The effects of water content and Mn-fiber surface conditions on measurement by emanation

(half-life, t1/2=3.64 days) has been used widely as a tracer. Its activity in natural waters can be measured by the emanation method [Rama, Todd, J.F., Butts J.L., and Moore, W.S., 1987. A new method for the rapid measurements of in natural waters. Mar. Chem., 22, 43–54.]. The measurement efficiency of is affected by Mn-fiber surface conditions and water content. We studied the effects of precipitated NaCl and water content on the emanation characteristics of from the adsorbed on Mn-coated fiber. The best emanation efficiency can be achieved when the Mn-fiber is covered by a water film with a thickness comparable to the recoil range of in water. By controlling the water content of the Mn-fiber, the measurement efficiency may be increased 2–3× compared to the very wet or very dry condition.