Introduction To Chemistry & Biology Flashcards
What are the two scales that must be considered when looking at ocean processes?
Spatial and Time
Give an example of a short, small scale ocean process
Capillary Waves
Give an example of a long, large scale ocean process
Climate Change
3 Methods of Collecting Ocean Data
- NIO Bottle
- Niskin Bottle
- Rosette
What should be considered when analysing seawater?
That it is more complex than freshwater, you need to preserve and maintain oxygen levels and the matrix effect should also be considered
How do you avoid absorption and contamination of trace elements?
Keep them in an acid solution
Is seawater electronically neutral? What do we also need to consider?
Yes it is but we have to think about atomic mass rather than % by weight. You can do this by comparing negative and positive atoms (e.g. Cl and Na)
What is the equation for calculating the number of moles of ions?
Moles of Ions = Concentration / Atomic Weight
What is the average concentration of dissolved salts in the oceans?
3.5% (35 ppt or 35 g/l)
What controls surface salinity?
Climate (Evaporation and Precipitation)
What is the global distribution of salinity?
Large in the tropics but low at the poles and directly on the equator
What is the Constancy of Composition of Seawater?
The concentrations of major dissolved ions can vary from place to place but their relative proportions will remain virtually constant
Which element is used for references Constancy of Composition of Seawater?
Chlorine
What are the 6 variations of the major Constancy of Composition of Seawater?
- Enclosed seas or estuaries
- Anoxic basins
- Shallow seas
- Hydrothermal vents
- Evaporates (e.g. Red Sea)
- Pore waters
What is conservative behaviour?
Major ions that are only affected by physical mixing processes
What is non-conservative behaviour?
Minor ions that are affected by biological and chemical processes, distribution is independent of salinity
What do we assume all elements in the seawater to come from?
The Geochemical Balance
How old are the oldest surface sediments on the seafloor and why aren’t there any older than this?
200 million years and because of plate tectonics
What are the three groups of elements?
- Those where the weathering supply is adequate and there is a removal mechanism
- Elements that are very reactive in seawater and absorb into particles
- Those where the weathering supply isn’t enough and another source is needed
What is a residence time?
It gives an idea as to how long an element will remain in solution before being removed
What do residence times assume?
That the ocean is in a steady state (rate of input = rate of removal)
What is the residence time equation?
T=A/Input so Amount/Amount per Time = Time
Why do we use residence times?
Because all chemical and biological processes have to be seen in a physical context
Major un-reactive elements have……
Long Residence Times
Minor reactive elements have…..
Short Residence Times
What concentration does a major element have?
> 1mg/l
What concentration does a minor element have?
<1mg/l
How many major elements are then in seawater?
11
