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过程，以至于“人类世”的概念，即人类是塑造地球的主导力量的地质时期，已被广泛接受。为了研究人类如何改变人类世的淡水资源，我们需要在与人类对这些资源的主要影响相关的时间尺度上可靠地确定这些变化的自然档案（如湖泊沉积物）。使用伽马射线光谱法测定湖泊沉积物的年代是基于对210 Pb（半衰期约为22年的放射性同位素）和铀（238 U）衰变系列的姊妹放射性核素的分析。这种测定湖泊沉积物岩心年龄的技术已经很成熟，可靠，并广泛用于跟踪过去150年来的环境变化。除了210 Pb的分析外，伽马射线光谱学还测量了人类产生的137 Cs的额外独立年代标记，该标记在核弹大气测试的高度（~1962年）达到峰值。我们提出的项目将允许购买一个尖端的伽马射线光谱仪，将被安置在卡尔顿大学和广泛使用的环境变化研究人员在卡尔顿，约克，艾利森山大学以及加拿大环境。这种尖端的伽马射线光谱仪技术将使我们的时间分辨率提高一倍，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.