GEOL 3070 Lecture 22: Ocean Carbon and Acidification
Premium

2 Pages
13 Views
Unlock Document

Department
Geological Sciences
Course
GEOL 3070
Professor
Thomas Marchitto
Semester
Spring

Description
Ocean Carbon and Acidification Thursday, March 23, 2017 10:59 AM 1. Carbon and pH A. Carbon in seawater • One of the 7 major elements in seawater • Basic building block of organic molecules • Occurs in seawater in several forms: ○ ~2% dissolved organic carbon (DOC) ○ ~98% dissolved inorganic carbon (DIC) ▪ ~1% carbon dioxide gas (CO ) 2 - ▪ ~90% bicarbonate (HCO ) 3 ▪ ~10% carbonate (CO ) 32- ○ Relative abundance of DIC species is related to pH B. pH + - Pure Water: a tiny fraction of H 2 dissociates into hydrogen (H ) and hydroxide (OH ) • Since H O 2s the only source of these ions in pure water, their abundances must be equal ○ E.G. [H ] = [OH ] = 10 mol/kg + • pH= -log[H ] = 7 for pure water (neutral) + - Seawater: [H ] & [OH ] are imbalanced because of the presence of numerous other ions that consumer or release [H ] or [OH ] - • [H ] is less abundant and [OH] is more abundant • Seawater pH is slightly basic --> pH ~7.5-8.5 **Presence of Hydrogen (H ) makes things more basic & vice versa** C. pH is affected by CO (Nat2ral & Anthropogenic) If DIC is naturally removed from the surface ocean • C0 +2H O -2> H CO -2> H 3 HCO + 3- and added to the deep ocean (as CO ),2what is your + • C0 a2dition: most (but not all) C0 bec2mes carbonic acid which dissociates into H prediction for the pH change with depth? & HCO 3- • Higher pH at the surface, lower pH at depth + 2- - • Most (but not all) of the H combines with the C0 3 to form HC0 3 • Basic at surface, Acidic at depth • NET RESULT: Higher [C0 lower p2],and lower [C0 ] (acidific3tion) + 2- • Because most of the H gets consumed by [C0 ] we sa3 that seawater is buffered • C0 removal reverses this (raises pH and [C0 ]) 2- 2 3 D. DIC speciation varies with pH • CO ad2ition changed the pH and the DIC speciation--> high carbon is more acidic??? II. Oceanic Carbon Cycling (natural) A. DIC distribution • Low at the sea surface and high in the deep ocean • Removed by photosynthesis and added by respiration B. CaCO diss3lution and pH • Dissolves under high pressure, low temperature, low pH • Preserved in shallower regions like snow on mountains • At a given temperature and pressure, seawater is saturated with respect to CaCO 3 once [Ca ][CO ] r3aches a certain value 2- • Since the deep ocean has lower pH due to CO addit2on, it's [CO ] is l3wer and it is therefore more under-saturated A. Air-sea exchange of CO 2 Of the three forms of DIC, only CO ca2 enter the atmosphere • At equilibrium, the partitioning of CO be2ween the atmosphere and ocean is d
More Less

Related notes for GEOL 3070

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit