黔西北麻窝山岩溶盆地沉积的新资料

给出麻窝山岩溶盆地环境近期变化的调查结果和沉积剖面137Cs深度分布的新资料,以回复吴攀先生的《论黔西北麻窝山岩溶盆地土壤堆积记录———兼答张信宝先生》一文(简称"吴文")。新资料表明:1)麻窝山岩溶盆地20世纪70年代前不是长期的湖泊环境。1958年落水洞阻塞,盆地下部低洼地段积水成湖,1973年泄流洞打通后,湖泊消失,复为农田。2)吴文和本文的盆地沉积物137Cs深度分布空间格局基本一致,其差异主要是:吴文的盆地下部3个孔,除剖面中下部部分层位含137Cs,且137Cs含量多高于2 Bq/kg外,其他大部分层位不含137C;本文的盆地下部3个孔,除剖面中下部个别层位不含137Cs外,其他大部分层位含137Cs,且活度多低于2 Bq/kg。因吴文未给出有关137Cs量测精度的探头类型和型号、检测限值、样品测量、量测时间和测试误差等技术参数,本文没有讨论吴文和我们的剖面土层137Cs活度存在差异的原因。

New data on sedimentation in the Mawoshan Karst Basin of Northwest Guizhou Province

This paper provided new data on recent environment changes and 137Cs depth distributions in the Mawoshan Karst Basin to reply the paper on ＂ Recording of soil sediment in the Mawoshan Karst Basin of Northwest Guizhou Province＂ from Mr.Wu Pang.New data indicated that： 1） The Mawoshan Karst Basin was not continuous lake environment before 1970s.As the sink hole was blocked,the lower part of the basin was impounded and became a lake in 1958.The lake was drained and returned to farming land when a drain tunnel was dug out in 1973.2） Spatial variations of 137Cs depth distributions over the basin were similar between this paper and Mr.Wu Pang’s paper.The major differences of 137Cs depth distributions in the three cores of the lower part of the basin between the two papers were ： except for a few layers in the middle and lower parts of the profile containing 137Cs with concentrations mostly greater than 2 Bq/kg,the rest layers contain little 137Cs in his paper,however,except for a few layers in the middle and lower parts of the profile containing little 137Cs,the rest layers contain 137Cs with concentrations mostly less than 2 Bq/kg in this paper.As the type and model number of detector,delectability,counting sample weight,counting time and analytical precision were not described in Mr Wu’s paper,the reasons for the differences of 137Cs concentrations of the layers in the cores were not discussed between the two papers.