Ocean Water. Why is the ocean salty? What is a salt?

Ocean Water

Why is the ocean salty?Why is the ocean salty?

What is a salt?

Salts are made from Ions

Elements

Electrons (-)

Protons (+)

Elements in the periodictable have equal numbersof protons (+) and electrons (-).

They are electrically neutral

Ions

Ions are stable forms of elements that acquirean electrical charge by gaining or losing electrons

Elemental Sodium (Na) 11 protons (+), 11 electrons (-)

Sodium ion (Na+) 11 protons (+), 10 electrons (-)

By losing an electron, sodium has more protons thanelectrons and becomes positively charged.

Na - 1e- = Na+

Na11 protons

e-

e-

e-

e-

e-

e-

e- e-

e- e- e-

+

Na+

Sodium Na

2Na + 2H20 2Na+ + 2 OH- + H2

http://video.google.com/videoplay?docid=-2158222101210607510&ei=syO5SuaVBJLiqgKWif37AQ&q=sodium+explosion&hl=en#

Ions

Ions are stable forms of elements that acquirean electrical charge by gaining or losing electrons

Elemental Chlorine (Cl) 17 protons (+), 17 electrons (-)

Chloride ion (Cl-) 17 protons (+), 18 electrons (-)

By gaining an electron, chlorine has more electrons thanprotons and becomes negatively charged.

Cl + 1e- = Cl-

Cl17 protons

e-

e-

e-

e-

e-

e-

e- e-

e- e-

e-

e-

e-

e-

e- e-

e-e- _

Cl-

Chlorine

Elements that lose electrons and becomepositively charged are called cations.

Na+, K+, Ca2+, Mg2+, Cu2+, Fe3+

Elements that gain electrons and becomenegatively charged are called anions.

Cl-, Br-, F-, I-

CO32-, SO4

2-, PO4-3

oxoanions

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

Na+ + Cl- = NaCl

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

NaCl

Cl-

Na+

Na ClCl

ClCl

Dissolution

Oceans have enormous amountsof salt (ions) dissolved in the water.

Where does it come from?

10%

90% of rainfall is on the oceans

Overland Flow (Runoff)

Evaporation / Transpiration

Aquifers/ Groundwater

Infiltration to Soil/Soil flow

Fate of Precipitation to Land

Streams, Rivers, LakesStreams, Rivers, Lakes

Watershed

River basinDrainage basinCatchment

Total land area that drains surface water to a common point.

Rain that falls anywhere within a given body of water's watershed or basin will eventually drain into that body of water.

AmazonWatershed

Atlantic

saltssalts

Watersheds, Erosion and Dissolution

saltssalts

Dissolution of salts; erosion of rocks and minerals

rain rain

Dissolved in water

water

water

water

Minerals and ErosionMinerals and Erosion

KAlSi3O8

CaAl2Si2O8

NaAlSi3O8

K+, Ca2+, Na+, Si4+

Feldspars KAlSi3O8

CaAl2Si2O8

NaAlSi3O8

granite

Dissolved Salts and Minerals

KCl

NaCl

MgCl2

CaCO3

CaSO4

KCl

NaCl

MgCl2

CaCO3

CaSO4

KAlSi3O8

CaAl2Si2O8

NaAlSi3O8

KAlSi3O8

CaAl2Si2O8

NaAlSi3O8

Rivers contain small amounts of dissolved salts that are delivered to the oceans

AmazonWatershed

Atlantic

K

Na

Mg

Cl

Ca

CO3

Ca

SO4

Si

K

Na

Mg

Cl

Ca

CO3

Ca

SO4

Si

Rivers < 500 mg/L

Oceans 35,000 mg/L

If rivers have low salt contents and theyare delivering salts to the oceans, why dooceans have such high salt contents?

Total SaltsTotal Salts

Salts left behind

evaporation

The primary factor leading to ocean salinity.

Salts are delivered to the oceans in small amounts

Evaporation removes water from theoceans, but leaves the salts behind.

Rainfall on land dissolves more salts, whichare subsequently delivered to the oceans

Microcosm: The Dead Sea

34% salt content

Elevation: 1400 ft below sea level

Endorheic sea

Lowest dry elevation on earth

59 inches of Evaporation/yr

10% of naturalflow now reaches the sea.

Sea levels are dropping by 3 ft/yr

Salt Works

1973

1987

2000

The Dead Sea is Dying

Great Salt Lake

5 to 27% Salt Content5 to 27% Salt Content

Railroad causeway

Remnant of Lake Bonneville (15,000 years ago)

one inch to six feet thick

JordanWeberBear

The Aral Sea (up to 8% salinity)

Amu Darya and Syr Darya rivers

60% loss in area80% loss in volume

Oceans and Rivers

4 billion tons of dissolved salts to the ocean annually

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, Sodium, and Sulfate

2.9% Na+ and Cl-

(85% of total)

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%

Carbonate, calcium and silicate are disappearingChloride and sodium are appearing

River Water has high amounts ofCalcium, Carbonate, and Silicate

Ocean Water has high amounts ofSodium and Chloride

If ocean salts come from rivers, some processis removing calcium, carbonate, and silicates from the river water, and sodium and chlorideare being enriched in ocean waters.

• Enrich Sodium, Chloride 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 dissolution in water

Enriching Sodium and Chloride

Once these types of ions reach the oceans they stay dissolved

Calcium Carbonate Removal

Incorporate into shells of marine invertebrates

• Remove Silica, Calcium, Carbonate

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

Other Constituents in Ocean Water

The Oceans and Carbon Dioxide

Chemical interaction between the Oceans and the Atmosphere

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-

-

+

Carbon Dioxide

Middle Ages

IndustrialRevolution

ocean removed about 118 billion metric tons.

Between 1800 and 1994, the

48 percent of all fossil fuel emissions

380 ppm

Solubility = 1.69 g/L

CO2

(Oxygen Solubility: 0.043 g/L)

GasGases/Heat

Present and Future Problems

Solubility = 1.69 g/LOxygen Solubility: 0.043 g/L

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

Copper and Silver Cleaning:

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

http://www.npr.org/templates/story/story.php?storyId=17243164

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

Corals live in very nutrient poor waters and have certain zones of tolerance to water temperature, salinity, UV radiation, opacity, and nutrient quantities. 

Anthropogenic Inputs

Homework II Oceanic Dead ZonesThis is an excerpt from a news story from June 21 by the AP concerning recent

Mid-west flooding and its potential impact on the dead zone in the Gulf of Mexico.

Flood, size of gulf dead zone linkedExtra farm runoff in the Mississippi to increase area with no oxygen

Associated Press June 21, 2008

WASHINGTON - Floodwaters loaded with farm runoff are heading down theMississippi River, and scientists fear that the deluge will sharply increase the expected

dead zone this summer in the Gulf of Mexico, covering an area the size of Maryland.

The dead zone is a region of the gulf that becomes starved for oxygen during much of the summer and cannot support fish or other sea life.

There are hundreds of dead zones around the world that wreak havoc on marine ecology and cut off vast areas for commercial fishing. The zone in the gulf

is the largest in the Western Hemisphere.