7_Ocean Water Chemistry

7/31/2019 7_Ocean Water Chemistry

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Ocean Water Chemistry


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http://www.nhptv.org/


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Distribution of Earths Water

Oceans 97.2 %

Ice Caps and Glaciers 2.15 %

Atmosphere 0.001 % Rivers and Lakes 0.009 %

Inland Seas 0.008 %

Groundwater 0.625 %


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Ocean Water is SALTY

Salinity: Total amount of dissolved solids Units: o/oo = 1/1000

Range: 33 37 o/oo

Increase in salinity: Increase in Density Decrease in Freezing Point Decrease in Vapor Pressure Increase in Osmotic Pressure


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Origin of Salts in Oceans

Rivers(largest transport of chemicals to ocean)

Rain + CO2 H2CO3 Si, Al, Na, K, Mg

Volcanoes Cl, S, CO2

Dust / Rain Fe, Si

Anthropogenic CO2, P


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Example Geochemical Cycle

Concept of Steady State


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Example 2 Geochemical Cycle


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Residence Time(T = Ocean amount/Output rate)

Concentration of elements in seawater isdetermined by their removal rate

Conservative elements:

Major Elements: Cl, Na, SO4, Mg, Ca, K- Minor Elements: Br, Sr, B, C, F

Non Conservative Elements

Nutrients: N, P, Si Dissolved gases: O2, CO2, N2 Trace Elements: Fe, Al, Mn Organic Compounds


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Residence Time - Concentration

Element Res. Time (yrs)

Na 60 000 000

Cl 80 000 000Mg 10 000 000

K 6 000 000

SO4 9 000 000Ca 1 000 000

Mn 7 000

Fe 100

ConcentrationCrust (%) Ocean (mg/l)

2.4 10 770

0.013 19 5002.3 1 290

2.1 380

0.026 9054.1 412

0.5 0.0002

2.4 0.002


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Dissolved Gases

Gas Solubility:Decreases with Temp. and Salinity

Increases with Pressure


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Gases in Atmosphere & Oceans

Percent Gas Phase by Volume

Gas Atmosphere Surface Ocean Total Ocean

N2 79% 48% 11%

O2 21% 36% 6%

CO2 0.04% 15% 83%


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Seawater pH

Pure water pH = 7

Seawater pH = 7.5 8.1

Seawater is very well buffered!

CO2(gas)+H2OH2CO3H++HCO32H

++CO32


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H2O: Universal Polar Solvent


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H20: Temperature and Density


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H2O: Frozen & Liquid density


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H2O: Heat Capacity

Heat Capacity: heat needed to changethe temperature of a substance

Water has higher heat capacity than:

All solids All liquids, except liquid ammonia

Latent heat of Vaporization: heatneeded to evaporate a liquid Water has the highest of all substances


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Seawater: Temperature and Density


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Seawater: Temperature and salinity


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Seawater: Ice Formation


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Electromagnetic wave penetration


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Open water(low productivity)

Coastal and Estuarine waters


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Coastal and Estuarine waters(high productivity)


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Nuclear Missile Submarine


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http://www.nhptv.org/

H d m s li ht p n t ti n?


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How do we measure light penetration?

Secchi Disc


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Water Refraction

Eschrichtius robustus


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Sound Velocity

Influenced by Salinity, Temperatureand Pressure Increases with Salinity

Increases with Temperature Increases with Pressure

Concept of Midwater Sound Channel

Study in Detail Fig 5-19!


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Sound Channel


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H b k Wh l


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Humpback WhalesMegaptera novaeangliae

G Wh l & S P s l


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Gray Whale & Sonar Proposal

Eschrichtius robustus

G Wh l Mi i


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Gray Whale Migration

A i P ll i


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Acoustic Pollution


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7_Ocean Water Chemistry