Journal Article

The use of δ 13C in CO to determine removal of CH4 by Cl radicals in the atmosphere

Arrieta, Jesús M, Röckmann, Thomas, Moss, Rowena, Meidan, Daphne, Mármol, Ignacio, Zaehnle, Sönke, Sperlich, Peter, Ramos, Ramón, Timas, Helder, van der Veen, Carina, Prats, Natalia, Johnson, Matthew S, Young, Dickon, Saiz-Lopez, Alfonso, Baños, Isabel, Brashear, Chloe, Li, Qinyi, van Herpen, Maarten, Gromov, Sergey, Barreto, Africa, Moossen, Heiko, Jordan, Armin

2024

Overview

The reaction of CH ₄ with chlorine (Cl) radicals in the atmosphere is associated with an extraordinarily strong isotopic fractionation, where ¹2 CH ₄ reacts about 70 ‰ faster with Cl than ¹3 CH ₄ . Therefore, although the Cl-based sink of CH ₄ constitutes only a small contribution to its total removal rate, the uncertainty in this small sink has been identified as one of the two largest uncertainties of isotope-based CH ₄ source apportionment at the global scale. The uncertainty arises from the fact that Cl levels in the atmosphere are so low that they cannot be detected directly. One very sensitive indirect method to identify and quantify the CH ₄ + Cl reaction in the atmosphere is the detection of the extremely ¹3 C-depleted reaction product carbon monoxide (CO) from this reaction. This article reviews the concept of this approach, its successful application in the atmosphere, its challenges and opportunities for identifying and quantifying Cl-based removal of CH ₄ at the regional and global scale and its potential to detect and evaluate possible attempts to enhance CH ₄ removal from the atmosphere.

• Publisher: IOP Publishing
• Subject: CH4 / δ 13C