北黄海水体的226Ra和228Ra

用锰纤维富集-射气法测定了北黄海海水中的镭同位素226Ra和228Ra,研究了该海域水体中镭同位素的含量和分布.研究结果表明北黄海水体夏季226Ra的比活度为1.80～4.35 Bq/m3,平均值为3.06 Bq/m3;冬季226Ra的比活度为2.08～5.20 Bq/m3,平均值为3.28 Bq/m3.北黄海夏季228Ra的比活度为3.85～25.60 Bq/m3,平均值为10.60 Bq/m3;冬季228Ra的比活度为3.14～15.60Bq/m3,平均值为7.66 Bq/m3.该数据范围和中国近海其他海域、孟加拉湾、泰国昭披耶河口、濑户内海等海域相近.北黄海东北部海域,渤海海峡靠近山东半岛的海区和中北部海区表层镭同位素活度较高.C1断面镭同位素的分布特征从镭同位素的方面证实了渤海海峡水交换表现为北进南出特征这一结论的正确性.226Ra和228Ra的垂直分布较为复杂,大部分站位呈现出底层活度变高的趋势,其他少数站位呈现出中间层活度高的分布特征,不同来源的镭同位素输入至该海域形成了这样的分布特征.

226Ra and 228Ra in seawater of the North Yellow Sea

226Ra and 228Ra in the seawater of the North Yellow Sea were measured using the Mn-fiber adsorption-emanation method.The concentrations and distributions of 226Ra and 228Ra in this sea area were determined as follows： 226Ra activities were 1.80 to 4.35Bq/m3 with an average of 3.06Bq/m3 in the summer and 2.08 to 5.20Bq/m3 with an average of 3.28Bq/m3 in the winter;228Ra activities were 3.85 to 25.60 Bq/m3 with an average of 10.60Bq/m3 in the summer and 3.14 to 15.60Bq/m3 with an average of 7.66Bq/m3 in the winter.These concentration ranges for radium isotopes in the northern Yellow Sea were similar to those recorded for other sea areas of the China Seas,the Bay of Bengal,the Chao Phraya River Estuarine mixing zone of Thailand,the Seto Inland Sea and more.There were three areas of high radium isotope concentrations in the North Yellow Sea： the northeast area,the South Bohai Strait,and the central and the north area.The radium isotope distribution of section C1 confirmed the suggested movement of sea water into the Bohai Strait from the North and the exit of water from the Strait in the South.Vertical distributions of 226Ra and 228Ra were complex with higher activities exhibited in the bottom layers at most stations and in the middle layers at a few stations.This variable distribution pattern was due to input of radium isotopes from different sources.