北黄海水体的^224 Ra

用锰纤维富集-射气法测量了北黄海水体的^224 Ra，研究了该海域夏季和冬季2个季节^224 Ra比活度及其垂直分布，并对其进行了比较研究．北黄海夏季^224 Ra比活度为0．24—3．48Bq／m2，平均值为1．14Bq／m2；冬季^224 Ra比活度为0．37～6．68Bq／m2，平均值为0．94Bq／m2．北黄海的表层水有3个^224 Ra高值区，分别位于东北部海域、渤海海峡南部和北黄海中北部海区．30m水深将^224 Ra比活度的垂直分布分成上层和下层2层．在0～30m水层，夏季，随着水深增加^224 Ra比活度逐渐增加，比活度变化较小；冬季部分站位由表层向下^224 Ra比活度逐渐降低．30m水深以下，^224 Ra比活度随着水深的增加而增加，而且变化幅度较大．由^224 Ra比活度的垂直分布得出该海域的垂直涡动扩散系数为2．5～43．5cm2／s，夏季北黄海冷水团中心海域底层溶解态化学物质输运补给到上层所经历的时间为9～15d左右．

~(224)Ra in seawater of northern Yellow Sea

~(224)Ra in seawater of northern Yellow Sea were measured using Mn-fiber adsorption-emanation method.The horizontal and vertical distribution of ~(224)Ra in the sea in summer and winter were studied.The ~(224)Ra activities were 0.24～3.48Bq/m~3 with an average of 1.14Bq/m~3 in summer and 0.37～6.68Bq/m~3 with an average of 0.94Bq/m~3 in winter.There were 3 high ~(224)Ra areas in the northern Yellow Sea:northeast area,southern Bohai Strait,and central and northern area.30m layer divided the ~(224)Ra vertical distribution into two parts:upper layer and lower layer.The upper layer,0～30m ~(224)Ra increased with the depth and varied slightly in summer and ~(224)Ra decreased with depth for some stations in winter.The layer below 30m,~(224)Ra increased with depth and varied greatly.The vertical eddy diffusion coefficients based on the vertical distributions of ~(224)Ra were 2.5～43.5cm2/s.It took 9～15d for the dissolved chemical matters in central area of the Yellow Sea cold water mass to transporte from the bottom layer to the upper layer in summer time.