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Renewable water resources are limited in arid and semiarid countries. The lack of surface waters and groundwater recharge makes the use of non-renewable groundwater resources inevitable. In many countries in the MENA Region (Middle East/North Africa), non-renewable groundwater is the major resource for both municipal and agricultural water demand. Integrated Management of non-renewable groundwater resources has to cope with the fact, that the resources are dwindling, and sustainability in terms of a balanced water budget cannot be achieved. Hence, focus must be set on the economic and social welfare resulting from the use of these limited resources. Long-term water management plans are needed to overcome economic inefficiencies within the water sector and to ensure a safe water supply for the present and future generations. In the MENA region, the technical development and rapid population growth lead to an overexploitation of the non-renewable groundwater resources, mainly by agricultural users, resulting in water quality deterioration, local water shortage, and establishment of expensive long-distance water supply systems. Here, todays major challenges of Integrated Water Management are: (1) to mitigate the user conflict between municipal and agricultural users, (2) to protect the dwindling resources, and (3) to implement an economic view on the water sector. Facing these challenges ensures the best use of the non-renewable resources, turning them into economic and social welfare for the population. [ABSTRACT FROM AUTHOR]

The management of groundwater resources in coastal environments within the Mediterranean basin has become of paramount importance, especially in the light of global changes. A typical example of such a hydrosystem is the Lavrio basin in Greece. This research site involves two aquifer types—granular and karstic formations—that are hydraulically interconnected. Furthermore, the proximity to the sea and the abstractions for irrigation and drinking water supply have led to the phenomenon of seawater intrusion. The present study aims at analyzing the hydraulic, hydrological, and hydrogeological conditions of the area by means of hydrochemical and isotopical data interpretation as supporting tools, which will inform and support the development of an integrated conceptual hydrogeological model of the area. Field investigations were conducted in order to collect piezometric and chemical data and use them to retrieve the quantitative and qualitative status of the local aquifer units. New interpretation of an older dataset gave an insight into how the karstic aquifer behaves in terms of hydraulics. The results have also demonstrated that there is a hydraulic connection between the different aquifers and the Mediterranean Sea, while natural recharge was quantified for both aquifer types. [ABSTRACT FROM AUTHOR]

The Cox’s Bazar region at the southeastern coast of Bangladesh has been gradually changed from a rural settlement into a densely populated urban area, caused by the rapid growth of tourism. Water demand is mainly covered by groundwater, and the hotels and resorts are typically operating their own groundwater wells without metering and regulations. In this study, the temporal and spatial variations in groundwater quality and hydraulic heads in the Cox’s Bazar area were evaluated over a period of 2 and 4 years respectively, to analyze the effects of the groundwater extractions on the status of the groundwater resources. Due to the pronounced seasonality of rainfall, the aquifer system was found to be highly dynamic even without human interference and seawater intrusion into the aquifers from the Bay of Bengal as well as from the Bakkhali river in the north was detected. The groundwater abstraction caused groundwater levels in some touristic centers to be already permanently below sea level, and a trend to a further lowering of hydraulic heads was observed. This coincides with an overall trend of increasing electrical conductivities in the groundwater. For a sound and sustainable development of the Cox’s Bazar region, water management strategies and a regulatory framework have to be developed that consider the specific conditions in such a coastal zone. [ABSTRACT FROM AUTHOR]

Thirty-two soil samples were collected from the study area in October 2020 for geochemical and pollutants investigation of Shwan Sub-basin soil. All soil samples were analysed for different geochemical analyses. The analysis results revealed that the pH values in soil samples ranged from 7.12 to 7.56 with a mean of 7.327. According to the pH values detected in the soil samples, the soil is classified as neutral soil. The electrical conductivity ranged from 0.92 mmhos/cm to 7.8 mmhos/cm with a mean of 1.53 mmhos/cm. Thus, according to the detected electrical conductivity values, the soil was classified as non-saline to slightly saline. The organic matter ranged from 1.14% to 1.45% with a mean value of 1.326 %, while total organic carbon ranged from 0.66 % to 0.84 % with a mean value of 0.769 % which indicated the soil was characterized by low organic content. The results of the geochemical analysis revealed that the major and minor element mean concentrations were in the order Si> Ca> Al> Fe> Mg > K> Ti> Na> P> Mn> S> Cl> N. The average concentrations of trace elements in soil samples followed the decreasing order Sr > Cr> Ba> Zr> Ni> V> Zn> Ta> Rb> Cu> Nb> Y> Pb> Co> Ga> Mo> As> Th> Br> Sn> I. Furthermore, the comparison between heavy metal concentrations in the soil of the study area and metal concentrations in the world soil limit and Indirect Geochemical Background revealed an increase in metal concentrations of Cr, Ni, Zn, Co, As, Mo and Ta. Multivariate statistical analyses, such as Principal Component Analysis and Agglomerative Hierarchal Cluster Analysis, identified the potential sources of pollutants in the soil. Most metals are from natural sources and some of them are from anthropogenic sources mostly from agricultural activities mainly fertilizers use and the waste of animals breeding on farms. Besides industrial activities such as deposits of pollutants from emissions of petroleum refineries located inside or close to the study area. In addition, building blocks and paint factories. [ABSTRACT FROM AUTHOR]

The Kirkuk region in northern Iraq hosts some of the largest oil fields in the Middle East. Several anticline structures enabled vertical migration and entrapment of the oil. Frequently, complex fracture systems and faults cut across the Eocene and middle Oligocene reservoirs and the cap rock, the Fatha Formation of Miocene age. Seepage of crude oil and oil field brines are therefore a common observation in the anticline axes and contamination of shallow groundwater resources is a major concern. In this study, 65 water samples were collected in the Kirkuk region to analyze and distinguish mixing processes between shallow groundwater resources, uprising oil field brines, and dissolution of gypsum and halite from the Fatha Formation. Hydrochemical analyses of the water samples included general hydrochemistry, stable water isotopes, as well as strontium concentrations and for 22 of the samples strontium isotopes ( 87 Sr/ 86 Sr). Strontium concentrations increased close to the anticline axes with highest concentrations in the oil field brines (300 mg/l). Strontium isotopes proved to be a valuable tool to distinguish mixing processes as isotope signatures of the oil field brines and of waters from the Fatha Formation are significantly different. It could be shown, that mixing of shallow groundwater with oil field brines is occurring close to the major fault zones in the anticlines but high concentrations of strontium in the water samples are mainly due to dissolution from the Fatha Formation. [ABSTRACT FROM AUTHOR]

• A unique experimental facility was built to assess MAR with STWW effluents. • Mixing zone of infiltrated STWW and resident groundwater is of special relevance. • Conservative model delineates processes of nutrients in capillary fringe and mixing zone. • Elevated concentrations of phosphate in STWW might trigger mobilisation of As. To mitigate groundwater level decline, managed aquifer recharge (MAR) with secondary treated wastewater (STWW) is increasingly considered and implemented. However, the effectiveness and potential risks of such systems need evaluation prior to implementation. In this study, we present a large-scale sand tank experiment to analyse processes related to the infiltration of real STWW through the vadose zone and subsequent mixing with oxic native groundwater. The varying composition of STWW from 15 infiltration cycles over six months of operation and the retention times were the main drivers of the observed processes, which were characterized by a wide range of analytical techniques such as in situ high-resolution oxidation–reduction potential (ORP) measurements, closed mass balances of solutes, characterization of dissolved organic carbon (DOC), stable nitrate isotopes analysis, as well as numerical flow and transport modelling. Depending on the composition and infiltration rates of the STWW, both nitrification and denitrification could be observed, even simultaneously at different locations in the tank. Furthermore, due to the variability of the real STWW we observed enhanced arsenic mobilisation during times of elevated phosphate concentrations of the infiltrating STWW. Additionally, uranium was mobilised in our experimental system via carbonate mineral dissolution caused by the infiltrating STWW which was undersaturated of calcite for all infiltration cycles. Overall, our results showed the importance of conducting studies with waters of complex matrix, such as real STWW, and considering mixing with groundwater to assess the full range of possible processes encountered at MAR field sites. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Removal of 12 organic contaminants from water using a microporous polypropylene hollow fiber membrane (HFM) module was studied under low strip gas flow to water flow ratios (≤5:1). Removal efficiencies were found to be strongly dependent on the Henry''s law constants indicating a substantial mass transfer resistance on the gas side. Vacuum can be either used to increase removal efficiencies, or to decrease the amount of strip gas that has to be treated without sacrificing efficiency. [Copyright &y& Elsevier]

Within the Ararat Valley (Armenia), a continuously growing water demand (for irrigation and fish farming) and a simultaneous decline in groundwater recharge (due to climate change) result in increasing stress on the local groundwater resources. This detrimental development is reflected by groundwater-level drops and an associated reduction of the area with artesian conditions in the valley centre. This situation calls for increasing efforts aimed at more sustainable water resources management. The aim of this baseline study was the collection of data that allows for study on the origin and age distribution of the Ararat Valley groundwater based on environmental tracers, namely stable (δ2H, δ18O) and radioactive (35S, 3H) isotopes, as well as physical-chemical indicators. The results show that the Ararat Valley receives modern recharge, despite its (semi-)arid climate. While subannual groundwater residence times could be disproved (35S), the detected 3H pattern suggests groundwater ages of several decades, with the oldest waters being recharged around 60 years ago. The differing groundwater ages are reflected by varying scatter of stable isotope and hydrochemical signatures. The presence of young groundwater (i.e., younger that the 1970s), some containing nitrate, indicates groundwater vulnerability and underscores the importance of increased efforts to achieve sustainable management of this natural resource. Since stable isotope signatures indicate the recharge areas to be located in the mountains surrounding the valley, these efforts must not be limited to the central part of the valley where most of the abstraction wells are located. [ABSTRACT FROM AUTHOR]

Sorption of hydrophobic organic contaminants onto thermally altered carbonaceous materials (TACM) constitutes a widely used technology for remediation of polluted waters. This process is typically described by sorption isotherms, with one of the most used models, the Polanyi-Dubinin-Manes (PDM) equation, including water solubility (S w) as a normalizing factor. In case of pharmaceutical active compounds (PhACs), S w depends on the pH of the environment due to the ionic/ionizable behavior of these chemicals, a fact frequently ignored in sorption studies of PhACs. In this work, we set the theoretical framework to include the variation of S w with pH in the definition of the PDM model, and we applied this approach to describe the effect of ambient pH in the competitive sorption of three commonly detected PhACs (carbamazepine, ibuprofen, and sulfamethoxazole) onto three carbonaceous sorbents (biochar, powder activated carbon, and colloidal activated carbon). Changes in the ambient pH and hence in the hydrophobicity of the compounds could explain the strong variations observed in single-solute sorption and also in competitive sorption. Furthermore, S w was used as a parameter for the linear regression model of sorption coefficients of our experiments, suggesting the incorporation of this variable as an improvement to existing approaches for prediction of PhACs sorption onto TACM. [Display omitted] • Sorption of PhACs on carbonaceous sorbents was studied at different pH values. • Distinct effects of ambient pH in PhACs adsorption for single and multi-solute systems. • Changes of PhACs solubilities with pH were included in isotherms and regression models. • New multilinear regression models are presented for prediction of PhACs sorption. [ABSTRACT FROM AUTHOR]

Groundwater resources have been extensively exploited in many areas around the globe for providing good quality water for drinking and other purposes. Groundwater flow models have been widely used as management, evaluation and prediction tools on many occasions, however, in the case of karstic aquifers, the use of modelling tools is often a task with increased complexity. In the light of this constrain, a new methodology for implementing field data into mathematical models developed for simulating flow in karstic aquifers is presented. The aim is to combine an existing groundwater flow model, field data and the MODFLOW CFP code to develop a model that adequately simulates the hydrological processes in the karstic aquifer. Results show that MODFLOW CFP can be used to model areas where karstic aquifers are developed, providing decisive information about hydrological processes taking place in these aquifers. • A new methodology is developed for combining field data and modelling applications. • Application of the method provides improved results compared to traditional models. • Sensitive parameters for MODFLOW CFP models are highlighted. [ABSTRACT FROM AUTHOR]

Adsorption and bioremediation are effective processes for remediation of benzene, toluene, and ethylbenzene (BTE) through Permeable Reactive Barriers (PRBs). A few researches focus on adsorption of natural zeolite because of its hydrophilic property. On the other hand, PRBs need to be replaced by fresh materials after a while when all the possible absorption positions were filled up. We tried to find a way to increase the efficiency of PRB, elongation of its replacement period and of course decreasing the cost of remediation. Equipping of PRB with microbial degradation system was the idea. The present study describes the performances of natural Clinoptilolite-Heulandite Zeolite (CH-Z) and three new strains (safe and low-cost media) utilized in a PRB for removing BTE from contaminated shallow groundwater. First, batch tests were conducted to recognize the optimal removal conditions for utilization of C-HZ and strains to remediate BTE compounds. Then, an aerobic PRB system filled with a natural zeolite was designed and investigated in a continuous flow sand-tank model to assess the efficiency of combined PRBs (zeolite + biosparging), for BTE-contaminated groundwater. Batch experiments showed that the BTE removal of zeolite was 89%, as well as, a consortium of three bacterial strains, Variovorax sp. OT16, Pseudomonas balearica OT17, and Ornithinibacillus sp. OT18 efficiently removed the BTE mixture. The process of BTE removal in the PRB under continuous-flow condition was divided into three phases: Phase I, in which the barrier was made of the only zeolite, and in Phases II and III the reactor was fed by microorganisms. This experiment revealed that in Phases I, the concentrations of BTE decrease (92%) due to zeolite adsorption. In Phase II and III, the degradation process became the principal removal mechanism (68% and 81%, respectively). Consequently, this research showed high ability of C-HZ in the BTE treatment, and a combination of Natural Zeolite, with a biological degradation system (CH-Z –PRB) improves the efficiency of BTE remediation. However, the slow biodegradation rates and the continuous injection of BTE in the model confirmed that longer time was needed for the PRB to function optimally. Finally, the combined method of CH-Z- BIO PRB showed the great potential in the restriction of the BTE migration that can be used at the field-scale after up-scaling. [Display omitted] • New Composite PRB prepared by natural Zeolite and new bacteria. • Clinoptilolite-Heulandite Zeolite (CH-Z) removed almost 90% of BTE in the PRB. • Bio-PRB removed almost 80% of BTE. • Biodegradation of BTE was accelerated by oxygen injection. • Longevity of PRBs proceeded by biodegradation to increase replacement time of PRB material. [ABSTRACT FROM AUTHOR]

Infiltration of treated wastewater (TWW) to recharge depleted aquifers, often referred to as managed aquifer recharge, is a solution to replenish groundwater resources in regions facing water scarcity. We present a mass balance approach to infer the amounts of five pharmaceuticals (carbamazepine, diclofenac, fenoprofen, gemfibrozil, and naproxen) degraded in column experiments based on concentrations of pharmaceuticals in the aqueous and solid (sorbed) phases. Column experiments were conducted under three different conditions: continuous infiltration, wetting and drying cycles, and wetting and drying cycles with elevated concentrations of antibiotics (which may reduce microbially aided degradation of other compounds). A mass balance comparing pharmaceutical mass in the water phase over the 16-month duration of the experiments to mass sorbed to the soil was used to infer the mass of pharmaceuticals degraded. Results show sorption as the main attenuation mechanism for carbamazepine. About half of the mass of diclofenac was degraded with wetting and drying cycles, but no significant degradation was found for continuous infiltration, while 32% of infiltrated mass sorbed. Fenoprofen was degraded in the shallow and aerobic part of the soil, but degradation appeared to cease beyond 27 cm depth. Gemfibrozil attenuated through a combination of degradation and sorption, with slight increases in attenuation with depth from both mechanisms. Naproxen degraded progressively with depth, resulting in attenuation of >90% of the mass. In the column with elevated concentrations of antibiotics, the antibiotics attenuated to about 50% or less of inflow concentrations by 27 cm depth and within this zone, less degradation of the other compounds was observed. [ABSTRACT FROM AUTHOR]

Abstract As more regions in the world look to replenish depleted aquifers, treated wastewater (TWW) is increasingly infiltrated in managed aquifer recharge (MAR) schemes. While MAR is a promising emerging technology, it also has the potential to generate pollutants along the infiltration flow path. In this study, we infiltrated treated wastewater through an organic-rich soil in column experiments operated with wetting and drying cycles. Ammonium, which was present only in trace concentrations in the TWW, increased in concentration with depth and exceeded the EU Water Framework Directive limit of 0.5 mg/L for up to a year, depending on the sampling depth. Pore water samples collected at the end of drying periods showed very high nitrate concentrations, indicating nitrification of some of the ammonium. Oxidation reduction potential often exceeded 200 mV during drying periods, showing conditions for nitrification, but dropped below −100 mV during wetting periods, creating several possible pathways for ammonium production. Potential sources of ammonium are (1) dissolved organic nitrogen in the TWW, (2) nitrate in the TWW, and (3) organic nitrogen in the soil. δ15N in ammonium in pore water samples (mean 4.7‰) was slightly higher than δ15N in the soil (2.4‰), indicating that the soil was likely the major source but also that nitrate (mean 17.2‰) may have been the source of some of the ammonium. Fractionation of 15N in nitrate as well as high concentrations of acetate (a labile organic carbon source) also indicate that dissimilatory nitrate reduction to ammonium may have formed some of the NH 4 +. Graphical abstract Image 1 Highlights • Infiltration of treated wastewater generated ammonium. • Conditions in the soil were strongly reducing and labile organic carbon was abundant. • Mass balance shows that soil nitrogen was a source of some of the ammonium. • Some ammonium may have been produced by dissimilatory nitrate reduction to ammonium. [ABSTRACT FROM AUTHOR]

Adding biochar to Zn-contaminated soil can immobilize excess Zn and promote plant biomass growth. This was seen previously over the course of a 180-day planted pot trial involving two types of biochar (cattle manure, CM, and grain husk, GH) in a Zn-contaminated soil. Both biochars alleviated Zn-induced phytotoxicity to Ficus by immobilizing Zn and reducing its uptake by the plant, but to different extents. The aim of the current study was to delve into the in-soil mechanisms involved in biochar-mediated Zn immobilization. Biochar particles were excavated from the pot soils. Fresh and aged biochar particles were examined by high-resolution scanning electron microscope (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), field-emission electron probe micro-analyzer (EPMA), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). The physical and chemical properties of the biochars had changed over the 180 days. SEM-EDS and EPMA indicated that organo-mineral micro-agglomerates had formed on biochar surfaces and in pores. Some of the Zn immobilized by the biochars was bound in the organo-mineral complexes of these agglomerates. XPS and FTIR showed that the complexes had a high concentration of oxygenated functional groups which facilitated Zn binding and encapsulation. The micro-agglomerates were similar in structure and composition to those observed on biochars having resided for much longer times in soils, or having been subjected to accelerated aging. Overall, Zn immobilization by the CM biochar was greater than by the GH biochar, due to its higher alkalinity, higher concentration of available negatively charged groups, and greater accretion of organo-mineral layers. These findings are suggestive that biochar-assisted phytorestoration of heavy metal-contaminated soils can be optimized through selection of biochar having such traits. It is hypothesized that metals may be continually taken up in such micro-agglomerates, since they continue to form over the lifetime of the biochar in the soil. [ABSTRACT FROM AUTHOR]

Many hydrologic studies require data on the oxygen and hydrogen stable isotope composition (δ 18 O, δ 2 H) of precipitation and various collector designs have been suggested for gathering corresponding samples. Yet, it is crucial that these collectors, also known as totalizers, prevent evaporation and associated isotope fractionation. Surprisingly, we were unable to find a comprehensive collector intercomparison in the literature, and much less one that addressed hot and arid conditions. In this study, we tested six different collector designs over a period of 32 days. They were filled to 20% of their total volume with water of known isotope composition and placed in a modified laboratory drying oven with a low relative humidity (5%) and a diurnal temperature change of 26 to 45 °C. Evaporative mass losses were determined gravimetrically daily while samples for isotope analyses were collected every four days. The classic Oil collector, featuring a layer of paraffin oil to prevent evaporation, showed the smallest mass losses and no detectable isotope shift. The Tube-dip-in-water collector with pressure equilibration tube also performed well, although we noted somewhat larger mass losses and isotope shifts. The latter accounted for 0.28‰ (Δδ 18 O) and 0.9‰ (Δδ 2 H) after 32 days, which is significant, but in view of the extreme conditions, these changes should be still acceptable for most studies. The remaining collectors (Ball-in-funnel, Floating balls, and Float based) all failed. Under the prevailing conditions, the Tube-dip-in-water collector with pressure equilibration tube seems to represent a good, oil- and thus contamination-free compromise. Nonetheless, also in this system small precipitation amounts are problematic. This may necessitate modifications of the standard design in terms of funnel diameter and bottle geometry. We strongly advise researchers to conduct own tests with their intended collector before field deployment. [ABSTRACT FROM AUTHOR]

The water resources that supply most of the megacities in the world are under increased pressure because of land transformation, population growth, rapid urbanization, and climate-change impacts. Dhaka, in Bangladesh, is one of the largest of 22 growing megacities in the world, and it depends on mainly groundwater for all kinds of water needs. The regional groundwater-flow model MODFLOW-2005 was used to simulate the interaction between aquifers and rivers in steady-state and transient conditions during the period 1981-2013, to assess the impact of development and climate change on the regional groundwater resources. Detailed hydro-stratigraphic units are described according to 150 lithology logs, and a three-dimensional model of the upper 400 m of the Greater Dhaka area was constructed. The results explain how the total abstraction (2.9 million m/d) in the Dhaka megacity, which has caused regional cones of depression, is balanced by recharge and induced river leakage. The simulated outcome shows the general trend of groundwater flow in the sedimentary Holocene aquifers under a variety of hydrogeological conditions, which will assist in the future development of a rational and sustainable management approach. [ABSTRACT FROM AUTHOR]

Summary The major groundwater resources of the Arabian Peninsula are stored in the large sedimentary basins in its eastern part. Evaporation from continental salt pans (playas) is an important process in water resources assessments of its upper principal aquifers – the Upper Mega Aquifer system – as it constitutes a significant sink. However, literature values on evaporation rates vary widely and usually report about coastal salt pans where seawater evaporation is assumed. The present study applies different methods to provide a comprehensive picture of groundwater evaporation from salt pans of the Upper Mega Aquifer system. A remote sensing approach provided the spatial distribution and total salt pan area of about 36,500 km 2 . Hydrochemical and isotopic investigations revealed that from about 10% (3600 km 2 ± 1600 km 2 ) of the mapped salt pan area seawater evaporates. To estimate the groundwater evaporation rate from continental salt pans a laboratory column experiment was set up, implying a mean annual evaporation rate of about 42 mm ± 13 mm. In-situ analysis of water table fluctuations in the field suggested about 3 mm a −1 originate from recently infiltrated rainwater leading to an annual net groundwater evaporation of 39 mm ± 13 mm. Relating this number to the mapped salt pan area, from which groundwater evaporates, provides a total annual groundwater loss of 1.3 km 3 ± 0.5 km 3 for the Upper Mega Aquifer system. [ABSTRACT FROM AUTHOR]

Only limited data on the isotopic and chemical composition of Riyadh rain are currently available. In this study, we complement these data by analyzing integral samples covering 28 precipitation events between 2009 and 2013. Results of stable isotope analyses are used to establish a Local Meteoric Water Line: δ 2 H = 5.22(± 0.38) · δ 18 O + 14.8(± 0.9) ‰. Moisture source-related isotopic fingerprints are masked by the continental effect, the altitude effect, sub-cloud evaporation, and moisture recycling. The study of one event for intra-storm variability revealed strong isotopic depletion due to rainout and Rayleigh distillation processes, thus highlighting the general need for integral samples. Tritium analyses of grab samples from 12 events yielded concentrations between 2.8 and 6.4 tritium units (TU), which are close to the natural background of a few TU. Major ion concentrations and ratios indicate that solutes are predominantly derived from atmospheric dust originating from limestone outcrops and sabkha deposits. The latter play a role with respect to the elevated Cl − and Na + contents, but are probably also responsible for the SO 4 2 − and a part of the Ca 2 + found in Riyadh rain. Observed intra- and inter-storm variabilities of major ion levels necessitate the collection of integral samples and the calculation of precipitation-weighted means, respectively. The obtained isotopic signatures and the precipitation-weighted mean Cl − concentration (9.5 mg L − 1 ) may be useful in groundwater assessments, e.g., for the identification of modern recharge and quantification thereof by means of the Chloride Mass Balance method. [ABSTRACT FROM AUTHOR]

Abstract: Applying a new hybrid numerical and analytical approach in the finite element simulator RockFlow/GeoSys for hydraulic flow and mass transport, the efficiency of the removal of organic contaminants from water using a microporous polypropylene hollow fiber membrane module (HFM) was accurately modeled for a large range of operating conditions. The modeling results were validated against 177 experimental measurements under a wide range of operating conditions for 12 organic compounds with different diffusion coefficients and a wide variety of Henry''s law constants, from Naphthalene at circa 0.017 to 1,1-dichloroethene with circa 1.19. The hybrid numerical analytical approach enables prediction of the removal efficiencies within a few minutes, whereas a pure numerical approach would require several hours to days due to numerical stability controls. The input parameters for the model are defined by the geometry of the HFM and the operating conditions, no empirical formulations are applied. This model allows the investigation of the main factors controlling the removal characteristics, e.g., the dependency on Henry''s law coefficient, gas side diffusional resistance, and aqueous diffusion limitation, and also enables the efficient design of further organic removal systems based on the HFM technology. [Copyright &y& Elsevier]

Increasing water salinity in coastal areas is a concern for the coastal environment. Increased salinity is affecting water quality, freshwater availability, and water-related ecosystems in the southwest coastal region of the Bengal Delta. The study used a synergies and robust approach to assess the possible factors for increasing water salinity in an embanked coastal island in the southwest Bengal Delta. The hydrochemical analysis revealed that surface and groundwater are enriching with Na+ and Cl− concentration, also controlling by seawater through the ion exchange mechanism (Ca2+ and Mg2+ replacing by Na+, and Cl−), mixing stage of water solution (freshwater-saltwater), and anthropogenic salt contamination by human activities (e.g., saltwater shrimp cultivation and excessive irrigation). Piper diagram showed that river water is occupying at the mixing stage of solution, where pond and groundwater are occupying at seawater (saline) zone. The water quality index showed that surface water is not fresh anymore and unsuitable for drinking purposes. The isotope analyses exposed the presence of strong precipitation variance in the study area. Cluster observation analysis showed a strong correlation between Na+, Cl−, and TDS (similarity is 97% to 99%). The remote sensing application illustrated that high salinity zones are in the northern part, and groundwater salinity is higher (7.5 to 8 ppt) in the northern part of polder 32. The salinity of both groundwater and surface water showed a positive correlation with land surface temperature and potential evapotranspiration. The study exposed four responding factors for increasing groundwater salinity in this region, which are - regional surface geological settings, hydrological settings, hydraulic head gradient, and human activities. A conceptual model illustrated the presence of lateral recharge of saltwater from the surrounding tidal rivers to the groundwater. Unlabelled Image • All waters in the study area are mainly Na-Cl types. • Groundwater salinity is approximately 7.5 to 8 ppt in wet season. • Groundwater salinity is higher at the northern part of polder 32 than the southern part. • Surface geology, hydrology, hydraulic head gradient and human activities are responsible for increasing waters salinity. • Waters are unsuitable for drinking purposes owing to increasing salinity in the study area. [ABSTRACT FROM AUTHOR]

The Hazaribagh industrial area in Dhaka city, the capital of Bangladesh, is considered one of the hotspots of chromium (Cr) pollution, due to excessive discharge of Cr contaminated waste over decades by approximately 150 tanneries. In 2000, elevated Cr concentrations were observed in the underlying Dupi Tila Aquifer (DTA), which is heavily deployed for drinking water supply of Dhaka city's population. In the following years, Cr concentrations in the DTA have dropped and apparently stayed low. In 2010, elevated Cr concentrations were found again in the DTA. This study aims to evaluate the status of the total Cr contamination in the surface waters, groundwater, and soils in the area, to clarify the temporal evolution of the total Cr contamination pattern in the DTA. For this, we collected water and soil samples in 2012, 2013, 2014, and 2019 for (hydro)chemical characterization and analyzed new groundwater level data on the development of the cone of depression below the city. Our study indicates that the temporal evolution of the total Cr contamination in the DTA is closely coupled to the groundwater dynamics. The rapid growth of the cone of depression due to excessive pumping resulted (i) in a disconnection of the groundwater table from the heavily contaminated Hazaribagh soils, and (ii) in an increased gradient between the contaminated surface waters and the groundwater, increasing infiltration into the groundwater. Finally, (iii) the further growth of the cone of depression resulted in an inflow of fresh groundwater from the west of Dhaka city, causing a dilution effect. Although in 2017 tanneries were moved out of the Hazaribagh area, the contaminated soils still pose a threat to groundwater quality when groundwater levels would recover. Unlabelled Image • Cr concentrations are highly variable in groundwater of Dupi Tila Aquifer. • Evolution of Cr concentrations in groundwater are coupled to groundwater dynamics. • Overpumping disconnected Cr contaminated soil and surface water from groundwater. [ABSTRACT FROM AUTHOR]

The potential of biochar to enhance phytorestoration of hexavalent chromium [Cr(VI)]-contaminated soils was investigated. Rooted cuttings of Ficus elastica Roxb. Ex Hornem were transplanted to soil treated with 0 or 25 mg kg−1 Cr(VI), ‒Cr and +Cr designations respectively, and amended with cattle manure-derived biochar at 0, 10 and 50 g kg−1. Plants were grown for 180 d in a temperature-controlled greenhouse. In the ‒Cr treatment, biochar addition enhanced plant growth without affecting plant water status, leaf nutrient levels, photochemical efficiency, or hormone levels. In the absence of biochar, Ficus growth in the +Cr treatment was stunted, exhibiting decreased leaf and root relative water content and photochemical efficiency. Adding biochar to +Cr soil resulted in decreased Cr uptake into plant tissues and alleviated the toxic effects of soil Cr(VI) on plant growth and physiology, including decreased leaf lipid peroxidation. High-resolution electron microscopy and spectroscopy elucidated the biochar role in decreasing Cr mobility, bioavailability, and phytotoxicity. Spectroscopic evidence is suggestive that biochar mediated the reduction of Cr(VI) to Cr(III), which was subsequently incorporated into organomineral agglomerates formed at biochar surfaces. The dual function of biochar in improving F. elastica performance and detoxifying Cr(VI) demonstrates that biochar holds much potential for enhancing phytorestoration of Cr(VI)-contaminated soils. • Biochar added to soil enhanced Ficus growth, biomass and physiology. • Biochar protected Ficus against ordinary in planta oxidative metabolic events. • Cr(VI) added to soil decreased photosynthesis and stunted plant growth. • Biochar suppressed Cr phytotoxicity by reducing Cr(VI) to Cr(III). • Biochar was sink for Cr(III) via formation of organomineral complexes. [ABSTRACT FROM AUTHOR]

• Remote sensing ET data is used for a spatially distributed parameter optimization. • The calibration approach is applied for a highly managed hydrological system. • Calibration success is limited due to missing spatial variance of remote sensing ET. • A modified remote sensing ET data set helps to improve calibration. Calibrating a spatially distributed hydrological model of a region with complex and highly diverse agricultural settings is a difficult task. It becomes even more challenging, if major parts of the hydrology are human controlled, e.g. through irrigation agriculture. In this study, a Soil and Water Assessment Tool (SWAT) was set up and calibrated for an entirely managed meso-scale irrigation scheme, where irrigation channels are the only water-courses and no natural streams exist. An automated and spatially distributed model calibration was applied, implementing the global Dynamically Dimensioned Search Algorithm (DDS), and using Kling-Gupta Efficiency (KGE) as objective function. To account for the spatio-temporal heterogeneity of water balance fluxes in the calibration process, remote sensing-derived evapotranspiration (ET) estimates with a spatial resolution of 1 km × 1 km, were used as observational data. Results showed that the automated and spatially distributed model calibration was able to increase the model ET simulation performance from 0.04 to 0.27 KGE. However, a strong land-use dependent goodness-of-fit, ranging from approx. −0.60 KGE to 0.60 KGE for individual land-use types, revealed that the information, extracted from remote sensing-derived ET estimates used in this study, is lacking the necessary spatial heterogeneity. An unsatisfactory spatial comparison between simulated ET and ET derived from remote sensing estimates showed to inhibit better calibration results for the study area, which is characterized by small-scale and diverse cropping patterns. Using a modified remote sensing-derived ET product, which accounts for land-use class dependent ET characteristics, improved the overall calibration results to 0.40 KGE. A cross-validation could indicate a successful application of this automated and spatially distributed model calibration approach, using the modified ET product. [ABSTRACT FROM AUTHOR]

Chlorine dioxide (ClO 2 ) is an oxidant applied in water treatment processes that is very effective for disinfection and abatement of inorganic and organic pollutants. Thereby phenol is the most important reaction partner of ClO 2 in reactions of natural organic matter (NOM) and in pollutant degradation. It was previously reported that with specific reaction partners (e.g., phenol), free available chlorine (FAC) could form as another byproduct next to chlorite (ClO 2 - ). This study investigates the impact of different functional groups attached to the aromatic ring of phenol on the formation of inorganic byproducts (i.e., FAC, ClO 2 - , chloride, and chlorate) and the overall reaction mechanism. The majority of the investigated compounds reacted with a 2:1 stoichiometry and formed 50% ClO 2 - and 50% FAC, regardless of the position and kind of the groups attached to the aromatic ring. The only functional groups strongly influencing the FAC formation in the ClO 2 reaction with phenols were hydroxyl- and amino-substituents in ortho - and para -positions, causing 100% ClO 2 - and 0% FAC formation. Additionally, this class of compounds showed a pH-dependent stoichiometric ratio due to pH-dependent autoxidation. Overall, FAC is an important secondary oxidant in ClO 2 based treatment processes. Synergetic effects in pollutant control and disinfection might be observable; however, the formation of halogenated byproducts needs to be considered as well.

Contamination of groundwater with pharmaceutical active compounds (PhACs) increased over the last decades. Potential pathways of PhACs to groundwater include techniques such as irrigation, managed aquifer recharge, or bank filtration as well as natural processes such as losing streams of PhACs-loaded source waters. Usually, these systems are characterized by redox-active zones, where microorganisms grow and become immobilized by the formation of biofilms, structures that colonize the pore space and decrease the infiltration capacities, a phenomenon known as bioclogging. The goal of this work is to gain a deeper understanding of the influence of soil biofilms on hydraulic conductivity reduction and the fate of PhACs in the subsurface. For this purpose, we selected three PhACs with different physicochemical properties (carbamazepine, diclofenac, and metoprolol) and performed batch and column experiments using a natural soil, as it is and with the organic matter removed, under different biological conditions. We observed enhanced sorption and biodegradation for all PhACs in the system with higher biological activity. Bioclogging was more prevalent in the absence of organic matter. Our results differ from works using artificial porous media and thus reveal the importance of utilizing natural soils with organic matter in studies designed to assess the role of soil biofilms in bioclogging and the fate of PhACs in soils.

Shwan sub-Basin is one of the substantial groundwater sources in northern Iraq. Along with an increase in population, agricultural and industrial activities synced with the change in climate conditions, all could have a negative impact on the hydrochemistry of groundwater. Therefore, it becomes crucial to investigate the different processes that could affect hydrochemistry and water quality. Thirty-two groundwater samples were collected from wells distributed in the study area, and one surface water sample from Lesser Zab River, all water samples were gathered during two seasons. Hydrogeochemical model was performed on physiochemical analysis results by using PHREEQC software to understand the geochemical reactions occurring in groundwater. The results of the Saturated Index showed supersaturated values for calcite, aragonite and dolomite in groundwater samples during the first season in a percent of 84%. While the second season samples were supersaturated in percent of 40.6%, 37.5% and 46.8% for aragonite, calcite and dolomite minerals respectively. The Saturated Index shows supersaturated values of quartz mineral in most groundwater samples, which are sourced from the abundance of silicate minerals that are primarily included within the ambient rock materials of the tertiary and quaternary clastic aquifer system in the study region. The saturated index showed undersaturated values with most minerals of feldspar, halide and sulfate. However, these minerals were in a dissolution state, releasing significant amounts of Ca 2+ , Na + , Mg 2+ , HCO 3 - , Cl ⁻ and SO 4 2- ions into the solution. Most of the groundwater samples were classified as earth-alkaline water with an increased portion of alkali with prevailing bicarbonate for two seasons, except the groundwater sample W2 was classified as earth-alkaline water with an increased portion of alkali with prevailing SO 4 2⁻ and Cl ⁻ . The water quality for human drinking was evaluated using the water quality index (WQI). The values of WQI were from 51.9 to 99.2 and from 53.9 to 88.5 for the first and the second seasons respectively. WQI revealed that most of the samples were classified as poor to very poor water quality, except the Lesser Zab River sample for the second season was good water quality and the sample W2 for the first season was unsuitable for drinking purposes., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Authors.)

In this study, we analyzed the concentration distributions of 20 polycyclic aromatic hydrocarbons (PAHs) in 41 water samples which were collected from the northern part of Taihu Lake during 4 field campaigns (201511, 201606, 201702 and 201709). The concentrations were determined with GC-MS, and their spatial and seasonal distribution characteristics were interpreted. The results show that 2-ring PAHs present considerably higher concentrations in warm seasons than cold seasons, but the concentrations of the other higher-ring PAHs are rather stable in warm and cold seasons. The distribution patterns of these PAHs might be mainly attributed to ambient temperature effects on the PAH solubility in the water body. Meanwhile, the spatial distributions of the PAH concentrations in cold seasons were rather various in the sampling area, while the distributions in the warm seasons were homogeneous. The different distributions could result from the water recharge from the Yangtze River during cold seasons, which diluted PAH concentrations in the northeastern part of the lake. Furthermore, via literature review on PAH concentrations in water body, PAHs are in a wide range of levels and their patterns are different among the studies, which should be more effected by local factors instead of general PAH properties. The results from this study also present special characteristics of PAHs in Taihu Lake, which exhibit more insight on PAHs existence in water bodies., (© 2022. The Author(s).)

Lake Urmia is one of the largest hypersaline lakes on earth with a unique biodiversity. Over the past two decades the lake water level declined dramatically, threatening the functionality of the lake's ecosystems. There is a controversial debate about the reasons for this decline, with either mismanagement of the water resources, or climatic changes assumed to be the main cause. In this study we quantified the water budget components of Lake Urmia and analyzed their temporal evolution and interplay over the last five decades. With this we can show that variations of Lake Urmia's water level during the analyzed period were mainly triggered by climatic changes. However, under the current climatic conditions agricultural water extraction volumes are significant compared to the remaining surface water inflow volumes. Changes in agricultural water withdrawal would have a significant impact on the lake volume and could either stabilize the lake, or lead to its complete collapse.

When biochar (BC) is applied to soil, one process that can alter its properties and contaminant sorption is the leaching of minerals and dissolved organic carbon (DOC). This study investigated changes in properties of three BCs (cattle manure, grain husk, and wood chips), due to leaching, and the subsequent impact on sorption of trichloroethylene (TCE) and tetrachloroethylene (PCE). The manure-derived BC released 27.4 mg g -1 DOC, which is over ten times more than that measured for the two plant-based BCs (2.5 and 1.5 mg g -1 DOC for grain husk and wood chips, respectively). In all leachates, potassium is the dominant cation, whereas chloride, sulfate, and phosphate are the main anions. In total, the manure-derived biochar released the highest sum of total ions (73.1 mg g -1 ), followed by BC produced from grain husk (15.5 mg g -1 ) and wood chips (1.2 mg g -1 ). Leaching increased external surface area, mesopore volume, and hydrophobicity of the manure-derived BC and decreased its polarity. This enhanced sorption via partitioning. In plant-based BCs, micropore volume and size distribution were altered, most likely through the un-blocking of pores, causing increased sorption via pore-filling for both TCE and PCE. The results indicate that, depending on feedstock material, BC leaching can alter the environmental fate of organic compounds.

In the present work, we analyzed the concentration patterns of 20 Polycyclic Aromatic Hydrocarbons (PAHs) in 25 surface sediments and 11 sediment cores from the northern part of Taihu Lake, China. Three of the cores were dated based on 137 Cs activity for the deposition age of the sediment. The spatial distributions of the PAH concentrations show that the inflow rivers into Zhushan Bay and Meiliang Bay were the main pathway for PAHs and sediment input to the northern part of the lake. This results in substantially higher PAH concentrations (up to 5000 ng/g) and sedimentation rates (higher than the average of 3-4 mm/a) in the area close to the river outlets. In addition, results also show that PAH concentrations in the sediments considerably increased from the early 1960s, but the decreasing concentrations in the upper layers of the sediment could be attributed to the introduction of measures on environmental improvement from ca. 2000. There were both anthropogenic and biogenic origins of perylene in the lake sediments, which were distinguished based on spatial distribution patterns and also the concentration proportions of perylene to the sum of the 20 PAHs. In the cores collected close to river outlets, the concentration proportions of perylene typically range from 0.02 to 0.18 and there are significant positive linear correlations between the concentration of perylene and three anthropogenic PAHs (Benzo[a]pyrene, Benzo[e]pyrene, Pyrene), suggesting that perylene was dominated by anthropogenic input. However, the cores collected further away from the river outlets show the concentration proportions between 0.13 and 0.96, and present significant negative correlations or no correlations between perylene and the three PAHs, suggesting that perylene was mainly formed by biogenic activities. Furthermore, the different perylene sources accompanied with the location distributions imply that anthropogenic activities could inhibit its biogenic formation., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The ability of a soil to sustain infiltration rates and to attenuate pollutants is critical for the design and operation of Managed Aquifer Recharge/Soil Aquifer Treatment and phyto-treatment schemes, also referred to as "Blue Infrastructures". We investigated the buffering capacity of a sediment sample and a peat soil sample for nutrients and selected pharmaceutical compounds and its evolution under continuous infiltration of secondary treated wastewater (TWW) in column experiments. Samples were obtained from two blue infrastructures, the Sant'Alessio Induced River Bank Filtration plant and the San Niccolò large-scale phyto-treatment plant in Italy, and were mainly different in their organic carbon contents (0.9 and 48%, respectively). In the column experiments, a constant infiltration rate of about 0.5 L/d was maintained for 6 months. After 4 months of operation, diclofenac and carbamazepine were spiked into the TWW to evaluate their fate. Water quality was monitored by periodic water sampling from the column inflow, at sampling ports along the column length, and at the outflow. Hydraulic conductivity (K) was also monitored. The hydraulic conductivity of the Sant'Alessio sediment decreased by a factor of 10 during the first 10 days of infiltration and then stabilized, while for the San Niccolò K (initially lower) remained constant for 50 days until it decreased following a change of the redox condition in the column. The different redox conditions, due to the two different soils tested, influenced also the concentration and mobility of PO 4 3- , Fe, Mn, and NPOC, and the speciation of the redox sensitive elements (nitrogen and sulfur). NOPC and phosphate were enriched during the filtration through San Niccolò peat soil (from 2 to 4 times, respectively), while they were buffered by the Sant'Alessio sediment (from 0.2 to 0.4 times, respectively). Diclofenac removal (69% and below 20% for San Niccolò and Sant'Alessio, respectively) was related to sorption and degradation processes and it was lower than the removal of carbamazepine in both soils (76 and 35%). The buffer capacity differences between the two soils were higher for diclofenac (62%) than carbamazepine (35%). Nevertheless, since no apparent degradation of carbamazepine was detected in both soils, its persistence in the soil may have a larger impact in case of desorption, posing contamination risk to groundwater. The results highlight the importance of the soils or sediments to be used as medium in such nature-based solutions for their operations. They also offer an approach to, e.g., tailor man-made soil layers in infiltration basins. We strongly suggest that soil characteristics and test duration are carefully considered in designing these infrastructures, when nature-based processes are the choice for dealing with reuse of treated wastewater management issues.

Biochar is increasingly deemed a potential sorbent for contaminants in soil and water remediation. We tested three biochars from different feedstocks (cattle manure, grain husk, and wood chips) produced at relatively low pyrolysis temperature (450 °C), for their sorption behavior towards trichloroethylene (TCE) and tetrachloroethylene (PCE) in single- and bi-solute systems. In single-solute experiments, all biochars show stronger sorption for TCE (about 50% based on solubility-normalized Freundlich coefficients). The lower sorption of PCE is attributed to steric effects, e.g. size exclusion in small micropores and specific interactions. Plant-derived, carbon-rich biochars with high specific surface area and microporosity predominantly sorb via pore-filling, as also observed in activated carbon. Biochar produced from manure, with higher ash content and polarity, and smaller total pore volume (PV tot ), shows significant contribution of partitioning. These findings also apply to bi-solute systems. TCE and PCE show different competition behavior depending on biochar properties. Plant-based biochars are pore-filling-dominated and show strong competition. However, competition behavior in microporous biochars depends on the concentration range. Manure biochar with high polarity and low PV tot shows significant partitioning and therefore less competition. Compared to the plant-based chars competition in manure biochar is not concentration-dependent. These results indicate that biochars with a large fraction of non-carbonized phase facilitate non-competitive sorption and might be a valuable sorbent in mixed contaminant systems., (Copyright © 2018 Elsevier Ltd. All rights reserved.)