Sources and behavior of trace elements in groundwater in the South Eastern Desert, Egypt

Assessment of the health risks associated with heavy metal contamination in the groundwaters of the Leh district, Ladakh

There has been a significant rise in cancer-related mortality in the Ladakh region during the past 10 years. The most common type of case is gastrointestinal cancer, which has been linked in theory by medical research to lifestyle factors, high altitude conditions, and the prevalence of Helicobacter pylori bacteria brought on by poor hygiene. Nevertheless, the precise cause of the rise in cancer cases is still unknown. Concurrently, there has been a significant change in Ladakh's water use practices due to development, improved basic utilities, and related vocational shifts. The local population has become increasingly reliant on groundwater since it provides a year-round, continuous water supply for home and agricultural uses. In this study, we assessed heavy metal contamination in groundwaters and associated human health risks. The results indicate that 46-96% of the groundwater samples have heavy metal pollution with a health hazard index > 1, which means using these groundwaters for drinking, food preparation, and agriculture is likely to result in carcinogenic and non-carcinogenic health hazards. The main heavy metal contaminants found in the groundwater of the Leh district include Cr, As, Hg, and U. According to the health risk assessment, 46-76% of the groundwater samples contain unsafe levels of Cr and As. Prolonged exposure to these levels is likely to cause gastrointestinal cancer in the local population. Acute to chronic exposure to U and Hg concentrations present in some groundwater samples is likely to result in various non-carcinogenic health risks.

Marine microplastics enhance release of arsenic in coastal aquifer during seawater intrusion process

Microplastics (MPs), omnipresent contaminants in the ocean, could be carried by seawater intrusion into coastal aquifers, which might affect the fate of heavy metals existing in aquifers. Herein, we investigated the release behavior of arsenic (As) in coastal aquifers during MPs-containing seawater intrusion by applying laboratory experiment and numerical simulation. We found that seawater with marine MPs enhanced the release of As in aquifers, especially for dissolved As(V) and colloidal As. Negatively charged MPs competed with As(V) for the adsorption sites on iron (hydr)oxides in aquifers, resulting in the desorption of As(V). In addition, MPs could promote the release of Fe-rich colloids by imparting negative charge to its surface and providing it with sufficient repulsive force to detach from the matrix, thereby leading to the release of As associated with Fe-rich colloid. We also developed a modeling approach that well described the transport of As in coastal aquifer under the impact of MPs, which coupled variable density flow and kinetically controlled colloids transport with multicomponent reactive transport model. Our findings elucidated the enhancement of MPs on the release of As in aquifers during seawater intrusion, which provides new insights into the risk assessment of MPs in coastal zones.

Assessment of heavy metals and radionuclides in groundwater and associated human health risk appraisal in the vicinity of Rooppur nuclear power plant, Bangladesh

This study was carried out to assess the groundwater quality through estimating trace and heavy metal concentration and radionuclide levels in the vicinity of the Rooppur Nuclear Power Plant (RNPP) sites. Twenty-six (26) parameters, including major cations (K, Na, Mg, Ca) and anions (SO₄^-2, NO₃^-), trace and heavy metals (Mn, Fe, Zn, Ni, Co, Pb, Cd, As, Hg, Cu, Li, Be, B, V, Ga, Sr, Ag, Ba) and radionuclides (¹³⁷Cs, ²²⁶Ra, ²²⁸Ra, and ⁴⁰K) were estimated in water samples in the study area. This study revealed that the concentration values (μg/L) of Mn (667.091 ± 7.481), Fe (191.477 ± 3.756), Sr (105.218 ± 13.424), and Zn (23.493 ± 1.134) were the dominant metals in the study area. Different pollution evaluation indices (i.e., HPI, HEI, NI, C_d) data revealed that the study area was under a low to medium level of pollution due to the presence of metals in water. Subsequently, non-carcinogenic and carcinogenic health risks assessments for both adults and children were conducted, which indicated that health risk for the carcinogenic metals were below the threshold level except As through oral exposure for both adult and children. The activity concentrations of ²²⁶Ra, ²²⁸Ra, and ⁴⁰K were measured to demonstrate probable radioactivity pollution using Gamma-ray spectrometry (High-resolution HPGe detector). The highest activity concentration of ²²⁶Ra, ²²⁸Ra, and ⁴⁰K in groundwater samples were 4.9 ± 1.24 Bq/L (RNPP-15), 1.71 ± 0.43 Bq/L (RNPP-15), and 15.43 ± 3.08 Bq/L (RNPP-15). Among the three studied radionuclides, ⁴⁰K has the highest average activity concentration. The radiological indicators referred to the annual effective dose (AED) is 0.4273 mSv yr-1, which implies no significant cause of radiological risks and hazards (UNSCEAR guideline value). This study provides a baseline of trace and toxic metal contamination, radioactivity, and radiation levels in the groundwater of the nuclear power plant (being built) area.

Analysis of the geological control on the spatial distribution of potentially toxic concentrations of As and F- in groundwater on a Pan-European scale

The distribution of the high concentrations of arsenic (As) and fluoride (F^-) in groundwater on a Pan-European scale could be explained by the geological European context (lithology and structural faults). To test this hypothesis, seventeen countries and eighteen geological survey organizations (GSOs) have participated in the dataset. The methodology has used the HydroGeoToxicity (HGT) and the Baseline Concentration (BLC) index. The results prove that most of the waters considered in this study are in good conditions for drinking water consumption, in terms of As and/or F^- content. A low proportion of the analysed samples present HGT≥ 1 levels (4% and 7% for As and F^-, respectively). The spatial distribution of the highest As and/or F^- concentrations (via BLC values) has been analysed using GIS tools. The highest values are identified associated with fissured hard rock outcrops (crystalline rocks) or Cenozoic sedimentary zones, where basement fractures seems to have an obvious control on the distribution of maximum concentrations of these elements in groundwaters.

State-of-the-art of research progress on adsorptive removal of fluoride-contaminated water using biochar-based materials: Practical feasibility through reusability and column transport studies

Fluoride (F^-) is one of the essential elements found in soil and water released from geogenic sources and several anthropogenic activities. Fluoride causes fluorosis, dental and skeletal growth problems, teeth mottling, and neurological damage due to prolonged consumption, affecting millions worldwide. Adsorption is an extensively implemented technique in water and wastewater treatment for fluoride, with significant potential due to efficiency, cost-effectiveness, ease of operation, and reusability. This review highlights the current state of knowledge for fluoride adsorption using biochar-based materials and the limitations of biochar for fluoride-contaminated groundwater and industrial wastewater treatment. Biochar materials have shown significant adsorption capacities for fluoride under the influence of low pH, biochar dose, initial concentration, temperature, and co-existing ions. Modified biochar possesses various functional groups (-OH, -CC, -C-O, -CONH, -C-OH, X-OH), in which enhanced hydroxyl (-OH) groups onto the surface plays a significant role in fluoride adsorption via electrostatic attraction and ion exchange. Regeneration and reusability of biochar sorbents need to be performed to a greater extent to improve removal efficiency and reusability in field conditions. Furthermore, the present investigation identifies the limitations of biochar materials in treating fluoride-contaminated drinking groundwater and industrial effluents. The fluoride removal using biochar-based materials at an industrial scale for understanding the practical feasibility is yet to be documented. This review work recommend the feasibility of biochar-based materials in column studies for fluoride remediation in the future.

Evolution Mechanism of Arsenic Enrichment in Groundwater and Associated Health Risks in Southern Punjab, Pakistan

Arsenic (As) contamination in groundwater is a worldwide concern for drinking water safety. Environmental changes and anthropogenic activities are making groundwater vulnerable in Pakistan, especially in Southern Punjab. This study explores the distribution, hydrogeochemical behavior, and pathways of As enrichment in groundwater and discusses the corresponding evolution mechanism, mobilization capability, and health risks. In total, 510 groundwater samples were collected from three tehsils in the Punjab province of Pakistan to analyze As and other physiochemical parameters. Arsenic concentration averaged 14.0 μg/L in Vehari, 11.0 μg/L in Burewala, and 13.0 μg/L in Mailsi. Piper-plots indicated the dominance of Na+, SO42-, Ca2+, and Mg2+ ions in the groundwater and the geochemical modeling showed negative saturation indices with calcium carbonate and salt minerals, including aragonite (CaCO3), calcite (CaCO3), dolomite (CaMg(CO3)2), and halite (NaCl). The dissolution process hinted at their potential roles in As mobilization in groundwater. These results were further validated with an inverse model of the dissolution of calcium-bearing mineral, and the exchange of cations between Ca2+ and Na+ in the studied area. Risk assessment suggested potential carcinogenic risks (CR > 10-4) for both children and adults, whereas children had a significant non-carcinogenic risk hazard quotient (HQ > 1). Accordingly, children had higher overall health risks than adults. Groundwater in Vehari and Mailsi was at higher risk than in Burewala. Our findings provide important and baseline information for groundwater As assessment at a provincial level, which is essential for initiating As health risk reduction. The current study also recommends efficient management strategies for As-contaminated groundwater.

Geochemical and Multivariate Statistical Evaluation of Trace Elements in Groundwater of Niğde Municipality, South-Central Turkey: Implications for Arsenic Contamination and Human Health Risks Assessment

This study was conducted to determine the concentrations of trace elements, their sources, and human health risks associated with arsenic contamination in groundwater of the Niğde Municipality, south-central Turkey. Fourteen groundwater samples were collected from groundwater supply sources fed by the Niğde water distribution system and were analysed for Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, and Ba concentrations. Multivariate statistical analyses were applied to decipher the source and interrelationships among trace elements in groundwater. The groundwater is mainly tapped from Quaternary alluvial and volcanic aquifers of the Niğde Massif. The pH of groundwater is slightly acidic to neutral, which controls the solubility and mobility of the trace elements. The mean concentrations of the trace elements vary in the order Zn > Fe > Ba > As > Cr > Ni > Se > Cu > Co > Mn > Al. All of the trace element concentrations comply with the maximum permissible values provided by the Turkish Standards Institution and the World Health Organization, except Zn, Cr, and As. However, approximately 7.14% of the studied samples are contaminated with Zn and Cr, whereas 86% are contaminated with As. The As concentrations range from 9.47 to 32.9 µg/L with an average value of 16.8 µg/L. Contamination assessment indicates that the As contamination is dominant in the southern and southwestern parts of the area. The primary source of As in groundwater is attributed to geogenic processes involving weathering and dissolution of bed rocks and other factors, such as pH conditions, adsorption, and surface complexation. Three bimetallic complex associations are distinguished in groundwater: Fe-coordination group, As-coordination group and Ba-coordination group, all showing strong positive correlation with Cu and Ni. The As-coordination group is the most dominant in groundwater, which resulted in the high As content of groundwater. Multivariate statistical analyses indicate that As mobilization in groundwater is associated with pH, EC, Ni, Cu, and Ba depending on the redox conditions of the aquifer, controlled mainly by geogenic processes. The carcinogenic risk of arsenic affecting children and adults reaches 2 × 10^-4 and 3 × 10^-4, respectively, exceeding the guideline value of 1 × 10^-4. The estimated hazard quotient for children is in the range of 1.79-6.21, whereas that of adults is 0.77-2.66, indicating that children in the municipality are more exposed to the noncarcinogenic effects of the consumption of high groundwater arsenic.

Nanocomposites for Electrochemical Sensors and Their Applications on the Detection of Trace Metals in Environmental Water Samples

The elevated concentrations of various trace metals beyond existing guideline recommendations in water bodies have promoted research on the development of various electrochemical nanosensors for the trace metals' early detection. Inspired by the exciting physical and chemical properties of nanomaterials, advanced functional nanocomposites with improved sensitivity, sensitivity and stability, amongst other performance parameters, have been synthesized, characterized, and applied on the detection of various trace metals in water matrices. Nanocomposites have been perceived as a solution to address a critical challenge of distinct nanomaterials that are limited by agglomerations, structure stacking leading to aggregations, low conductivity, and limited porous structure for electrolyte access, amongst others. In the past few years, much effort has been dedicated to the development of various nanocomposites such as; electrochemical nanosensors for the detection of trace metals in water matrices. Herein, the recent progress on the development of nanocomposites classified according to their structure as carbon nanocomposites, metallic nanocomposites, and metal oxide/hydroxide nanocomposites is summarized, alongside their application as electrochemical nanosensors for trace metals detection in water matrices. Some perspectives on the development of smart electrochemical nanosensors are also introduced.

Hydrogeochemical investigation of arsenic in drinking water of schools and age dependent risk assessment in Vehari District, Punjab Pakistan: a multivariate analysis

Globally, a large number of school-aged children is suffering from water-borne diseases, particularly in low-income countries. Arsenic (As) is a hazardous and potentially carcinogenic metal(loid) in drinking water. Nowadays, alarming levels of As have been reported in the groundwater of Vehari District, Punjab Pakistan. In this study, drinking water supplies for high and higher secondary schools were examined in Vehari District. A total of 164 water samples were collected from schools and subjected to heavy metal(loid) analysis (As) and basic water physicochemical parameters. The results were analyzed with respect to sampling area, school type, school education level, sources of sample collection, and the depth of the source. The results revealed that As concentration of water samples in boys' and girls' schools was 12.8 μg/L and 9.2 μg/L, respectively. However, when the As concentration in drinking water was evaluated at the school education level, a notable higher concentration of As was observed in the higher secondary schools than the high schools with an average of 19.5 and 9.7 μg/L, respectively. The risk assessment indices were calculated based on education level and different age groups of the children (primary, elementary, high, and higher secondary). High carcinogenic (cancer risk = 0.001) and non-carcinogenic (hazard quotient = 2.0) risks were noted for the children in higher secondary school. The current findings anticipated that the drinking water of schools in Vehari District did not meet the requirement of the World Health Organization (WHO) drinking water quality guidelines. Safe drinking water is crucial for the development and growth of children. Therefore, it is important for educational authorities to take steps for provision of As free safe drinking water to students and local inhabitants.