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chemical oceanography > ch 3 > Flashcards

ch 3 Flashcards

1
Q

percentage of chloride, salt, and water in ocean

A

96% water

55% chloride

30% salt

the rest is sulfate and other things

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2
Q

what elements are found in seawater

A

most of the 90 naturally occurring elements but in relative proportions different to those in crustal rocks

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3
Q

molarity

A

mols/L

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4
Q

molality

A

moles/kg

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5
Q

what units do we use for organic matter compounds

A

not molarity or molality, we use g/l bc the molecuels are huge and highly variable

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6
Q

solute size

A

less than 1 nm

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7
Q

colloid size

A

bc 1 nm to 0.1 um

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8
Q

solids size

A

greater than 0.1 um

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9
Q

residence time formula

A

pool size/ (sum of fluxes in OR sum of fluzxes out)

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10
Q

if mixing time < than residence time

A

the substances are conservative properties of water and their relative ratios dont change - they are all diluted to the same extent

CONSTANT PROPORTIONS

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11
Q

what is the mixing time of the world oceans

A

around 1000 years

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12
Q

what is the law that describes conservative substances

A

the law of constant porportions

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13
Q

how can we get an excelent approximation of Salinity by measuring one concentration

A

measure chlorinity or [cl-] which is easier to measure and multiply by 1.81

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14
Q

how does a CTD work

A

apply a volatge from a positive and negative electrode and the sodium ions flow and create a current

measuring the waters conductivity

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15
Q

why are the non conservative elemnts not conservative

A

they cycle rapidly and are used in biological processes

found in small and highly variable amounts

not uniformly distributed

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16
Q

what elements are non conservative

what compounds are non conservative

A

C,N,O,P

nitrates, ammonium, phosphates

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17
Q

what kind of elements are the trace elements

A

atomic number greater than 20

transition metals

metal and heavy metals

alkalai metals

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18
Q

what is the concentration of trace elements

A

less than 0.05 umol.kg

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19
Q

what are the sources of trace metals

A

runoff/ river- mobilized during weathering

atmosphere

human sources/ anthropogenic

diagenesis

hydrothermal activity

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20
Q

what is the atmosphere a source of trace metal for

A

As and Pb

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21
Q

what is diagensis

A

sinking particles attatch to larger things and go to the bottom of the ocean

chemical. reactions solubilize them and they then diffuse across the sediment water interface

22
Q

what are the antrhopogenix sources of trace metals

A

burning of fossil fuels

mining and and industrial activities

23
Q

what are the sinks for trace metals

A

adsorption- onto surfaces

percipitation

incorporation into biological material

they are already in such small amounts and these processes remove them

24
Q

what are the macronutrients

A

C

N

P

25
Q

atom =

A

nucleus + electrons

26
Q

what dictates the chemical properties and reactivity of an element

A

the number of electrons

27
Q

what is the nuclear number

A

the number of protons and electrons

28
Q

what are unstable isotopes

A

radioactive isotopes or radionucleotides

they decay over time and release particles to become different elements

29
Q

what is the radioactive decay law

A

rate at which a radionuclide
decays is directly proportional to the number of atoms
presen

30
Q

what is the decay constant

A

the statistical likelihood that an
average atom of a given radionuclide will decay in a certain TIME

31
Q

what are the three sources ofr radionucleotides

A

primordia

cosmogenic

artificail

32
Q

primordial radionucleotides

A

present at the creation of the earth

billion of years half lives of U235,238 and Th 232 and then become daughter Pb 206-208 with much shorter half lives

33
Q

what are cosmic rays

A

in cosmogenic radionucleotides

protons and alpha particles- charges praticles that enter the earths atmosphere from outer space

high energy

cause SPALLATION- fragmentation of gas nuclei

34
Q

comsogenic radionucleotide of N

A

N attacks- releases proton and becomes unstable C14

releases y and electron and becomes N14 again

35
Q

what does radioactive decay lead to

A

exponential decrease in nucleotide numbers over time

36
Q

how can we calculate the age of radioactive elemnts

A

if we know the current and initial CONCENTRATION of parent and daughter nucleotides

37
Q

what do we use for dating of radioactive elements

A

Primordial and Cosmogenic

38
Q

what is the starting assumption of measuring parent c 14 today

A

that the ratio of c14/12 is the same

not true bc c14 has since decayed, production is not constant

due to atmospheric flux of cosmic rays (sunspot activity and earths magnetic field)

anthropogenic input from atom bomb testing (increases c14) and burning of fossil fuels (decreases fossil fuels bc they have low 14)

39
Q

suess effect

A

burning fossil fuels in the 1850s introduced old carbon to the atmosphere reducting the C14/12 ratio

dilute current cO2 with cO2 that has high c12 and no c14

40
Q

So what to do with the variable production rates of C-14
in the past?

A

can use values from literature or nearest value we can get

41
Q

using radioactive tracers from atom bomb testing and leakage from nuclear plants

A

use C14 as it is a fission product

since testing was from 1958-1965, we can see the spikes in ocean and track its movement

seeing horiontally how far it has gone- THC and horizontal currents

how far it made it into the deep ocean- vertical mixing, advection

42
Q

When dealing with small concentrations of a tracer:

A

it is much easier to calculate such concentrations of
substance by counting the number of the
radioactive decays per unit time

43
Q

non radiocative tracers

A

like CFCs – have to be
measured by more traditional chemical analytical
methods -> much bigger error bars

44
Q

stable carbon isotopes

A

c12 and 13- dont break down over time, redistributed in processes that may favour one over the other and leads to the changing of the ratio

45
Q

Since the isotopes have the
same number of protons and
electrons ->they have
practically the same

A

chemical properties

46
Q

But having different number
of neutrons, they have

A

different atomic mass – so
they will have different
PHYSICAL properties

47
Q

what elements isotopes will we use for climate

A

o and h bc they are in water

O18 is heavier, easier to percipitate, harder to evaporate

measure how much 018 there is, tells us volume of ice at glacial period and indirectly the water and air temp

easier to percipitate- tells us how far the air masses moved

in the glacial period- the water is enriched in heavier isotope of O and the ice is enricehed in lighter O isotope

48
Q

what is another application of stable isotpes

A

B11 and 10

the ratio in water is preserved in shells of microfossils and the ratio depeneded on the pH at the time so we would know the partial pressure of CO2 in the water when they formed

49
Q

exceptions to the rule of constant proportions

A
  1. where river water enters
  2. SO42– anoxic enviroments used by bacteria to respire organic mater and decrease SO42- and increase s2-
  3. salt excluded from ice during formation
  4. deviations in Ca due to CaCO3 formatino and dissolution- surface dwelling plankton
  5. hydrothermal emission- depleted in SO42- and Mg2+
  6. shallow water- high E and low P- evaporites formed in areas of restricte dmixing
  7. bursting and aeorosol formation from bubble ejection- different ions ejected to diff degrees
  8. water trapped in sediments- pore / interstitial water- limited exchange
50
Q
A

chemical oceanography (15 decks)

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