11 Flashcards
how does the inorganic carbon, calcium, and carbonate dissolution affect us
buffering changes in ocean acidity
climate (ocean as a sink or source for CO2)
solubility of CaCO3 (geology, sediments, biology, calcareous organisms)
is affected by human CO2 emissions (ocean acidification)
what are the species of inorganic carbon found dissolved in the ocean
CO2
H2CO3
HCO3-
CO32-
when CO2 dissolves
it reacts with water to form carbonicacid H2CO3
what changes pk1 and pk2 for formation of CO32-
decrease with T and weaker with S
what is the use of bicarbonate HCO3-
acts as a buffer in the ocean
weak acid and base as it is part of two reactions
micture of acid HCO3- and its congugate base CO32- that resist change in pH when acid or base is added
what is the pH of the ocean
7.4- 8.2
distribution of carbonic acid forms
bc it is a weka acid, its distribution depends on pH and we can use this pH and the two Kas to estimate the distribution at diff pH values
what is the distribution of the bicarbonate forms in the ocean pH
dominated by bicarbonate HCO3- (87%) and
second is carbonate CO32- 10%
what species control air sea fluxes
CO2 at less than 0.5%
inventory of DOC and POC
2%
PIC invintory
0.01%
how can we describe the carbon system
for a given T,S, P, we can describe it using any of the two systems
DIC
TA
pH
pCO2
we typically measure the first two to get the other two
DIC=
[CO2]+[H2CO3]+[HCO3-]+[CO32-]
the first two terms typically equal less than 1%
how is DIC measured
acidifying seawater to convert all carbonate and bicarbonate to cO2
bubbling inert gas through solution
measuring gas phase CO2
what is TA
total alkalinity
total amount of charges available to buffer strong acids
units- eq/kg
stads for equivalent of a mole of charges
what is TA=
[HCO3-]+2[CO32-] account for most of the cabonate alkalinity
+ means species that could remove H+
- are species that could add H+
would a change in pressure or temp change DIC or TA
no bc we dont add or remove C or charges
would uptake of 100umol/kg of 100 umol/ kg of CO2 from the atmosphere affect DIC or TA
dic would inc by 100 and TA wouldnt change
we added C but no charge
what effect would formation of 25 umol/kg of CaCO3 have on DIC and TA
DIC decreases by 25 and TA decreases by 50 becasue removed CO32- but 2 charges
dissolution of CaCO3 would have the opposite effect
what effect would formation of POC have on DIC and TA
both change exactly the same depneding on the POM ration if we assume the classic redfield ratio of C:N:P
if one species C then -106 = DIC bc youre forming
TA = 16+1= 17
what effect would aerobic respiration/ decomposition of POM have on DIC and TA
the opposite effect of formation of POC
DIC would increase and TA would decrease
what is the purpose of parallel lines on the DIC/TA graph
allows us to find the past CO2 and pH
what happens graphically when you form Corg in the DIC/TA graph
decrease DIC and slightly increase alkalinity
what happens graphically when you have CaCO3 dissolution or formation in the DIC/TA graph
dissolution- increases DIC and TA
formation- decrease DIC and TA
why is the formation and burial of CaCO3 not a net sink for atm CO2
formation of CaCO3 reduces alkalinity more than DIC-
leads to lower pH
shifts larger portion of DIC in surrounding water to CO2
leads to higher pCO2 in water
less room in water for CO2 from air
what are the polymorphs of calcium carbonate
aragonite
calcite
same chemical composition but diff crystal structures
aragonite is stronger physicially but more chemically vulnerable
what causes the formation of one form over the other of the different polymorphs of calcium carbonate
depends on the Mg levels in the ocean
high Mg- aragonite seas
what happens when Mg subs for Ca
high Mg calcite which is less stable and very soluble
what kind of reaction is the incorporation of Mg as an impurity in calcite
endothermic process
more likely in warmer waters
what is the use of formatino of Mg calcite being endothermic
using the Mg/Ca ratio in shells of microfossils as a paleothermometer
how does CaCO3 enter the oceans
through riverine inputs
or
percipitated biogenically - 4x larger
most CaCO3 dissolves following organism death while 25% sinks to sea floor and is buried escaping dissolution
abiotic percipitation of CaCO3
not a srouce
kinetically unfacourable even in oversaturated solutions
where is CaCO3 in the ocean floor found
equally distributed in coastal and open ocean regions
what is the inorganic carbon pump/ carbonate pump
sinking of calcareous hard parts to the deep sea and sediments
sinking of CaCO3 versus riverine
the sinking by sediment burial is almost equal to the riverine source
leaving the ocean in a steady state with respect to CaCO3
what are the most important planktonic calcifers
foraminifera
1/2 of PIC exported to sediments from them- they are protozoa
layout of foraminifera
some benthic- deep ocean, others pelagic
contain skeleton made from calcite
large variation in size, shape, and density
what is the second most important organisms for sedimentary PIC
coccolithophora- calcite nanofossils
coccolithophora as a source of CaCO3
deposit CaCO3/ calcite in overlapping plates caleld coccoliths that form their external shell
create and shed the plates continually every hour
where are coccolithophora found
geographically widespread and form blooms
can be detected by satelite
what is another important calicifer
pteropods
contain pen shaped internal structure amde of aragonite
