Ocean alkalinity enhancement – avoiding runaway CaCO<sub>3</sub> precipitation during quick and hydrated lime dissolution
نویسندگان
چکیده
Abstract. Ocean alkalinity enhancement (OAE) is a method that can remove carbon dioxide (CO2) from the atmosphere and counteract ocean acidification through dissolution of alkaline minerals. Currently, critical knowledge gaps exist regarding different minerals suitable for OAE in natural seawater. Of particular importance to understand how much mineral be dissolved before secondary precipitation calcium carbonate (CaCO3) occurs, since CaCO3 reduces atmospheric CO2 uptake potential OAE. Using two types proposed OAE, quick lime (CaO) hydrated (Ca(OH)2), we show both (<63 µm diameter) seawater within few hours. No occurred at saturation state (?A) ?5, but form aragonite above an ?A value 7. This limit lower than expected typical pseudo-homogeneous precipitation, i.e. presence colloids organic matter. Secondary low (? 7) was result heterogeneous onto surfaces, most likely added CaO Ca(OH)2 particles. Most importantly, runaway observed, condition where significantly more total (TA) removed initially added. Such could reduce efficiency ? 0.8 mol per mole TA down 0.1 TA. Runaway appears avoidable by dilution below threshold 5, ideally hours additions minimise initial precipitation. Finally, simulations suggest same threshold, amount would 3 times higher 5 ?C 30 ?C. The maximum addition also increased equilibrating levels (i.e. pCO2 416 µatm) during addition. allow without inducing using its removal potential.
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ژورنال
عنوان ژورنال: Biogeosciences
سال: 2022
ISSN: ['1726-4189', '1726-4170']
DOI: https://doi.org/10.5194/bg-19-3537-2022