Simultaneous determination of ²³⁸U series nuclides in waters of Arabian Sea and Bay of Bengal

Abstract

Analytical procedures for the simultaneous determination of Th-234, U-238, Po-210, Pb-210 and Ra-226 in seawater are described. Except Ra-226, all these nuclides are simultaneously co-precipitated with Fe(OH)3 and separation of short-lived nuclides Th-234 and Po-210 is accomplished within 2 d of sample collection. Chemical recoveries of Th, Pb and Po in most of the samples are in the range of 40-80%. The vertical concentration profiles measured in the Arabian Sea and Bay of Bengal show that the dissolved activities of Th-234 and Po-210 in surface waters are significantly less than those of the parent nuclides U-238 and Pb-210, respectively. This deficiency of Th and Po is interpreted in terms of removal onto particles which occurs on short time scales of few days. A comparison of the Th-234 profiles shows that the intensity of chemical scavenging is relatively more pronounced in the Arabian Sea. In general the particle reactivity of these nuclides varies as Th-234>Po-210>Pb-210.