Germanium gamma-ray spectrometer for high resolution dating of lake sediment records

在过去的150年里，人类活动改变了许多生态系统的过程，以至于“人类世”的概念已经被广泛接受，在这个地质时期，人类是塑造地球的主要力量。为了研究人类如何在人类世改变淡水资源，我们需要可靠地确定这些变化的自然档案(如湖泊沉积物)的年代，这与人类对这些资源的重大影响有关。湖泊沉积物的伽马能谱测年是基于~22年半衰期的放射性同位素~(210)Pb和铀(~(238)U)衰变系列的姊妹放射性核素的分析。这种湖泊沉积岩心测年技术成熟、可靠，广泛用于追踪过去150年来的环境变化。除了对210Pb的分析外，伽马射线光谱学还测量了另一个独立的人类产生的137Cs的时间标记，该标记在核弹大气试验的高峰期(~1962)达到顶峰。我们提议的项目将允许购买一台尖端的伽马射线能谱仪，该仪器将安装在卡尔顿大学，并被卡尔顿大学、约克大学、埃里森山大学以及加拿大环境部的环境变化研究人员广泛使用。这项尖端的伽马射线光谱仪技术将使我们的年代分辨率提高一倍，减少年龄估计误差，并将我们目前的湖泊沉积物记录测年成本降低约80%，从而使我们的研究资金更多地用于本科生和研究生的直接培训。

Over the last ~150 years human activities have altered many ecosystem processes to the point that the concept of the “Anthropocene”, a geological period where people are a dominant force shaping planet Earth, has become widely accepted. To study how humans have altered freshwater resources in the Anthropocene we need to reliably date natural archives of these changes (such as lake sediments) at timescales relevant to major human impacts on these resources. The dating of lake sediments using gamma-ray spectroscopy is based on the analysis of 210Pb (a radioistope with a half life of ~22 years) and sister radionuclides of the uranium (238U) decay series. This technique of dating lake sediment cores is well established, robust, and widely used to track environmental changes over the last ~150 years. In addition to the analysis of 210Pb, gamma-ray spectroscopy also measures an additional independent chronological marker of the human produced 137Cs that peaks at the height of atmospheric testing of nuclear bombs (~1962). Our proposed project will allow for the purchase of a cutting-edge gamma-ray spectrometer that will be housed at Carleton University and be widely used by environmental change researchers at Carleton, York, and Mount Allison universities as well as Environment Canada. This cutting-edge gamma-ray spectrometer technology will double our chronological resolution, reduce age estimation errors, and cut our current costs of dating lake sediment records by ~80% allowing for more of our research funding to be spent on the direct training of both undergraduate and graduate students.