marine chemistry Flashcards
what are the other major constituents in sea water other than water and major salts
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
what are salts dissolved in seawater preset as
ions
what is the major cation and anion in sea water
Na+ = cation
Cl- = anion
what are the minor constituents in seawater
particulate matter - things that don’t pass through a particle filter pore size
main sources of particulate matter
Aeolian (things in atmosphere e.g. dust, smoke)
Rivers
Biological production
what are Conservative constituents
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+)
what are non-conservative constituents
Their concentrations are altered by chemical + biological processes - therefore their concentrations can VARY dramatically in time and space
Examples: nutrients, gases, trace meta
what is Residence time
average time that a substance remains in the ocean
what are Major constituents in seawater controlled by
hydrological + geological processes
what are the 2 main sources of the chemicals LEAVING the ocean
- 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
what are the two equations that can represent Residence time
rate of introduction of element by river OR
rate of removal as sediment
what chemicals are shown to have the largest residence time
The 6 major constituents
what is mixing time
average time to “mix” the entire ocean (ca. 1000 year)
what is the Principle of constant proportions
regardless of variations in salinity, the ratios between the major constituents remain the same
how can the total salinity of seawater vary
by adding water (precipitation) or removing water (evaporation)
Although the relative proportions of the major ions in seawater are constant
why does evaporation dip near the equator
warmer - means more more evaporation but more clouds which reduces the rate of evaporation as there is less sunlight coming in
why does precipitation increase near equator
more evaporation = more rainfall
why does precipitation increase near poles
Cool air from the poles = more rainfall
why is the water saltier near the equator
more evaporation
why is the water less salty near the poles
Effected by the amount of land - amount of salinity follows the water movement
what are the 6 Major constituents of air
nitrogen, oxygen, carbon dioxide, argon, helium, neon
what does dissolved CO2 into water make
carbonic acid (H2CO3)
physical factors that affect gas concentrations (amount of gas that can dissolve in water)
- Wave and turbulence
- Temperature ↑… Gas dissolution ↓
- Salinity ↑… Gas dissolution ↓- less room for gas molecules
- Water pressure ↑… Gas dissolution ↑(think fizzy drinks!)
Biological processes that affect gas concentrations
- Photosynthesis: removes CO2 and adds O2
- Respiration: adds CO2 and removes O2
- Decomposition: think of it as microbial respiration; adds CO2 and removes O2
what is hypoxia
a condition when oxygen concentrations fall below the level necessary to sustain most animal life (ca. 2 mg O2 l-1)
what is anoxia
total absence of O2
explain ocean acidification
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
what is acidity based on
concentration of hydrogen ions (protons)
why is ocean acidification an issue for organisms
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
in a base are there more H+ or OH-
OH-
3 components in The Ocean carbon cycle
Solubility pump – atmosphere -> water
Carbonate pump – chemistry of surface water
Biological pump
Molecules and ions in the carbonate cycle
carbon dioxide, water, carbonic acid, hydrogen ion, bicarbonate, carbonate, calcium carbonate
what’s does Gas transfer rate between water + atmosphere depend on
- 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
what is the solubility pump Equilibrium dependent on
Temperature
Salinity
CO2 atmospheric concentration (Henry’s law)
how does the Solubility pump draw CO2 concentration down
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
2 major processes affecting CO2 system in the ocean
- Addition / removal of CO2 by organisms (respiration/photosynthesis)
- Bicarbonate mineral precipitation and dissolution
Carbonate pump purpose
returns CO2 to surface & atmosphere - Keeps surface waters lower in CO2 than deeper waters
