Catalysis and chemical mechanisms of calcite dissolution in seawater [Earth, Atmospheric, and Planetary Sciences]
Near-equilibrium calcite dissolution in seawater contributes significantly to the regulation of atmospheric
CO2 on 1,000-y timescales. Despite many studies on far-from-equilibrium dissolution, little is known about the detailed mechanisms
responsible for calcite dissolution in seawater. In this paper, we dissolve 13C-labeled calcites in natural seawater. We show that the time-evolving enrichment of
𝜹13C in solution is a direct measure of both dissolution and precipitation reactions across a large range of saturation states.
Secondary Ion Mass Spectrometer profiles into the 13C-labeled solids confirm the presence of precipitated material even in undersaturated conditions. The close balance of precipitation
and dissolution near equilibrium can alter the chemical composition of calcite deeper than one monolayer into the crystal.
This balance of dissolution–precipitation shifts significantly toward a dissolution-dominated mechanism below about
Ω= 0.7. Finally, we show that the enzyme carbonic anhydrase (CA) increases the dissolution rate across all saturation states, and
the effect is most pronounced close to equilibrium. This finding suggests that the rate of hydration of
CO2 is a rate-limiting step for calcite dissolution in seawater. We then interpret our dissolution data in a framework that incorporates
both solution chemistry and geometric constraints on the calcite solid. Near equilibrium, this framework demonstrates a lowered
free energy barrier at the solid–solution interface in the presence of CA. This framework also indicates a significant change
in dissolution mechanism at
Ω= 0.7, which we interpret as the onset of homogeneous etch pit nucleation.
Keeping up-to-date with research can feel impossible, with papers being published faster than you'll ever be able to read them. That's where Researcher comes in: we're simplifying discovery and making important discussions happen. With over 19,000 sources, including peer-reviewed journals, preprints, blogs, universities, podcasts and Live events across 10 research areas, you'll never miss what's important to you. It's like social media, but better. Oh, and we should mention - it's free.
Researcher displays publicly available abstracts and doesn’t host any full article content. If the content is open access, we will direct clicks from the abstracts to the publisher website and display the PDF copy on our platform. Clicks to view the full text will be directed to the publisher website, where only users with subscriptions or access through their institution are able to view the full article.