## 1 Introduction  
Heavy metals are ubiquitous in soil environment, and their main source is natural and human activities [1, 2]. The addition of chemical fertilizers and pesticides and sewage irrigation in agricultural production can lead to the accumulation of heavy metals in soil [3]. Heavy metals are important indicators of environmental health and are closely related to the health of animals, plants, and humans [2, 4]. Accumulation of high concentration of heavy metals in soil leads to decline in soil function and seriously threatens crop growth [5, 6]. Moreover, it affects not only crop yield and quality but also the quality of the environment and water bodies, thereby threatening the health of animals and humans through food chain [7]. Soil is the main source of trace elements for plants and pollutants. Soil-to-plant transfer of trace elements is a part of the chemical element cycle in nature. This is a complex process influenced by both natural and human factors [8].  
Different plants have different characteristics of absorbing elements, which depend on multiple internal and external factors. For example, _Fagopyrum esculentum_ is efficient in accumulating Co, whereas corn and rice efficiently accumulate Cr and Ge [9]. In most cases, the concentration of elements in plants reflects their abundance in the growth medium (soil, nutrient solution, or water) and air. Some trace metals, such as Cu, Fe, Mn, and Zn,play a key role in plant metabolism and are components of various enzymes. However, metal poisoning can occur when a certain threshold is exceeded. [PERSON] et al. (1999) proposed that excess trace metals cause biochemical changes in plants, which are similar to the responses caused by pathogenic attack [10]. However, during the evolution process, plants have developed mechanisms for adapting to or avoiding stressors. In addition, metal elements absorbed in plants interact with each other and exhibit antagonism and synergy in varying degrees, which may occur within cells, membrane surfaces, and around plant roots. Although this interaction can greatly contribute to the chemical balance in plants, the accumulation of heavy metals in plants can still pose a threat to human health, particularly in case of perennial Chinese herbal medicines [11].  
Chinese herbal medicines (CHMs) play an important role in Chinese healthcare and are now widely used globally [12]. American ginseng (_Panax quinquefolium_ L.) is a valuable perennial herb. It has various pharmacological effects such as antioxidant, antidiabetic, and anticancer and enhances the central nervous system function [13; 14; 15; 16; 17]. Studies have reported that CHM and other herbal supplements can be contaminated with heavy metals, even reaching toxic levels in some cases [18; 19; 20]. As an important herbal medicine, American ginseng has attracted much attention for its safety, particularly its potential safety hazards such as heavy metal content exceeding the standard levels. Heavy metal elements such as copper (Cu), manganese (Mn), arsenic (As), lead (Pb), cadmium (Cd), chromium (Cr), and nickel (Ni) are frequently detected in CHM. When these heavy metal elements are taken up by human body, they are gradually accumulated and are difficult to eliminate [21; 22; 23].  
At present, specialized and systematic research on the problem of excessive heavy metal content in CHM is lacking; particularly, the distribution of heavy metals in various parts of plants is rarely studied. In this study, we aimed to assess the content and accumulation characteristics of seven heavy metals including Cu, Mn, As, Pb, Cd, Cr, and Ni in various parts of American ginseng and analyzed this content with reference to the limits given in the _Chinese Pharmacopoeia_ promulgated by China. Furthermore, we explored the effect of soaking of American ginseng plant for various time intervals on the heavy metal content. This study provided a reference for heavy-metal-free cultivation of high-quality American ginseng and for sustainable development of the American ginseng industry.