A correlational study of uranium in groundwater with other physicochemical parameters using GIS mapping in Godda district of Jharkhand, India.

The present research concentrates on the cumulative use of GPS and GIS technologies, which are excellent resources for analyzing and monitoring divergent physicochemical parameters in groundwater, including pH, TDS, EC, ORP, Ca+2, Mg+2, NO3-, F-, SO4-2, Cl- and PO4-3 with explicit regard to uranium. Garmin GPS is used to record the locations of the sampling points in the Godda study area. The research aims to offer a thorough understanding of the relationship between soil and water, its impact on public health and the extent to which water can be used in various ways based on its quality. Utilizing the inverse distance weighted (IDW) technique, it is examined how these groundwater parameters and the Water Quality Index (WQI) can be estimated spatially. Additionally, a correlation analysis of the water quality parameters is computed to estimate the local population's cancer risk living in the study area. Except for calcium and magnesium, which are present in excess concentrations throughout the study area with the highest values of 325 and 406 mg/l, respectively at Amediha and Meherma, the results showed that the maximum concentration parameters are within limits with the standard. The main reason might be the area's predominance of Alfisol soil type. The radioactive element uranium is found to be in a limited  range. Chemo-toxicity and radiological risk assessment of the whole area lie far below the restricted cancer risk limit i.e., 30 ppb with the highest concentration of 14 ppb in the 'Sunderpahari' region, following the results obtained. The WQI for the area ranges from 'good' to 'very poor.' The results were favorable but a few sites such as 'Boarijor' and its surroundings, require additional attention to enhance groundwater quality. Given uranium's low availability in groundwater the region's cancer risk assessment is below average.

Uranium and lanthanum in Norwegian drinking water - Is there cause for concern?

Due to natural conditions such as geology, topography, and climate, and historical features such as resource utilization, land use, and settlement patterns, the drinking water supply in Norway is separated into many public and private water supply systems. This survey sheds light on whether the Drinking Water Regulation's limit values provide a sufficient basis for ensuring safe drinking water for the Norwegian population. Participating waterworks, both private and public, were spread throughout the country, in 21 municipalities with different geological conditions. The median value for the number of persons supplied by the participating waterworks was 155. The two largest waterworks, both of which supply >10,000 people, have water sources from unconsolidated surficial sediments of latest Quaternary age. Fourteen waterworks have water sources from bedrock aquifers. Raw and treated water were analysed for 64 elements and selected anions. The concentration of manganese, iron, arsenic, aluminium, uranium, and fluoride exceeded the respective drinking water regulations' parametric value given in Directive (EU) 2020/2184. Regarding the rare earth elements, neither WHO, EU, USA nor Canada have established any limit values. However, concentration of lanthanum in groundwater from a sedimentary well exceeded the health-based guideline value that applies in Australia. Results from this study raise the question of whether increased precipitation can have an impact on the mobility and concentration of uranium in groundwater from bedrock aquifers. Furthermore, findings of high levels of lanthanum in groundwater create uncertainty as to whether the current quality control of Norwegian drinking water is sufficient.

Historic and Contemporary Surface Disposal of Produced Water Likely Inputs Arsenic and Selenium to Surficial Aquifers.

Oil and gas development generates large amounts of wastewater (i.e., produced water), which in California has been partially disposed of in unlined percolation/evaporation ponds since the mid-20th century. Although produced water is known to contain multiple environmental contaminants (e.g., radium and trace metals), prior to 2015, detailed chemical characterizations of pondwaters were the exception rather than the norm. Using a state-run database, we synthesized samples (n = 1688) collected from produced water ponds within the southern San Joaquin Valley of California, one of the most productive agricultural regions in the world, to examine regional trends in pondwater arsenic and selenium concentrations. We filled crucial knowledge gaps resulting from historical pondwater monitoring by constructing random forest regression models using commonly measured analytes (boron, chloride, and total dissolved solids) and geospatial data (e.g., soil physiochemical data) to predict arsenic and selenium concentrations in historical samples. Our analysis suggests that both arsenic and selenium levels are elevated in pondwaters and thus this disposal practice may have contributed substantial amounts of arsenic and selenium to aquifers having beneficial uses. We further use our models to identify areas where additional monitoring infrastructure would better constrain the extent of legacy contamination and potential threats to groundwater quality.

Investigation of Potential Drivers of Elevated Uranium Prevalence in Indian Groundwaters with a Unified Speciation Model.

Elevated uranium (U) (>WHO limit of 30 µg L-1) in Indian groundwaters is primarily considered geogenic, but the specific mineralogical sources and mechanisms for U mobilization are poorly understood. In this contribution, statistical and geochemical analyses of well-constrained metadata of Indian groundwater quality (n = 342 of 8543) were performed to identify key parameters and processes that influence U concentrations. For geochemical predictions, a unified speciation model was developed from a carefully compiled and updated thermodynamic database of inorganic, organic (Stockholm Humic model), and surface complexation reactions and associated constants. Critical U contamination was found at shallow depths (<100 m) within the Indo-Gangetic plain, as determined by bivariate nonparametric Kendall's Taub and probability-based association tests. Analysis of aquifer redox states, multivariate hierarchical clusters, and principal components indicated that U contamination was predominant not just in oxic but mixed (oxic-anoxic) aquifers under high Fe, Mn, and SO4 concentrations, presumably due to U release from dissolution of Fe/Mn oxides or Fe sulfides and silicate weathering. Most groundwaters were undersaturated with respect to relevant U-bearing solids despite being supersaturated with respect to atmospheric CO2 (average pCO2 of reported dissolved inorganic carbonate (DIC) data = 10-1.57 atm). Yet, dissolved U did not appear to be mass limited, as predicted solubilities from reported sediment concentrations of U were ∼3 orders of magnitude higher. Integration of surface complexation models of U on typical aquifer adsorbents, ferrihydrite, goethite, and manganese dioxide, was necessary to explain dissolved U concentrations. Uranium contamination probabilities with increasing dissolved Ca and Mn exhibited minima at equilibrium solubilities of calcite [∼50 mg L-1] and rhodochrosite [∼0.14 mg L-1], respectively, at an average groundwater pH of ∼7.5. A potential indirect control of such U-free carbonate solids on U mobilization was suggested. For locations (n = 37) where dissolved organic carbon was also reported, organic complexes of U contributed negligibly to dominant U speciation at the groundwater pH. Overall, the unified model suggested competitive dissolution-precipitation and adsorption-desorption controls on U speciation. The model provides a quantitative framework that can be extended to understand dominant mobilization mechanisms of geogenic U in aquifers worldwide after suitable modifications to the relevant aquifer parameters.

Nitrogen and phosphorus budget in an intensive irrigation area and effects on littoral water and groundwater (Yaqui Valley, Northwestern Mexico).

The Yaqui River Irrigation District is a region in Mexico with intensive agricultural production; thus, large quantities of fertilizers are used, and excess fertilizer can affect the quality of water bodies. The aim of this work was to estimate the water budget and nitrogen (N) and phosphorous (P) mass budgets to evaluate possible contamination of a littoral water body (Tóbari Bay) and leachates into an aquifer (Yaqui Valley aquifer). Wheat and corn crops were studied, climate information was compiled, and soil and water samples were collected for analysis. The water budget showed excess irrigation occurred due to the need for soil washing to prevent salinization. A total of 24% of all irrigation water was used for crops, 60% was discharged into the bay through runoff of the drainage system, and 16% corresponded to effective infiltration (aquifer recharge). The N budget showed that of the 100% N input, the highest percentage was used by plants (63%), and only minimal loss occurred through runoff (11%) and leachate into the aquifer (7%). The remaining N stayed in the soil (18%) or was volatilized (1%). These results indicate that the drainage system prevented large amounts of N from entering the aquifer; thus, the N concentrations in the groundwater did not exceed the regulated maximum limit for drinking water (10 mg N-NO3/L). In terms of the water pollution level in the bay, the presence of NO3- was minimal (concentrations below the quasintifiable limit). Of the 100% of P that was applied, 55% was used by the plants, and 40% remained in the soil; therefore, the P that was transported by runoff or was leached was minimal (3 and 2%, respectively). However, this minimal amount of P ranged from 0.1 to 0.2 mg/L in the bay, and these values exceeded the suggested values for the protection of aquatic life (0.01 mg/L). The administrators of the irrigation district must pay special attention to phosphate fertilizer management and implement irrigation techniques that increase water use efficiency.

Comprehensive assessment of water quality and associated health risks in an arid region in south Iran.

This study aims at investigating the quality of drinking water and evaluating the non-carcinogenic risk of fluoride and nitrate ions in drinking water, and fluoride in tea in Zarrin Dasht, Iran. We focus on tea since it is the most popular drink among Iranian people and in the study region. We collected and analyzed 23 drinking water samples and 23 tea samples from different locations in the study region. Based on the water quality index, the consumed drinking water does not have a good quality in most Zarrin Dasht areas. Accordingly, the water quality index (WQI) is poor and very poor in 70% and 13% of the water samples, respectively. The average fluoride concentration of the tea samples is 2.71 mg/L. The mean values of Fluoride Hazard Index (HIfluoride) are 3.77, 2.77, and 2.33 for children, teenagers, and adults, respectively, which are higher than the safe limit of 1. The Nitrate Hazard Index (HInitrate) is higher than the safe limit of 1 in 8.7% of the samples. The results of the Monte Carlo simulation demonstrate that HIfluoride and HInitrate are higher than 1 in all the groups, except for adults. According to the results of the sensitivity analysis, ingestion rate and body weight have a large effect on HIfluoride and HInitrate, but body weight is inversely associated with sensitivity. According to the Piper diagram, saline water is the predominant type in Zarrin Dasht. Besides, the results of the principal component analysis (PCA) show a high correlation between fluoride and pH, which could be related to the effect of pH on fluoride dissolution and ion exchange. Therefore, appropriate measures are recommended to be taken in order to reduce the amount of fluoride in the drinking water resources of this region. Reduction of tea consumption can also be considered an important factor in decreasing the amount of fluoride intake.

Assessment of U and As in groundwater of India: A meta-analysis.

More than 2.5 billion people depend upon groundwater worldwide for drinking, and giving quality water has become one of the great apprehensions of human culture. The contamination of Uranium (U) and Arsenic (As) in the groundwater of India is gaining global attention. The current review provides state-of-the-art groundwater contamination with U and As in different zones of India based on geology and soil texture. The average concentration of U in different zones of India was in the order: West Zone (41.07 µg/L) > North Zone (37.7 µg/L) > South Zone (13.5 µg/L)> Central Zone (7.4 µg/L) > East Zone (5.7 µg/L) >Southeast Zone (2.4 µg/L). The average concentration of As in groundwater of India is in the order: South Zone (369.7 µg/L)>Central Zone (260.4 µg/L)>North Zone (67.7 µg/L)>East Zone (60.3 µg/L)>North-east zone (9.78 µg/L)>West zone (4.14 µg/L). The highest concentration of U and As were found in quaternary sediments, but U in clay skeletal and As in loamy skeletal. Results of health risk assessment showed that the average health quotient of U in groundwater for children and adults was less than unity. In contrast, it was greater than unity for As posing a harmful impact on human health. This review provides the baseline data regarding the U and As contamination status in groundwater of India, and appropriate, effective control measures need to be taken to control this problem.

Identification and quantification of chemical reactions in a coastal aquifer to assess submarine groundwater discharge composition.

In coastal aquifers, two opposite but complementary processes occur: Seawater intrusion (SWI), which may salinize heavily exploited aquifers, and Submarine groundwater discharge (SGD) which transports oligo-elements to the sea. Aquifers are expected to be chemically reactive, both because they provide abundant surfaces to catalyze reactions and the mixing of very different Fresh Water (FW) and Sea Water (SW) promote numerous reactions. Characterizing and quantifying these reactions is essential to assess the quality and composition of both aquifer water, and SGD. Indeed, sampling SGD is difficult, so its composition is usually uncertain. We propose a reactive end-member mixing analysis (rEMMA) methodology based on principal component analysis (PCA) to (i) identify the sources of water and possible reactions occurring in the aquifer and (ii) quantify mixing ratios and the extent of chemical reactions. We applied rEMMA to the Argentona coastal aquifer located North of Barcelona that contains fluvial sediments of granitic origin and overlies weathered granite. The identification of end members (FW and SW) and the spatial distribution of their mixing ratios illustrate the application procedure. The extent of reactions and their spatial distribution allow us to distinguish reactions that occur as a result of mixing from those caused by sediment disequilibrium, which are relevant to recirculated saltwater SGD. The most important reaction is cation exchange, especially between Ca and Na, which promotes other reactions such as Gypsum and Fluorite precipitation. Iron and Manganese are mobilized in the SW portion but oxidized and precipitated in the mixing zone, so that Fe (up to 15 µEq/L) and Mn (up to 10 µEq/L) discharge is restricted to SW SGD. Nitrate is reduced in the mixing zone. The actual reaction amounts are site-specific, but the processes are not, which leads us to conjecture the importance of these reactions to understand the SGD discharge elsewhere.

Assessment of groundwater geochemistry using multivariate water quality index and potential health risk in industrial belt of central Odisha, India.

Groundwater in India has been shown to have a variety of water quality issues, including fluoride, nitrate, and uranium pollution, all of which pose a health risk to humans. In the present study, a total of 106 groundwater samples from the Angul district of Odisha, an industrialized region in India, were analyzed for 14 different hydrochemical parameters. In almost 30%, 34.9%, and 4.7% of the groundwater samples, the concentrations of F-, NO3- and uranium, respectively, exceeded the permissible limit set by WHO. In addition to the fixed-weight groundwater quality index (GWQI), the entropy-weighted water quality index (EWQI), the principal component analysis (PCA) factor (or rotated factor) loading based water quality index (PCWQI) and human health risk assessment were used. Depending on the models, about 19.1 ± 0.9%, 70.5 ± 1.9% and 10.38 ± 1.9% of water samples were classified as "Excellent", "Good" and "Medium" quality, respectively, across four water quality indexes with a nominal rating disagreement of 11.3%. More than 90% of samples are unanimously classified as excellent or good across the WQI rating. For children and adults, approximately 54.7% and 24.5% of samples exceeded the permitted limit for F-, (hazard quotient HQ > 1), posing non-carcinogenic health hazards, respectively. In contrast, 71.7% and 34.9% of NO3- samples respectively, surpassed the allowed limit and caused non-carcinogenic health concerns for children and adults. In terms of carcinogenic HQ values, about 13.2% and 7.5% of samples exhibit an uranium related carcinogenic health risk in children and adults, respectively. The existence of significant amounts of Cl -, NO3-, and especially HCO3- ions in groundwater in some samples, as well as their positive interdependence, may increase uranium pollution in the future through uranium dissolution.

Integrated remediation for organic-contaminated site by forcing running-water to modify alkali-heat/persulfate via oxidation process transfer.

As organic pollution of soil and groundwater increases, the effective and economical remediation of contaminated sites has drawn growing attention. In this study, running-water (RW) was designed to modify alkali-heat/persulfate (MAH/PS) for integrated remediation of an actual organic-contaminated site. The degradation efficiency mainly reached 60%-99% for Benz[a]anthracene, Benzo[a]pyrene and total petroleum hydrocarbons (TPHs). MAH/PS was more effective in degrading Benzene and 1,2-Dichloroethane with simple molecular configurations. The pollutant degradation efficiencies decreased with increasing site depth and increased with increasing pollutant concentrations. Migration with RW enhanced site remediation. By monitoring the groundwater after remediation, it was found that residual TPHs presented anomalous diffusion; SO42- ranged from 8.00 to 237.00 mg L-1 to 8.00-290.00 mg L-1 and pH presented alkalescence (7.00-8.20). Mathematical models were established to describe the reaction process including the solubility equilibrium of calcium hydroxide, temperature equilibrium, and reaction kinetics. Moreover, MAH/PS provided a cost-saving approach for site remediation.

Inflammation response after the cessation of chronic arsenic exposure and post-treatment of natural astaxanthin in liver: potential role of cytokine-mediated cell-cell interactions.

Ongoing groundwater arsenic contamination throughout China was first recognized in the 1960s. Groundwater arsenic contamination is a high risk for human and animal health worldwide. Apart from drinking water, diet is the second pathway for arsenic to enter the human body and eventually cause liver injury. Natural astaxanthin extracted from the green algae Haematococcus pluvialis has dominated the nutraceutical market for potential health benefits. Nevertheless, the molecular mechanism underlying the protective effect post astaxanthin against arsenic-induced hepatotoxicity remains largely obscure. In this study, we investigate the effect of natural astaxanthin (derived from Haemotococcus pluvialis) on oxidative stress and liver inflammatory response in rats after the cessation of chronic arsenic exposure. Wistar rats were given astaxanthin (250 mg kg-1) daily for 2 weeks after the cessation of exposure to sodium arsenite (300 µg L-1, drinking water, 24 weeks) by intragastric administration. The results showed that post treatment with astaxanthin attenuated liver injury induced by long-term exposure to arsenic in rats. Most importantly, post treatment with astaxanthin decreased the increasing of inflammatory cytokine NF-κB, tumor necrosis factor-α, interleukin-1ß, oxidative stress level, and total arsenic content in livers of rats exposed to arsenic. In addition, post treatment with astaxanthin reversed the increasing of protein levels of alpha-smooth muscle actin and collagen Iα1, which are the activation markers of hepatic stellate cells (HSCs). Collectively, these data demonstrate that post astaxanthin treatment attenuates inflammation response in the liver after the cessation of chronic arsenic exposure via inhibition of cytokine-mediated cell-cell interactions. Daily ingestion of natural astaxanthin might be a potential and beneficial candidate for the treatment of liver damage after the cessation of chronic exposure to sodium arsenite.

Sobol sensitivity analysis for risk assessment of uranium in groundwater.

The exposure to uranium (U) in the natural environment is primarily through ingestion (eating contaminated food and drinking water) and dermal (skin contact with U powders/wastes) pathways. This study focuses on the dose assessment for different age-groups using the USEPA model. A total of 156 drinking water samples were tested to know U level in the groundwater of the study region. Different age-groups were selected to determine the human health impact due to uranium exposure in the residing populations. To determine the relative importance of each input, a variance decomposition technique, i.e., Sobol sensitivity analysis, was used. Furthermore, different sample sizes were tested to obtain the optimal Sobol sensitivity indices. Three types of effects were evaluated: first-order effect (FOE), second-order effect (SOE) and total effect. The result of analysis revealed that 17% of the samples had U concentration above 30 µg l-1 of U, which is the recommended level by World Health Organization. The mean hazard index (HI) value for younger age-group was found to be less than 1, whereas the 95th percentile value of HI value exceeded for both age-groups. The mean annual effective dose of U for adults was found to be slightly higher than the recommended level of 0.1 m Sv year-1. This result signified that adults experienced relatively higher exposure dose than the children in this region. Sobol sensitivity analysis of FOE showed that the concentration of uranium (Cw) is the most sensitive input followed by intake rate (IR) and exposure frequency. Moreover, the value of SOE revealed that interaction effect of Cw - IR is the most sensitive input parameter for the assessment of oral health risk. On the other hand, dermal model showed Cw - F as the most sensitive interaction input. The larger value of SOE was also recorded for older age-group than for the younger group.

Occurrence and Distribution of Uranium in a Hydrological Cycle around a Uranium Mill Tailings Pond, Southern China.

Uranium (U) mining activities, which lead to contamination in soils and waters (i.e., leachate from U mill tailings), cause serious environmental problems. However, limited research works have been conducted on U pollution associated with a whole soil-water system. In this study, a total of 110 samples including 96 solid and 14 water samples were collected to investigate the characteristics of U distribution in a natural soil-water system near a U mining tailings pond. Results showed that U concentrations ranged from 0.09 ± 0.02 mg/kg to 2.56 × 104± 23 mg/kg in solid samples, and varied greatly in different locations. For tailings sand samples, the highest U concentration (2.56× 104 ± 23 mg/kg) occurred at the depth of 80 cm underground, whereas, for paddy soil samples, the highest U concentration (5.22 ± 0.04 mg/kg) was found at surface layers. Geo-accumulation index and potential ecological hazard index were calculated to assess the hazard of U in the soils. The calculation results showed that half of the soil sampling sites were moderately polluted. For groundwater samples, U concentrations ranged from 0.55 ± 0.04 mg/L to 3.36 ± 0.02 mg/L with a mean value of 2.36 ± 0.36 mg/L, which was significantly lower than that of percolating waters (ranging from 4.56 ± 0.02 mg/L to 12.05 ± 0.04 mg/L, mean 7.91 ± 0.98 mg/L). The results of this study suggest that the distribution of U concentrations in a soil-water system was closely associated with hydrological cycles and U concentrations decreased with circulation path.

Bioavailability of selenium (Se) in cattle population in Sri Lanka based on qualitative determination of glutathione peroxidase (GSH-Px) activities.

Glutathione Peroxidase activity in whole blood is well correlated with the Selenium (Se) levels in cattle hence can be used effectively to assess the supply of Se to farm animals. In this study, Se status of cattle from five different geographic regions of Sri Lanka were assessed based on glutathione peroxidase (GSH-Px) activity. The GSH-Px activity was determined in whole blood samples collected from 80 cattle from 31 different farms in five districts viz. Kandy, Anuradhapura, Batticoloa, Trincomalee and Jaffna using photometric method. Mean GSH-Px activity was found to be 825, 1239, 1039, 849 and 1307 µkat L-1 in above districts, respectively while the reference value was considered as 665.4 µkat L-1. Among the studied animals, insufficient Se levels were detected in 50%, 17%, 9%, 27% and 5%, respectively, from above districts. Kruskal Wallis test indicated a significant variation among the sampled locations with respect to the GSH-Px activity (p = 0.001). Selenium content in pasture and water collected from studied locations varied from 6.0 to 554 µg kg-1 and < 0.03-1.14 µg L-1, respectively. The lower Se levels in feeds recorded from Kandy region infer the lower GSH-Px activity in the animals from the same region. This variability may be due to differences in nutrient supply, age and species of cattle, and lactation stage. Although the assessing method has some limitations, the activity of GSH-Px of the samples indirectly confirms that considerable numbers of cattle from Sri Lanka are with insufficient selenium levels.

Assessment of radioactivity contents in bedrock groundwater samples from the northern region of Saudi Arabia.

Recognizing the vast uses of water in human life, the presence of α and ß particles emitting radionuclides in groundwater of northern Saudi Arabia has been evaluated as a means of water quality assessment of the region. A liquid scintillation counting technique was used to determine the gross α/ß, and 228Ra radioactivities in water samples, while the radioactivity concentrations of 234,238U and 226Ra were determined using alpha spectrometry after the separation process. Present results show that all water samples contain a higher level of gross α and ß radioactivity than the WHO recommended limits; the average gross α activity is about 7 times greater than the limit value of 0.5 Bq L-1, while the average gross ß activity value is about 3.5 times greater than the limit value of 1 Bq L-1. Correlations of TDS and pH with gross α and ß radioactivity in the studied samples were investigated. The activity ratio of the measured U and Ra alpha emitters to the gross α radioactivity and the ratio of the measured ß emitters to gross ß radioactivity were also discussed. Furthermore, interesting information on thorium abundance and radioactive disequilibrium in U series were observed by studying the activity ratio of 228Ra/226Ra, 226Ra/238U, and 234U/238U. Although these samples are not directly used for human being drinking, and mainly used in irrigation, the higher gross α/ß radioactivity may cause health risks to humans, since these radionuclides may enter the food chain through irrigation water. Thus, further radioactive risk assessment is highly recommended.

Quantification of Elemental Contaminants in Unregulated Water across Western Navajo Nation.

The geologic profile of the western United States lends itself to naturally elevated levels of arsenic and uranium in groundwater and can be exacerbated by mining enterprises. The Navajo Nation, located in the American Southwest, is the largest contiguous Native American Nation and has over a 100-year legacy of hard rock mining. This study has two objectives, quantify the arsenic and uranium concentrations in water systems in the Arizona and Utah side of the Navajo Nation compared to the New Mexico side and to determine if there are other elements of concern. Between 2014 and 2017, 294 water samples were collected across the Arizona and Utah side of the Navajo Nation and analyzed for 21 elements. Of these, 14 elements had at least one instance of a concentration greater than a national regulatory limit, and six of these (V, Ca, As, Mn, Li, and U) had the highest incidence of exceedances and were of concern to various communities on the Navajo Nation. Our findings are similar to other studies conducted in Arizona and on the Navajo Nation and demonstrate that other elements may be a concern for public health beyond arsenic and uranium.

Removal of U(VI) by sugar-based magnetic pseudo-graphene oxide and its application to authentic groundwater using electromagnetic system.

Uranium U(VI) is toxic even at trace levels in aqueous solution and has adverse impacts on the health of human beings. In this study, a sugar-based magnetic pseudo-graphene oxide (SMGO) composite was prepared for the removal of U(VI) from groundwater by graphitization of sugar and ozonation, as well as synthesis with nano-size magnetite particles. To investigate the applicability of SMGO, U(VI)-spiked groundwater as well as U(VI)-contaminated groundwater samples were used in electromagnetic system. The pH-edge adsorption results suggest that adsorption occurs via an inner-sphere surface complex with an optimized pH of 4, where UO22+ is the dominant U(VI) species. The adsorption isotherm results confirmed that the adsorption of U(VI) onto SMGO occurred via a monolayer process on the homogeneous surface of SMGO and the maximum removal capacity of U(VI) was 28.2 mg/g. The high-gradient magnetic separation (HGMS) principle was applied to U(VI) removal using SMGO to facilitate recovery and the repeated use of the adsorbent during multiple batch cycles. The results indicated that the initial U(VI) concentration (439.1 µg/L) was reduced to a value less than the standard level of U(VI) for drinking water (30 µg/L) during six batch cycles and the separation efficiency was 95.2%. As such, SMGO and electromagnetic system using the HGMS principle are promising technologies for the removal of U(VI) in groundwater.

Mapping the contaminant plume of an abandoned hydrocarbon disposal site with geophysical and geochemical methods, Jiangsu, China.

The management and remediation of abandoned hydrocarbon-contaminated sites require detailed information on the distribution of contaminant plumes. In areas where groundwater is active, the formation of contaminant plumes is associated with hydrodynamics, the nature of the sedimentary layers, and the nature of the pollutants and the degradation process. A comprehensive survey is needed to determine this information. An abandoned hydrocarbon disposal site is located in an area where groundwater is very active. In the investigation of contaminant plumes, we combined the geophysical method with accurate geochemical analysis of subsoil and groundwater samples. Ground-penetrating radar and electrical resistivity tomography images of the electrical anomalies potentially originating from hydrocarbon pollution were used to select sites for subsurface sampling. Total petroleum hydrocarbons, total dissolved solids, and groundwater pH were measured. The results showed that the source zone had undergone long-term natural attenuation, and it was unable to continuously output organic matter to support the expansion of contaminant plumes. Low-resistivity anomalies and enhanced attenuation in the study area were caused by hydrocarbon degradation products and enhanced mineral weathering. Delineating the distribution of contaminant plumes in areas where the resistivity was below 15 Ω m. The distribution of the plume in the vertical direction was related to the hydrocarbon release history (release rate and volume) and was affected by fluctuations in the groundwater level. The contaminant plume moved very slowly along the direction of the hydraulic gradient and was in a basically stable state. The results showed that the combined application of the geoelectrical method and the geochemical method can effectively describe the distribution of underground contaminant plumes in an aged pollution site.

The behaviour of irrigation induced Se in the groundwater-soil-plant system in Punjab, India.

Selenium is of special interest in different research fields due to its narrow range between beneficial and toxic effects. On a global scale, Se deficiency is more widespread. Biofortification measures have successfully been applied to specifically increase Se concentrations in food crops. Still not much is known about the behaviour and long-term fate of externally supplied Se. Over many years, natural but external selenate is regularly introduced into the soil-plant system via irrigation at our study sites in Punjab which makes it also an ideal natural analogue to investigate the long term effect of biofortification. For our study, we combined total and species specific analysis of Se in soil and plant material. Selenium is clearly enriched in all investigated topsoils (0-15 cm) with concentrations of 1.5-13.0 mg kg-1 despite similar background Se concentrations (0.5 ± 0.1 mg kg-1) below 15 cm depth. Irrigation is indicated to be the primary source of excess Se. Processes like Se species transformation, uptake by plants and plant material decomposition further influence both the Se speciation and extent of Se enrichment in the soils. The Se concentration in different plants and plant parts is alarmingly high showing concentrations of up to 738 mg kg-1 in wheat. Irrigation induced selenate can be considered as an easily available short term pool of Se for plants and thus strongly controls their total Se concentration and speciation. The long-term pool of Se in the topsoil mainly consists of selenite and organic Se species. These species are readily retained but still sufficiently mobile to be taken up by plants. The formation of elemental Se can be considered as a non-available Se pool and is thus, the major cause of Se immobilization and long-term enrichment of Se in the soils. Our study clearly shows that biofortification with selenate, despite its effectiveness, bears the risk of easily increasing Se levels in plants to toxic levels and producing food with less favourable inorganic Se species if not done with care. Excess selenate is either lost due to biomethylation or immobilized within the soil which has to be considered as highly negative from both an economic and ecological point of few.

Spatial assessment of pesticide leaching risk to groundwater: sub-national decision making and model output aggregation.

BACKGROUND: This study compares standard regulatory methodology (fixed scenarios and models) to spatial modelling at a 1 km landscape resolution for the evaluation of predicted environmental concentrations of pesticides in groundwater. The use of spatial modelling in the decision-making processes is discussed and three options for the sub-national evaluation and restriction of substances based on spatial environmental fate modelling are examined. Wheat and sugar beet are tested with two modified FOCUS substances (A and D) in the PEARL and GeoPEARL models. The 80th percentile value in time and space, aggregated to three different sub-national divisions of interest to a regulator, is used as a regulatory relevant output. RESULTS: Means and medians of predicted environmental concentrations at the national level are not useful summary statistics in the age of extensive and freely available geospatial data. A better statistic to use is the P80 (or other desired threshold/percentile combination) in time and space of predicted environmental concentration, combined with flexible and adaptable sub-divisions of the country based on the desired protective target. CONCLUSION: Tier 3b modelling is shown to provide an increase in localism and regulatory nuance over Tier 1 scenarios when combined with soil and aquifer type sub-national units. © 2019 Society of Chemical Industry.