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New Equation of State for Iron
The behavior of metals such as iron in Earth’s outer core is not well understood. Simulating the boundary between the inner and outer cores and the rate of heat transfer requires an equation of state (EOS) that accurately describes the behavior of iron at high temperatures and pressures inside Earth. A Livermore team has presented a family of EOS models for iron—the most abundant metal in Earth’s core—to inform uncertainty assessments and applications in planetary science and manufacturing. The results are published in the July 1, 2023, issue of Physical Review B.
An EOS encapsulates a material’s thermodynamic properties such as melting behavior to describe its state of matter under a given set of conditions. To generate the EOS for iron in Earth’s core, the team examined existing data on iron’s thermodynamic behavior, then supplemented conditions lacking data using quantum simulations. The new EOS can address which solid phases are likely to be present in certain regions within Earth and inform planetary evolution and geodynamics models.
The team is optimistic about the impact of their EOS on uncertainties about conditions inside Earth. “We hope and anticipate that the new EOS will prove useful to a range of applications involving iron, and we are actively seeking to collaborate with experimentalists and theorists to conduct more studies and resolve some of the many uncertainties that still exist,” says lead author Christine Wu.
Contact: Christine Wu (925) 424-4096 (wu5 [at] llnl.gov (wu5[at]llnl[dot]gov)).
Viruses in Soil Thrive during Wet-Up
In Mediterranean biomes, an increase in microbial die-off and carbon dioxide release occurs during seasonal wet-up, the period immediately following the first rain after a dry period. Researchers from Livermore and the University of California, Berkeley, discovered that nearly half of this annual microbial death could be attributed to viral infection. The research was published in Nature Communications 14 on September 20, 2023.
The researchers simulated wet-up in the laboratory using water with a molecular label and tracked movement of the label into DNA—in bacteria, archaea, and viruses—to understand how the microbial community grew during incubation. Microbes such as bacteria and other unicellular organisms proliferate rapidly, and the soil viruses that prey on these organisms saw similar growth. The team found that a low biomass of diverse viruses endures in the soil during the dry season, and a subset thrives following wet-up. “We found that viruses drive a measurable and continuous rate of cell infections, contributing up to 46 percent of microbial deaths one week after wet-up,” says lead author Steven Blazewicz.
Microbial death can lead to a release of carbon dioxide into the atmosphere if the necromass (dead cells parts) is consumed by other microbes, or it can lead to an increase in soil carbon if the necromass is stabilized. Understanding soil microbiome dynamics could inform innovative techniques for carbon sequestration in the soil, a potential mitigation strategy for climate change.
Contact: Steven Blazewicz (925) 423-1506 (blazewicz1 [at] llnl.gov (blazewicz1[at]llnl[dot]gov)).
Proteins Affect Radioactive Elements’ Behavior
Lanmodulins (LanM) are proteins with high affinity for rare earths and certain actinides. Nuclear waste containing actinides is problematic, as actinides linger in the environment for thousands of years after initial nuclear activity. A study by researchers at Lawrence Livermore and Pennsylvania State University found that interactions with LanM render certain actinides more soluble than predicted under typical environmental conditions, increasing the potential for further migration of these radioactive elements from their initial locations. The findings appear on the cover of the December 12, 2023, issue of Environmental Science & Technology.
Actinides such as americium and curium contribute heavily to the long-term radiotoxicity of nuclear waste, an increasingly relevant concern amidst renewed interest in nuclear energy as a clean electricity source. Nuclear waste is typically stored in deep underground repositories and isolated until its radioactivity lowers to a level similar to that of naturally radioactive ores. Understanding wastes’ reactions with the natural environment, including the minerals, groundwater, metal chelators, and microorganisms, is crucial in informing long-term management strategies and decisions.
LanM has yet to be robustly studied in the presence of actinides, and the team aims to raise awareness about this area of need. “Studying the chemistry of radioelements under environmentally relevant conditions is critical to assess the long-term behavior of nuclear waste,” says Gauthier Deblonde, lead author of the study.
Contact: Gauthier Deblonde (925) 423-2068 (deblonde1 [at] llnl.gov (deblonde1[at]llnl[dot]gov)).
