ch 3 Flashcards
percentage of chloride, salt, and water in ocean
96% water
55% chloride
30% salt
the rest is sulfate and other things
what elements are found in seawater
most of the 90 naturally occurring elements but in relative proportions different to those in crustal rocks
molarity
mols/L
molality
moles/kg
what units do we use for organic matter compounds
not molarity or molality, we use g/l bc the molecuels are huge and highly variable
solute size
less than 1 nm
colloid size
bc 1 nm to 0.1 um
solids size
greater than 0.1 um
residence time formula
pool size/ (sum of fluxes in OR sum of fluzxes out)
if mixing time < than residence time
the substances are conservative properties of water and their relative ratios dont change - they are all diluted to the same extent
CONSTANT PROPORTIONS
what is the mixing time of the world oceans
around 1000 years
what is the law that describes conservative substances
the law of constant porportions
how can we get an excelent approximation of Salinity by measuring one concentration
measure chlorinity or [cl-] which is easier to measure and multiply by 1.81
how does a CTD work
apply a volatge from a positive and negative electrode and the sodium ions flow and create a current
measuring the waters conductivity
why are the non conservative elemnts not conservative
they cycle rapidly and are used in biological processes
found in small and highly variable amounts
not uniformly distributed
what elements are non conservative
what compounds are non conservative
C,N,O,P
nitrates, ammonium, phosphates
what kind of elements are the trace elements
atomic number greater than 20
transition metals
metal and heavy metals
alkalai metals
what is the concentration of trace elements
less than 0.05 umol.kg
what are the sources of trace metals
runoff/ river- mobilized during weathering
atmosphere
human sources/ anthropogenic
diagenesis
hydrothermal activity
what is the atmosphere a source of trace metal for
As and Pb
what is diagensis
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
what are the antrhopogenix sources of trace metals
burning of fossil fuels
mining and and industrial activities
what are the sinks for trace metals
adsorption- onto surfaces
percipitation
incorporation into biological material
they are already in such small amounts and these processes remove them
what are the macronutrients
C
N
P
atom =
nucleus + electrons
what dictates the chemical properties and reactivity of an element
the number of electrons
what is the nuclear number
the number of protons and electrons
what are unstable isotopes
radioactive isotopes or radionucleotides
they decay over time and release particles to become different elements
what is the radioactive decay law
rate at which a radionuclide
decays is directly proportional to the number of atoms
presen
what is the decay constant
the statistical likelihood that an
average atom of a given radionuclide will decay in a certain TIME
what are the three sources ofr radionucleotides
primordia
cosmogenic
artificail
primordial radionucleotides
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
what are cosmic rays
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
comsogenic radionucleotide of N
N attacks- releases proton and becomes unstable C14
releases y and electron and becomes N14 again
what does radioactive decay lead to
exponential decrease in nucleotide numbers over time
how can we calculate the age of radioactive elemnts
if we know the current and initial CONCENTRATION of parent and daughter nucleotides
what do we use for dating of radioactive elements
Primordial and Cosmogenic
what is the starting assumption of measuring parent c 14 today
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)
suess effect
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
So what to do with the variable production rates of C-14
in the past?
can use values from literature or nearest value we can get
using radioactive tracers from atom bomb testing and leakage from nuclear plants
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
When dealing with small concentrations of a tracer:
it is much easier to calculate such concentrations of
substance by counting the number of the
radioactive decays per unit time
non radiocative tracers
like CFCs – have to be
measured by more traditional chemical analytical
methods -> much bigger error bars
stable carbon isotopes
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
Since the isotopes have the
same number of protons and
electrons ->they have
practically the same
chemical properties
But having different number
of neutrons, they have
different atomic mass – so
they will have different
PHYSICAL properties
what elements isotopes will we use for climate
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
what is another application of stable isotpes
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
exceptions to the rule of constant proportions
- where river water enters
- SO42– anoxic enviroments used by bacteria to respire organic mater and decrease SO42- and increase s2-
- salt excluded from ice during formation
- deviations in Ca due to CaCO3 formatino and dissolution- surface dwelling plankton
- hydrothermal emission- depleted in SO42- and Mg2+
- shallow water- high E and low P- evaporites formed in areas of restricte dmixing
- bursting and aeorosol formation from bubble ejection- different ions ejected to diff degrees
- water trapped in sediments- pore / interstitial water- limited exchange
