Nui Phao mine in Thai Nguyen Province, Vietnam, is the second-largest tungsten (W) open-pit mine in the world, but the level of environmental impacts is not well known. In order to examine the heavy metal contamination in the ecosystem of this mining area, we analyzed six trace elements (As, Cd, Cr, Cu, Pb and Zn) in the collected soil samples. The analytical results showed that all the soil samples were contaminated by Cd and As. Most of the soil samples were contaminated by As (mean value 50.93 ± 55.44 mg/kg) and Cd (mean value 15.22 ± 9.51 mg/kg), which figures are up to 16 and 23 times higher, respectively, compared with the Vietnamese soil quality standard for agriculture (QCVN 03-MT:2015/BTNMT) of 15 mg/kg for As and 1.5 mg/kg for Cd. Contamination factor (CF), enrichment factor (EF), geo-accumulation index (Igeo), principal component analysis (PCA) and hierarchical clustering analysis (HCA) were used to identify the influence of mining activity in the contamination. The CF, EF, pollution index (PI) and Igeo indicated that this area was extremely polluted by Cd, severely to moderately–heavily polluted by As and slightly to moderately polluted by other elements such as Cr, Cu, Pb and Zn. The PCA and HCA results also attribute the source of As, Pb and Zn contamination and enrichment of Cd, Cr and Cu in the study area to Nui Phao mining activities. The PI and contamination degree (C_d) values of soil quality indicate that the study area was contaminated with particular reference to Cd and As and the level of contamination was decreased in the order of Pb > Cr > Cu > Zn. The study area had high potential ecological risk, and the carcinogenic risk value was higher than the acceptable value (1 × 10⁻⁶ to 1 × 10⁻⁴). This means that the local resident health is strongly affected by Nui Phao mining activities both directly and indirectly via food consumption, when rice plant grown in the paddy field is the dominant crop in the study area.

越南泰国阮省的Nui Phao矿山是世界第二大钨（W）露天矿，但对环境的影响程度却鲜为人知。为了检查该矿区生态系统中的重金属污染，我们分析了收集的土壤样品中的六种微量元素（As，Cd，Cr，Cu，Pb和Zn）。分析结果表明，所有土壤样品均被镉和砷污染。大部分土壤样品都被As（平均值50.93±55.44 mg / kg）和Cd（平均值15.22±9.51 mg / kg）污染，分别比越南土壤高16倍和23倍。农业质量标准（QCVN 03-MT：2015 / BTNMT）的砷含量为15 mg / kg，镉的含量为1.5 mg / kg。污染因子（CF），富集因子（EF），地积累指数（Igeo），主成分分析（PCA）和层次聚类分析（HCA）用于确定采矿活动对污染物的影响。CF，EF，污染指数（PI）和Igeo表示该区域受到Cd的极度污染，被As重度至中度至重度污染，并被Cr，Cu，Pb和Zn等其他元素轻度至中度污染。PCA和HCA结果也将研究区的As，Pb和Zn污染源以及Cd，Cr和Cu的富集归因于Nuphao采矿活动。PI和污染度（As被重度至中度重度污染，Cr，Cu，Pb和Zn等其他元素轻度至中度污染。PCA和HCA结果也将Nua Phao采矿活动归因于研究区域中As，Pb和Zn污染的来源以及Cd，Cr和Cu的富集。PI和污染度（As被重度至中度重度污染，Cr，Cu，Pb和Zn等其他元素轻度至中度污染。PCA和HCA结果也将研究区的As，Pb和Zn污染源以及Cd，Cr和Cu的富集归因于Nuphao采矿活动。PI和污染度（土壤质量的C _d）值表明研究区域受到了特别是Cd和As的污染，污染水平按Pb> Cr> Cu> Zn的顺序降低。研究区具有较高的潜在生态风险，致癌风险值高于可接受值（1×10 ^-6至1×10 ^-4）。这意味着，当稻田中种植的水稻植物是研究区域的主要农作物时，Nui Phao采矿活动直接或间接地通过食物消耗极大地影响了当地居民的健康。