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Chemical Processes of the Ocean - Coggle Diagram

- - - -  Atmospheric precipitation (rain or snow) or river in flow or evaporation will not significantly effect the composition of salts
      - The ocean is in a steady state over the long term
  - - - Major constituents – e.g. salt (NaCl)
      - Minor constituents – e.g. Li, rubidium, I, Ba, molybdenum, arsenic
      - Trace components – generally concentration less than 1 part per billion (nanomolar and picomolar) e.g. heavy metals like copper etc and periodic table rows 5, 6 and 7
      - Nutrients e.g. phosphorus, nitrates (NO^3-), nitrites (NO^2-), urea, NH3
      - Gases e.g. oxygen
      - Organics - not part of the salinity – dissolved and particulate material of biological origin, living or dead organic matter
    - - Some of these are alkali metals, some are earth metals and some are halogens, generally all elements are found in the ocean
    - - Riverine inputs: weathering of rocks/crust produces cations and anions and fluvial (found in river) inputs (some very abundant elements in the crust won't be as abundant in the sea because they're insoluble eg Si), some of these inputs are conservative (eg Na won't get changed by the oceans biological processes) and some are non-conservative (eg NO3^- can change to fit the oceans biological processes)
      - The atmosphere: volcanic emissions supply anions, biogenic (produced or brought about by living organisms), wind blown, cosmogenic materials and may be in rainfall or dry deposition
      - Hydrothermal vents
      - Glacial transport from polar regions and mountains it's less significant for salt balance but causes variance in regions
  - - - Residence time (yr) = Total amount of substance in reservoir (tonnes) / Sum of fluxes into or out of reservoir (tonnes per year)
    - - 3) Finally do the equation for residence time
      - 2) Sum of fluxes into or out of reservoir (tonnes per year) by converting rate of water flowing from Km^3yr^-1 to Lyr^-1, then multiply river water conc (mgL^-1) with the rate of water (L cancels out leaving mgyr^-1), then convert to tonnes (1 tonne = 10^9 mg)
      - 1) Find the total amount of substance in reservoir (tonnes) by changing the Km^3 unit to litres (do this by x 10^12) then multiply the concentration (units gL^-1) to cancel off the L leaving a unit in grams then convert it to tonnes (1 tonne = 10^6g)
- - - - Weathering - rocks break down into sediment over time or in storms, this process is resulted from the hydrological cycle (water cycle including evaporation, condensation, precipitation, sublimation, transpiration, runoff, and infiltration)
      - Hydrothermal vents - where ions from the earths crust enter the sea via hydrothermal vents (CO2, H2S, CH4, Mn, Fe and He enter this way)
    - - Sediments like clay and ooze can be produced
      - Subduction - the sideways and downward movement of the edge of a plate of the earth's crust into the mantle beneath another plate
    - - It's a cycle of physical (waves), biological (decay, photosynthesis) and chemical (marine spray puts ions on land) systems to maintain the ion input and outputs
      - For major ions the inputs to and outputs from the ocean are balanced, oceanic stirring time is about 500 - 1000 years, calculated residence times for ions like Na and Cl are in the millions of years so overall it's well mixed
  - - - Composed of water crystals, salts are excluded leaving pockets where the leftover concentrated brine sits.
      - Sea forms differently in calm vs rough water, rough water starts with a thin layer of ice which gets tossed about to form pancake ice which combines with more pancake ice causing it to get thicker meanwhile in calm water it's congealed (becomes semi solid) from grease ice.
    - - Brine can trickle from ice into the sea which increases the density, this can especially happen when ice is thawing
      - The colder the water, these less particle movement, the more dense so it sinks.
- - - - Saturation rate can be too high eg the bends in divers that rise too quickly causing bubbles to form in their blood
        
        Oxygen can become supersaturated by being in rockpools (little volume of water at equilibrium with lots of air)
        
        Due to the variation in temperature globally, surface oxygen concentration also varies, it's less concentrated in the equator where it's warm and more concentrated at the poles where it's cooler
        
        Thermohaline circulation and thermocline also effect the dissolved oxygen concentration at the depths as many marine species live at certain depths and their biological processes impact the concentration
    - - N2O, CO, CH4 made from biological processes
      - SO2 from volcanoes
      - CO2 from respiration
- - - - More respiration = more ΣCO2 = more acidic More photosynthesis = less ΣCO2 = more alkali
      - ΣCO2 = [CO2] + [H2CO3] + [HCO3-] + [CO3 2-]
        most Σ CO2 = [HCO3-] + [CO3 2-]
      - (Fractional contribution means the 1 is 100% 0.1 is 10% etc)
    - - 1) Atmospheric CO2 equilibrates with the seawater CO2(g) <===> CO2(aq)
        
        2) It becomes hydrated CO2(aq) + H2O(l) <===> H2CO3(aq)
        
        3) Carbonic acid dissociates H2CO3(aq) <===> H+(aq) + HCO3-(aq)
        
        4) HCO3-(aq) <===> H+(aq) + CO3^2-(aq)
  - - - Aragonite - less stable, shells dissolve at shallower depths/ in low carbonate concentrations
      - Calcite - more stable, shells survive at larger depths/ in high carbonate concentrations
  - - - pH measures the scale for expressing the concentration in moles per litre of the [H3O+] or [H+] (acidity)
      - In pure water at 25C one in 10 million (10^7) water molecules are dissociated – this gives a concentration of H+ ions of 10^-7 (using the equations above this proves pH of pure water is 7)
      - pH =-log10[H+(aq)] or [H+(aq)] = 10^-pH
      - Globally, there's a small variation in the surface pH, slightly lower pH around equator
      - pH of seawater is 8.1
      - pH slightly lower in depths due to lack of phytoplankton which consume CO2
    - - Ocean acidification is proof the ocean buffers do have their limits
      - Oceans are well buffered by mix of carbonates, borates,
        phosphates, silicates and organic compounds
      - A buffered solution resists changes in pH when it is diluted or when acid or base is added (it's made of a weak acid/base and its salt)
- - - - Nitrogen fixation (converting N2 to fixed Nitrogen)
        
        Method 2: The haber process converts N2(g) to nitrate via oxidation then are taken up by primary producers, consumers etc to be made into organic nitrogen eg proteins
        
        Method 1: Cyanobacteria converts N2(g) into ammonia which can then be used in biological processes to convert it to organic nitrogen
      - The nitrogen travels through the food chain (eating, excreting, dying) and then recycling (oxidising) bacteria recycles it (even the benthic stuff although very little N reaches the deep ocean) to nitrate and the cycle continues, also denitrifying bacteria can convert nitrate to N2(g)
    - - Also the thermocline limits mixing due to it's stability so only upwelling can bring nitrate back up (btw downwelling brings low nitrate conc water down and then conc increases because of the benthic organic matter)
- - - - Manganese nodules - Low O2 conc = more concentrated manganese, nodules found near vents, sediment accumulates slowly in the deep abyssal plains, deoxygenation may release trace metals, nodules start by forming around a starting grain eg a sharks tooth