## 1 Introduction  
The exploitation of mineral resources has greatly promoted the development of regional economies, but long-term mining and the stacking of tailings have also become the source of environmental hazards under economic prosperity [1, 2]. In particular, the release, migration, and transformation of heavy metals in the environmental medium have a great impact, causing serious pollution to the surrounding soil, water bodies, and habitats, threatening the ecological balance and human security [3, 4, 5], and restricting the construction of an ecological civilization. Soil is the most important medium to maintain balance and stability of an ecosystem, especially the soil quality of agricultural land [6, 7]. The content of heavy metals in soil is mainly controlled by soil-forming parent materials and human activities. Human activities such as sewage irrigation, mining and smelling of metal ores, and combustion of industrial wastes and fossil fuels have been proven to be the main causes of heavy metal pollution in the soil of China [8; 9; 10]. Among them, the mining of metals, beneficiation, and smelting activities are the main human activities that cause heavy metal pollution in soil, water, and the biosphere [11]. It is reported that the area of polluted soil is increasing at a rate of 46,700 \(\mathrm{hm}^{2}\) every year due to mining in China [12]. Therefore, the phenomenon of heavy metal pollution in soil related to mining activities has always been a research hotspot. In recent years, studies have shown that mining activities cause soil heavy metal pollution [13]. In many parts of the world, heavy metals produced by mining activities cause serious environmental problems, especially when they pollute the surrounding farmland [14]. Concerns and research surrounding heavy metal polluted soil caused by mining are increasing all over the world. [PERSON] et al. evaluated the environment quality of the Barramiya gold mine area in the eastern desert of Egypt and found that there are 318-500 t tailings in the area, which cause serious heavy metal pollution to the surrounding environment due to erosion, weathering, and surface runoff [15]. [PERSON] et al. analyzed the heavy metals of different solid mine wastes in a Ghana mining area and found that the degree of ecological risk varies with the type of wastes: tailings > sulfide > oxide [16]. [PERSON] et al. studied heavy metals in farmland around an abandoned gold mine in South Korea and found that farmland types have an impact on the spatial distribution of heavy metals in soil [17]. The geochemical characteristics of ore samples and of stream-sediment samples from the Tri-State district indicated that past mining activities and leaded gasoline have had significant effects on lead concentrations in river sediments [18]. [PERSON] et al. investigated heavy metals (Cd, Cu, Pb, and Zn) from the Pb-Zn-Ag and Cu mines at Mount Isa, Queensland, Australia, and showed that the heavy metal content in the surface soil near the mining area (within 2 km) was obviously higher than that far away and that the ecological risk level of lead was very high [19]. Dachang Town in Guangdong is an important tin polymetallic production area in China. It is known as \"China's Cenozoic tin capital\" and has long-term mining history. However, in the process of early development and utilization, large amounts of tailings were not fully utilized and accumulated on the surface due to the constraints of technical conditions and production concepts. The tailing dumps have been under the action of oxidation for a long time, and the heavy metal elements (e.g., Cu, Pb, Zn, and Cd) have been gradually activated, invading the surrounding soil through rainwater leaching, atmospheric dust, and other ways, threatening the ecological environment of farmland soil and endangering the health of residents through food chain enrichment. Therefore, it is urgent to carry out research on heavy metal pollution of soil in the area.