Abstract

Marine CO2 removal (CDR) using enhanced-alkalinity seawater discharge was simulated in the estuarine waters of the Salish Sea, Washington, US. The high-alkalinity seawater would be generated using bipolar membrane electrodialysis technology to remove acid and the alkaline stream returned to the sea. Response of the receiving waters was evaluated using a shoreline resolving hydrodynamic model with biogeochemistry, and carbonate chemistry. Two sites, and two deployment scales, each with enhanced TA of 2997 mmol m−3 and a pH of 9 were simulated. The effects on air-sea CO2 flux and pH in the near-field as well as over the larger estuary wide domain were assessed. The large-scale deployment (addition of 164 Mmoles TA yr−1) in a small embayment (Sequim Bay, 12.5 km2) resulted in removal of 2066 T of CO2 (45% of total simulated) at rate of 3756 mmol m−2 yr−1, higher than the 63 mmol m−2 yr−1 required globally to remove 1.0 GT CO2 yr−1. It also reduced acidity in the bay, ΔpH ≈ +0.1 pH units, an amount comparable to the historic impacts of anthropogenic acidification in the Salish Sea. The mixing and dilution of added TA with distance from the source results in reduced CDR rates such that comparable amount 2176 T CO2 yr−1 was removed over >1000 fold larger area of the rest of the model domain. There is the potential for more removal occurring beyond the region modeled. The CDR from reduction of outgassing between October and May accounts for as much as 90% of total CDR simulated. Of the total, only 375 T CO2 yr−1 (8%) was from the open shelf portion of the model domain. With shallow depths limiting vertical mixing, nearshore estuarine waters may provide a more rapid removal of CO2 using alkalinity enhancement relative to deeper oceanic sites.

Details

Title
Mixing and dilution controls on marine CO2 removal using alkalinity enhancement
Author
Khangaonkar, Tarang 1   VIAFID ORCID Logo  ; Carter, Brendan R 2 ; Premathilake, Lakshitha 1 ; Su, Kyong Yun 3   VIAFID ORCID Logo  ; Ni, Wenfei 3 ; Stoll, Mary Margaret 4 ; Ward, Nicholas D 5   VIAFID ORCID Logo  ; Hemery, Lenaïg G 5   VIAFID ORCID Logo  ; Carolina Torres Sanchez 5 ; Subban, Chinmayee V 3 ; Ringham, Mallory C 6 ; Eisaman, Matthew D 7 ; Pelman, Todd 6 ; Tallam, Krti 6   VIAFID ORCID Logo  ; Feely, Richard A 8 

 Energy and Environment Directorate, Pacific Northwest National Laboratory , Seattle, WA 98109, United States of America; University of Washington , Seattle, WA, United States of America 
 University of Washington , Seattle, WA, United States of America; Pacific Marine Environmental Laboratory, NOAA , Seattle, WA, United States of America 
 Energy and Environment Directorate, Pacific Northwest National Laboratory , Seattle, WA 98109, United States of America 
 University of Washington , Seattle, WA, United States of America 
 Marine and Coastal Research Laboratory, PNNL , Sequim, WA, United States of America 
 Ebb Carbon , Inc., San Carlos, CA, United States of America 
 Department of Earth & Planetary Sciences, Yale University , New Haven, CT, United States of America; Yale Center for Natural Carbon Capture, Yale University , New Haven, CT, United States of America 
 Pacific Marine Environmental Laboratory, NOAA , Seattle, WA, United States of America 
First page
104039
Publication year
2024
Publication date
Oct 2024
Publisher
IOP Publishing
e-ISSN
17489326
Source type
Scholarly Journal
Language of publication
English
ProQuest document ID
3101550860
Copyright
© 2024 The Author(s). Published by IOP Publishing Ltd. This work is published under https://creativecommons.org/licenses/by/4.0/ (the “License”). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.