青海湖西岸镭同位素的解吸和扩散特征

摘要

Two laboratory experiments for Radium desorption and diffusion were conducted in this work, which included 1) the Ra-dium desorption of sediments that were under different salinities (2.8‰, 5.8‰, 8.8‰, 11.8‰and 14.8‰) from the lake water and the potential of hydrogen from Buha River estuary. 2) Radium diffusive fluxes with time in the overlying water of lake sedi-ments and in river sediments. We have got the desorbed activity of Radium from the suspended particles and Radium diffusion flu-xes from surface sediments. The results show that the desorption activities of 224 Ra are higher than those of 226 Ra and 228 Ra, and the desorption degrees of 224 Ra, 226 Ra and 228 Ra have reached the maximum value when the salinity near 12‰. The desorption of 226 Ra activities are greater than that of 228 Ra when salinity<9‰, however, when salinity>9‰, the desorption activities of 226 Ra is less than that of 228 Ra, which may be associated with the local rich uranium. The diffusion fluxes of 226 Ra and 228 Ra of sediments from Buha River are 0.039 and 0.290 dpm/(m2.h), respectively, and they are 0.018 and 0.092 dpm/(m2.h) from Lake Qinghai, respectively. The Radium diffusion fluxes of sediments in Lake Qinghai are less than that of the river.%对青海湖布哈河河口悬浮颗粒物、底部沉积物和青海湖湖底沉积物中的镭（ Ra）同位素进行不同盐度和pH值的解吸实验以及扩散实验，得到不同盐度湖水（2.8‰、5.8‰、8.8‰、11.8‰和14.8‰）对悬浮颗粒物中镭的解吸活度，和不同时间段沉积物中镭同位素的扩散速率，探讨盐度、pH值与颗粒物中镭同位素解吸的关系.结果表明，224 Ra的解吸活度均高于226 Ra和228 Ra的解吸活度；在盐度为12‰附近时布哈河河口悬浮颗粒物中223 Ra、226 Ra和228 Ra的解吸程度达到最大值，当盐度＜9‰时，226 Ra解吸活度大于228 Ra，当盐度＞9‰时，228 Ra的解吸活度大于226 Ra，这可能与当地岩石中富铀矿有关.河流沉积物226 Ra和228 Ra的扩散速率分别是0.039和0.290 dpm／（ m2.h）；湖底沉积物226 Ra和228 Ra的扩散速率分别为0.018和0.092 dpm／（ m2.h），湖底沉积物扩散速率小于河流沉积物扩散速率.