Abstract
Surface samples of sea water collected in the Seto Inland Sea were analyzed for232Th and228Th. The concentrations of232Th were generally less than 2 dpm/1,0001 and these values are probably an upper limit for the232Th concentration in surface waters of the Seto Inland Sea. The228Th concentrations ranged between 4.2 to 42.3 dpm/1,0001. Remarkable seasonal and temporal variations in228Th concentrations were found, in comparison with the minimal variations in228Ra concentrations reported previously. The activity ratios of228Th/228Ra were about 0.18 in the southern part of the Kii and the Bungo Channels, and decreased markedly from the open ocean toward the central region of the Seto Inland Sea. The average value of the228Th/228Ra ratio in the central region of the Seto Inland Sea was 0.032±0.020. This suggests that removal residence time of228Th can be estimated to be about 34±22 days in surface waters of the Seto Inland Sea.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call