Introduction

Groundwater plays a vital role on the planet Earth, which is considered to be pure and also a natural resource. All over the world, groundwater is typically used for drinking, agricultural and also industrial purposes, because of its aptness, quality, availability, and cleanliness. Thus, groundwater is a natural elixir of life, providing virtually half of all the drinking water in the world (Sheng et al. 2023; Haggerty et al. 2023). In addition, groundwater plays a crucial role in rural regions as well as arid and semi-arid regions of the world, where the supply of surface water and precipitation is predominantly inadequate (Xiao et al. 2021; Roy et al. 2021). Therefore, dependence on groundwater is steadily escalating in this modern era of globalization and technology. In recent decades, groundwater quality is progressively a growing issue throughout the world due to excessive usage of fertilizers, agricultural practice, industrial pollution, improper usage of manures, global population growth, urbanization, gigantic construction development activities, and climate change (Oskay et al. 2023; Hussainzadeh et al. 2023; Dhaliwal et al. 2021; Sheng et al. 2023; Adimalla et al. 2022). In addition, overexploitation of groundwater is one of the major issues in arid and semi-arid regions of the world, which obviously leads to a decline in the groundwater level as well as increasing ionic concentrations in it (Adimalla and Qian 2023; Okofo et al. 2021; Kim et al. 2021). Those two phenomenal processes are gradually augmenting groundwater contamination, and simultaneously posing a severe hazard to human health, sustainable socioeconomic development, and also deteriorating/arising water quality issues.

The quality of groundwater is potentially influenced by various factors, including land use and human activities, geology of the area, recharge and discharge ratio, environmental and climate conditions of the region (Tum et al. 2023; Adimalla and Qian 2020, 2021; Roy et al. 2021; Lin et al. 2021). Importantly, it is fundamentally identified through the literature review that the contamination of groundwater characteristically emanated through two major sources such as geogenic and anthropogenic (Adimalla and Qian 2023; More et al. 2021; Li et al. 2021; Khan et al. 2022). Since, geogenic sources naturally emerge and unfortunately it is not under control of the humans, while anthropogenic sources are fully under control of the human, which means groundwater contamination from anthropogenic sources are technically monitored and also minimize the intensity of the pollution rate. On the contrary, contamination of groundwater is more severe in rural communities, developing countries, and truthfully, it is now becoming a worldwide issue (Hussainzadeh et al. 2023; Shakeri et al. 2023; da Silva et al. 2023; Giri et al. 2021). Therefore, identification of the key factors of groundwater contamination is one of the most predominant processes that enable us to formulate the strategic steps to prevent contamination at various levels and also helps in developing appropriate sustainable management strategies for improving the natural resources and environments. Consequently, it is most suitable that this thematic issue entitled “Groundwater quality and contamination and the application of GIS” focuses specifically on studies of the unique challenges associated with the contamination of groundwater in various countries in the worldwide, including India, South Africa, China, Pakistan, Korea, Mexico, Iran, Ghana, Nigeria, Ukraine, Kuwait, Turkey, and Brazil. As can be seen from Fig. 1 (Supplementary Figure S1) the countries, where the research is conducted and the results of the contamination of groundwater are systematically reported in this thematic issue. Interestingly, Fig. 1 visualizes the high submissions received from the Eastern hemisphere. Specifically, the thematic issue covers a wide range of topics on the main theme of the title of the thematic issue which includes (1) novel techniques for monitoring the groundwater quality, and contamination process, (2) the latest methods for understanding the major source of groundwater pollution from geogenic and anthropogenic sources, (3) estimate the spatial distribution trend of groundwater quality, and characterize the groundwater chemistry, (4) determine the risks to human populations, considering various routes of exposure through contaminated groundwater, and identify the hydrochemical characteristics and water types of groundwater.

Fig. 1
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Eastern and western hemispheres, location of the countries, where the groundwater research was conducted and the several groundwater contamination studied in the articles published in this thematic issue

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Articles in the thematic issue

A total of 33 research papers were included in this thematic issue. These papers were mainly received by active researchers from India, South Africa, China, Pakistan, Korea, Mexico, Iran, Ghana, Nigeria, Ukraine, Kuwait, Turkey, and Brazil (Fig. 1; Table 1). The research topics of these articles were fairly diverse, and covered a range of groundwater contamination issues, mainly from anthropogenic and geogenic contamination, identification of pollution sources using various geostatistical methods, human risk assessment, and application of GIS (geographic information system). A word could map was generated using the repeatedly appearing words in the titles and abstracts of the papers in this thematic issue, which was obviously depicted in Fig. 2. It can be observed (Fig. 2) that the word could display the most commonly used technical terms in the articles are groundwater, groundwater quality, contamination, pollution, geostatistical methods, water quality index (WQI), geographic information system (GIS), hydrogeochemistry, hydrochemical approach, irrigation, drinking water quality, evaluation, human health risk (HRA), classification, pollution of water, evaluation, controlling factors, GIS application, etc. Actually, these technical terms prominently reflect the main topic of the articles, which typically cover the evaluation of groundwater quality, groundwater contamination/pollution, suitability of groundwater for various purposes, assessment of the concentration of physicochemical parameters, fluoride, nitrate, toxic metals in groundwater and its impact on human health risk, and distribution pattern of pollutants. In this thematic issue, the articles were categorized into five topic clusters (groundwater contamination, and its impact on human health risk assessment, characteristics and geochemistry of groundwater quality issues, water resources, hydroecosystems and influencing factors, and identifying spatiotemporal variations in the physicochemical parameters), which are presented in Table 1. Importantly, each article of these five clusters in this thematic issue is encapsulated below:

Table 1 Classification of published articles in this thematic issue
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Fig. 2
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Word cloud was created based on the article titles, abstracts, and keywords in this thematic issue

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As can be seen from Table 1, the first cluster “groundwater contamination and its impact on human health risk assessment” consists of six articles. Consumption of excessive amounts of trace and heavy metals, fluoride, nitrate, arsenic, etc., creates detrimental effects on both the physical and environmental health of billions of people worldwide (Xu et al. 2023; Adimalla and Qian 2023; Sheng et al. 2023; Madhav et al. 2021). More et al. (2021) conducted a study in Telangana state in south India to estimate the fluoride concentration in groundwater for both pre-monsoon and post-monsoon seasons and quantify human health risks for both children and adults. Furthermore, the high fluoride level in groundwater was reported in post-monsoon season, at concentrations up to 3.85 mg/L. In terms of non-carcinogenic health risks, children were more vulnerable to exposure to high fluoride through drinking water as compared to the adults in the study region (More et al. 2021). In another article, Kadam et al. (2021) adopted chemometric and geostatistical methods to understand the seasonal variations of groundwater contamination and also human health risks to people in the hard rock terrain of western India. The authors reported the children in the study region were exposed to more risk of fluorosis than adults. The article by Khan et al. (2021) designates the assessment of groundwater quality and health risks from fluoride and nitrate contamination in the region of Tamil Nadu and Puducherry, India. Kurakalva et al. (2021) assessed the groundwater quality and human health risks from ingestion of fluoride and nitrate contaminated groundwater in the urban region of South India. Madhav et al. (2021) studied the hydrogeochemical estimation of groundwater quality and potential health risks to human beings in an area of Bhadohi in India. These authors generated the non-carcinogenic health risk map to assist the policy and decision makers in instigating the necessary precautionary measures to improve the quality of groundwater as well as reduce the intensity of adverse health risks to human beings. The paper by Dhaliwal et al. (2021) implemented multi-indices analysis to identify the seasonal variations in heavy metals in water, soil and food, including Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn, and evaluated the human health risk from Ni, Cd, and Cr contamination in the northern part of India. Their research results concluded that children are of the more susceptible age group due to carcinogenic risk from exposure to the Ni, Cd, and Cr through ingestion and also inhalation pathways in the investigated region.

The second topic cluster (characteristics and geochemistry of groundwater quality issues) includes eight articles contributed by researchers from Nigeria, Mexico, India, Iran, China, Ghana, Turkey, and Brazil. The optimal use of groundwater is very crucial in the arid and semi-arid regions of the globe, where the scarcity of water resources. In another article by Giri et al. (2021) applied the hydrogeochemical plots and also statistical analysis to identify the major controlling factors of groundwater chemistry in West Singhbhum, India. The authors concluded that the chemistry of groundwater is majorly controlled by the both geogenic and anthropogenic activities of the region. Furthermore, overall the groundwater quality was almost useful for both drinking and agriculture purposes in West Singhbhum, India. Hussainzadeh et al. (2023) investigated the geochemical assessment of groundwater resources in the Zanjan Plain, northwest of Iran. They noticed the concentration of HCO3−, SO42−, Fe, Pb, Zn, and NO3− exceeded the drinking water guideline. The leaching from industrial activities and also municipal dumpsites were the prominent sources of groundwater pollution in the northwest of Iran (Hussainzadeh et al. 2023). Roy et al. (2021) estimated the geochemical characteristics of shallow groundwater in the drought prone region of Mexico. Nwankwoala et al. (2023) conducted a study on the evaluation of groundwater quality for irrigation purposes in Khana and Gokana LGA in Rivers State in Nigeria. They used several indices: irrigation water quality index (IWQI), residual sodium carbonate (RSC), sodium adsorption ratio (SAR), magnesium ratio (MR), permeability index (PR), potential salinity (PS) and Kelly’s ration (KR) and as well as USSL classification, and Wilcox diagram to assess the groundwater quality for irrigation purposes in the drought prone region of Mexico, and Nigeria, respectively.

The topic cluster three consists of six articles (Table 1). The study by Xiao et al. (2021) showed the hydrogeochemical status and formation mechanisms of groundwater resources in the arid Golmud alluvial fan plain on the Tibetan plateau. They applied several indices, the first one was the entropy-weighted water quality index to estimate the suitability of groundwater for drinking purposes. In the context of irrigation water quality, they used sodium adsorption ratio (SAR), percentage of sodium (%Na), permeability index (PI), Doneen and USSL diagrams. The third one was the cumulative function to estimate the human health risk from fluoride and boron contaminated groundwater. Tyagi and Sarma (2021) studied the comprehensive quality estimation and also seasonal variability analysis of the groundwater resources in the semi-urban region of Uttar Pradesh, India. Dhakate et al. (2021) proposed a hydrogeophysical and groundwater modeling approach for assessing groundwater flow direction and water level monitoring in the rural part of Telangana State, India. Krishan et al. (2021) assessed the groundwater salinity and isotope characterization in the southwest Malwa region of Punjab, India. They also used groundwater level and contour maps, hydro-geochemical parameters and also suggested a few significant groundwater management measures for improving the groundwater quality. Kravchenko et al. (2022) used the ion exchange properties of these materials for removing Cs+, Sr2+, Cu2+, Co2+ and Cd2+ from the water. In another article by Saha et al. (2022) studied the concentration of Cd, Cr, Co, Pb and Cu metals in surface and groundwater in the eastern part of India. Furthermore, they noticed that the concentration of these metals in surface water reached a higher level compared to groundwater.

In total, there were four articles included in the fourth cluster, as shown in Table 1. Sabarathinam et al. (2021) adopted the major ion ratios, standard plots, geophysical techniques, isotopic techniques, and modelling methods to estimate the geochemical interrelationship between coastal saline groundwater and seawater from the coastal region of Kuwait. In another article on this thematic issue by Gopinath et al. (2021), collected several groundwater as well as sea and surface water samples to assess the groundwater–seawater interaction in the coastal region of Tamil Nadu state in India. These authors also used isotope studies, ionic ratios of Cl/Br and Br/Si, thermodynamic stability plots to estimate the source of salinity, the evolution process of salinity in groundwater, and seawater interaction in the coastal regions. Kim et al. (2021) specifically used the hydrogeological, hydro-geochemical, geostatistical multivariate statistical and also isotopic analysis were investigated to groundwater from Busan Metropolitan City of Korea. The paper by Prakash et al. (2021), terrestrial and recirculated submarine groundwater discharge derived nutrient fluxes were assessed in the Bay of Bengal from Coleroon river estuary, India.

As shown in Table 1, eight articles were included in the fifth cluster named “Identifying spatiotemporal variations in groundwater quality”. In fact, groundwater is the single most resource for drinking, agriculture, and industrial purposes in developing countries (DCs). In cluster five, the eight articles were received by active researchers very from the DCs such as India, China, South Africa, and Pakistan. Khan et al. (2022) investigated the groundwater quality resources for irrigation purposes using regression analysis, analysis of hydro-economic model and GIS, for sustainable groundwater development for practical agricultural production growth in the two major districts, i.e., Faisalabad and Toba Tek Singh of Punjab province, Pakistan. Jesuraja et al. (2021) assessed the drinking water quality index (DWQI), agricultural water quality index (AWQI), sodium adsorption ratio (SAR), sodium percentage (%Na), residual sodium carbonate (RSC), permeability index (PI) and GIS to improve groundwater conditions for irrigation purposes in the Tiruchendur coastal city, southern Tamil Nadu, India. Chakraborty et al. (2022) used sensitivity analysis, map removal sensitivity analysis, DRASTIC, and GIS to delineate the groundwater vulnerable zonal map to enhance groundwater quantity in unfavorable zones of the upper Dwarakeshwar river basin, India. Li et al. (2021) conducted a comprehensive study on hydrochemical analysis, ion ratio coefficient, hydrochemical types of groundwater, entropy-weight water quality index (EWQI), and GIS to assess the groundwater quality for various purposes in the northwest of Shandong province, China. Bhunia and Shit (2021) evaluated the descriptive characteristics of groundwater quality assessment parameters, and water quality index (WQI) for the identification of suitability of groundwater quality for drinking purposes and GIS for identifying the spatial distribution of ionic concentration and delineating the groundwater potential zones in Surguja district of Chhattisgarh, India. All these authors have used the prominent GIS tool to exemplify the groundwater potential zones, and also delineate the safe and unsafe zones to maximize the utility of groundwater for various purposes. Furthermore, strategically implementing the sustainable development steps to protect and improve the groundwater resources for future generations. Patience et al. (2021) conducted a study on the occurrence and distribution of trace metals in groundwater in the Luvuvhu catchment, South Africa. The article revealed that the distribution of trace metals (Li, Pb, Zn, B, and Cr) in the groundwater of Luvuvhu catchment was unevenly distributed, whereas, higher concentrations of silica, fluoride and nitrate were noticed due to mineral dissolutions and also from wastewater infiltration process. The article by Shukla et al. (2021) describes a study of the spatial distribution of groundwater quality and potential human health risks from fluoride and nitrate contamination in rural parts of Lalganjtehsil in Raebareli district, Uttar Pradesh, India. In this article, the authors also used the pollution index of groundwater (PIG) and geographic information system (GIS) to estimate groundwater quality for drinking purposes. Furthermore, children, female and male were judged to face human health risk from consumption of fluoride and nitrate through drinking water, but children were at highest risk than female and male in the rural part of India. Over all, Geographic Information System (GIS) is the most popular technical tool used in this thematic issue focus, where the authors aims to classify the geographical trend/spatial distribution of the ionic concentrations as well as distinguish the safe and perilous zones of water for various purposes in a study region.

Future research

Groundwater contamination is not only increasing rapidly in developing countries but is also recognized as a global problem. Mitigating the groundwater pollution issues requires close collaboration with scientists, researchers in universities as well as research organizations particularly at the national and also international level, industries, and private and public/government policymakers. This close collaboration genuinely creates an efficient and scientifically proven method to solve the specific groundwater contamination problems in an investigated region, because each problem has its own set of consequences and also limitations. Therefore, full-scale studies on groundwater quality are necessary to be conducted with the following general aspects.

  • Groundwater quality estimation studies should be initiated regularly to monitor the quality of groundwater for various purposes, specifically drinking uses, as groundwater is the major resource for drinking water supply in many developing countries (Xu et al. 2023; Adimalla and Qian 2023). Notably, implementing the latest methodologies, technologies and also geostatistical applications will surely enable us to identify not only the groundwater quality zones but also the major source of groundwater contamination in a study region. Groundwater researchers and scientists have to adopt new technologies such as machine learning (ML), artificial intelligence (AI), stable isotope analysis, geostatistical analysis, geographic information system (GIS), remote sensing, artificial neural network (ANN), various groundwater quality index and modeling methods for the better understanding of the groundwater contamination issues.

  • Multi-scale approaches (climate change, urban regions, human activities, agricultural, industrial influence, geological factors, regional scale, etc.) of the groundwater quality studies should be considered to uncover the actual geochemical mechanism of the hydrological process as well as the key factors of groundwater pollution sources. Understanding the groundwater quality changes by influencing various factors and key elements should meticulously be investigated and recognized.

  • Specifically, in many developing countries a high number of people rely on groundwater for drinking purposes that are unfortunately contaminated with various contaminates which directly creates a wide range of human health issues (Kim et al. 2021; Adimalla and Qian 2021). Thereby, the government (public and private organizations) need to allocate special research grants, particularly for focusing on groundwater quality studies in developing countries and also encourage researchers and scientists for conducting hydrogeochemical studies in urban and rural regions to comprehensively understand the quality of groundwater and also identify the source of groundwater contamination.