Catalytic efficiencies for atmospheric methane removal in the high-chlorine regime

12 October 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Catalytic production of chlorine atoms from iron salt aerosols (ISA) has been suggested as a means of achieving atmospheric methane reduction (AMR). The feasibility of this approach its efficiency and the optimum conditions for deployment must be determined. Success is not obvious because it depends on nonlinear atmospheric free radical chain reactions; under some conditions added chlorine is known to increase methane lifetime. Here we evaluate the catalytic efficiency of atmospheric methane oxidation, initiated by the photocatalytic conversion of chloride to chlorine by iron chlorides Fe(III)Cl(3−n)n , using a OD box model. While HOx and high NOx behaviours are well known, a new regime is characterized by high ClOx conditions ypified by CH3O2 reacting with ClO rather than NO or HO2. We find that at NOx mixing ratios below 50 ppt or above 390 ppt, methane removal per iron atom is always net positive regardless of the Cl2 addition rate. However, between these NOx mixing ratios and for a chlorine production rate below 1×10^6 Cl2 /(cm3 s) the net effect is negative, increasing CH4 concentrations. The efficiencies seen in the model range from -0.26 to 2.63 CH4/Cl.


Atmospheric Methane Removal
0D box Model
Iron-Salt Aerosol
High ClOx regime

Supplementary materials

Model description, sensitivity analyses and supplementary figures.
Supplementary information contains model starting conditions, full list of reactions and their sources. Additionally, the sensitivity analyses of ClONO2 and O3 are explained and the ozone loss reactions and alternative NOx world map is presented.


Comments are not moderated before they are posted, but they can be removed by the site moderators if they are found to be in contravention of our Commenting Policy [opens in a new tab] - please read this policy before you post. Comments should be used for scholarly discussion of the content in question. You can find more information about how to use the commenting feature here [opens in a new tab] .
This site is protected by reCAPTCHA and the Google Privacy Policy [opens in a new tab] and Terms of Service [opens in a new tab] apply.