Le Chatelier's Principle in the Ocean Surface
- Page ID
- 50885
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Carbon sinks are important terrestrial reservoirs in reducing overall carbon dioxide concentrations in the atmosphere. These sinks, both natural and artificial, play a vital role sequestering or capturing gaseous carbon dioxide into an aqueous or solid chemical compound for an indefinite length of time. Artificial carbon sinks constructed by humans include landfills and carbon capture and storage; for example, the capture and compression of emissions from a fossil fuel power plant. However, out of all carbon dioxide emitted into the atmosphere, natural sinks account for half of the carbon taken up where a quarter is drawn into land plants and the remaining quarter taken by the oceans. Although land plants are vital in sequestering carbon dioxide through photosynthesis, this sequestration is balanced in the short-term by the annual decay and recycling of plant matter back into carbon dioxide through decomposition.
In oceans, the situation is somewhat more permanent as once a carbon molecule is dissolved, it normally stays below the depths for an average of 500 years before cycling back into the atmosphere through oceanic movements. Generally, two processes dominate the sequestration of carbon in oceans and its eventual release in a later point in time: a solubility pump through achieving equilibrium in the direct air-to-sea exchange of carbon dioxide and a biological pump where inorganic matter such as dead organisms or calcifying organisms forming shells sink downward.
The solubility pump manages its work by the imbalance of positively charged species that exists in the oceans as opposed to negatively charged ones allowing an equilibrium reaction to occur between carbon dioxide and the ocean. As the ocean contains an ample abundance of positive species, the equilibrium of this system prefers the formation of negatively charged species so as to achieve net neutrality. This global example of Le Chatelier’s principle demonstrates the consequences of changing chemical equilibrium, “When a stress is applied to a system at equilibrium, the equilibrium shifts to relieve the stress.”
The overall exchange at the ocean surface is summarized in the following acid-base equations where each equation is in dynamic equilibrium with each other:
\[\ce{CO2 (aq) + H2O (l) <-> H2CO3 (aq)}\label{1}\]
\[\ce{H2CO3 (aq) + H2O (l) <-> HCO3- (aq) + H3O+ (aq)}\label{2}\]
\[\ce{HCO3- (aq) + H2O (l) <-> CO3(2-) (aq) + H3O+ (aq)}\label{3}\]
In Equation \(\ref{1}\), after carbon dioxide dissolves into water into an aqueous form (an overall process occurring over hundreds to thousands of years) it reacts with water. The weak acid product from \(\ref{1}\), carbonic acid, reacts slightly and reversibly in water to form an acidic hydronium ion and a bicarbonate ion, HCO3-, in equation \(\ref{2}\). The last equation \(\ref{3}\) involves a further deprotonation of bicarbonate ion into carbonate ion and the production of an additional hydronium ion. This net increase of hydronium ion into the ocean decreases the pH, a reason why oceans have a normal pH around 5.5 instead of a neutral 7. Oceans typically hold an excess of positively charged cations (Na+, K+, Mg2+, Ca2+) leaving a net imbalance of positive charged species. In regards to the carbonate system and Le Chatelier’s principle, negative ions are lacking which causes a shift towards these products in seawater, hence promoting the oceanic uptake of carbon dioxide into carbonate species.