A Global Survey of Helium in the Troposphere: Advancing the Application of Helium as a Tracer of Natural Gas Usage and Stratosphere-Troposphere Exchange

该项目旨在根据先前开发的测量技术对惰性气体氦进行全球调查。氦气是一种难以测量的气体，但它可以用作大气示踪剂，这意味着新的测量方法可以帮助我们更好地理解各种过程，包括南北半球之间的大规模大气输送，以及像天然气开采这样的小规模氦排放过程。在这个项目中收集的氦的独特测量将为各种大气传输现象提供新的见解，并将增加我们对氦和潜在的其他稀有气体的来源和变异性的理解。早期职业科学家和一名研究生将在整个项目过程中得到支持，收集的数据将与更广泛的科学界共享。在这个项目中，新的观测将是氦气（He）和氮气（N2） （He/N2）之间的比率，通过一种新的质谱测量技术，使用双捕获系统和低温富集入口，这是在以前的国家科学基金会资助的项目中开发的。本文提出了四个研究问题：(1)最丰富的氦同位素4He的年际变化是什么？(2) He/N2的空间梯度，尤其是南北半球间的空间梯度；(3) He/N2的季节变化幅度如何？(4)通过检查高频He变异性可以了解到什么？这项拟议的工作将使用三种测量来源：从以前的工作中收集的历史烧瓶样本表明，在过去的50年里，大气中的He水平呈上升趋势；正在进行的由斯克里普斯氧气计划常规收集的烧瓶样本，这是一个由遍布太平洋的10个表面烧瓶站组成的网络，能够解析全球尺度的信号；以及在加利福尼亚州拉霍亚的斯克里普斯码头采集的准连续环境样本。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project seeks to conduct a global survey of the noble gas helium building upon a previously developed measurement technique. Helium, which is a difficult gas to measure, can be used as an atmospheric tracer, meaning that new measurements could help us better understand a wide range of processes including large-scale atmospheric transport between the northern and southern hemispheres as well as small-scale processes that emit helium such natural gas extraction. The unique measurements of helium to be collected in this project will provide new insight into a variety of atmospheric transport phenomena and will increase our understanding of the sources and variability of helium and potentially other noble gases. Early career scientists and a graduate student will be supported throughout the course of this project, and the data collected will be shared with the wider scientific community.The new observations to be made during this project will be of the ratio between the gases helium (He) and nitrogen (N2) (He/N2) via a new mass spectrometric measurement technique using a dual-trapping system and cryo-enrichment inlets developed under a previous NSF-funded project. There are four research questions being asked in this proposed work: (1) what is the interannual variability of the most abundant helium isotope 4He?; (2) what are the He/N2 spatial gradients, particularly between the northern and southern hemispheres?; (3) what is the magnitude of seasonal He/N2 variations?; and (4) what can be learned by examining high frequency He variability? This proposed work will use three sources of measurement: historic flask samples collected from previous work that has demonstrated an increasing trend in atmospheric He levels over the last 50 years, the ongoing collection of flask samples collected routinely by the Scripps oxygen program, which is a network of 10 surface flask stations spread out around the Pacific Ocean capable of resolving global-scale signals, and quasi-continuous ambient samples taken at the Scripps Pier in La Jolla, California.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.