Scientific American Editors - Ask the Experts: Chemistry

Ask the Experts

Chemistry

From the Editors of Scientific American
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Letters to the Editor
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ISBN: 978-1-948933-00-1

Climate Gone Wild

Theres one issue that will define the contours of this century more dramatically than any other, and that is the urgent threat of a changing climate. President Barack Obama

The Great Barrier Reef, located off of the coast of Queensland, Australia, is the largest coral reef system (and, indeed, the largest living thing) on the planet. Made up of over 600 types of corals, it is home to a diverse array of wildlife including fish, dolphins, whales, turtles, and mollusks and it is dying. Since 2016, scientists have sounded the alarm regarding widespread coral bleaching and coral death caused by rising ocean temperatures associated with climate change. Some scientists even compare the status of the Earths coral reef with the Earth itself. As the corals go so goes planet Earth. In this eBook, Climate Change: Planet Under Pressure, we look at the effect that the Earths changing climate has on weather systems, ecosystems and human habitability. Then in light of these changes, we look at what the future has in store.

We begin by reviewing recent (and devastating) weather events and the possible link to climate change. In What We Know About the Climate Change-Hurricane Connection, Michael E. Mann, Thomas C. Peterson and Susan Joy Hassol explore the role of human-caused climate change in the immediate aftermath of Hurricane Harvey. This is followed by investigations of El Nino, the Gulf Stream and the Northern Hemisphere Jet Stream, the recent erratic behavior of these systems and how they may effect (and are effected by) climate change.

Section 2 takes a closer look at global ecosystems that are in peril because of their changing environments. We explore changes in various environments from the artic to the worlds oceans and how the plant and animal life that inhabit them are fighting for survival.

Next, we examine how climate change has affected the habitability of the globe for human life. In What Lies Beneath, Sara Goudarzi reports on how the thawing of the permafrost around the globe is causing the release ancient microorganisms that are deadly to humans. The section goes on to explore how extreme weather has inversely affected the people of Bangledesh and how climate change has a part to play in the Syrian refugee crisis.

In Section 4, we wrap up this discussion on climate change by looking toward the future. How will we live and what will be our quality of life going forward if we dont take action? With How Will Climate Change Us? journalist and data visualization designer Katie Peck provides us with an infographic that shows how much warmer the Earth will be in 2100 and how precipitation patterns will change. The infographic also provides callouts that explain how people around the world will be affected by these changes. Other selections in the section explore changing the tone around climate change discussions and how our military views the changing climate as a national security matter.

From the collapsing ecosystem of Great Barrier Reef to devastation in the US Gulf coast to the displacement of Syrian citizens, the damaging effects climate change are evidenced around the world. In this eBook, Climate Change: Planet Under Pressure, we aim to survey the current effects of climate change and explore how this will alter all of our futures.

-- Karin Tucker
Book Editor

Does Plutonium Ever Occur Naturally?

John W. Poston, Sr., is head of the nuclear engineering department at Texas A&M University and is a Fellow of theAmerican Nuclear Society. He offers the following explanation:

Conventional wisdom tells us that plutonium (Pu) does not exist in nature.Plutonium and other so-called transuranic elements are considered by most to beman-made elements. Thus, they assume that when plutonium is found in theenvironment, human technology has put it there.

This element has usually been considered synthetic because it is produced mostefficiently in nuclear reactors. But in the strictest sense, the answer to the question isyes, plutonium does occur naturally. Plutonium appears at very low concentrationsin nature, on the order of one part in 1011 in pitchblende, the ore of uranium (U).

The element plutonium was discovered by Nobel LaureateGlenn T. Seaborg and his colleagues in February 1941. It wasthe second transuranic element to be discovered; neptunium(Np) was identified in 1940. The 60-inch cyclotron atUniversity of California at Berkeley produced the first isotopeof plutonium, Pu-238. It was made by bombarding a U-238target with deuterons, producing Np-238. This material had abrief radioactive half-life--the time required for half of theatoms in a sample to decay or transform--of 2.12 days. Theradionuclide Np-238 decayed (by emitting beta-radiation) toPu-238, which has a half-life of 87.7 years.

The isotope Pu-239 was produced on March 28, 1941 bybombarding a U-238 target with neutrons to produce U-239(half-life of 23.5 minutes). This radionuclide decayed by beta emission to Np-239 (half-life of 2.12 days), which subsequently decayed bybeta emission to Pu-239 (which has a very long half-life of 24,600 years).

Plutonium is produced in nature through the reasonably well-understood process discussed above. Uranium is a naturally occurringelement that is ubiquitous in the Earth's crust. The isotopes of uranium decay primarily by alpha-particle emission, but there is also aprocess called "spontaneous fission" that occasionally competes with alpha decay.

In spontaneous fission, the nucleus splits ("fissions") and additional neutrons are released. There is a possibility that these releasedneutrons are absorbed (captured) by another U-238 nucleus. If this occurs, it triggers a process that produces Pu-239 in a mannersimilar to that discussed above. Thus, we have plutonium produced naturally in the environment (admittedly in trace quantities). Thisreaction has been going on since the creation of the Earth.