This study assessed heavy metal contamination and associated health risks in soils and crops in the vicinity of a mercury mine located in Tongren, Guizhou Province, China, focusing on mercury (Hg), cadmium (Cd), arsenic (As), lead (Pb), and chromium (Cr). The study used the Index of Geological Accumulation (Igeo) and Health Risk Assessment (HRA) to quantify the level of contamination and assess the potential risks. The results showed that Area I was the most severely contaminated, with 94.24% of the sample sites being heavily contaminated with mercury, followed by Area II and Area III with severe cadmium contamination. The health risk assessment showed that children were exposed to non-carcinogenic risks of mercury and cadmium that exceeded the safety thresholds, with mercury being the major non-carcinogenic factor, especially through oral intake. The study also assessed the contribution of each heavy metal to pollution, with mercury contributing the most to ecological and health risks, especially in Areas I and III. The study highlights the urgent need to strengthen pollution control strategies, focusing on mining activities and agricultural inputs, to reduce risks and protect public health.

The low-temperature formation of dolomite (CaMg(CO₃)₂) is undoubtedly a long and interesting geological problem, which has troubled many researchers for centuries to explore the formation of dolomite. Recently, efforts have been made by synthesizing dolomite analogues such as norsethite (BaMg(CO₃)₂), PbMg(CO₃)₂, with Ba and Pb to replace Ca and investigating their reaction pathways. In this study, we reported our efforts to synthesize dolomite-related complex carbonates by using the mechanical ball milling method as a new approach to control the solid–water ratio compared to the commonly used solution method. Two analogues of norsethite and PbMg(CO₃)₂ have been simply obtained even at stoichiometric molar ratio of Ba/Mg = 1:1 and Pb/Mg = 1:1 with various parameters examined; and product properties including morphology and phase compositions were investigated by a range of techniques, including XRD, SEM-EDS, and FTIR. Finally, we attempted to synthesize dolomite and compared the differences from the synthesis of analogues. In conclusion, we have synthesized norsethite and PbMg(CO₃)₂ in one step by the ball milling method, which greatly reduces the reaction time compared with the conventional solution method and may provide other choices for the formation of dolomite.

Heavy metal pollution severely affects soil and rice quality in China. In a one-year field experiment conducted in Hg-Cd co-contaminated farmland in Tongren, Guizhou, we examined the effects of low-accumulation rice cultivars, soil amendments (Fupei (D1), Wansan (D2), Shengwujun (D3), and Shigou (D4)) and foliar barrier agents on Hg and Cd transport and uptake. The rice cultivar Longliangyouhuanglizhan (P1) showed lower Hg and Cd accumulation. When combined with amendments, P1 further reduced health risks. All amendments effectively reduced non-carcinogenic health risks, with Fupei reducing Hg and Cd accumulation in rice by 65.16% and 97.54%, respectively, achieving a 91.74% reduction in health risks. Foliar barrier agents further decreased heavy metal content in rice. Additionally, D1 was the most cost-effective option. Soil assessments showed amendments reduced available Hg content by 66.67–70.51%, while Cd content increased by 3.51–16.67%. Mechanistic analysis indicated that D1 and D2 mainly immobilized heavy metals through adsorption and precipitation, while D3 facilitated removal via microbial reduction, and D4 relied on adsorption. Overall, D1 was most effective in mitigating heavy metal risks and improving soil quality, providing a comprehensive strategy for managing contamination in rice production with important implications for food safety and sustainable agriculture.