Physico-chemical characteristics and hydrogeological mechanisms in groundwater with special reference to arsenic contamination in Barpeta District, Assam (India)

Evaluating trends in groundwater quality of coastal alluvial aquifers of Eastern India for sustainable groundwater management

Groundwater is a precious natural element which ensures global water, food, and environmental security in the twenty-first century. Systematic monitoring, sustainable utilization, preservation and remediation are critical aspects of efficient groundwater resource management. This study deals with the analysis of spatial variability and trend in groundwater chemistry as well as identification of possible contamination sources in a coastal alluvial basin of eastern India. Pre-monsoon season data of 14 groundwater-quality variables measured in 'leaky confined' and 'confined' aquifers were analyzed for ten years (2012-2021). Mann-Kendall (M-K) test with the Sen's Slope Estimator, Spearman Rank Order Correlation (SROC) and Innovative Trend Analysis (ITA) tests were employed to assess decadal (2012-2021) trends. The analysis of the results indicated that the 'critical' water-quality parameters exceeding the acceptable limits for drinking are TDS, EC, TH, pH, Mg2+, Na+, K+, Fe2+, HCO3-, Cl- and NO3-. Weak negative correlations between rainfall and groundwater elevation for both the aquifers reveal poor rainfall recharge into the aquifers. Therefore, a reduction in groundwater abstraction and augmentation of groundwater recharge is recommended. Trend analysis results indicated that the concentrations of TH, Mg2+ and Fe2+ exhibit significant increasing trends in the 'leaky confined aquifer'. In contrast, significant rising trends in TH, Mg2+, Na+, Fe2+, HCO3- and NO3- concentrations are identified in the 'confined aquifer'. Further, the SROC test could not detect the trends in groundwater quality in most blocks and for many parameters. On the other hand, the ITA test revealed significant trends in most of the parameters of the two aquifers in almost all the blocks. Trend magnitudes of the groundwater-quality parameters based on the Sen's Slope Estimator and the ITA test vary from -63.7 to 58.65 mg/L/year for TDS, -14 to 39.07 mg/L/year for TH, -1.49 to 4.83 mg/L/year for Mg2+, -7.14 to 22.96 mg/L/year for Na+, -0.32 to 0.44 mg/L/year for Fe2+, -8.33 to 20.75 mg/L/year for HCO3-, -26.52 to 31.01 mg/L/year for Cl- and 1.29 to 3.76 mg/L/year for NO3- over the study area. The results of M-K and ITA tests were found in agreement in all the blocks for both the aquifers. Groundwater contamination in both the aquifers can be attributed to weathering, geogenic processes, mineral dissolution, seawater intrusion, poor recharge pattern and injudicious anthropogenic activities. It is strongly recommended that concerned authorities urgently formulate efficient strategies for managing groundwater quality in the 'leaky confined' and 'confined' aquifers which serve as vital sources of drinking and irrigation water supplies in the study area.

Distribution, toxicity load and risk assessment of heavy metals in the groundwater of Dhemaji, Assam, India

Metal contamination in drinking water has drawn attention since it gravely jeopardizes human health. This study was conducted in pre- and post-monsoon season in 2021 at Dhemaji, Assam, India. It characterized metal pollutants in groundwater, their distribution, possible sources, and evaluated the potential toxicity and associated health risk assessment. The seasonal mean concentration of Fe in both seasons is observed highest followed by Mn, Zn, Cu, As, and Ni. Furthermore, the metal concentrations during pre-monsoon are comparatively higher. The geogenic processes and agricultural practices are the major sources of groundwater metal contamination as evident from the statistical analysis. The different pollution indices viz. Heavy-metal Pollution Index (HPI), Heavy-metal Evaluation Index (HEI) and Degree of Contamination (Cd) suggested that groundwater is not suitable for drinking uses. The Heavy Metal Toxicity Load (HMTL) suggesting As, Co, Mn and Hg should be removed from the groundwater to ensure safety. Water pollution indices (WPI) suggest that Fe, Mn, As and Ni are the main pollution-causing metals in the study area which may be restored under the BIS and WHO limit by diluting the water. The human health risk has been calculated by carcinogenic and non-carcinogenic risk assessment. The non-carcinogenic risk for adults and children is within the threshold limit. The carcinogenic risk shows that continuous exposure of As and Ni may give rise to cancer among adults and children in the region. Therefore, comprehensive groundwater quality monitoring with well-planned treatment should be needed to provide safe and clean drinking water in the studied area.

Technological and economic analysis of electrokinetic remediation of contaminated soil: A global perspective and its application in Indian scenario

Globally million hectares of land annually is getting contaminated by heavy metalloids like As, Cd, Cr, Hg, Pb, Co, Cu, Ni, Zn, and Se, with current concentrations in soil above geo-baseline or regulatory standards. The heavy metals are highly toxic, mobile, and persistent and hence require immediate and effective mitigation. There are many available remediation techniques like surface capping, encapsulation, landfilling, soil flushing, soil washing, electrokinetic extraction, stabilization, solidification, vitrification, phytoremediation, and bioremediation which have been evolved to clean up heavy metal-contaminated sites. Nevertheless, all of the technologies have some applicability and limitations making the soil remediation initiative unsustainable. Among the available technologies, electrokinetic remediation (EKR) has been comparatively recognized to mitigate contaminated sites via both in-situ and ex-situ approaches due to its efficiency, suitability for use in low permeability soil, and requirement of low potential gradient. The work critically analyzes the EKR concerning techno, economic, and sustainability aspect for evaluating its application on various substrates and environmental conditions. The current soil contamination status in India is presented and the application of EKR for the heavy metal remediation from soil has been evaluated. The present work summaries a comprehensive and exhaustive review on EKR technology proving its effectiveness for a country like India where the huge amount of waste generated could not be treated due to lack of infrastructure, technology, and economic constraints.

Evaluation of surface water quality in basins of the Chilean Altiplano-Puna and implications for water treatment and monitoring

Water quality characterization and assessment are key to protecting human health and ecosystems, especially in arid areas such as northern Chile, where water resources are scarce and rich in pollutants. The objective of this study was to review and assess available official water quality data in the Chilean Altiplano-Puna basins for a 10-year period (2008-2018), including water treatment systems. Within the 43,600 km² of Chilean Altiplano-Puna territory, only 16 official water quality monitoring stations had up-to-date data, and the sampling frequency was less than 3 per year. Most of the water samples collected at the evaluated stations exceeded the drinking and irrigation water Chilean standards for arsenic, boron, and electrical conductivity. Moreover, the characteristics of the Altiplano-Puna affect water quality inside and beyond the area, limiting water usage throughout the Altiplano-Puna basins. Drinking water treatment plants exist in urban and rural settlements; however, the drinking water supply in rural locations is limited due to the lack of adequate treatment and continuity of service. Wastewater treatment plants operate in some urban locations but rarely exist in rural locations. Limited data impede the proper assessment of water quality and thus the evaluation of the need for treatment systems. As such, the implementation of public policies that prioritize water with appropriate quantity and quality for local communities and ecosystems is imperative.

Environmental and Health Risks Posed by Heavy Metal Contamination of Groundwater in the Sunan Coal Mine, China

Groundwater is often used for domestic and irrigation purposes, even in mining areas. Mine drainage, rainfall, and infiltration cause heavy metal enrichment, adversely affecting the groundwater and harming human health. In this study, water samples (October 2021) in the Suzhou southern coal mining area were analyzed for the heavy metals As, Cr, Cu, Fe, Mn, Pb, and Zn to determine potential effects of heavy metal contamination on environmental quality and human health. It was found that 22% and 31% of the sampling sites had “excellent” and “good” water quality, respectively. Excessive concentrations of Fe and Mn were detected in 47% and 72% of the samples, respectively. The non-carcinogenic health risk values of As, Cr, Cu, Fe, Mn, Pb, and Zn were below the negligible levels of health risk set by various environmental agencies. Content ranking was as follows: Fe > Mn > Cr > Cu > Pb > Zn > As, with Fe accounting for 43%. All sampling points exceeded the maximum acceptable level of Cr recommended by the agencies. Chromium, the major carcinogenic factor in the study area, contributed to 95.45% of the total health risk. Therefore, the authorities in this region must closely monitor three heavy metal elements—Fe, Mn, and Cr.

Evaluation of water quality index and geochemical characteristics of surfacewater from Tawang India

In this study,the water samples were collected from 31 sites of Tawang, Arunachal Pradesh, India (North-Eastern Himalaya), during the winter season to check the suitability of water for drinking and irrigation purposes.The study scientifically demonstrates the estimation of Water quality index (WQI) andhydrogeochemical characteristics of surface water samples by utilizing multivariate statistical methods. The main water quality parameters considered for this study were TDS, conductivity, salinity, pH, hardness, cations and anions. WQI was calculated in order to find out the deviation in the water quality parameters particularly with respect to BIS permissible limits.The major influencing factors responsible for the variation in these parameters were derived by using Principal component analysis (PCA) and Correlation matrix.To check the suitability of water for drinking purpose, hydrogeochemical facies and rock water interaction was derived by using well established methods such as Piper Plot (determine water type), WQI (Quality monitoring), and saturation index (for mineral dissolution). The results revealed that the silicate weathering was the main ionic source in comparison to carbonate weathering which is due to the higher dissolution capacity of silicate minerals.The results of the scattered plot between (Ca²⁺ + Mg²⁺)-(HCO₃- + SO₄²-) versus (Na⁺ + K⁺)-Cl- (meq/L) highlighted thation exchange occurs between Mg²⁺ and Ca²⁺ofsurface water with Na⁺ and K⁺of rock /soil. This means that calcium ion was getting adsorbed, and sodium ion was getting released. The Ca²⁺-Mg²⁺-HCO₃-, Na⁺-HCO₃-and Na⁺-Cl- type of surface water suggested permanent and temporary hardness respectively in the studied region. The dominant cations of this study were Na⁺ and Ca²⁺ while the dominant anions were HCO₃- and SO₄²-. In order to check the suitability of water sources for irrigation, parameters like, Magnesium hazard (MH), Total hardness (TH), Permeability Index (PI), Kelly Index (KI), Sodium adsorption rate (SAR), Sodium percentage (Na%), and Residual sodium carbonate (RSC) were determined. The results showed that 93% of the samples had PI score < 75, which indicates the suitability of the water for irrigation. Also the WQI calculation showed an average WQI value of 82.49, amongst which 61% samples were in the range of 0-50 being considered as good for drinking, while 39% were catageorised as unsuitable for drinking showing a value of > 50. Hence the above findings reveal that geogenic activities play a major role in influencing the water quality of Tawang region. Hence suitable water treatment technologies or methods might be used to eliminate thenon desirable elements and minerals present in surface water.

Spatial distribution and health risk assessment of As and Pb contamination in the groundwater of Rayong Province, Thailand

This study investigates the presence of arsenic (As) and lead (Pb) in groundwater and their spatial distribution in Ban Khai District, Rayong Province, Thailand. Forty groundwater samples were collected at different locations in the dry and wet seasons during March and August of 2019, respectively. The hydrochemical facies illustrate that the major groundwater types in both seasons mainly consisted of Ca-Na-HCO_3, Ca-HCO₃-Cl and Na-HCO₃ types. The concentration of As ranged from <0.300 to 183.00 μg/L, accounting for 22% (18 of 80 samples), exceeding the WHO guidelines of 10 μg/L. The spatial distribution of As was distinctly predominant as a hot spot in some areas during the wet season. The wells may have been contaminated from human activity and thus constituted a point source in the adjacent area. For Pb, its concentration in all the wells were not exceeded 10 μg/L of the WHO guidelines, appearing as a background concentration in this area. Most of the wells were shown to be in an oxidation state, supporting As^V mobility. Moreover, the area also had a nearly neutral pH that promoted As^V desorption, while the presence of undissolved Pb in the aquifers tended to increase. Furthermore, chemical applications to agricultural processes could release the As composition into the groundwater. The health risk resulting from oral consumption was at a higher risk level than dermal contact. The non-carcinogenic risk affecting the adult population exceeded the threshold level by approximately 27.5% of the wells, while for the children group, the risk level was within the limit. Total cancer risk (TCR) of adult residents exceeded the acceptable risk level (1 × 10^-6) in all wells, causing carcinogenic health effects. Therefore, health surveillance is important in monitoring the toxic effects on the local residents who use groundwater from these contaminated wells. Furthermore, a sanitation service and an alternative treatment of the water supply will be needed, especially in wells with high As levels.

Purohit M, Stålsby Lundborg C, Diwan V. Physicochemical quality monitoring of groundwater for drinking purposes in rural Ujjain, Central India: findings of a 2-year longitudinal study

Rampant use of groundwater for drinking purposes in several parts of the world has raised the concern over its quality. Owing to increasing population, overuse, and pollution of surface water sources, the use of groundwater has increased to considerable extent. Despite this, little attention is paid towards the monitoring of groundwater resources to assess their suitability for drinking purposes. To assess the groundwater quality in rural areas of Ujjain District of Madhya Pradesh, India, in order to check its suitability for drinking purpose, water quality analysis was done at seven time points during the two study years in six villages of Ujjain District, Central India. A total of 868 groundwater samples from 124 households were collected, and standard analytical methods were employed for analysis. Overall groundwater quality of the area is good and qualified for drinking. However, occurrence of high amount of dissolved solids (> 800 mg/L) and hardness (> 400 mg/L) is the issue of concern, as long-term use of such water might result in variety of health ailments, such as kidney stones and atopic dermatitis in children. Regular monitoring and long-term surveillance of drinking water sources are necessary to keep track of the changes occurring in the system.

Arsenic health risk assessment and the evaluation of groundwater quality using GWQI and multivariate statistical analysis in rural areas, Hashtroud, Iran

Arsenic (As) is a toxic metalloid that can cause significant health issues through drinking water. The present study was aimed to evaluate As distribution and the related health risks from drinking groundwater in rural areas of Hashtroud, Iran. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) were also applied to better explain relationship pattern between different resources. The samples were taken from 51 locations in 37 villages. Arsenic concentration was determined by a polarograph device, and the corresponding carcinogenic and non-carcinogenic health risks were calculated based on US Environmental Protection Agency (EPA) guideline. PCA analysis extracted four main components that explained nearly 62% of data variance. Results pointed severe As contamination in the studied area, where As was detected in 78% of the samples ranging from less than 0.001 to 0.250 mg/L. Forty percent of the contaminated places violated guideline value of 10 μg/L suggested by EPA and institute of standards and industrial research of Iran (ISIRI). Based on our findings, 1329 people including 239 children were living in the areas with higher As contamination. Hazard quotient (HQ) in 72%, 59%, and 33% of the samples was higher than one for children, adolescent, and adult age groups, respectively. Excess life time cancer risk (ELCR) in almost 80% of all age groups was significantly higher than EPA recommended guideline (10^-4 or 10^-6). In summary, from the view point of arsenic HQ and ELCR, water resources in the studied areas were not appropriate for drinking and hygienic purposes; necessary and urgent management strategies to guarantee water supply and health safety for local residents should be considered.

Assessment of groundwater quality and determination of hydrochemical evolution of groundwater in Shillong, Meghalaya (India)

Deterioration of surface water quality in various parts of India due to increasing urbanization has led to the extensive usage of groundwater for various domestic and irrigation needs, thereby raising concerns over its quality. However, there are very few studies focussing over the issue of groundwater quality in North-Eastern region of India. In order to make an assessment of the quality of groundwater for drinking and irrigation purposes, this study was carried out in Shillong—the Capital City of Meghalaya State in North-East India during pre-monsoon and post-monsoon seasons of 2018. Standard sampling and analytical procedures were followed for groundwater quality assessment. Minimal variation was observed in the water quality of pre- and post-monsoon seasons. However, the study found that groundwater samples are having acidic pH and presence of nitrate is also reported. Some of the samples also showed the presence of mercury, nickel, and cadmium. The presence of these contaminants could be attributed to the industrial activities in the state. Overall, the groundwater quality was found suitable for drinking and irrigation purposes after conventional treatment. Hydrochemical studies further inferred that groundwater properties in the region are influenced by the rock weathering along with the atmospheric precipitation.

Microbial and plant-assisted heavy metal remediation in aquatic ecosystems: a comprehensive review

Heavy metal (HM) pollution in aquatic ecosystems has an adverse effect on both aquatic life forms as well as terrestrial living beings, including humans. Since HMs are recalcitrant, they accumulate in the environment and are subsequently biomagnified through the food chain. Conventional physical and chemical methods used to remove the HMs from aquatic habitats are usually expensive, slow, non-environment friendly, and mostly inefficient. On the contrary, phytoremediation and microbe-assisted remediation technologies have attracted immense attention in recent years and offer a better solution to the problem. These newly emerged remediation technologies are eco-friendly, efficient and cost-effective. Both phytoremediation and microbe-assisted remediation technologies adopt different mechanisms for HM bioremediation in aquatic ecosystems. Recent advancement of molecular tools has contributed significantly to better understand the mechanisms of metal adsorption, translocation, sequestration, and tolerance in plants and microbes. Albeit immense possibilities to use such bioremediation as a successful environmental clean-up technology, it is yet to be successfully implemented in the field conditions. This review article comprehensively discusses HM accumulation in Indian aquatic environments. Furthermore, it describes the effect of HMs accumulation in the aquatic environment and the role of phytoremediation as well as microbe-assisted remediation in mitigation of the HM toxicity. Finally, the review concludes with a note on the challenges, opportunities and future directions for bioremediation in the aquatic ecosystems.

Groundwater geochemical facie: implications of rock-water interaction at the Chamba city (HP), northwest Himalaya, India

The present study describes geochemical facie and implications of rock-water interaction at the groundwater of Chamba city. The influence of rock dominance at the groundwater may be due to its flow and longtime rock-water interaction, whereas atmospheric precipitation dominance owing to high recharge and continuous outflow of groundwater that cause a short time interaction. The comparison among Ca²⁺ + Mg²⁺ versus Na⁺ + K⁺ and total cations indicated carbonate weathering as a main ionic source relative to silicate weathering, due to rich lithology and higher dissolution capacity of carbonate minerals. The chloro-alkaline indices (CAI-1 and CAI-2) and scatter plot of (Ca²⁺ + Mg²⁺) - (HCO₃- + SO₄²-) versus (Na⁺ + K⁺) - Cl- (meq/L) inferred the presence of ion exchange process causing adsorption of Ca²⁺ and release of Na⁺. The Ca²⁺ - Mg²⁺ - Cl-, Na⁺ - HCO₃-, and Ca²⁺ - Mg²⁺ - HCO₃- types of groundwater suggested permanent and temporary hardness in the region. The Ca²⁺ and Na⁺ are observed as the dominant cations whereas HCO₃^- and SO₄^2- as the dominant anions. The parameters like NH₄⁺, NO₃^-, F^-, and Br^- are generated from different natural sources. The groundwater is found to be suitable for drinking purposes based on water quality index (14.24-61.13) and the Bureau of Indian Standards (BIS 2012) prescribed limit. The influence of carbonate minerals dissolution over TDS and salinity at groundwater of the city is also observed. The rock-water interaction confirmed mixing pattern of carbonate, silicate, and evaporites in the groundwater of the Chamba city.

Hydrogeochemical Characterization and Suitability Assessment of Groundwater: A Case Study in Central Sindh, Pakistan

Groundwater is the most important water resource, on which depends human geo-economic development and survival. Recent environmental changes and anthropogenic activities render groundwater severely vulnerable. Groundwater in Central Sindh, Pakistan, is facing a similar situation. Hydrogeochemical characteristics of the groundwater in the said region were investigated by analyzing 59 groundwater samples via agricultural and drinking indices, using various statistical methods and graphical approaches to identify factors affecting groundwater. Major reactions occurring in the groundwater system were quantified by hydrogeochemical modeling. A statistical summary reveals the abundance of cations is Na⁺ > Ca²⁺ > Mg²⁺ > K⁺, while the abundance of anions is HCO₃⁻ > Cl⁻ > SO₄². Groundwater chemistry is mainly of rock dominance. Correlation analysis and graphical relationships between ions reveal that ion exchange and rock weathering such as the dissolution of halite, albite, and dissolution of carbonate minerals are important rock–water interactions, governing the evolution of groundwater chemistry. Hydrochemical facies are predominantly of mixed CaMgCl and Na-Cl type, with few samples of Ca-HCO₃ type, which constitutes fresh recharged water. Based on the Water Quality Index (WQI), 28.82% samples were found to be unsuitable for drinking. A United States Salinity Laboratory (USSL) diagram, Wilcox diagram, and other agricultural indices indicate that majority of the groundwater samples fall within the acceptable range for irrigation purposes.

Prepubertal exposure to low doses of sodium arsenite impairs spermatogenesis and epididymal histophysiology in rats

For the first time, juvenile toxicity of inorganic arsenic (As) was investigated in male rats, focusing on reproductive effects. As is a metalloid naturally occurring in the environment, being the inorganic forms the most toxics. Contaminated drinking water and agricultural products are the main prospectors of intoxication for general population. In the present study, Wistar male rats (21 days old) were distributed into three groups (n = 10/group): control (received vehicle-filtered drinking water), As1 (received AsNaO₂ at 0.01 mg L^-1 ) and As2 (received AsNaO₂ at 10 mg L^-1 ). The animals were euthanized on PND 53. Testicular damages increased in As1 and As2 compared to control (ie, presence of vacuolization, acidophilic cells, and epithelium degeneration). Testicular interstitium of As1 and As2 presented fluid's increase and intense inflammatory infiltration. In the epididymis there was reduction of sperm amount in the lumen, besides epithelium areas presenting cribriform aspect in As1 and As2, exfoliation of cells in the light (in As1) and vacuoles (in As2). In epididymis interstitium, inflammatory infiltrates were observed in initial segment of As1 and As2. AsNaO₂ changed immunolabeling pattern for androgen receptor in epididymis of As2, although serum testosterone levels was statistically comparable to control. Mass spectrometry revealed higher As concentrations in testis and epididymis of As2 compared to As1 and Control. These results indicate compromise of spermatogenesis and epididymal histophysiology in AsNaO₂ -treated animals, possibly impairing sperm quality and fertility in long-term, even at low levels of exposure. Investigations about the reversibility of reproductive damages are necessary to better understand the mechanisms of As reproductive toxicity.