Validating OCS in PPT Dilutions to Improve Carbon Cycle Models

The University of Arizona’s Meredith lab is working to form climate models at parts‑per‑trillion (ppt) dilution levels to better understand the delicate balance of carbon cycles and their effect in climate change. By validating carbonyl sulfide (OCS) as a tracer molecule and observing its uptake in photosynthesis and the release of carbon respiration, the lab seeks to provide key insights into the future impact of global carbon levels.

To accomplish this, Dr. Laura Meredith and her team required precise gas blending techniques to dilute and regulate OCS concentrations. This article explores their methods, and the advanced technologies used to aid in their research.

One of the least understood aspects of the carbon cycle is the method by which carbon moves between the soil and atmosphere and how that movement is influenced by plant, fungal, and microbial communities. With the onset of climate change, it is critical to close this knowledge gap.

Without a tracer molecule, however, it is difficult to determine how much carbon is taken up by photosynthesis vs. how much is released through respiration. Dr. Laura Meredith at the University of Arizona seeks to validate and use the tracer molecule, carbonyl sulfide (OCS), to learn about these complex relationships.

While OCS is taken up during photosynthesis, it is not respired. This means OCS can be used to gauge total carbon uptake by plants. It also provides insight into the distinct contributions of photosynthesis and respiration.

“It’s important to be able to break this out because we can’t be confident that climate change will affect photosynthesis and respiration in the same way, which could create an imbalance in the system. To build better models, we need to be able to resolve and study these two processes independently. The balance between the two is critical to understanding how much carbon is kept in the ground vs. how much is released into the atmosphere.”

 

— Dr. Laura Meredith

The Meredith lab planned an experiment to determine the correlation between OCS concentration and subsequent OCS uptake. Understanding this relationship as well as the reaction parameters and required enzymes is key to determining the reaction rate and confirming the use of OCS as a tracer molecule.