Confirmed: Atmospheric helium levels are rising
A by-product released by use of fossil fuels has been increasing since
1974
Date:
May 9, 2022
Source:
University of California - San Diego
Summary:
Scientists used an unprecedented technique to detect that levels
of helium are rising in the atmosphere, resolving an issue that
has lingered among atmospheric chemists for decades.
FULL STORY ========================================================================== Scientists at Scripps Institution of Oceanography at UC San Diego used
an unprecedented technique to detect that levels of helium are rising in
the atmosphere, resolving an issue that has lingered among atmospheric
chemists for decades.
==========================================================================
The atmospheric abundance of the 4-helium (4He) isotope is rising because
4He is released during the burning and extraction of fossil fuels. The researchers report that it is increasing at a very small but, for the
first time, clearly measurable rate. The 4He isotope itself does not add
to the greenhouse effect that is making the planet warmer, but measures
of it could serve as indirect markers of fossil-fuel use.
The National Science Foundation-supported study appears today in the
journal Nature Geoscience.
"The main motivation was to resolve a longstanding controversy in the
science community about atmospheric helium concentrations," said study
lead author Benni Birner, a former graduate student and now postdoctoral researcher at Scripps Institution of Oceanography at UC San Diego.
The isotope 4He is produced by radioactive decay in the Earth's crust and accumulates in the same reservoirs as fossil fuels, in particular those
of natural gas. During the extraction and combustion of fossil fuels,
4He is coincidentally released, which creates another means to evaluate
the scale of industrial activity.
The study's breakthrough is in the technique the Scripps Oceanography
team used to measure how much helium is in the atmosphere. Birner and
Scripps geoscientists Jeff Severinghaus, Bill Paplawsky, and Ralph
Keeling created a precise method to compare the 4He isotope to levels
of the common atmospheric gas nitrogen. Because nitrogen levels in the atmosphere are constant, an increase in He/N2 is indicative of the rate
of 4He buildup in the atmosphere.
Study co-author and Scripps Oceanography geochemist Ralph Keeling,
overseer of the famed carbon dioxide measurement known as the
Keeling Curve, describes the study as a "masterpiece of fundamental geochemistry." Though helium is relatively easy for scientists to detect
in air samples, present at levels of five parts per million of air,
no one had done the work to measure it carefully enough to observe an atmospheric increase, he said.
The study also provides a foundation for scientists to better understand
the valuable 3-helium (3He) isotope, which has uses for nuclear fusion, cryogenics, and other applications. Proposals to acquire the scarce gas
from the moon are an indication of the lengths to which manufacturers
will go to harvest it.
According to previous work by other researchers, the 4He isotope exists
in the atmosphere in what appears to be an unvarying ratio with 3He. The atmospheric rise of 4He isotope measured at Scripps therefore implies
that the 3He isotope must be rising at a comparable rate as 4He. The
research by Birner's team raises several questions about the accuracy
of scientists' previous assumptions about how 3He is produced and in
what quantity.
"We don't know for sure, but I wonder if there is more 3He coming out of
the Earth than we previously thought, which could perhaps be harvested
and fuel our nuclear fusion reactors in the future," Birner said.
"The study lays in starker relief a controversy surrounding the rare
helium isotope 3He," said Keeling. "The implications are far from clear,
but it begs additional work."
========================================================================== Story Source: Materials provided by
University_of_California_-_San_Diego. Original written by Robert
Monroe. Note: Content may be edited for style and length.
========================================================================== Journal Reference:
1. Birner, B., Severinghaus, J., Paplawsky, B. et al. Increasing
atmospheric
helium due to fossil fuel exploitation. Nat. Geosci., 2022 DOI:
10.1038/ s41561-022-00932-3 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2022/05/220509112102.htm
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