To provide a comprehensive insight into the enrichment mechanism of gallium and indium in No. 9 coals, eighteen samples were collected from Anjialing mine, Ningwu Coalfield, Shanxi Province for coal petrological, mineralogical and geochemical analyses. The results suggested that Ga and In enrichment mainly hosted in the top horizons, with average concentration coefficients of 8.99 and 2.73 respectively, compared with the rest of horizons (2.46 for Ga and 1.69 for In). Source apportionment indicated that Ga and In were mainly derived from bauxite of Benxi Formation in Yinshan Oldland, while In could originate from felsic magmatic rocks in Yinshan Oldland as well. In addition, weak oxidation condition, medium to intensive weathering, transgression and input of terrestrial higher plants had positive effects on Ga and In enrichment. With the rapid expansion of emerging electronics manufacturing, Ga and In, of which potential risks on human health were neglected previously, were recently considered as hazardous elements. Therefore, this paper also discussed the potential pathways that these elements threatened human health. We suggested that potential risks on environment and human health caused by Ga and In enrichment in coals and coal-related products should be taken into account besides their economic value.

中文翻译：

---

华北宁武煤田安家岭煤矿9号煤中镓和铟的富集机理及其潜在健康风险的初步探讨

为了全面了解9号煤中镓和铟的富集机理，从山西省宁武煤田安家岭矿采集了18个样品，用于煤岩石学，矿物学和地球化学分析。结果表明，Ga和In的富集主要集中在顶层，平均浓度系数分别为8.99和2.73，而其余各层（Ga为2.46，In为1.69）。来源解析表明，Ga和In主要来源于银山古地本溪组的铝土矿，而In也可能来源于银山古地的长英质岩浆岩。此外，弱氧化条件，中度至强烈风化，海侵和陆生高等植物的输入对Ga和In的富集有积极作用。随着新兴电子制造业的快速发展，Ga和In被视为有害元素，而Ga和In在先前已忽略了对人体健康的潜在风险。因此，本文还讨论了这些元素威胁人类健康的潜在途径。我们建议，除煤和煤炭相关产品的经济价值外，还应考虑到Ga和In富集对环境和人类健康造成的潜在风险。