Radioactive Disequilihrium of Uranium and Thorium Nuclide Series in Hot Spring and River Water from Peitou Hot Spring Basin in Taipei

Abstract

The distributions of the naturally occurring radionuclides 238 U, 234 U, 232 Th, 230 Th, 228 Th, 228 Ra, and 226 Ra in river and hot spring water within the Peitou hot spring basin at the northern part of Taiwan were studied by using alphaand gamma-spectrometric methods and liquid scintillation counting method. The respective concentration ranges of 238 U, 234 U, 232 Th, 230 Th, 228 Th, and 226 Ra in river and hot spring water were 0.80 −48, 1.2−51, 0.05−44, 0.09−39, 0.19−342, 3.0−22.5 mBq/L and 2.3−85, 2.9−91, 0.67−73, 1.14−66, 1.01−630, and 4.5−36.5 mBq/L, respectively. In general, the distributions of uranium-series and thorium-series nuclides in river water, hot spring water were all pH dependent. The respective radioactivity ratios of 234 U/ 238 U in river and hot spring water are observed to be 1.0−1.5 and 1.03−1.5, however, the radioactivity ratios of 228 Th/ 232 Th in river and hot spring water are 1.4 −19 and 1.5−8.8, respectively. The high 228 Th/ 232 Th activity ratios showed that besides the recoil effect, enrichment of 228 Ra to 232 Th in the waters was another possible factor causing an excess of 228 Th. Because radium may exist as (Pb, Ba, Ra)(SO4)X pseudo-colloid in hot spring water, which is the same as the more famous mineral of Peitoustone (Hukutolite), therefore, 228 Ra and 226 Ra are more abundant in the hot spring sediments, which radioactivity are18−3010 and 16−230 Bq/kg (dry), respectively.