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Composition of Ocean Waters
Salts and Salinity
Ions
Ions are stable forms of elements that acquirean electrical charge by gaining or losing electrons
Elements that lose electrons and becomepositively charged are called cations.
Elements that gain electrons and becomenegatively charged are called anions.
Cations: K+, Na+, Mg2+, Ca2+
Anions: Cl-, CO3-2, SO4
-2
Salts
KCl, NaCl, MgCl2, CaCO3, CaSO4
Cations: K+, Na+, Mg2+, Ca2+
Anions: Cl-, CO3-2, SO4
-2
Salts are formed by combining cations andanions to form solids that have no charge.
K+ + Cl- = KCl
Ca+2 + 2Cl- = CaCl2
Conversely, if solid salts are mixed with water they dissolve and the ions go into solution
KCl K+ + Cl-
NaCl Na+ + Cl-Water
Water
solid solution
CaCO3
CaSO4
Ca+2 and CO3-2
Ca+2 and SO4-2
Ocean Salinity originates from dissolutionof salts and erosion of rocks and minerals
as water moves at or below the earth surface
River water contains dilute amounts of dissolved salts that are ultimately delivered to the oceans
As water evaporates, the oceans concentrate the salts to levels farexceeding those found in rivers.
Average Ocean Salinity = 3.5%
What kind of Salts?
KCl
NaCl
MgCl2
CaCO3
CaSO4
KCl
NaCl
MgCl2
CaCO3
CaSO4
River Water35.1520.3912.14 11.675.685.793.412.12
IonCarbonateCalciumSulfate SilicateChlorideSodium
MagnesiumPotassium
River Salt Composition
Dominated by Carbonate, Calcium, Sulfate, and Silicate
KAlSi3O8
CaAl2Si2O8
NaAlSi3O8
KAlSi3O8
CaAl2Si2O8
NaAlSi3O8
Ocean Salt Composition
IonChlorideSodiumSulfate
Magnesium Calcium
Potassium Carbonate
Silicate
Sea Water (%)55.0430.627.683.69 1.151.100.40
.0004
Dominated by Chloride and Sodium
Na+ and Cl-(85% of total)
Cl- Na+
River Water35.1520.3911.6712.14 5.685.793.412.12
Sea Water.40
1.15.00047.68
55.0430.623.691.10
IonCarbonateCalciumSilicateSulfate ChlorideSodium
MagnesiumPotassium
Percentage of Total Dissolved Minerals
} 79%
} 85%
• Enrich Chloride and Sodium in ocean water
Remove Silica, Calcium, Carbonate from river water
Alterations
sodium, potassium, and ammonium salts are soluble
chloride, bromide and iodide salts are soluble.
NaCl Solubility 350 g/L
Solubility: ease of salt dissolution in water
Enriching Sodium and Chloride
Once these types of ions reach the oceans they stay dissolved
IonChlorideSodiumSulfate
Magnesium Calcium
Potassium Carbonate
Silicate
Sea Water (%)55.0430.627.683.69 1.151.100.40
.0004
Both chloride salts and sodium salts areextremely soluble in water and do not
combine with other elements to form solids
• Enrich Chloride and Sodium in ocean water
Remove Silica, Calcium, Carbonate from river water
Alterations
Calcium and Carbonate Removal
Incorporation into shells of marine invertebrates
Ca2+ + CO32- = CaCO3
Diatoms
Life and Silica
• Remove Silica, Calcium, Carbonate
Use silica as structural material
River Water35.1520.3911.675.685.793.412.12
12.14
Sea Water.40
1.15.000455.0430.623.691.107.68
IonCarbonateCalciumSilicateChlorideSodium
MagnesiumPotassium
Sulfate
Percentage of Total Dissolved Minerals
Extra Credit Questions
1. Cations become positively/negatively charged by gaining/losing electrons.
2. The dominant ion in river water is ___
3. The dominant ion in sea water is ___
4. Marine invertebrate shells are made from ____
Other Constituents in Ocean Water
The Oceans, Heat, and Carbon Dioxide
Middle Ages
IndustrialRevolution
380 ppm
CO2
Global Temperature
Ocean Temperature
Oceans can buffer changesin atmospheric temperature
GasGases/Heat
Present and Future Problems
Warmer oceans ?
October, 2005
Rising CO2 and Ocean Chemistry
Gases Dissolve in Water
GasGases
dissolution
Composition of the Atmosphere
Gases
Nitrogen 78.1%Oxygen 20.9%Argon 0.93%CO2 0.038%
Oxygen
Solubility: 0.043 g/L(20oC)
Carbon Dioxide
C
O
O-
-
+
Solubility = 1.69 g/L
Middle Ages
IndustrialRevolution
removed about 118 billion metric tons of CO2.
Between 1800 and 1994, the oceans have
Equivalent to 48 percent of all fossil fuel emissions
380 ppm
Solubility = 1.69 g/L
CO2
Buffering
Carbon Dioxide also is an Acid
CO2
WaterAcid
CO2 + H2O H2CO3
H2CO3 H+ + HCO3-
H+ is acid
Acids (H+) are reactive and dissolve a number of substances
Dissolution of Carbon Dioxide
Common Acid Dissolution
CuO + 2HCl → CuCl2 + H2O
Ag2O + 2 HCl → 2 AgCl + H2O
CaCO3 + H+ Ca2+ + HCO3-
Fe2O3 + 6H+ 2Fe3+ + 3H2OFe2O3
CaCO3
Invertebrate shells and skeletons largely CaCO3
Corals, “lithic” plankton, clams, oysters
CaCO3 + H+ Ca2+ + HCO3-
CO2
WaterH+
Acidification of the oceans Inhibits the calcification and
growth of invertebrates
Analysis of coral cores shows a steady drop in calcification over the last 20 years
pH change: 8.179 to 8.104
Coral Reef Bleaching
http://www.npr.org/templates/story/story.php?storyId=17243164
Temperature and Acidity
Anthropogenic Inputs of Solutes to the Oceans
Homework II Oceanic Dead Zones
Due Friday, October 2nd in class
Assignment is posted on the website
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