With the imminent industrial growth and population increase, Nigeria will continue to experience significant shifts in the quality of water, with a rise in emerging contaminants. This will increase the irregularity and complexity of the water quality information. Therefore, using the PRISMA meta-analysis approach, this review systematically identified the commonly used water quality assessment techniques in Nigeria, the drawback in the application of these techniques as well as the gaps in the area of water quality assessment and monitoring from 2003 to 2023. Recommendations were also made based on the evaluation of a new research direction; through the review of the effectiveness of advanced techniques for monitoring water quality in Nigeria. Sixty-eight published articles were chosen for the meta-analysis while the VOSviewer program was used to perform bibliographic coupling and visualization. The review revealed that the application of machine learning in water quality prediction has not been well explored in Nigeria. This is attributed to limited data availability and poor funding by the government. It was found that southwestern Nigeria has a greater amount of research on groundwater quality monitoring and evaluation than other regions. The variability was explained by variations in the underlying geology, aquifer features; variability in anthropogenic activities, and level of literacy among various geopolitical zones. Further studies should focus on the application of soft-computing and integrated biomonitoring techniques for effective prediction and monitoring of emerging contaminants for improved water quality. Effective collaboration between environmental stakeholders and government agencies is recommended for effective water resource sustainability.

The presence of pollutants like uranium and arsenic in the groundwater can have a terrible impact on people\'s health (both radiologically and toxicologically) and their economic conditions. Their infiltration into groundwater can occur through geochemical reactions, natural mineral deposits, mining and ore processing. Governments and scientists are working to address these issues, and significant progress has been achieved, but it\'s challenging to deal with and mitigate without adequately understanding the different chemical processes and the mobilization mechanism of these hazardous chemicals. Most of the articles and reviews have focused on the particular form of contaminants and specific sources of pollution, such as fertilizers. However, no literature report exists explaining why particular forms appear and the possible basis of their chemical origins. Hence, in this review, we tried to answer the various questions by devising a hypothetical model and chemical schematic flowcharts for the chemical mobilization of arsenic and uranium in groundwater. An effort has been made to explain how chemical seepage and excessive groundwater use resulted in the change in aquifers\' chemistry, as evidenced by their physicochemical parameters and heavy metal analysis. Many technological advancements have taken place to mitigate these issues. Still, in low-middle-income countries, especially in the Malwa region of Punjab, also known as Punjab\'s cancer belt, paying a high amount for installing and maintaining these technologies is an unviable option. In addition to working to improve people\'s access to sanitary facilities and clean water to drink, the policy-level intervention would focus on increasing community awareness and continued research on developing better and more economical technologies. Our designed model/chemical flowcharts will help policymakers and researchers better understand the problems and alleviate their effects. Moreover, these models can be utilized in other parts of the globe where similar questions exist. This article emphasises the value of understanding the intricate issue of groundwater management through a multidisciplinary and interdepartmental approach.

Fluoride contamination in the groundwater has got great attention in last few decades due to their toxicity, persistent capacity and accumulation in human bodies. There are several sources of fluoride in the environment and different pathways to enter in the drinking water resources, which is responsible for potential effect on human health. Presence of high concentration of fluoride ion in groundwater is a major issue and it makes the water unsuitable for drinking purpose. Availability of fluoride in groundwater indicates various geochemical processes and subsurface contamination of a particular area. Fluoride-bearing aquifers, geological factors, rate of weathering, ion-exchange reaction, residence time and leaching of subsurface contaminants are major responsible factors for availability of fluoride in groundwater. In India, several studies have reported that the groundwater of several states are contaminated with high fluoride. The undesirable level of fluoride in groundwater is one of the most natural groundwater quality problem, which affects large portion of arid and semiarid regions of India. Rajasthan, Andhra Pradesh, Telangana, Tamil Nadu, Gujarat, and West Bengal are the relatively high-fluoride-contaminated states in India. Chronic ingestion of high doses of fluoride-rich water leads to fluorosis on human and animal. Over 66 million Indian populations are at risk due to excess fluoride-contaminated water. Therefore, groundwater contamination subject to undesirable level of fluoride needs urgent attention to understand the role of geochemistry, hydrogeology and climatic factors along with anthropogenic inputs in fluoride pollution.