Uranium isotopes and several heavy elements in selected waters in Quang Nam-Da Nang provinces, Central Vietnam

²³⁸U and ²³⁴U concentrations, ²³⁸U/²³⁴U ratios and Na, Ca, Mg, K, Al, As, Cd concentrations were measured in selected surface waters (streams, rivers and lakes), ground waters (dug wells) and underground waters (drill wells and thermal waters) in Quang Nam and Da Nang provinces, Central Vietnam. The mineralization was < 500 mg L⁻¹ and Al, As, Cd contents were a few tenths of µg L⁻¹. ²³⁴U and ²³⁸U activities were between 0.47–27.6 mBq L⁻¹ and 0.6–15.0 mBq L⁻¹ respectively, these values are lower than WHO recommended limits. Uranium contents trended as U_rivers < U_streams < U_lakes < U_{dig wells} < U_{thermal water} < U_{drill wells.} The ²³⁴U/²³⁸U ratio ranged from 0.69 to 2.31 with 1.26 on average. For groundwaters, the ratio scattered around one. Effects of Nong Son uranium deposit located in Quang Nam region were not observed.