Oceanography: Salts & Gases
What are the major gases in seawater?
N2, O2 and CO2
What are the major nutrients found in ocean water?
Nitrogen, Phosphorous and Silicon
Is the ocean getting saltier? Why or why not?
No; salts going in = salts going out
Describe the gas cycle.
O2: Photosynthesis produces O2 (plants) Respiration & Organic matter decay uses up O2 CO2 Respiration and organic matter decay produce CO2 (animals) Photosynthesis uses up CO2
Why is oxygen (O2) abundant along the surface of our oceans?
Plants need sunlight; therefore live near the surface. Plants undergo photosynthesis: CO2 + H2O + light --> O2 + sugar
Between 200 m - 1000 m depth, O2 is decreasing and CO2 is increases slightly. Why?
Respiration is dominant: O2 + energy --> CO2
Be able to calculate salinity and chlorinity using the formula given
Salinity = 1.8065 x chlorinity i.e. If chlorinity is 18.5‰, what is the salinity?
List the major constuents of seawater.
Sulfate (SO4)2- magnesium (Mg)2+ calcium (Ca)2+ potassium (K)+ and bicarbonate (HCO3)-
Why are calcium (Ca) and silica (Si) less abundant in ocean water than river water?
because organisms (calcareous and siliceous oozes) use them for shell formation
What does the Principle of Constant Proportions mean? How does this help us determine the amount of salt present?
Although the amount of salt varies depending on location, the relative proportions are constant. Because of constant proportions, you only need to measure 1 ion to determine the amount of total dissolved salts present
How does CO2 control acidity?
CO2 (carbon dioxide) + H2O (water) --> H2CO3 (carbonic acid) The more CO2, the more acidic (lower pH)
Explain how CO2 acts as a carbonate buffering system.
CO2 + H2O --> H2CO3 (carbonic acid) H2CO3 --> [HCO3]- + [H]+ [HCO3]- --> attaches to acids [H]+ --> attaches to bases Prevents large shifts in pH
At depths greater than 1000 m O2 increases slightly. Explain how this happens.
Cold, salty, oxygenated polar waters sink and trasnsport O2 to depth
Why are chlorine and sodium the most abundant elements in the ocean?
They have the longest residence times (time a substance stays in solution)
What are 2 ways of determining salinity?
calculations salinometers (electrical conductivity)
What are the 2 most abundant elements found in the ocean?
chloride & sodium
What contributes to the increase of CO2 with depth?
dissolved CO2 from atmosphere respiration organic matter decay cold water holds more CO2
List 3 ways to get fresh H2O from salt H2O. Be able to explain each.
distillation electrodialysis reverse osmosis
What are some of the effects of salinity?
freezing point depression; boiling point elevation changes density changes vapor pressure (↑ ‰, ↑ P)
What factors affect salinity?
precipitation evaporation river runoff freezing
With regards to chemical constituents, what are the differences between river water and seawater?
rivers are abundant in bicarbonate (HCO3), calcium (Ca), and silica (Si) Seawater is abundant in sodium (Na) and chloride (Cl)
What are 2 sources of salts?
rocks & gases from mantle
Why is the ocean salty?
salts come from (1) rivers that dissolve salts from land, and (2) gases from volcanic eruptions along mid-ocean ridges
In what ways does salt leave the ocean?
sea spray evaporates biological processes (fecal pellets, shell formation) adsorption (clays) re-uptake at mid-ocean ridges
What is salinity? What is the average salinity in our oceans?
total amount of dissolved solids expressed in grams per kilogram of water 35‰, 35 ppt, or 35 g/kg
