marine chemistry

Question 1

what are the other major constituents in sea water other than water and major salts

Answer 1

chloride, sodium, sulfate, magnesium, bicarbonate, calcium, potassium – these salts are >99% of the total chemicals in seawater
- these are shown to have the largest residence time

Question 2

what are salts dissolved in seawater preset as

Answer 2

ions

Question 3

what is the major cation and anion in sea water

Answer 3

Na+ = cation
Cl- = anion

Question 4

what are the minor constituents in seawater

Answer 4

particulate matter - things that don’t pass through a particle filter pore size

Question 5

main sources of particulate matter

Answer 5

Aeolian (things in atmosphere e.g. dust, smoke)
Rivers
Biological production

Question 6

what are Conservative constituents

Answer 6

Their concentrations are only altered by PHYSICAL processes such as addition and removal of water - therefore their concentrations remain CONSTANT in seawater
Examples: the major ion (Na+)

Question 7

what are non-conservative constituents

Answer 7

Their concentrations are altered by chemical + biological processes - therefore their concentrations can VARY dramatically in time and space
Examples: nutrients, gases, trace meta

Question 8

what is Residence time

Answer 8

average time that a substance remains in the ocean

Question 9

what are Major constituents in seawater controlled by

Answer 9

hydrological + geological processes

Question 10

what are the 2 main sources of the chemicals LEAVING the ocean

Answer 10

• Chemicals being absorbed onto the surfaces and precipitating out of the water collumn
• Organisms take up the chemicals + intergrate them into their bodies which sink to the bottom of the ocean and go into the sea bed

Question 11

what are the two equations that can represent Residence time

Answer 11

rate of introduction of element by river OR
rate of removal as sediment

Question 12

what chemicals are shown to have the largest residence time

Answer 12

The 6 major constituents

Question 13

what is mixing time

Answer 13

average time to “mix” the entire ocean (ca. 1000 year)

Question 14

what is the Principle of constant proportions

Answer 14

regardless of variations in salinity, the ratios between the major constituents remain the same

Question 15

how can the total salinity of seawater vary

Answer 15

by adding water (precipitation) or removing water (evaporation)
Although the relative proportions of the major ions in seawater are constant

Question 16

why does evaporation dip near the equator

Answer 16

warmer - means more more evaporation but more clouds which reduces the rate of evaporation as there is less sunlight coming in

Question 17

why does precipitation increase near equator

Answer 17

more evaporation = more rainfall

Question 18

why does precipitation increase near poles

Answer 18

Cool air from the poles = more rainfall

Question 19

why is the water saltier near the equator

Answer 19

more evaporation

Question 20

why is the water less salty near the poles

Answer 20

Effected by the amount of land - amount of salinity follows the water movement

Question 21

what are the 6 Major constituents of air

Answer 21

nitrogen, oxygen, carbon dioxide, argon, helium, neon

Question 22

what does dissolved CO2 into water make

Answer 22

carbonic acid (H2CO3)

Question 23

physical factors that affect gas concentrations (amount of gas that can dissolve in water)

Answer 23

• Wave and turbulence
• Temperature ↑… Gas dissolution ↓
• Salinity ↑… Gas dissolution ↓- less room for gas molecules
• Water pressure ↑… Gas dissolution ↑(think fizzy drinks!)

Question 24

Biological processes that affect gas concentrations

Answer 24

• Photosynthesis: removes CO2 and adds O2
• Respiration: adds CO2 and removes O2
• Decomposition: think of it as microbial respiration; adds CO2 and removes O2

Question 25

what is hypoxia

Answer 25

a condition when oxygen concentrations fall below the level necessary to sustain most animal life (ca. 2 mg O2 l-1)

Question 26

what is anoxia

Answer 26

total absence of O2

Question 27

explain ocean acidification

Answer 27

Atmospheric CO2 ↑… pH in ocean ↓(more acidic) - Even a small change in pH matters
- Sea water pH = 8.1-8.2 - stays constant due to buffering effect of carbonate chemistry

Question 28

what is acidity based on

Answer 28

concentration of hydrogen ions (protons)

Question 29

why is ocean acidification an issue for organisms

Answer 29

pH ↓… carbonate ↓ (tends to dissolve) - Many marine organisms need carbonate
- more carbonate is converted to bicarbonate - becomes more difficult for organisms to obtain carbonate to build shells and skeleton

Question 30

in a base are there more H+ or OH-

Answer 30

OH-

Question 31

3 components in The Ocean carbon cycle

Answer 31

Solubility pump – atmosphere -> water
Carbonate pump – chemistry of surface water
Biological pump

Question 32

Molecules and ions in the carbonate cycle

Answer 32

carbon dioxide, water, carbonic acid, hydrogen ion, bicarbonate, carbonate, calcium carbonate

Question 33

what’s does Gas transfer rate between water + atmosphere depend on

Answer 33

• Difference in partial pressure of CO2 – bigger difference = faster transfer
• Water temperature – warmer = faster transfer
• Wind velocity – higher winds = faster transfer
• Sea state – choppier seas = faster transfer

Question 34

what is the solubility pump Equilibrium dependent on

Answer 34

Temperature
Salinity
CO2 atmospheric concentration (Henry’s law)

Question 35

how does the Solubility pump draw CO2 concentration down

Answer 35

by converting them to ions
CO2 -> H2CO3 (carbonic acid) -> H+ (proton) and HCO3- (bicarbonate) **if there are high proton concentrations we will get a second bicarbonate ion

Question 36

2 major processes affecting CO2 system in the ocean

Answer 36

• Addition / removal of CO2 by organisms (respiration/photosynthesis)
• Bicarbonate mineral precipitation and dissolution

Question 37

Carbonate pump purpose

Answer 37

returns CO2 to surface & atmosphere - Keeps surface waters lower in CO2 than deeper waters