Effects of Synechococcus sp. cyanobacteria inert biomass on olivine dissolution: Implications for the application of enhanced weathering methods

摘要

Abstract Chemical weathering of silicates represents an essential process of both the rock and carbon cycles. The application of this natural process on a global scale could be used to mitigate excess CO2 in the atmosphere. This concept is known as enhanced weathering where fine mineral powder is spread over the land surface for carbonation of silicates and expected CO2 sequestration. Within this context, organic matter, may promote or inhibit the processes of enhanced weathering, however this has not yet been fully quantified. Motivated by this knowledge gap, the present work studied the dissolution behaviour of olivine under inorganic conditions and in the presence of inert Synechococcus sp. biomass in batch reactor setups at various ionic strengths with a constant input of atmospheric CO2. Olivine, which represents one of the most obvious candidates for use in enhanced weathering, showed no significant statistical differences in the release of dissolved cations for all studied organic and inorganic experimental setups. For batch reactors containing inert biomass, a moderate increase in alkalinity and pH is found with respect to the inorganic conditions, which points to the buffering of H2CO3 by deprotonated functional groups on the inert biomass surface. Overall, the experimental results of this study indicate a negative combined effect of inert biomass and high ionic strengths on the olivine dissolution rates in natural aquatic systems. This suggests reduced carbonation rates on the Earth's surface and a lower potential of artificially dispersed olivine powder for CO2 sequestration. Highlights ? Interaction of inert cyanobacteria biomass with olivine inhibits mineral dissolution. ? Inert biomass cell surface functional groups may interact with Mg-O active sites. ? No enhancement observed in the rates of olivine dissolution in presence of inert biomass. ]]>