Objective To inwestigate the level and distribution characteristics of 5 common selenium speciation in drinking water of 14 cities in key river basins and lakes of China, and to provide basis for selenium pollution control and limit revision.

Methods A total of 84 water samples of source water, finished water and tap water were collected from 28 municipal water plants which were selected as monitoring points in 14 cities of nine key river basins and one key lake(Chaohu) from November to December 2020. The speciation and concentration of selenium were determined by high performance liquid chromatography inductively coupled plasma mass spectrometry (HPLC-ICP-MS). The selenium form content in different water sample types and different water source types were analyzed by Kruskal-Wallis H test and Mann-Whitney U test.

Results Three organic selenium speciation were not detected in the drinking water of 14 cities in China. The Median (minimum, maximum) of Se(IV), Se(VI), total inorganic selenium, and the total amount of the five selenium forms were 0.03 (0.03, 0.39), 0.18 (0.03, 0.58), 0.23 (0.06, 0.79) and 0.45 (0.34, 1.01) μg/L, respectively. The concentration of Se(IV) in source water was higher than that of finished water and tap water (P < 0.05), there was no statistically significant difference of Se(VI), total inorganic selenium and the total amount of the five selenium forms in source water, finished water and tap water (H values were 3.12, 0.86 and 0.86, respectively, P>0.05). Se(IV), Se(VI), the total inorganic selenium and the total amount of the five selenium forms in surface water were higher than those of groundwater (Z values were -2.72, -2.98, -3.50 and -3.50, respectively, P < 0.05).

Conclusion Three organic selenium were not detected in the drinking water samples in this study, and the selenium in the water mainly exists in the form of inorganic selenium Se(IV) and Se(VI). Se(IV) and Se(VI) were detected to different degrees in different water sample types and different water source types, but the detected concentration levels did not exceed the standard. The total inorganic selenium level will not pose a health risk to the human body, but it is still necessary to strengthen the monitoring of the selenium form level in drinking water, and people could supplement their dietary intake of organic selenium.