The Laboratory in the News

Aligning Air Pollution and Drizzle

Laboratory scientists working with researchers from the Scripps Institution of Oceanography and international collaborators enhanced their understanding of rainfall’s aerosol-scavenging effects on pollution through improvements to two state-of-the-art global climate models that result in better agreement with observed drizzle rates. Their findings appear in the January 11, 2021, issue of Nature Geoscience.

Atmospheric aerosols, which have a significant effect on the Earth’s radiative energy balance and air quality, can be influenced by rainfall through wet removal processes. The research team demonstrated that more frequent, but less intense, rainfall has a disproportionate control on aerosol burden making it more effective at removing pollutants from the atmosphere than heavy rain. By improving the representation of convection in two global climate models, the Department of Energy (DOE) Energy Exascale Earth System Model version 1 and the National Science Foundation/DOE Community Atmosphere Model version 5, the relative frequency of light rain is reduced and the anticipated aerosol burden in the atmosphere increased 17 percent.

“The current models include too much light rain, washing out pollutant projections,” says Shaocheng Xie, one of the Livermore authors. “In future climate projects, even if precipitation is expected to increase, its impact on modeled aerosol concentration would depend on the occurrence of light rain changes.” This change to the model, according to researchers, addresses underestimation of aerosols in the atmosphere, especially over regions in tropical rain belts. In its paper, the team notes that aerosol radiative effect is a major source of uncertainty in climate change projections.
Contact: Shaocheng Xie (925) 422-6023 (xie2@llnl.gov).

Reconstructing the Primordial Solar System

Livermore scientists have linked planetary bodies, shuffled by the gravitational effect of the formation of Jupiter and Saturn, to their initial locations by studying the compositions of meteorites originating from the asteroid belt between Mars and Jupiter. The research appears in the February 1, 2021, issue of Earth and Planetary Science Letters.

Tracing the source material of planetary bodies requires signatures established during planetary body formation. Isotopic anomalies of nucleosynthetic origin are powerful tools for fingerprinting the building material from which planetary bodies amassed. The asteroid belt contains a collection of materials swept up from the solar system and multiple, spectroscopically distinct asteroid families. The meteorites located there derive from at least 100 distinct parent bodies with diverse chemical and isotopic signatures. “The significant reorganization of the early solar system due to giant planet migration has hampered our understanding of where planetary bodies formed,” says Jan Render, Livermore postdoc and lead author of the paper. “By looking at the makeup of meteorites from the asteroid belt, we determined that their parent bodies must have accreted from materials from very different locations in the early solar system.”

The researchers measured the nucleosynthetic isotope signatures in the elements neodymium and zirconium from meteorite samples and determined that the elements were characterized by relative deficits in isotopes hosted by a certain type of presolar material. Their data correlates with nucleosynthetic signatures observed in other elements, demonstrating that the protoplanetary matter in the early solar system was distributed as a gradient according to heliocentric distance.
Contact: Gregory Brennecka (925) 423-8502 (brennecka2@llnl.gov).

Advancing Hemodialysis

Laboratory researchers have discovered that carbon nanotube membrane pores could enable ultra-rapid dialysis processes to greatly reduce treatment time for hemodialysis patients. The pores could also provide a solution to the permeability-versus-selectivity tradeoff, allowing to sieve out larger molecules without reducing the ion filtration rate. Initial results were published in the February 3, 2021, issue of Advanced Science.

Carbon nanotube membrane pores are graphitic cylinders with diameters thousands of times smaller than a human hair. By applying a concentration gradient across a porous membrane, ions or molecules smaller than the pore diameters can be driven from one side of the membrane to the other while blocking anything too large to fit through the pores. Small ions, such as potassium, chloride, and sodium, were found to diffuse through these tiny pores more than an order of magnitude faster than when moving in bulk solution. “The general consensus in the literature has been that diffusion rates in pores of this diameter should be equal to, or below, what we see in bulk,” says Livermore scientist Steven Buchsbaum, lead author of the paper. “We did not expect this result.”

Enhanced ion transport could also enable supercapacitors with high power density even at pore sizes approaching those of the ions. Livermore capabilities in computational simulation and nuclear magnetic resonance spectroscopy supported the team’s study of ion movement inside carbon nanotubes. “Our findings provide a new example of exciting nanofluidic phenomena,” says Francesco Fornasiero, the principal investigator.
Contact: Francesco Fornasiero (925) 422-0089 (fornasiero1@llnl.gov).