CDI Project: Radiation Atmospheric Dynamics Chamber

Left: The chamber body, as received. PNNL engineers and scientists worked with vendors to design the entire system from ground up. Center: Modeling of the light intensity in the chamber. PNNL’s team worked to minimize the variation in the light intensity and heating, providing the most consistent environment for chemical transformations. Right: Synthesis of radiolabeled compounds. PNNL’s radiochemical team is developing new techniques for creating the radiolabeled compounds for use in the chamber.
Left: The chamber body, as received. PNNL engineers and scientists worked with vendors to design the entire system from ground up. Center: Modeling of the light intensity in the chamber. PNNL’s team worked to minimize the variation in the light intensity and heating, providing the most consistent environment for chemical transformations. Right: Synthesis of radiolabeled compounds. PNNL’s radiochemical team is developing new techniques for creating the radiolabeled compounds for use in the chamber to maximize the efficiency of the radioactive material.

Return to Nuclear Incident Characterization Use Case

PI: David Abrecht

Project Team: John Shilling, Nathaniel Smith, Lance Hubbard, Jake Bair, Andrew Ritzmann, Chuck Soderquist, Cindy Warner, Jon Wahl

Project Term: October 2018 to September 2021

Key Science Questions:

  • Can we directly measure the rate constants of cyclic atmospheric reactions using radiotracers?

  • What enhancement of kinetic isotope effects occurs in atmospheric reaction cycling?

  • How does the complex chemical/photolytic environment of the atmosphere affect the make-up of semi-volatile species in the atmosphere?

Project Description: The project team is designing and installing a radioactive material-capable environmental chamber to investigate the fundamental chemical kinetics of molecular transformations under controlled conditions representative of the troposphere. The project goal is to study chemical transformations using radioactive tracers, allowing for advanced tracking of complex chemical transformations. The effects under study include:

  • identifying chemical reaction mechanisms

  • establishing chemical kinetic rate constants for those mechanisms

  • identifying kinetic isotope effects in cyclic reactions that would otherwise shift the expected behavior of isotopes in the transformations

The chamber will reproduce tropospheric conditions of temperature, pressure, humidity, trace gas concentrations, and UV irradiation. It will be used to study reaction pathways of chemicals of interest, utilizing radiotracers to both improve understanding of chemical transformation kinetics and mechanisms and to identify isotopic effects on those transformations.

The unconventional use of radiotracers in the chamber will enable tracking of atoms as they cycle between different molecules, allowing direct measurements of reaction mechanisms. When combined with the CDI modeling and data integration efforts, the project team’s work will improve uncertainty in atmospheric chemical mechanisms, leading to a greater understanding of the complex atmospheric chemistry of radiotracers.