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This technique increases the CO<jats:sub>2<\/jats:sub> uptake capacity of seawater through weathering of fine\u2010grained (mafic) rocks and minerals in marine environments. The weathering process has been extensively tested in laboratory studies and verified by numerical models. Field experiments scaling the CO<jats:sub>2<\/jats:sub> uptake under natural conditions are still lacking. In a methodological approach, a novel in situ experiment was designed and installed in a salt marsh at Ria Formosa coastal lagoon, southern Portugal. The experiment comprised deployments of different sizes of olivine and basalt substrates, and a control site, which were tidally submerged twice a day. A monthly monitoring scheme of supernatant and porewater properties from each deployment and control site was established, and procedures for temperature, salinity, oxygen, pH, total alkalinity, nutrient, and trace metal analyses were defined. This paper is devoted to the methods and describes the design, a protocol for the analyses, and an evaluation of experimental performance and reliability. Data from the first 6\u00a0months are presented for validation of the experiment. They demonstrated elevated total alkalinity in water samples, mostly in porewater after the deployments, while salinity, oxygen, and pH reflect the control conditions. Significant alkalinity differences were observed between the treatments and the natural background conditions monitored at the control site, during the 6\u00a0months of the experiment. The methodological approach is presented with strengths, limitations, and recommendations for an upscaling as CO<jats:sub>2<\/jats:sub> removal measure, servicing, and subsequent investigations.<\/jats:p>","DOI":"10.1029\/2024jg008591","type":"journal-article","created":{"date-parts":[[2025,3,11]],"date-time":"2025-03-11T13:55:10Z","timestamp":1741701310000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Novel Field Experiment on Alkalinity Enhancement in Intertidal Environments\u2014A Trailblazer for Natural Climate Solutions"],"prefix":"10.1029","volume":"130","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-7004-7910","authenticated-orcid":false,"given":"I.","family":"Mendes","sequence":"first","affiliation":[{"name":"Centro de Investiga\u00e7\u00e3o Marinha e Ambiental (CIMA) Rede de Infraestrutura em Recursos Aqu\u00e1ticos (ARNET) Universidade do Algarve  Faro Portugal"}]},{"given":"J.","family":"Lu\u0308bbers","sequence":"additional","affiliation":[{"name":"Centro de Investiga\u00e7\u00e3o Marinha e Ambiental (CIMA) Rede de Infraestrutura em Recursos Aqu\u00e1ticos (ARNET) Universidade do Algarve  Faro Portugal"}]},{"given":"J.","family":"Scho\u0308nfeld","sequence":"additional","affiliation":[{"name":"GEOMAR Helmholtz\u2010Zentrum f\u00fcr Ozeanforschung Kiel  Kiel Germany"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2319-4640","authenticated-orcid":false,"given":"A.","family":"Baldermann","sequence":"additional","affiliation":[{"name":"Institute of Applied Geosciences Graz University of Technology &amp; NAWI Graz Geocenter  Graz Austria"}]},{"given":"A. 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