Resumen
The contents of major and trace elements were analyzed in 204 different types of water samples in 138 villages across 51 counties and cities of Tibet. The average concentrations of arsenic (As), selenium, and fluorine for each water category decreased in the following order: arsenic (in µg/L: hot spring 241.37 > lake 27.46 > stream 22.11 > shallow well 11.57 > deep well 6.22), selenium (in µg/L: deep well 0.85 > shallow well 0.68 > stream 0.62 > hot spring 0.39 > lake 0.36), and fluorine (in mg/L: hot spring 2.10 > lake 1.06 > deep well 0.45 > stream 0.20 > shallow well 0.15). The distribution of arsenic in Tibetan waters ranged between 77.35 µg/L in Ali prefecture and 1.17 µg/L in Chamdo prefecture, with intermediate values of 4.39, 2.52, 2.10, 1.68, and 1.51 µg/L in the prefectures of Shigatse, Nagchu, Lhasa, Lhoka, and Nyingchi, respectively. Carbonatite is a major source of elements in these waters. The non-carcinogenic risk in Tibet caused by heavy metals in drinking water is low overall, except in Ali prefecture?s surface and shallow ground waters, which contain high levels of As. Thus, deep well water in Tibet is safe to drink.