Measurement Mobilized

LIVERMORE, Calif. — Researchers at Sandia National Laboratories have designed and built a mobile research facility to trace and identify the origin of greenhouse gases.

In addition to pinpointing the chemicals’ location, the unique mobile facility can help researchers learn whether the gases are biogenic (coming from plant sources) or anthropogenic (coming from man-made sources). This is important when officials look at ways to mitigate emission impacts in their communities, regions, or states.

“Information from this kind of facility should be useful to both researchers and policymakers,” said Hope Michelsen, a combustion and atmospheric chemist at Sandia and one of the lead researchers on the project. “To figure out whether emissions reduction policies are effective, we need a way to measure emissions by emissions sector, such as power generation or transportation. We currently don’t have the tools in place to do these types of measurements, so we hope our idea can be part of the solution.”

The mobile system consists of two moving van-sized trucks, each equipped with instrumentation and equipment. Included are instruments that measure greenhouse gases, such as carbon dioxide (CO2) and methane (CH4), and species co-emitted with greenhouse gases, such as sulfur dioxide (SO2), nitrogen oxide (NOx), carbon monoxide (CO), ozone (O3), and other traditional pollutants.

“Elected officials who have enacted new policies to help reduce unwanted greenhouse gas emissions could conceivably find a mobile facility to be of great use,” said Michelsen. “To figure out whether emissions reduction policies are effective, we need a way to measure emissions by emissions sector, such as power generation or transportation,” Michelsen continued. “We currently don’t have the tools in place to do these types of measurements, so we hope our idea can be part of the solution.”

The mobile system consists of two moving van-sized trucks, each equipped with instrumentation and equipment. Included are instruments that measure greenhouse gases, such as carbon dioxide (CO2) and methane (CH4), and species co-emitted with greenhouse gases, such as sulfur dioxide (SO2), nitrogen oxide (NOx), carbon monoxide (CO), ozone (O3), and other traditional pollutants.

While the instruments are all commercially available, another current project funded internally at Sandia aims to build an instrument to more accurately measure black carbon soot, formed through the incomplete combustion of fossil fuels, biofuels, and biomass. Black carbon soot is believed by atmospheric scientists to be one of the strongest absorbers of solar radiation.

Atop each truck sits an antennae-like mast that draws in air, sends it down into the truck, and distributes it to the various instruments, including a mass spectrometer that sorts out hydrocarbons and helps to distinguish between emission sources, which can range from traffic to pine trees.

A piece of equipment provided by Lawrence Livermore National Laboratory (LLNL) captures samples in flasks for analysis at LLNL’s Center for Accelerator Mass Spectrometry to measure the radiocarbon (14C) fractionation of CO2 (14C is a radioactive isotope of carbon).

Because 14C is severely depleted in fossil fuels, it is a powerful indicator of man-made CO2 sources. Some of these samples were also sent to the National Oceanic and Atmospheric Administration and to the University of California, Davis for further trace gas and isotopic analysis.

The mobile laboratory has already been deployed once to the Atmospheric Radiation Measurement (ARM) facility in Oklahoma, The ARM location in Oklahoma, said Sandia researcher Ray Bambha, was selected because of its solid history as a climate research site, and ARM instruments were used to validate some of the measurements from the mobile lab. Bambha served as the principal investigator for the field experiment, alongside several other Sandians serving in key roles. Collaborators from both LLNL and Los Alamos National Laboratory joined the Sandia team for portions of the Oklahoma deployment.

The pilot deployment, Bambha said, was successful in that the system collected large quantities of data, which are still in the process of being analyzed. It allowed the team to test instruments that hadn’t been used previously, and it helped them to understand the atmospheric community’s need for an “uncertainty quantification” capability – a method of assigning a confidence level to an estimate – and tracer measurements, which provide a more effective method for identifying the source of certain emissions. Michelsen said Sandia is in the process of building a team of researchers that can take the next step with the system and begin to use wind information and inverse modeling to more accurately identify emission sources.

In the short-term, Michelsen said, program development efforts are well under way in hopes of securing follow-on funding for other test deployments. The long-term vision for the program calls for a full network of mobile facilities that could be deployed strategically in select regions, states, or cities, to enable the capturing of a broad spectrum of emissions and related information.