Toxic heavy metals are deposited in soils from natural and human activities [47]. As a consequence of environmental and health issues, soil heavy metal pollution has a huge interest [35]. The A horizon is called “topsoil”, in this layer, minerals are present which are generated from the parent material with the organic matter accumulating. The B horizon is called “subsoil” or “zone of accumulation”, the mineral seeps down from the A or E horizons and accumulates in this layer. However, the variation of the elemental concentrations is higher in the A and B horizons. The B horizon, or the third layer of soil, contains the majority of heavy metals [48]. This layer comprises components that were dissolved in the higher layer (the A horizon) and subsequently moved down or sidelong into the inferior layer, where they were dumped, and heavy metals are drawn to the B horizon because it has a high content of iron oxyhydroxides and clay, both of which can absorb cationic aspects [48]. Microorganisms cannot degrade heavy metals in the soil; therefore, they accumulate, influence the soil’s properties, and are assimilated and enhanced in biomass [49]. Cadmium (Cd) pollution is a major problem in China’s agriculture [23]. Pb, Cd, polybrominated biphenyls (PBBs), polybrominated diphenyl ethers (PBDEs), and polychlorinated biphenyls (PCBs) have appeared in high quantities in rice and organic contaminants have been found in vegetables growing surrounding unmanaged e-waste recycling locations [19]. E-waste soil samples frequently contain persistent organic pollutants (POPs), including polycyclic aromatic hydrocarbons (PAHs) and PBDEs. In 2011 (0.59 mg/kg) and 2016 (0.40 mg/kg), researchers found high molecular weight polycyclic aromatic hydrocarbons (PAHs) in paddy soils close to e-waste recycling areas in Taizhou, China [50]. The principal pollutants of concern in e-waste-affected soil are Pb and Cd [50]. According to [19], the maximum Pb (629–7720 mg kg⁻¹) and Cd (3.05–46.8 mg kg⁻¹) contents found in soils around e-waste combustion operations far surpassed Chinese farming soil requirements (Pb: 250 mg kg⁻¹; Cd: 0.3 mg kg⁻¹). Metal concentrations were highest in historic e-waste incineration locations, with an average of 17.1 mg kg⁻¹ of Cd, 11,140 mg kg⁻¹ of Cu, 4500 mg kg⁻¹ of Pb, and 3690 mg kg⁻¹ of Zn. Metals in high amounts could seep out of the locations and contaminate pond water and sediment [19].

Apart from soil pollution, which can contribute to water quality degradation and various negative environmental effects, heavy metal replication across the food supply chain has serious health impacts [51]. The global demand for freshwater is steadily increasing. Because arsenic (As) pollution affects such a broad population, the toxicity resulting from As enrichment in sedimentary aquifers beyond prescribed limits, which causes drinking water contamination, is a global concern [52]. Because As species are proven carcinogens, their presence in the environment is a primary public concern and is linked to severe health hazards [53]. The possible polluting roots from agriculture, including fertilizer, urban (such as wastewater), and industrial (including spills and leaks), and groundwater contact with surface water sources including rivers and lakes. This refers to the spread of new infections due to pesticides, and it is a threat to human health [55].

Chronic exposure to harmful contaminants in groundwater has negative health consequences and leads to serious diseases such as cancer, neurological disorders, reproductive system damage, congenital malformations, and, more recently, diabetes mellitus [55]. Enormous amounts of wastewater are released during the liquid and solid separation [56]. Pollutants can enter the groundwater system through karstic soils [55]. Karst covers around 30% of China’s land surface, and karst aquifers provide a quarter of the country’s groundwater supplies (200 billion m³ per year) [57]. Many karst locations worldwide have experienced rocky desertification, particularly in southwest China’s karst area, known as the world’s biggest karst area with constant carbonate rock outcrops [58]. Contamination in the atmosphere in the karst area is difficult to dissipate before precipitating again due to its unique geomorphological properties, as the environmental fragility of the karst aquifer in southwestern China is widely recognized [57]. According to [59], currently, no research has been done on the impact of karst water with various chemical properties on dissolved organic matter (DOM) leaching into karst soils. According to the various contaminants, heavy metals are numerous important and dangerous contaminants for groundwater [60]. The Lianjiang River was found to be polluted by As, Cr, molybdenum (Mo), selenium (Se), lithium (Li), and antimony (Sb), whereas the Nanyang River had higher levels of Ni, Zn, Cu, Pb, cobalt (Co), and silver (Ag) [50]. Toxic heavy metals have been found in wastewater discharged from tailing ponds: Pb, Zn, Cu, Cr, Ni, and As at average concentrations of 4.33, 269.90, 2.40, 1.69, 1.04, 11.40, and 24.62 g/L, respectively [61].

In China, 28% of groundwater examinations surpassed the WHO limit contamination level (10 mg N L⁻¹) between 2000 and 2012. Up to 36% of the river sectors and 40% of the main lakes in China did not fulfill the quality standards to be used as drinking water sources in 2010 [62]. Rainwater, surface runoff, and groundwater in karst environments frequently have high Ca²⁺ levels [59]. Surface waters (from springs and streams to rivers and lakes) can transport heavy metals across long distances, and their chemical structure varies depending on the geological characteristics through which they travel [48]. Furthermore, surplus nutrients in rivers are transferred to seas, resulting in nearly 500 instances of hazardous algae blooms in China’s shore waters between 2006 and 2012, posing a threat to human health and shore ecosystems [62]. For a sustainable future, technologies that improve the efficiency of agriculture irrigation are required to grow more food or biomass with less water [63]. Because of socioeconomic and climate changes, this scenario is predicted to deteriorate in the future [62]. The hydrological cycle can forecast several climate change consequences [64]. In e-waste operations, there is still a severe lack of evidence about the origins and characteristics of heavy metal pollution. Groundwater is quickly depleting due to global climate change, and this process is threatening to overrun the entire water cycle. Because the rain cycle follows a four-step procedure in which groundwater is used in the evaporation and condensation process, the aquifer is an important aspect of the rain cycle. Unfortunately, global warming has disrupted the entire cycle.