ocean chemistry Flashcards
whats The Hydrologic Cycle
Cycle of Precipitation + evaporation driven by solar radiation
**Water spends a very long time in the ocean before its recycled into the atmosphere
what 2 components is a solution made from
- Solvent – usually a liquid, always the more abundant
- Solute – often a dissolved solid or gas, always the less abundant
difference between solution and mixture
- true solution has uniform properties (e.g. sugar in well-stirred tea)
- mixture = different substances retain separate identities
whats an ion
an atom/small group of atoms with an unbalanced electrical charge (gained or lost one or more electrons) e.g. Sodium ions (Na + ), chloride ions (Cl- )
one major historical belief to solve pollution
“The solution to pollution is dilution”
*water polar property allows it to dissolve many things
what percent of the ocean is dissolved substances
3.5% - most are salts
what are trace elements
Elements less than one part per million in volume
- Only 14 elements have concentrations in seawater greater than this
what happens to the heat capacity of water with increasing salinity
decreases
why does seawater evaporate more slowly than freshwater
Osmotic pressure increases - salinity levels
5 Processes That Regulate the Major Constituents in Seawater
rain, river discharge, volcanic activities, ridge systems
what is Forchhammer’s principle and how does it relate to the ocean
principle of constant proportions
- The Ratio of Dissolved Solids in the Ocean Is Constant
- The total amount of dissolved solids (salinity) may vary among samples, but the ratio of major salts was constant in samples of seawater from many locations (HMS Challenger)
- The ocean is in chemical equilibrium
what is the mixing time of the ocean
~ 1,600 years
what are Conservative constituents and how are they determined
substances that remain in constant proportions or change very slowly through time (long residence time)
- Residence time > mixing time = Conservative constituents
what are non conservative constituents and how are they determined
substances dissolved in seawater that
are tied to biological or seasonal cycles or to very short geological cycles (short residence times)
- Residence time < mixing time = Nonconservative constituents
how is Salinity calculated
by Seawater’s Conductivity
- water samples at predetermined depths are collected using a group of sampling bottles
- The bottles are hauled to the surface and their contents analyzed by a salinometer
what parts of the ocean do gases dissolve in more readily
in cold water + at the surface
top 3 gases dissolved in the ocean
N2 – most conc at sea surface
O2
CO2 – most conc in ocean as a whole
how does Concentrations of Oxygen + Carbon Dioxide Vary with Depth
O2 levels higher at the surface - decrease with depth
CO2 lower at surface - increases with depth
what is an acid
a substance that releases a hydrogen ion in solution
what is a base
a substance that combines with a hydrogen ion in solution
whats the pH of seawater
8
what form in dissolved CO2 in seawater
carbonic acid
how does the oceans natural buffer work
can turn carbonic acid into bicarbonate + carbonate – reduces its acidity
how does pH differ with depth
Deep, cold seawater (below 4,500 meters) has a pH of around 7.5 - more acidic as co2 dissolves more readily
- A drop to a pH of 7 can occur at the deep ocean floor when bottom bacteria consume oxygen and produce sulfide
why is ocean acidification a problem for organisms with shells
carbonate ions from dissolved co2 combines with hydrogen to make carbonic acid instead - organism’s supply of essential carbonate goes down
