Abstract Myanmar, in Southeast Asia, is categorized as a Least Developed Country, facing substantial challenges towards meeting 2030 Sustainable Development Goal targets, including ensuring access to safe water and sanitation. The occurrence of geogenic contaminants, notably arsenic, in Myanmar groundwaters is relatively poorly understood, particularly as compared to other countries in South/Southeast Asia. Improving the understanding of groundwater quality in Myanmar is hence a major concern and relevant to the health of millions of local inhabitants who extensively use groundwater. A groundwater survey was undertaken at 85 sites across five distinctly contrasting zones within three of Myanmar's main river basins (Chindwin-Ayeyarwady, Sittaung, and Salween) to assess the occurrence of arsenic and other potentially harmful elements, and to study the dominant geochemical controls in each zone/basin. A significant number of samples were affected by water quality issues, based on World Health Organization (WHO) guidelines, including elevated arsenic (>10 μg.L−1) in 14% of all samples within the basins studied. Fluoride, nitrate, salinity, iron, manganese, and aluminum also exceeded WHO drinking water guidelines in some locations. Arsenic typically occurred as inorganic AsIII and largely arose from the reductive dissolution of Fe(Mn)-(hydro)xides and was broadly associated with relatively high HCO3 and NH4. Variable dominant geochemical controls on groundwater composition were identified, notably (i) calcite and dolomite dissolution in the Salween basin; (ii) cation exchange, carbonate dissolution and saline intrusion in the Ayeyarwady delta; and (iii) gypsum dissolution, silicate weathering, and cation exchange in Chindwin-Middle Ayeyarwady. This reconnaissance study provides new information on groundwater composition and corresponding geochemical controls across contrasting, and previously underrepresented, areas of Myanmar and may help to inform further hazard assessment, monitoring and/or mitigation strategies.

中文翻译：

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缅甸中部和南部的主要和微量（包括砷）地下水化学

摘要 东南亚的缅甸被归类为最不发达国家，在实现 2030 年可持续发展目标方面面临重大挑战，包括确保获得安全用水和卫生设施。人们对缅甸地下水中地质污染物（尤其是砷）的发生情况知之甚少，尤其是与南亚/东南亚其他国家相比。因此，提高对缅甸地下水质量的了解是一个主要问题，并且关系到数百万广泛使用地下水的当地居民的健康。在缅甸三个主要河流流域（钦德温-伊洛瓦底、实当和萨尔温江）的五个截然不同区域的 85 个地点进行了地下水调查，以评估砷和其他潜在有害元素的发生情况，并研究每个区域/盆地的主要地球化学控制。根据世界卫生组织 (WHO) 指南，大量样本受到水质问题的影响，包括在所研究流域内 14% 的所有样本中砷含量升高 (>10 μg.L-1)。在某些地方，氟化物、硝酸盐、盐分、铁、锰和铝也超过了世卫组织的饮用水指南。砷通常以无机 AsIII 的形式出现，主要来自 Fe(Mn)-（氢氧化物）氧化物的还原溶解，并且与相对较高的 HCO3 和 NH4 广泛相关。确定了对地下水组成的可变主要地球化学控制，特别是 (i) 萨尔温江盆地的方解石和白云石溶解；(ii) 伊洛瓦底江三角洲的阳离子交换、碳酸盐溶解和盐分侵入；(iii) 石膏溶解，Chindwin-Middle Ayeyarwady 的硅酸盐风化和阳离子交换。这项勘察研究提供了关于地下水组成和相应地球化学控制的新信息，跨越缅甸对比鲜明且以前代表性不足的地区，并可能有助于为进一步的灾害评估、监测和/或缓解策略提供信息。