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Preprints
https://doi.org/10.5194/egusphere-2024-625
https://doi.org/10.5194/egusphere-2024-625
14 Mar 2024
 | 14 Mar 2024

Ocean liming effects on dissolved organic matter dynamics

Chiara Santinelli, Silvia Valsecchi, Simona Retelletti Brogi, Giancarlo Bachi, Giovanni Checcucci, Mirco Guerrazzi, Elisa Camatti, Stefano Caserini, Arianna Azzellino, and Daniela Basso

Abstract. Ocean liming has gained attention as a potential solution to mitigate climate change by actively removing carbon dioxide (CO2) from the atmosphere. The addition of hydrated lime (Ca(OH)2) into oceanic surface water leads to an increase in alkalinity, which in turn promotes the uptake and sequestration of atmospheric CO2.

Despite the potential of this technique, its effects on the marine ecosystem are still far to be understood, and there is currently no information on the potential impacts on the concentration and quality of Dissolved Organic Matter (DOM), that is the largest, the most complex and yet the least understood mixture of organic molecules on Earth. The aim of this study is to provide the first experimental evidence about the potential effects of pH peaks, that might be generated by the Ca(OH)2 dissolution in seawater, on DOM dynamics by assessing changes in its concentration and optical properties (absorption and fluorescence).

To investigate the effects of liming on DOM pools with different concentrations and quality, seawater was collected from two contrasting environments: the oligotrophic Mediterranean Sea (MedSea), known for its Dissolved Organic Carbon (DOC) concentration comparable to that observed in the oceans, and the eutrophic Baltic Sea (BalSea), characterized by high DOM concentration mostly of terrestrial origin. Ca(OH)2 was added in both waters, to reach a pH of 9 and 10.

Our findings reveal that the addition of hydrated lime has a noticeable effect on DOM dynamics in both the MedSea and BalSea, determining a reduction in DOC concentration and a change in the optical properties (absorption and fluorescence) of DOM. Thes effects, detectable at pH 9, become significant at pH 10 and are more pronounced in the MedSea than in the BalSea. These potential short-term effects should be considered within the context of the physico-chemical properties of seawater and the seasonal variability.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
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Journal article(s) based on this preprint

18 Nov 2024
Ocean liming effects on dissolved organic matter dynamics
Chiara Santinelli, Silvia Valsecchi, Simona Retelletti Brogi, Giancarlo Bachi, Giovanni Checcucci, Mirco Guerrazzi, Elisa Camatti, Stefano Caserini, Arianna Azzellino, and Daniela Basso
Biogeosciences, 21, 5131–5141, https://doi.org/10.5194/bg-21-5131-2024,https://doi.org/10.5194/bg-21-5131-2024, 2024
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

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To the best of our knowledge, there is no study investigating the impact of ocean liming on...
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