Presentacin de PowerPoint

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INSTITUTO DE INVESTIGACIONS MARIÑAS (CSIC)
The Carbonate System on Seawater
Fiz Fernández Pérez
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Atmosphere
borate
SO4
F-
Cl-
OH-
280 ppm ? 380 ppm (36)
Thermodynamic ? Operational?
pCO2
fugacity
Scales
Revelle
Br-
SO4H-
1.6 ppm.y-1 ? (0.4)
temperature
salinity
pressure
Alkalinity
carbonate alkalinity
TITRATION
wind
CO2(g)
transfer velocity
pH
IONIC STRENGH
SOLUBILITY
Org Mat?
K1
K2
CO22 H2O ? H3OHCO3- ? H3OCO32-
Na
Ocean
K
Mg
Ca
2000 µmol.ksw-1? 2072 µmol.ksw-1 (3.6)
0.9 µmol.ksw-1.y-1 ? (0.04)
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Lets be pragmatic
Which are the measurable carbonate
variables?What is their variability?How
accurate are the measurements?
Lamb et al. 2002 Consistency and synthesis of
Pac.Ocea CO2 DSR II 49 21-58.
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S/N(2415-2280)/2 68
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S/N(2260-2060)/2 100
Annual increase/N0.9/2 0.45
Annual increase0.9/(2000) 0.04
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pHT25
S/N(8.05-7.50)/0.002 275
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Processes affecting carbonate system
CT/AT? CO225ºC CT/AT? pH25ºC
AT/NO3? -1 CT/NO3? 6.6
PA ATNO3PO4H2
AT/CaCO3? -2 CT/CaCO3? -1
Fraga et Alvarez-Salgado
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Variability of fCO2
fCO2 factor(T,p)pCO2fCO2 (0.99560.0001t)p
CO2pCO2 (patm-pwatersat)xdryCO2Pag61-66
(105-(-135)/370 65
S/N(105-(-135))/1 240
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KHltlt1 CO2(aq) H2O ? H2CO3
fCO2 x(CO2)? patm CO2/?0(S,T) pH -log
H3O
7 unknows 5 equations 2 variables to be
measured
CT AT pH fCO2
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Effect of temperature, salinity and pressure
Ks increase with temperature, pressureand
salinity
The salt effect -ionic strength -ion pairs
pag 13-14
I 0.5CiZi2 19.924S/(1000-1.005S) 0.7
molkg-1
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Effect of pH in CaCO3
0.3 decrease of pH produce a increase of 1.8 on
solubility of CaCO3
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Effect of pressure on CaCO3 solubility
KCAL, KARG CaCO3(s) ? CO32- Ca2
By 2100
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Saturation Profiles
However, a recent review of the global carbonate
budget performed by Milliman et al. (1999) showed
evidence that a considerable portion of
surface-produced calcite, as much as 60-80,
dissolves in the upper 1000 m, above the
lysocline, as a result of biological mediation
stimulated in micro-environments such as marine
snow, zooplankton guts, etc.
20-200m
sediment
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Total Alkalinity (AT) or Titration Alkalinity
AT Na 2Mg2 2Ca2 K 2Sr2
- Cl- - 2SO42- - Br- - F-
ATHCO3-2CO32-B(OH)4-OH--H3O
ACHCO3-2CO32- 96 of AT
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Total Alkalinity (AT) or Titration Alkalinity
10-pHSWS
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Total Alkalinity (AT) or Titration Alkalinity
The total alkalinity of natural waters is thus
defined as the number of hydrogen ions equivalent
to the excess of proton acceptors (bases formed
from weak acids with a dissociation constant
Kgt10-4.5, at 25ºC and zero ionic strength) over
proton donors (acids with Kgt10-4.5) in one
kilogram of sample Dickson, 1994
This modern definition of AT is (only)
conceptually different from the operational
definition presented above
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Contribution of the phosphoric system to AT
APO4 (3PO43- 2HPO42- H2PO4-)pH 8.2
- - (3PO43- 2HPO42-
H2PO4-)pH 4.4 ((310.8288.410.8) -
(22.297.7))PO4T/100 1.08PO4T
ASi Si(OH)3O- 4.210-2SiT
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pH scales and the dissociation constants
The field of pH scales in sea water is one of
the more confused areas of marine chemistry
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pH measurements
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What are the best pairs to measure?
Table 3 Millero et al. (1993) with the estimates
errors in the calculated parameters of the CO2
system using various input measurements
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The CRM is a good operational solution
Give it a shot of preventive medicine Have one
or two takes of CRM bottles every station and
your data will remarkably recover its tone,
significance and strength and remember A good
set of CRM comparisons also gives you that little
extra confidence youve been looking for in your
data. Take your chance!!!!!!
THE CRM