[Heavy Metal Pollution Characteristics and Risk Assessment of Soil-crop System in Gold Mine Activity Area]

A contamination analysis was conducted on the soil and crops in the Liu Jia Dian gold mining area of the Pinggu District, Beijing, utilizing the contents and seven-step forms of heavy metals （Hg, Cd, Cr, Pb, and As） in soil and the heavy metal contents in crops at the same location. An assessment of ecological risk caused by heavy metal contamination in the soil and crops was carried out using the enrichment coefficient method and the risk assessment coding method. The study investigated the process of heavy metal absorption and enrichment in the soil-crop system, aiming to establish a scientific foundation for preventing and controlling soil pollution, as well as ensuring the safety of edible crops in the study area. Evidence indicated the presence of soil contamination by heavy metals in the study area, with Cd, Pb, and As being the primary pollutants. Moreover, the distribution of pollution levels could be categorized as severe, moderate, and mild, with proportions of 26.09%, 4.35%, and 10.87%, respectively. The content of each heavy metal decreased following the implementation of environmental governance； however, the ecological risk remains present. Hg, Cr, Pb, and As posed minor ecological risks； however, Cd had a high ecological risk, making it the primary soil ecological risk factor. Fruits, nuts, and cereals in the Pinggu gold mining area remained uncontaminated. Various degrees of contamination were found in melons, rhizomes, and leafy vegetables. The Chinese cabbage, Chinese chive, radish, and eggplant were heavily contaminated, with Cd and Pb being the primary sources of contamination. The accumulation of heavy metals in crops was intricately linked to gold mines and their mining operations. The accumulation of Cd in crops was mainly influenced by the high availability of Cd in soil, whereas the accumulation of Pb was mainly influenced by the high concentration of Pb in the soil. The concentration of heavy metals in the soil and their bioavailability in the Pinggu gold mining area indicated the accumulation of metal elements in crops and impacted the geographical distribution of heavy metal pollution in crops. The physiological characteristics of crops could affect the degree of heavy metal enrichment in the gold mining area. The order of heavy metal accumulation, from highest to lowest, was as follows： leafy vegetables, melons, rhizomes, cereal, fruits, and nuts. Peppers and eggplants were limited in their planting variations for melons, while leeks and cabbages were restricted for leafy vegetables, given the current agricultural planting conditions in the study area.