Alkalinity enhancement with sodium hydroxide in coastal ocean waters - Preprint

[Geoengineering News]

https://www.researchsquare.com/article/rs-7042100/'https://www.researchsquare.com/article/rs-7042100/v1

Authors: Cathryn A. Wynn-Edwards, Wayne Dillon, John Akl Uhril, Craig Neill, Harris Anderson, Hui Sheng Lim, Mathieu Mongin, Elizabeth H. Shadwick

https://doi.org/10.21203/rs.3.rs-7042100/v1

27 October 2025

Abstract

Carbon Dioxide Removal (CDR) is increasingly recognised as essential for achieving net zero emissions to limit the impacts of climate change. Ocean Alkalinity Enhancement (OAE) presents a scalable marine CDR (mCDR). Here we report on the first OAE field trial in Australia, conducted at a coastal site in Tasmania using continuous addition of aqueous sodium hydroxide (NaOH). The resulting plume of modified seawater was effectively tracked, and changes in surface carbonate chemistry were quantified using a containerised laboratory. At the point of NaOH release, partial pressure of CO 2 (pCO 2) decreased by up 370 µatm with alkalinity increasing by approximately 545 µmol kg −1. Maximum downstream decreases in pCO 2 ranged from 22 to 77 µatm, corresponding to signal strengths of < 1-5%. This small-scale field trial confirmed that the dispersion of a plume of modified seawater occurs rapidly and within meters of the site of addition, and that with appropriate tools, these changes can be measured directly in a coastal ocean location. These results suggest that the deployment of shore-based OAE, in combination with local coastal infrastructure and regional models, have potential as an mCDR approach.

Source: Research Square