Post on 15-Jan-2016
Chemistry and Biogeochemical Cycling:Chemicals dissolved in water
2 2 2 3 3 3CO H O H CO H HCO H CO 2 2 2 3 3 3CO H O H CO H HCO H CO 2 2 2 3 3 3CO H O H CO H HCO H CO
2 2
23
,
,
Ca Mg
CO
Na
2 2
23
,Ca Mg
CO
2 3 24 3 4 4
,
, , , ,
Na K
SO Cl NO PO SiO
Abundant Less Abundant (not trace)
Chemistry and Biogeochemical Cycling:Solubility of Gases
Chemistry and Biogeochemical Cycling:Oxygen Solubility and temperature
Chemistry and Biogeochemical Cycling:Pressure and Solubility
Chemistry and Biogeochemical Cycling:supersaturation
http://weberian.handrewlynch.net/
Solubility of oxygen:Differences in fresh and salt water
Thank you to Tianlu Shen for this question!
Snoeyink, V.L. and D. Jenkins. 1980. Water Chemistry. John Wiley & Sons, New York, New York, 463 pp. [text]
http://www.ionizers.org/water.html [images]
Due to the polar nature of the water molecule, it associates with ions or other molecules (including other water molecules) possessing a positive or negative charge.
Solubility of oxygen:The salting out effect When dissolved in water,
NsCl dissociates into a positively charged sodium ion and a negatively charged chloride ion. Water molecules are attracted to these ions and orient around them as waters of hydration.
Thus, less oxygen will dissolve in water with a high salt content than in ‘fresh’ water.
Gases such as oxygen dissolve less readily in water that is bonded in this manner. We might say that the salt ‘competes’ with the gases for the water molecules. Where there is a great deal of salt present, as in marine waters, a significant number of water molecules are present as waters of hydration.
Chemistry and Biogeochemical Cycling:Ph
2 2 2 3 3 3CO H O H CO H HCO H CO 2 2 2 3 3 3CO H O H CO H HCO H CO 2 2 2 3 3 3CO H O H CO H HCO H CO
2 [ ] [ ]H O H OH
141 10 @ 25wK H OH x C 141 10 @ 25wK H OH x C 141 10 @ 25wK H OH x C
14[ ][ ] 1 10wK H OH x In pure water …
and since pH is defined as…
[ ] [ ]H OH and thus …7 1[ ] 10H moles L
log[ ]pH H , 7pH for pure water
[Note that a little H+ goes a long way in terms of effect!]
2 2 2 3 3 3CO H O H CO H HCO H CO 2 2 2 3 3 3CO H O H CO H HCO H CO 2 2 2 3 3 3CO H O H CO H HCO H CO
1 2
2 2 2 3 3 3
K K
CO H O H CO H HCO H CO
141 10 @ 25wK H OH x C 141 10 @ 25wK H OH x C 141 10 @ 25wK H OH x C
731 1
2 3
[ ][ ]5 10 ; 6.3
H HCOK x pK
H CO
2113
2 23
[ ][ ]5 10 ; 10.3
H COK x pK
HCO
Chemistry and Biogeochemical Cycling:the carbonate system
2 2 2 3 3 3CO H O H CO H HCO H CO 2 2 2 3 3 3CO H O H CO H HCO H CO 2 2 2 3 3 3CO H O H CO H HCO H CO
1 2
2 2 2 3 3 3
K K
CO H O H CO H HCO H CO
taking the negative log of both sides …
31 2 3 3
2 3
[ ]log ; [ ] [ ]
[ ]
HCOpK pH H CO HCO
H CO
and when
pH = pK1
223
2 3 33
[ ]log ; [ ] [ ]
[ ]
COpK pH HCO CO
HCO
and whenpH = pK2
Chemistry and Biogeochemical Cycling:The carbonate system
2 2 2 3 3 3CO H O H CO H HCO H CO 2 2 2 3 3 3CO H O H CO H HCO H CO 2 2 2 3 3 3CO H O H CO H HCO H CO
0.0
0.2
0.4
0.6
0.8
1.0
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0
f (T
-DIC
)
pH
2 3H CO 23CO
3HCO
1pH pK 2pH pK
• at pH<pK1, carbonic acid dominates• at pH between pK1 and pK2, bicarbonate dominates; and• at pH>pK2, carbonate dominates
Chemistry and Biogeochemical Cycling:The carbonate system
2 2 2 3 3 3CO H O H CO H HCO H CO 2 2 2 3 3 3CO H O H CO H HCO H CO 2 2 2 3 3 3CO H O H CO H HCO H CO
The fraction of DIC present in each form can be calculated as f (pH)(Chapra, 1997, p. 685
2
2 3 21 1 2
13 2
1 1 2
2 1 23 2
1 1 2
[ ]( )
[ ] [ ]
[ ]( )
[ ] [ ]
( )[ ] [ ]
Hf H CO
H K H K K
K Hf HCO
H K H K K
K Kf CO
H K H K K
Chemistry and Biogeochemical Cycling:The carbonate system
Chemistry and Biogeochemical Cycling:The carbonate system
2 2 2 3 3 3CO H O H CO H HCO H CO 2 2 2 3 3 3CO H O H CO H HCO H CO 2 2 2 3 3 3CO H O H CO H HCO H CO
and the concentration of each component is given by …
2 3 2 3 ,
3 3 ,
2 23 3 ,
[ ] ( )
[ ] ( )
[ ] ( )
T DIC
T DIC
T DIC
H CO f H CO C
HCO f HCO C
CO f CO C
Chemistry and Biogeochemical Cycling:The carbonate system
2 2 2 3 3 3CO H O H CO H HCO H CO 2 2 2 3 3 3CO H O H CO H HCO H CO 2 2 2 3 3 3CO H O H CO H HCO H CO
photosynthetic withdrawal of carbon dioxide …
1 2
2 2 2 3 3 3
K K
CO H O H CO H HCO H CO
According to LeChatlier’s Principle, the equilibrium would move to the left, consuming H+ and raising the pH.
While, at first glance, this looks to reduce the concentration of carbonate, the increase in pH re-distributes the DIC species, leading to an increase in the carbonate concentration.
2 2 2 3 3 3CO H O H CO H HCO H CO 2 2 2 3 3 3CO H O H CO H HCO H CO 2 2 2 3 3 3CO H O H CO H HCO H CO
0.0
0.2
0.4
0.6
0.8
1.0
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0
f (T
-DIC
)
pH
2 3H CO 23CO
3HCO
1pH pK 2pH pK
Chemistry and Biogeochemical Cycling:The carbonate system
ss demo
Chemistry and Biogeochemical Cycling:Whiting event in lake michigan
2 2 2 3 3 3CO H O H CO H HCO H CO 2 2 2 3 3 3CO H O H CO H HCO H CO 2 2 2 3 3 3CO H O H CO H HCO H CO
earthobservatory.nasa.gov
3
2 2, 3[ ][ ]sp CaCOk Ca CO
Chemistry and Biogeochemical Cycling:alkalinity
2 2 2 3 3 3CO H O H CO H HCO H CO 2 2 2 3 3 3CO H O H CO H HCO H CO 2 2 2 3 3 3CO H O H CO H HCO H CO
3 32Alk HCO CO OH H
141 10 @ 25wK H OH x C 141 10 @ 25wK H OH x C 141 10 @ 25wK H OH x C
Chemistry and Biogeochemical Cycling:Organic carbon - sources
allochthonous: carbon fixed within the watershed
Chemistry and Biogeochemical Cycling:Organic carbon - sources
autochthonous: carbon fixed within the lake
Chemistry and Biogeochemical Cycling:Organic carbon - sources
“don’t it make your brown eyes blue”
Chemistry and Biogeochemical Cycling:Organic carbon – Redox reactions
2 2( )C H O EA CO RS
2 2 2 2( )C H O O CO H O
2 2( )
(0) (4 )
C H O CO
C C
In each redox reaction, an electron donor contributes electrons and is oxidized (i.e. becomes more positive) and electron acceptor receives electrons and is reduced (i.e. becomes more negative).
For oxidation of organic carbon by oxygen,
the half-reactions are,
2 2
2 2(0) (4 )
O CO
O O
Chemistry and Biogeochemical Cycling:Organic carbon – Ecological Redox series
2 22 2C CO H O + O + H O
3 222 2 4H 5CO5CH O 7H O2N 4NO
+22
2+2 2 4H CO2MnO 2C 3H OH Mn O
+22
2+2 8H CO4Fe 7H O4OOHCH FeO
4 2 22 22 2H 2CO 2H2CH O O OS H S
2 24 CH2CH O + CO
Oxygen Reduction (aerobic respiration)
Nitrate reduction (denitrification)
Manganese Oxide Reduction
Iron Oxy-Hydroxide Reduction
Sulfate Reduction
Methanogenesis
Stoichiometry after Berg et al. 2003 and Boudreau 1996).
Chemistry and Biogeochemical Cycling:Organic carbon – Redox in sediments
Depletion ofDepletion of
Oxygen Nitrate
swi swi swi
methanogenesis methanogenesis methanogenesis
sulfate reduction
sulfate reduction
sulfate reduction
denitrification
denitrificationoxygen reduction
Chemistry and Biogeochemical Cycling:Organic carbon – carbon cycle
Chemistry and Biogeochemical Cycling:oxygen
22, 2,( )a sat measured
dOk O O
dt
la
Kk
H
0.864l wK U
( 20), ,20
Ta T ak k
Chemistry and Biogeochemical Cycling:Oxygen – photosynthesis and respiration
2 2 2 2( )CO H O C H O O
2 2 2 2( )C H O O CO H O
Chemistry and Biogeochemical Cycling:Nitrogen - species
Component Formula Significance
Nitrogen gas sources: atmosphere and denitrificationactivity: nitrogen fixationimpact: none
Ammonia sources: loads, direct excretion and DON diagenesisactivity: nitrification impact: plant nutrient (marine), toxic; oxygen demand
Nitrite sources: nitrification intermediate; transientactivity: nitrificationimpact: toxic; oxygen demand
Nitrate sources: loads, precipitation, nitrificationactivity: nitrification, denitrificationimpact: plant nutrient (marine)
DON/PON sources: loads, biosynthesis/decomposition of organic matter activity: ammonificationimpact: none
2N
3NH
3NO
3NO
AA
Chemistry and Biogeochemical Cycling:Nitrogen – amino acids
Chemistry and Biogeochemical Cycling:Nitrogen cycle
Chemistry and Biogeochemical Cycling:Phosphorus – nutrient limitation
The Supplies
The Product
Chemistry and Biogeochemical Cycling:Phosphorus – the divided lake
Chemistry and Biogeochemical Cycling:Phosphorus – forms of p in lakes
particulate
soluble
inorganic organic
PIP POP
SRP DOP
PP
TDP
TP
34PO 3
4R PO
Chemistry and Biogeochemical Cycling:Phosphorus cycle
Chemistry and Biogeochemical Cycling:iron
http://www.flickr.com/photos/inoneear/3498341514/
2
8
1
33
4
( ) 1
( ) 10
0
sp
spFe OH K
Fe OH K
Chemistry and Biogeochemical Cycling:sulfate
2 24SO S
Chemistry and Biogeochemical Cycling:silicon