楚科奇海陆架区表层沉积物放射性核素的分布

Distribution of radionuclides at surface sediments in Chukchi Shelf

对中国首次北极科学考察期间在楚科奇海采集的9个表层沉积物样品进行了γ谱分析。结果表明,2 1 0 Pb的比活度介于16.0～76.6Bq·kg 1 之间,平均为3 6.9Bq·kg 1 ,低于大多数中低纬度区表层沉积物的2 1 0 Pb比活度,反映出研究海域低的大气2 1 0 Pb输入通量。2 2 6 Ra、1 37Cs、2 38U的放射性比活度范围和平均值分别为11.4～2 0 .9、1.7～2 .9、3 2 .4～5 3 .4Bq·kg 1 和17.6、2 .2、44 .4Bq·kg 1 。研究海域表层沉积物中的2 2 6 Ra/2 38U ) A .R .介于0 .3 5～0 .47之间,低的2 2 6 Ra/2 38U) A .R .表明U、Ra的地球化学行为存在差异。2 1 0 Pb、2 1 0 Pbex、1 37Cs、4 0 K比活度和灼烧失重率均随离岸距离的增加逐渐减小,而2 2 6 Ra和2 38U则具有各自不同的分布特征,分别与研究海域表层沉积物Si和Ca的分布比较类似。对核素间相关关系的分析表明,研究海域表层沉积物中1 37Cs和2 1 0 Pbex含量与灼烧失重率之间存在良好的线性正相关关系,证实有机物质在2 1 0 Pb、1 37Cs的生物地球化学循环中起着重要作用。

The surface sediments were collected at nine stations in the Chukchi shelf onboard the R/V Xuelong during chinese first arctic expedition. Activity concentrations of 210 Pb, 226 Ra, 238 U, 137 Cs, 40 K were determined by γ spectrometer with HPGe detector. The results showed that the specific activities of 210 Pb ranged from 16.0 Bq·kg -1 to 76.6Bq·kg -1 , with a mean of 36.9 Bq·kg -1 . The 210 Pb concentrations in study area were lower than those in the low latitude regions, which was ascribed to the low input of atmospheric 210 Pb to the sediments. The specific activities of 226 Ra, 137Cs and 238 U range from 11.4～20.9 (averaging 17.6), 1.7～2.9 (averaging 2.2) and to 32.4～53.4 (averaging 44.4) Bq·kg -1 respectively. The spatial distribution showed that the activity concentrations of 210 Pb, 210 Pbex, 137 Cs, 40 K and percentage of the mass loss under combustion were decreased with the increasing distance to the shore, whereas those of 226 Ra and 238 U followed the variability of Si and Ca in study areas. A positive linearly relationship between the activity concentrations of 137 Cs, 210 Pbex and the content of TOM was observed in study sediments collected from the Chukchi Shelf, and showed the important role of organic matter in scavenging of 210 Pb and 137 Cs in the water column.