Ten and five cycles of 1,2-dichloropropane degradation experiments were conducted in deionized water and actual groundwater. These results suggested that the Fe3O4 could retain 80 % of its original activation capacity after 5 cycles, but partial oxidation of Fe3O4 eventually occurred. Production of some Cl-containing degradation-resistant intermediates from degradation of 1,2-DCP was observed and could be mitigated under specific conditions. The results show that Fe3O4 has a long-term effect in activating persulfate for contaminant degradation, which is promising for applications such as permeable reactive barriers and nanoparticle injection for groundwater remediation.