低本底高纯锗γ能谱仪在天津海岸带现代地质环境变化研究中的应用

The Application of Low Background HPGe γ Spectrometer on the Modern Geo-environmental Changes of Tianjin Coast

现代沉积物测年已经成为海岸带地区百年以来的现代地质过程重建的重要定量方法。笔者系统总结了利用低本底高纯锗γ能谱仪进行比活度测试样品的取样、样品前处理、测试、比活度计算和数据解释方法的全过程,并介绍了由此获得的测年数据在海岸带地区经济建设中的实际应用。以天津海岸带为例,现代沉积物测年研究始于20世纪80年代末,首次开展的工作是针对天津港附近海区的现代沉积速率研究。此后,处于停顿期,直至20世纪90年代末,在国土资源大调查项目的支持下,天津地质调查中心复又开展了现代沉积速率的研究。至今,已基本掌握了天津沿海低地、潮间带及部分浅海区的现代沉积特征,从而填补了现代地质环境演化和趋势预测的一个重要定量指标—现代沉积速率的空白。同时,天津地调中心还籍此在海岸带地区开展了探索性的应用研究,如对活动断层百年以来活动性的评价和对海区活体牡蛎礁所处的建礁阶段的判定等。

Modern sediment dating has become an important quantitative method for reconstructing the modern geo-environmental changes of coastal area since last hundred years. In this paper, the authors summarize the modern sediment dating by low-background HPGe γ Spectrometer systematically, which include the sampling of undisturbed short core in coastal zone, sub-sample pretreatment, sample measurement, specific activity calculation in lab and data interpretation, and then practical application of economic construction that was made by the resulting chronological data in coastal zones. Take Tianjin costal zone as an example, modern sediment dating was first used for studying the modern sedimentation rates of the shallow sea area near Tianjin New Port in late 1980s. Since then, the work came to standstill. In the end of 1990s, with the support of Land Resources Survey Projects; the work of studying modern sedimentation rate was re-launched by Tianjin Center of Geological Survey. Until now, the modern sedimentary characteristics of Tianjin coastal lowlands, intertidal zone and part of the shallow sea area have been obtained. As an important quantitative indicator, the work of studying modern sedimentation rate fills a gap in the field of evolution of the modern geo-environment and trend prediction. Meanwhile, based on these results, the exploratory work have been done, such as the evaluation of fault activity during the past 100 years, the evaluation stage of the ecosystem of the living oyster reef in shallowsea, and so on.