An in-situ analysis and measurement of thorium-234, uranium isotopes in seawater

A low-level β counting-α spectrum apparatus used for the detection of the β radiation of thorium-234 and α spectrum of thorium-228 simultaneously and an easy operating procedure for the enrichment,radiochemical separating,sampling and measurement of thorium-234 and uranium-238 in the ocean are developed based on the requirements of analyzing export productivity in the euphotic zone via thorium-234-uranium-238 radioactivity disequilibrium.The detecting efficiency both of β and α radiation is higher than 20%.The background of β radiation is less than 0.5 min^-1,and the energy resolution of α detector is better than 1%.Total recycle ratio of thorium-234 is about 75%.Using the above apparatus and procedure,the radioactivities of dissolved thorium-234 and uranium-238,particle thorium-234 and uranium-238 in seawater of the South China Sea,the Southern Ocean and the Arctic Ocean were analyzed.