Groundwater Components Research Articles

Degradation of sulfamethazine by amorphous zero-valent iron microspheres (A-mZVI) activated peroxydisulfate in groundwater

Amorphous zero-valent iron microspheres (A-mZVI) were synthesized by introduction of ethylenediamine (EDA) and used to activate peroxydisulfate (PDS) to eliminate sulfamethazine (SMT) in groundwater. Experimental results indicated that the A-mZVI/PDS system exhibited a much better performance in the removal of SMT (93.2%) than conventional crystalline nanoscale ZVI (C-nZVI) induced PDS activation system (45.3%). The A-mZVI/PDS system had a better performance under neutral and alkaline conditions than the acidic condition, showing excellent decontamination performance in actual groundwater. The co-existing groundwater components (Na+, Ca2+, Cl−, SO42−, humic acid) had no obvious impact on the removal of SMT except for HCO3−. Characterization of as-synthesized A-mZVI particles demonstrated that the addition of EDA resulted in the formation of amorphous structure of ZVI, and there is an optimum EDA/Fe(II) molar ratio. It was proposed that the amorphous structure favored the release of electrons from the iron core to the surface of A-mZVI to continuously generate ≡Fe(II), leading to the generation of abundant free radicals (both SO4•−and •OH) via the activation of PDS. The intermediates and possible degradation pathways of SMT were revealed, and the developmental toxicity and bioaccumulation factors of SMT and its intermediates were predicted by quantitative structure-activity relationship (QSAR) analysis.

A newly isolated indigenous metal-reducing bacterium induced Fe and Mn oxides synergy for enhanced in situ As(III/V) immobilization in groundwater

Iron-manganese binary oxides (Fe-Mn oxides) have the potential to immobilize arsenite/arsenate [As(III/V)] in situ in natural environments. However, the As(III/V) immobilization performances of Fe-Mn oxides in the presence of indigenous metal-reducing bacteria in reducing groundwater systems have received limited attention. Here, As(III/V) immobilization by Fe-Mn oxides and the interactions of Fe and Mn oxide components in groundwater in the presence of a newly isolated indigenous metal-reducing bacterium (Bacillus sp. FMR) were investigated. Microcosm experiments were performed with artificial groundwater and mineral phases (Fe, Mn and Fe-Mn oxides) with As(III) or As(V) in the presence or absence of strain FMR under anoxic conditions. The Fe oxides in anaerobic cultures without bacteria exhibited better immobilization performances for As(III) [69% As(T) removal efficiency] and As(V) (70%) than Mn oxides (19% and 17%, respectively). Comparably, the involvement of bacteria induced the re-release of arsenic adsorbed on the single Fe and Mn oxides under anoxic conditions, whereas this shift in arsenic adsorption–desorption was not observed in Fe-Mn oxide systems because the Mn oxide components inhibited the reductive dissolution of the Fe oxide components. The As(T) removal efficiencies of Fe-Mn oxides in the presence of bacteria increased by 17% for As(III) and 16% for As(V) compared with anaerobic incubation without bacteria. The interaction of Fe and Mn oxides in Fe-Mn oxides resulted in a slightly increased mobilization of As(III/V) in the absence of bacteria, whereas there was a synergistic effect in the presence of bacteria. The favorability of indigenous bacteria for As(III/V) immobilization and the synergy between Fe and Mn oxides provide novel insights for in-situ As(III/V) immobilization in high arsenic-containing groundwater.

Impact of road transport on groundwater quality

Road transport is one of the sources of groundwater pollution. The aim of the article is to find out whether the largest roads in Poland have a negative impact on groundwater quality and to assess the extent of their influence. The water chemistry in the area of roads with heavy traffic in north-west and central Poland in 2007–2020 was analyzed. The groundwater quality status and the dynamics of changes in concentrations of selected chemical constituents were assessed. Data was taken from the national chemical monitoring network managed by the Polish Geological Institute - National Research Institute. The results of monitoring tests at 42 selected points were subject to detailed statistical analysis. The mentioned points were located within 100 m from the roads. A statistical analysis of selected chemical parameters and a correlation matrix for selected components were performed. The distribution of electrolytic conductivity in the analyzed 42 points in 2019 is presented in the form of a contour map against the background of the main roads in the analyzed area. Based on archival data, a 7-year prediction of changes in concentrations of selected chemical components, using the autoregressive method, was made. The predicted distribution of concentrations of individual chemical components in groundwater indicates that the vicinity (up to 50 m) of roads may negatively affect the groundwater quality. The increased concentration of chloride and sodium ions was found in most sites. An upward trend was also observed for specific electrolytic conductivity.

Geochemical factors controlling natural background levels of phosphate in various groundwater units in a large-scale urbanized area

Assessing natural background levels (NBLs) of groundwater chemical components is useful to the identification of geochemical factors controlling the origin of high levels of chemical components in groundwater. This study assessed the NBLs of phosphate in various groundwater units in the Pearl River Delta (PRD) where urbanization is a large-scale by the combination of a modified pre-selection method and Grubbs’ test, and discussed main geochemical processes controlling the origin of high levels of phosphate in groundwater. Here, the PRD is divided into four groundwater units according to its hydrogeological conditions. The modified pre-selection method consists of detected organic contaminants, the oxidation capacity, as well as the high levels of ammonium and nitrate in groundwater. Results showed that the NBL of phosphate in the coastal-alluvial aquifer was abnormal high (1.8 mg/L), and was >4 times that in other groundwater units. This is mainly attributed to the co-release of phosphate, bicarbonate, and Fe(II) accompanied with the elevated pH and decreased Eh, which resulted from the mineralization of organic matter accompanied with the reductive dissolution of Fe(III)-(hydr)oxides as well as the desorption of other secondary minerals such as aluminum oxyhydroxides in the overlaid marine stratum. Besides, unlike other groundwater units, the property of discharge area of the coastal-alluvial aquifer with more reducing environment also contributes the higher NBL of phosphate in the coastal-alluvial aquifer than in other groundwater units.

Assessing the Impact of Fractured Zones Imaged by ERT on Groundwater Model Prediction: A Case Study in a Chalk Aquifer in Voort (Belgium)

Fractured and karst aquifers are important groundwater reservoirs and are widely used to provide drinking water to the population. Because of the presence of the fractures with varying geometry and properties providing preferential flow paths, fractured aquifers are highly heterogeneous and difficult to characterize and model. In this context, geophysical methods can provide relevant spatially distributed data about the presence of fractures, that can be further integrated in hydrological and groundwater models. In this contribution, we present a case study of a groundwater extraction site in a fractured chalk aquifer in Voort (Belgium), used for the production of drinking water. First, the presence of fractures in the vicinity of the extraction site and their orientation is imaged using electrical resistivity tomography. Based on the available data and the objectives of the study, it is chosen to model only the groundwater component and to simplify the unsaturated zone processes through an average recharge rate. Then, the detected fractures are included in the groundwater model to improve the calibration and the predictive capacity of the model. The results show that a set of parallel fractures crosses the modeled area, whose orientation is in accordance with the tectonic setting. Including these fractures in the model, a more satisfactory calibration was achieved, helping to better understand the hydrogeological behavior of the aquifer. Finally, the acquired knowledge is used to propose new management scenarios for the extraction site minimizing its impact.

Interactions between anthropogenic pollutants (biodegradable organic nitrogen and ammonia) and the primary hydrogeochemical component Mn in groundwater: Evidence from three polluted sites

Anthropogenic pollutants (organic nitrogen and ammonia) can change the dynamic balances of hydrogeochemical components of groundwater, and this can affect the fates of the pollutants and groundwater quality. The aim of this paper is to assess the long-term impact of pollutants on groundwater component concentrations and species in three sites that has been polluted with illegal discharge wastewater containing organic nitrogen and ammonia, in order to reveal the interactions between nitrogen species and Mn. We analyzed semi-monthly groundwater data from three sites in northwestern China over a long period of time (2015–2020) by using statistical analyses, correlation analyses, and a correlation co-occurrence network method. The results showed that wastewater entering groundwater from surface changed the hydrogeochemical component concentrations and species significantly. The main form of inorganic nitrogen species changed from nitrate to ammonia. The Mn concentration increased from undetectable (<0.01 mg/L) to 1.64 mg/L (the maximum), which surpassed the guideline value suggested by China and WHO. The main mechanism for Mn increase is the reductive dissolution of Mn oxide caused by the oxidation of organic nitrogen. Mn‑nitrogen species interaction complicates the transformation of nitrogen components. Chemoautotrophic denitrification and dissimilatory nitrate reduction to ammonium (DNRA) mediated by Mn are the major mechanisms of nitrate attenuation when dissolved oxygen is greater than 2 mg/L. Mn oxides reductive dissolution and reoxidation of Mn by nitrate reduction cause Mn to circulate in groundwater. The results provide field evidence for interactions between nitrogen species transformation and Mn cycle in groundwater. This has important implications for pollution management and groundwater remediation, particularly monitored natural attenuation.

Deep groundwater physicochemical components affecting actinide migration

To better understand the migration behavior of actinides in deep groundwater (GW), the interactions between doped tracers and deep GW components were investigated. La, Sm, Ho, and U tracers (10 or 100 ppb) were doped into sedimentary rock GW samples collected from 250 to 350 m deep boreholes in the experimental gallery of the Horonobe Underground Research Laboratory (URL), Hokkaido, Japan. To evaluate the effect of GW composition on the chemical speciation of actinides, the same tracers were doped into crystalline rock GW samples collected from 300 to 500 m deep boreholes in the experimental gallery at the Mizunami URL, Gifu Prefecture, Japan. Each GW sample was sequentially filtered through a micro-pore filter (0.2 μm) and ultrafilters with a 10 kDa nominal molecular weight limit. Next, the filtrate solutions were analyzed using inductively coupled plasma–mass spectrometry to determine the concentration of tracers retained in solution during each filtration step, and the used filters were analyzed using time-of-flight secondary ion mass spectrometry element mapping and X-ray absorption fine structure spectroscopy to determine the chemical species of the tracers trapped on each filter. It was determined that lanthanide migration was controlled by the amount of phosphates in the Horonobe GW. Therefore, it was expected that the solubility of minor actinides (MAs), which exhibit a similar chemical behavior to that of lanthanides, would be controlled by the formation of phosphates in sedimentary rock GW. Moreover, the data on the Mizunami GW indicated that a fraction of lanthanides and MAs formed hydroxides and/or hydroxocarbonates.

Retraction Note: Detection of rare earth elements in groundwater based on SAR imaging algorithm and fatigue intervention of dance training

This paper studies the detection of rare earth elements (REEs) in groundwater and the intervention of dance training fatigue based on synthetic aperture radar (SAR) imaging algorithm. Among them, the radar 3D imaging technology is to add a new synthetic aperture in the direction perpendicular to the 2D SAR imaging plane, so that 3D imaging can be carried out. The two-dimensional SAR plane image is obtained by two-dimensional matched filtering of the echo signal. It is the result of the projection of the real three-dimensional space on the range azimuth plane. Each pixel value of the two-dimensional SAR plane image is the result of the superposition of all scattering points with different heights in the same range azimuth unit in the three-dimensional space. There are geometric distortions such as overlap, shadow and stretch, which results in the lack of three-dimensional information. Groundwater is the main water source of the plain, accounting for more than 70% of the total water supply. The study of evolution law of groundwater chemical composition based on SAR imaging algorithm is not only helpful to provide scientific data for the sustainable development and utilization of groundwater in plain, but also helpful to further understand the hydrogeochemical process of groundwater in plain. The spatial distribution, temporal development and REE distribution of the main components of shallow groundwater and deep groundwater in North China Plain were investigated. Finally, according to the theory of modern physiology and traditional medicine about the research results of sports burnout, this paper selects the university students who specialize in sports dance as the research object and uses the methods of literature, question table, interview and mathematical statistics to investigate. It can be found that among the three kinds of sports burnout, physical burnout starts first, and then visceral burnout, the last is the sense of mental weariness. There are some differences between boys and girls in fatigue parts. Modern dance is more likely to cause chronic fatigue than Latin dance.

Water Resource Management through Understanding of the Water Balance Components: A Case Study of a Sub-Alpine Shallow Lake

Water availability is a crucial factor for the hydrological balance of sub-alpine shallow lakes and for their ecosystems. This is the first study on water balance and water management of Lake Candia, a small sub-alpine, shallow morainic lake. The aims of this paper are to better understand the link between surface water and groundwater. The analyses carried out included: (i) evaluation of water balance, (ii) identification of trends for each component of water balance, (iii) detection of the presence of a break point or change in the behavior of each component, and (iv) regression analyses of the terms of hydrological balance and their relative importance. The analyses revealed a high variability mainly regarding the groundwater component, and very good correlation between rainfall and volume variation, between rainfall and the water inflow, and between groundwater source and outflow. Volume variation is linked with rainfall, outflow, groundwater source, and surface water inflow. Despite the fact that the groundwater component does not seem to have a great importance relative to direct rainfall on the lake, it is necessary to study the component with careful resource management policies that point toward the protection of the water resource, sustainable uses, and protection of the Lake Candia ecosystem.

Water Balance of Pit Lake Development in the Equatorial Region

In recent years, Indonesia has become the largest coal exporter in the world, and most of the coal is being mined by means of open-pit mining. The closure of an open-pit mine will usually leave a pit morphological landform that, in most cases, will be developed into a pit lake. One of the main issues in developing a pit lake is the understanding of the pit lake filling process. This paper discusses the hydrological model in filling the mineout void in a coal mine in Kalimantan which is located close to the equatorial line. The J-void is a mineout coal pit that is 3000 m long and 1000 m wide, with a maximum depth of 145 m. The development of the J-void pit lake after the last load of coal had been mined out experienced a dynamic process, such as backfilling activities with an overburden as well as pumping mine water from the surrounding pits. There are two components in the model, i.e., overland/subsurface and pit area. The overland zone is simulated using the Rainfall-Runoff NRECA Hydrological Model approach to determine the runoff and groundwater components, whereas the pit area is affected by direct rainfall and evaporation. The model is validated with the observation data. The main source of water in the J-void pit lake is rainwater, both from the surrounding catchment area as well as direct rainfall. As this coal mine area is characterized as a multi-pit area and, consequently, several pit lakes will be formed in the future, the result of the hydrological model is very useful in planning the future pit lakes.

An Open‐Source Web Application for Regional Analysis of GRACE Groundwater Data and Engaging Stakeholders in Groundwater Management

AbstractSince 2002, National Aeronautics and Space Administration’s Gravity Recovery and Climate Experiment (GRACE) allows scientists of various disciplines to analyze and map changes in total water storage globally. Although the raw data are available to the public, the process of viewing, manipulating, and analyzing GRACE data can be difficult for those without strong technological backgrounds in programming or geospatial software. This is particularly true for water managers in developing countries, where GRACE data could be a valuable asset for sustainable water resource management. To address this problem, we developed an open‐source utility for subsetting GRACE datasets to selected regions of interest and packaged that utility in a web application that allows water managers to quickly and easily access and visualize GRACE data. For a selected region, we use data from the three Global Land Data Assimilation System land surface models: Noah, variable infiltration capacity, and Catchment Land Surface Model, and decompose the GRACE data for total water storage into surface water, soil moisture, and groundwater components along with associated uncertainty estimates. The resulting groundwater data are in the form of groundwater storage changes over time, and a better understanding of groundwater storage trends helps water managers to more effectively respond to drought and agricultural demand in a selected region and thereby more sustainably manage groundwater resources. We demonstrate these uses in a case study from the Hindu‐Kush Himalayan region.

Hydrochemical evaluation of groundwater quality and human health risk assessment of nitrate in the largest peninsula of China based on high-density sampling: A case study of Weifang

Groundwater is an important source of water, and the assessment of its hydrochemical characteristics, quality, and health risks is of great practical significance to ensure safe water use for residents and stable socioeconomic development. This study used high-density groundwater sampling data (1398 water samples) for Weifang to assess the groundwater quality and the health risks associated with drinking nitrate (NO3−)-contaminated groundwater. The results indicated that the major chemical components of groundwater varied widely and had high coefficients of variation. The NO3− concentration in groundwater ranged from 0.1 to 984 mg/L; it exceeded the Chinese standard groundwater quality threshold (88.57 mg/L) in 587 samples (41.99% of all samples). A Piper diagram indicated that the groundwater in Weifang is mainly of the SO4·Cl–Ca·Mg type and the HCO3·Ca·Mg type, and that groundwater with high NO3− concentrations (>300 mg/L) is mainly of the SO4·Cl–Ca·Mg type. Hydrochemical analysis indicates that the groundwater chemistry in Weifang is mainly influenced by the weathering of silicate and carbonate rocks, cation exchange, and human activities. In addition, the NO3− concentration in groundwater considerably influences its quality. The NO3− concentration in the groundwater in Weifang is higher than that in many other regions of China, and is primarily attributed to agricultural activities. The calculated water quality index (WQI) shows that the groundwater in Weifang is mainly medium -quality water, but extremely poor -quality water is distributed extensively in some parts of the study region. The spatial distribution of the hazard quotient (HQ) is consistent with the spatial variation in groundwater NO3− concentrations. Overall, the health risks associated with NO3− in drinking water were greatest for infants, followed in decreasing order by children, teenagers, and adults.

Predictability of initial hydrogeochemical effects induced by short-term infiltration of ∼75 °C hot water into a shallow glaciogenic aquifer

Despite their potential in heating supply systems, thus far high-temperature aquifer thermal energy storages (HT-ATES) currently lack widespread application. Reducing the potential risks by improving the predictability of hydrogeochemical processes accelerated or initiated at elevated temperatures might promote the development of this technology. Therefore, we report the results of a short-term hot water infiltration field test with subsurface temperatures above 70 °C, along with associated laboratory batch tests at 10, 40 and 70 °C for 28 sediment samples to determine their usability for geochemical prediction.Most groundwater components had lower maximal concentrations and smaller concentration ranges in field samples compared to the batch tests. This indicates that the strongest geochemical effects observed in laboratory tests with sufficient site-specific sediment samples will likely be attenuated at the field scale. A comparison of field measurements with predicted concentration ranges, based on temperature induced relative concentration changes from the batch tests, revealed that the predictive power was greatest, where the hot infiltrated water had cooled least and the strongest geochemical effects occurred. The batch test-based predictions showed the best accordance with field data for components, with significant temperature-induced concentration changes related to ion exchange and (de)sorption processes. However, accurate prediction of concentration changes based on other processes, e.g. mineral dissolution, and downstream reversals in concentrations, requires further investigation.The here presented procedure enables the prediction of maximal expectable temperature-dependant concentration changes for most environmentally relevant ancillary groundwater components, e.g. As, with limited effort.

Hydrogeological Characteristics of a Riverine Wetland in the Nakdong River Delta, Korea

Investigating the physical and chemical properties of riverine wetlands is necessary to understand their distribution characteristics and depositional environment. This study investigated the physical (particle size, color, and type) and chemical properties (organic, inorganic, and moisture contents) of sediments in Samrak wetland, located in the Nakdong River estuary area in Busan, South Korea. The particle size analysis indicated that the hydraulic conductivity values for the coarse grain and the mixture of coarse and fine grains ranged from 2.03 to 3.49×10−1 cm s−1 and 7.18×10−3 to 1.24×10−7 cm s−1 , respectively. In-situ water quality and laboratory-based chemical analyses and radon-222 measurement were performed on groundwater and surface water in the wetland and water from the nearby Nakdong River. The physical and chemical properties of Samrak wetland was characterized by the sediments in the vertical and lateral direction. The concentrations of chemical components in the wetland groundwater were distinctly higher than those in the Nakdong River water though the wetland groundwater and Nakdong River water equally belonged to the Ca-HCO3 type.

RETRACTED ARTICLE: Detection of rare earth elements in groundwater based on SAR imaging algorithm and fatigue intervention of dance training

This paper studies the detection of rare earth elements (REEs) in groundwater and the intervention of dance training fatigue based on synthetic aperture radar (SAR) imaging algorithm. Among them, the radar 3D imaging technology is to add a new synthetic aperture in the direction perpendicular to the 2D SAR imaging plane, so that 3D imaging can be carried out. The two-dimensional SAR plane image is obtained by two-dimensional matched filtering of the echo signal. It is the result of the projection of the real three-dimensional space on the range azimuth plane. Each pixel value of the two-dimensional SAR plane image is the result of the superposition of all scattering points with different heights in the same range azimuth unit in the three-dimensional space. There are geometric distortions such as overlap, shadow and stretch, which results in the lack of three-dimensional information. Groundwater is the main water source of the plain, accounting for more than 70% of the total water supply. The study of evolution law of groundwater chemical composition based on SAR imaging algorithm is not only helpful to provide scientific data for the sustainable development and utilization of groundwater in plain, but also helpful to further understand the hydrogeochemical process of groundwater in plain. The spatial distribution, temporal development and REE distribution of the main components of shallow groundwater and deep groundwater in North China Plain were investigated. Finally, according to the theory of modern physiology and traditional medicine about the research results of sports burnout, this paper selects the university students who specialize in sports dance as the research object and uses the methods of literature, question table, interview and mathematical statistics to investigate. It can be found that among the three kinds of sports burnout, physical burnout starts first, and then visceral burnout, the last is the sense of mental weariness. There are some differences between boys and girls in fatigue parts. Modern dance is more likely to cause chronic fatigue than Latin dance.

Natural Background Level and Contamination of Shallow Groundwater Salinity in Various Aquifers in a Coastal Urbanized Area, South China

Assessing natural background levels (NBLs) of chemical components in groundwater is useful for the evaluation of groundwater contamination in urbanized areas. The present study assessed the NBL of total dissolved solids (TDS) in various groundwater units in the Pearl River Delta (PRD) where urbanization is a large scale and discussed factors controlling groundwater salinity contamination in the PRD. Results showed that the NBL of TDS in groundwater in the coastal-alluvial plain was more than 1.5 times that in other groundwater units because of the seawater intrusion in this groundwater unit. By contrast, interactions of water and soils/rocks were the main factors controlling the NBLs of TDS in other groundwater units. Groundwater salinity contamination in the PRD was positively correlated with the urbanization level. Wastewater from township-village enterprises and industrial wastewater were likely to be the main sources for groundwater salinity contamination in the PRD. Moreover, the wastewater leakage from sewer systems was one of the main pathways for groundwater salinity contamination in urbanized areas, because the proportion of groundwater salinity contamination in urbanized areas formed in 1988–1998 was more than 1.5 times that in urbanized areas formed in 1998–2006 regardless of groundwater units. Besides, sewage irrigation and leakage of landfill leachate were also important sources for groundwater salinity contamination in the PRD.

Contribution of local factors to the status of a groundwater dependent terrestrial ecosystem in the transboundary Gauja-Koiva River basin, North-Eastern Europe

A pilot study was carried out in the Matsi spring fen, southern Estonia to test a proposed methodology (Terasmaa et al., 2020) for identifying potential effects of groundwater bodies on groundwater dependent terrestrial ecosystems (GDTE). A comprehensive hydrochemical and isotopic dataset was collected and analyzed using multivariate statistical methods to assess the origin of the groundwater discharging in the spring fen and to determine both the quantitative and qualitative aspects of GDTE-groundwater interdependence. The hydrochemical findings were complemented with the hydrogeological, hydrodynamical and botanical observations, and summarized into a conceptual model of the study site. The results show that the status of the spring fen is influenced both by groundwater inflow from the regional Middle Devonian sandstone aquifer (D2gj-ar) in the transboundary Gauja/Koiva River basin, but also by discharge of the shallow aquifer found in Quaternary (Q) deposits of local extent. By using multivariate statistical methods, the mixing of the two main groundwater sources in the spring fen discharge was quantified. On average, the regional D2gj-ar and local Q aquifer contributed 67% and 33%, respectively, to the spring fen discharge. The groundwater was generally more mineralized in the D2gj-ar aquifer while more nutrient-rich in the shallow Q aquifer. Agricultural activities in the arable lands adjacent to the spring fen have resulted in the elevated loads of macronutrients and halogens in the shallow Q aquifer (Ntot=1.95 ± 2.6 mg N/l, Ptot=0.59 ± 0.8 mg P/l). Although generally in pristine state, the elevated macronutrient loading from the Q aquifer and perhaps the beaver activity, has led to deterioration of the status of the spring fen communities in the upstream parts of the main fen polygon. The N:P ratios were occasionally above the 16:1, indicating nitrogen limitation and phosphorus excess, which is likely due to increased upland loading of phosphorus from fertilizers. The results of the study show that poor chemical status of a GDTE can result from local pollution sources and land-use even in cases when the related regional GW body itself is in good chemical status. Also, the usefulness of analyzing minor groundwater components (e.g Ba, Sr, Al, F, SiO2) in a GDTE assessment in establishing the end-member mixing relationships has been shown. All in all, it is one of the first comprehensive studies of the interactions between a groundwater body and a groundwater-dependent terrestrial ecosystem in the Estonian context.

Influence of several crucial groundwater components on the toxicity of nanoscale zero-valent iron towards Escherichia coli under aerobic and anaerobic conditions

In this paper, the effects of several groundwater components (heavy metals, inorganic anions, and organics) on the cytotoxicity of nanoscale zero-valent iron (NZVI) towards Escherichia coli (E. coli) under aerobic/anaerobic conditions were studied. The results showed that NZVI exhibited much higher toxicity in anaerobic conditions than aerobic conditions. Under the state of air-saturation, corrosion of NZVI occurred rapidly, at the same time, it could stably and continuously generate Fe (Ⅱ) and trigger reactive oxygen species (ROS), which led to oxidative stress in E. coli. While in the deareated state, the TEM images showed that the integrity of the cell membrane was destroyed, which validated that the main mechanism of NZVI cytotoxicity was the rapid membrane damage of E. coli. The presence of Cr (Ⅵ) reduced the toxicity of NZVI through oxidation-reduction with NZVI, especially under anaerobic conditions. In contrast, the presence of Cd (Ⅱ) could be adsorbed onto NZVI to increase the cytotoxicity of NZVI. The presence of phosphate and humic acid greatly improved the survival rate of E. coli through the complex reaction with Fe (Ⅱ), especially under aerobic conditions. On the one hand, the formed Fe (II)-phosphate/humic acid complex could reduce the production of ROS. On the other hand, the complex accumulated on the outer surface of E. coli cells could provide steric hindrance to impede the contact between NZVI and cell. These findings were crucial for practical significance to evaluate environmental risk during the groundwater remediation process by using NZVI.

Groundwater dependence of riparian woodlands and the disrupting effect of anthropogenically altered streamflow.

Riparian ecosystems fundamentally depend on groundwater, especially in dryland regions, yet their water requirements and sources are rarely considered in water resource management decisions. Until recently, technological limitations and data gaps have hindered assessment of groundwater influences on riparian ecosystem health at the spatial and temporal scales relevant to policy and management. Here, we analyze Sentinel-2-derived normalized difference vegetation index (NDVI; n = 5,335,472 observations), field-based groundwater elevation (n = 32,051 observations), and streamflow alteration data for riparian woodland communities (n = 22,153 polygons) over a 5-y period (2015 to 2020) across California. We find that riparian woodlands exhibit a stress response to deeper groundwater, as evidenced by concurrent declines in greenness represented by NDVI. Furthermore, we find greater seasonal coupling of canopy greenness to groundwater for vegetation along streams with natural flow regimes in comparison with anthropogenically altered streams, particularly in the most water-limited regions. These patterns suggest that many riparian woodlands in California are subsidized by water management practices. Riparian woodland communities rely on naturally variable groundwater and streamflow components to sustain key ecological processes, such as recruitment and succession. Altered flow regimes, which stabilize streamflow throughout the year and artificially enhance water supplies to riparian vegetation in the dry season, disrupt the seasonal cycles of abiotic drivers to which these Mediterranean forests are adapted. Consequently, our analysis suggests that many riparian ecosystems have become reliant on anthropogenically altered flow regimes, making them more vulnerable and less resilient to rapid hydrologic change, potentially leading to future riparian forest loss across increasingly stressed dryland regions.

Implementation of groundwater protection measures, particularly resource-directed measures in South Africa: a review paper

Abstract This review paper on groundwater protection measures in South Africa focuses on the actual implementation of groundwater protection measures, in particular, the resource-directed measures (RDM) as described in Chapter 3 of the National Water Act (NWA). Significant catchment-wide implementation of RDM has taken place in a phased manner throughout various catchments since 2012. By 2015, approximately R380 million had been expended on the catchment-wide implementation of the water resource protection measures over a period of 15 years. Considerable effort went into refining the RDM methodology, taking into account the groundwater component of the overall resource. In this paper, we contend that RDM, in its present form, will not make a significant contribution to groundwater resource protection and security in the country. This is a major concern because the Groundwater Strategy of the Department of Human Settlements, Water and Sanitation (DHSWS) had declared the protection of groundwater as a national priority. This paper also examines institutional and governance arrangements (or lack thereof) as well as providing recommendations to support the effective implementation of groundwater protection provisions as prescribed by South Africa's water legislation.