DOE User Facilities Join Forces to Study Molecular Processes with Global Effects
EMSL will analyze aerosol samples gathered at an ARM site to better understand how microscopic particles and processes affect climate on a global scale
Two U.S. Department of Energy (DOE) user facilities are sponsoring scientists to learn more about aerosols, tiny particles that are suspended in the atmosphere, and the role they play in weather and climate systems. The Atmospheric Radiation Measurement (ARM) Climate Research Facility is providing aerosol samples from its Southern Great Plains (SGP) atmospheric observatory to be analyzed at EMSL, the Environmental Molecular Sciences Laboratory.
The SGP, near Lamont, Oklahoma, is the world’s largest and most extensive climate research facility. With substantial measurement capabilities, the SGP is the ARM Facility’s premier research site.
“The idea of the joint call is to use the joint capabilities to do science that couldn’t be done at either facility on its own,” John Shilling, EMSL Atmospheric Aerosol Systems Science Theme leader, said. Investigators only needed to submit one proposal to be considered for both ARM and EMSL support, streamlining the process and encouraging researchers to consider problems that would benefit from the use of both facilities.
- Proposals include:
- Analyzing the composition of particles collected at the SGP during the Holistic Interactions of Shallow Clouds, Aerosols, and Land-Ecosystems campaign (HI-SCALE)
- Investigating the role of organic, or carbon-containing, compounds on particle growth and cloud formation
- Measuring how cloud-forming particles grow when they interact with other substances in the atmosphere
- Exploring how soil particles are thrown into the atmosphere during rainfall
- Quantifying how different parts of aerosol particles mix together and evolve.
Particle Formation on the Prairie
Currently, SGP is hosting the Holistic Interactions of Shallow Clouds, Aerosols, and Land-Ecosystems (HI-SCALE) campaign. HI-SCALE lead scientist Jerome Fast, Pacific Northwest National Laboratory, has prepared an ARM/EMSL proposal to support analyzing the composition of particles collected at SGP.
The HI-SCALE campaign is working to describe climate-relevant atmospheric processes that are on spatial scales as small as a kilometer, many of which are driven by even smaller-scale interactions at the molecular scale. Climate models can’t fully capture processes that tiny, and so it’s important to understand and be able to describe the minute particles and processes in a way that can be passed into the models.
Fast’s proposal will bring in a single-particle mass spectrometer from EMSL to complement a smaller version deployed on ARM Aerial Facility’s Gulfstream-1 aircraft. Using EMSL’s measurement capabilities at the ARM site, Fast is examining how new particles form out of gases and eventually grow into cloud condensation nuclei (CCN), which means they’re large enough for clouds to start to form around them.
Using both facilities to link new particle formation with larger-scale climate-relevant atmospheric processes should “greatly help to develop coupled aerosol and cloud parameterizations in large-scale models,” Fast said.
Compounds and Particle Growth: Measuring Complex Molecules
With support from an ARM/EMSL joint proposal, James Smith, University of California at Irvine, and Susanne Hering, Aerosol Dynamics Inc., will investigate the role of organic compounds on particle growth. There are a number of ways that aerosols can grow from a nanoparticle to a CCN. This proposal will find out more about the different pathways and the makeup of the particles along each one.
A major challenge is actually finding out what chemical compounds make up the particles. First, researchers have to collect the particles. However, the very thing they’re trying to measure—the way the particles grow—makes them difficult to collect: “If a molecule is good at forming particles, it can get stuck in sample inlets,” Smith said.
His previous method of gathering particles required them to be heated before they could be analyzed using mass spectrometry. The heating caused the particles to degrade and fragment, affecting the quality of the results.
Working with Smith, Herring developed a new sampling instrument that collects particles in a way that retains their complexity. The samples collected at SGP are sent to EMSL, where they are dissolved into a liquid and then analyzed in a mass spectrometer, with no heating involved.
Growing from Nanometer-Scale to Clouds
Jian Wang, Brookhaven National Laboratory, is using the ARM/EMSL support to collect particles of specific sizes and measure how they grow and change as they interact with other compounds in the atmosphere. By understanding how newly formed particles grow, Wang and his team can assess the probability of ultrafine particles surviving and growing into CCN.
Earlier measurements at the SGP showed frequent new particle formation, and Wang hopes to collect particles from small to large to see how they change as they grow. He’ll use an instrument that automatically sorts the particles and allows for analysis in a variety of machines. Samples will be sent to EMSL as well as Lawrence Berkeley National Laboratory (LBNL) to determine sizes, shapes, and the composition of individual particles.
“What we find out about added materials tells us about the process,” Wang said about the proposal. “We’re happy we can use the sensitive instruments at EMSL to tell us what materials are being added as particles grow.”
Puddle Splashes Lead to Particle Emissions
In 2014-2015, Alex Laskin, EMSL, and Mary Gilles, LBNL, discovered a new aerosol pathway at SGP that could influence macroscopic climate-relevant processes. Now they’re back again to collect more samples and take more measurements.
In a previous campaign, they were surprised to find large particles at the SGP—large particles are generally associated with pollution or sea salt, and the Oklahoma plain is far from both pollution sources and the ocean. They also noticed that the large particles were associated with rainfall.
This association led them to observe how rainwater forms tiny pools with dissolved soil matter in it. They saw that falling raindrops created bubbles in these pools, which burst and eject a fine mist, like the bubble-bursting process in sea spray.
“It never occurred to anyone that particles were produced from rain landing on soil surfaces,” Gilles said. “Is it a fluke we saw these particles? Are the formed every time it rains?” Gilles and Laskin are returning to the SGP with a joint ARM/EMSL proposal to answer those questions.
The Parts of a Particle
Ryan Moffet, University of the Pacific, is supported by ARM and EMSL to aid in sample collection and lead experiments that focus on how different parts of particles are mixed together. His team is interested in how the chemical components in organic aerosols evolve in the atmosphere, over time and exposed to a variety of factors.
Since the mixing state of an aerosol is strongly tied to how the particle absorbs or reflects sunlight, this type of parameterization is key to modeling the effects of aerosols on climate change. Two aerosols might have a similar chemical makeup, but if the internal arrangement is different, they could have opposite effects on climate.
Collecting Data and Advancing Science
Data collected routinely throughout the SGP are supplemented by temporary field research campaigns like the ones resulting from the ARM/EMSL call. Both routine and field campaign data are transmitted to the ARM Data Archive and are made available at no cost to the global scientific community.
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The ARM Climate Research Facility is a national scientific user facility funded through the U.S. Department of Energy's Office of Science. The ARM Facility is operated by nine Department of Energy national laboratories.
EMSL, the Environmental Molecular Sciences Laboratory, a DOE Office of Science user facility located at Pacific Northwest National Laboratory in Richland, Washington. EMSL offers an open, collaborative environment for scientific discovery to researchers around the world, and its integrated computational and experimental resources enable researchers to realize important scientific insights and create new technologies.