Nuclear signals could mark start of Anthropocene epoch
FILIPINO and Japanese scientists have proposed, as a result of their study, that the beginning of the new Anthropocene epoch, or its “golden spike,” is best recorded as “nuclear bomb peaks.”
Scientists are deep into the study on the start of the proposed new period of human activities called the Anthropocene epoch.
The Holocene epoch immediately preceded the Anthropocene. Holocene began 11,700 years ago after the last major ice age.
All periods, including the Jurassic Age, has a start flag called the golden spike, an event marker that signals a tremendous physical, chemical, or biological change across the Earth, the Department of Science and Technology’s-philippine Nuclear Research Institute Nuclear Materials Research Section (DOST-PNRI NMRS) said in a news release.
The Filipino and Japanese scientists involved in the research— were two Filipinos from the DOSTPNRI, two from The University of Tokyo, and one each from Rikagaku Kenkyūjyo (Riken, or Institute of Physical and Chemical Research of Japan), Hirosaki Univercity and Hokkaido University.
‘Excellent candidate’
THE scientists found the peaks of the radionuclide iodine-129, or I-129, in an ice core at the Greenland Southeast Dome site as an “excellent candidate for the Anthropocene period’s golden spike.”
“The ice core was taken in August 2015,” said Dr. Angel Bautista VII, Scientist I, Supervising Science Research Specialist, and section head of the Nuclear Materials Research Section, Atomic Research Division at the DOSTPNRI, one of the Filipino scientists involved in the research, and who was its first and corresponding author.
“I started this work as part of my PHD dissertation, but continued on even after my graduation in 2016, then finally culminated with the publication of our work in May 2023,” Bautista told the Businessmirror in a social media interview.
He explained that the Greenland Southeast Dome is an “excellent site” for the study because the location features “high amounts of precipitation, resulting in high accumulation rates of the ice core.”
“The ice thickness increases significantly more as time passes, compared to other sites. Practically, this means we can analyze at a higher resolution. Particularly, in our study’s case, we reconstructed the history of nuclear impacts at a resolution of every four months—one of the most detailed reconstructions of the effects of nuclear activities to date,” Bautista pointed out.
Scientific debate
IDENTIFYING the Anthropocene’s golden spike is a comprehensive scientific debate that started in 2009 and has been ongoing for years.
A growing consensus within the scientific community is that the most pronounced global start of the Anthropocene is within the mid-20th century.
Called the “Great Acceleration,” it is a period of exponential human population, economic and technological growth at a scale that caused massive changes in the Earth’s environment.
Quest for the golden spike
SCIENTISTS have explored several probable golden spikes in the Great Acceleration.
Among those considered were the global fallout signals from nuclear weapons testing, particularly of the radionuclides carbon-14 (C-14) and plutonium-239 (Pu-239)..
However, these radionuclides will decay and disappear a few hundred thousand years into the future, and their signals will be impossible to be found by humans by then. Thus, they may not be quite enduring to serve as the golden spike, the DOST-PNRI NMRS explained.
In their quest, the Filipino and Japanese scientists found a more fitting golden spike indicator—iodine-129, whose half-life is 15.7 million years. This means that its signals can be found by humans even millions of years into the future.
Bautista further explained that there were many other possible markers that were explored—such as increases in carbon dioxide, fly ash, organic compounds and heavy metals.
“However, nuclear bomb peaks are a prime candidate—if not the best one—because they can be observed/measured all over the earth virtually at the same time. They can be measured in a variety of material—such as tree rings, ice core, corals, sediments—meaning it can be found anywhere easily. This degree of global ubiquity and synchronicity makes nuclear bomb peaks a great candidate,” he pointed out.
Ice recordings
THE authors in the study measured I-129 in ice deep in the Greenland Southeast-dome site, even as they explored its potential as the likely Anthropocene golden spike.
As they took the core out from the 90-meter deep ice drilling, the researchers found that the I-129 in the ice core recorded almost the entire history of the nuclear age, particularly the period 1957 to 2007.
“It was in unprecedented detail at a resolution of about every four months,” the Filipino and Japanese scientists said.
More specifically, the I-129 in the ice core recorded signals from nuclear weapons testing in 1958, 1961 and 1962, the Chernobyl Accident in 1986, and other various signals from nuclear fuel reprocessing within the same year, or a year after.
The relationships between I-129 in the ice core and the human nuclear activities were defined and quantified through a mathematical model, they said.
Most importantly, having the I-129 nuclear signals were also seen in other records from different locations and environments worldwide, which means that these signals can be found virtually anywhere—a good characteristic of a potential golden spike, they added.
This global presence is comparable with those of the C-14 and Pu-239 bomb signals, but the much longer half-life of I-129 makes it a more enduring and ideal golden spike.
The study was published in Science of the Total Environment, one of the world’s leading environmental science journals with an impact Factor of 10.75.