## 1 Introduction  
Urbanization has emerged as one of the most significant trends of the 21 st century, and more than half of the global population resides in urban areas nowadays [1, 2, 3]. The sustainable development of urban environments is inextricably linked to a stable and reliable supply of freshwater resources, which are essential not only for the prosperity of agriculture and industry but also for economic growth and the maintenance of healthy ecosystems [3; 4; 5]. Thus, research on the availability of freshwater resources is crucial for the development of natural systems and the human community. Groundwater is widely acknowledged as a preferred water supply source due to its wide distribution, low pollution, steady flow, and quality [6]. Globally, it provides drinking water for billions of people and supports a wide range of economic activities, including agriculture and industry [7; 8; 9]. With the rapid urbanization taking place across many regions, ensuring an adequate supply of high-quality groundwater is more and more essential for socioeconomic development. However, it should be realized that groundwater resources are also facing threats from continuous global population growth, accelerated urbanization, and intensified climate change impacts, bringing mounting challenges for sustainable groundwater utilization [10; 11; 12]. The availability of groundwater depends not only on quantity but also on quality [13]. Therefore, groundwater chemistry and quality assessments are of paramount importance to provide the necessary scientific foundation for creating management strategies to safeguard groundwater and ensure its sustainable use in urbanized regions [14; 15; 16]. Normally, groundwater chemistry is the result of various natural factors, such as recharge water property, lithology of aquifers, and evaporation intensity [17; 18; 19]. Human activities have played an increasingly significant role in influencing the groundwater components over the past decades, resulting in heavy salinization and pollution of groundwater [20; 21; 22]. Plenty of studies have indicated the serious negative impacts that groundwater degradation has on human survival and ecosystem balance [23; 24; 25]. In agriculture, the use of highly saline groundwater for irrigation operations will be harmful to both soil and plants, leading to adverse consequences such as soil consolidation, decreased fertility, and reduced crop yields [25; 26]. In daily water consumption, it is globally acknowledged that nitrate and fluoride are the most common pollutants deteriorating the groundwater quality [27; 28]. Generally, anthropogenic inputs are the main factors contributing to excessive nitrate and fluoride in groundwater in comparison with natural processes [27; 29; 30]. Especially, it is reported that anthropogenic practices such as fertilizer overuse and improper disposal of manure sewage are the main causes of groundwater nitrate contamination [31; 32; 33]. Apparently, understanding groundwater chemistry means clarifying the specific processes of natural and anthropogenic factors that regulate groundwater geochemistry [34]. As serious groundwater pollution becomes prevalent, the corresponding health problem has been a concern for drinking in many regions [14; 35]. Reportedly, drinking groundwater with surplus nitrate could lead to human diseases, including cardiovascular disease and blue baby syndrome [12; 36]. Also, over intake of fluoride through groundwater could damage human health with the diseases of dental fluorosis and skeletal fluorosis [37; 38]. A number of studies have investigated the human health risks associated with groundwater pollutants, donating significantly to the healthy groundwater supply around the world [39; 40; 41; 42; 43; 44; 45]. However, still inadequate attention has been paid to the valley basins in arid and semi-arid regions [46]. Valley basins are important landform units for human settlement in arid and semi-arid regions, besides alluvial fan plains.