marine chemistry
BIO 4400
(Ketil Hylland)
content
● flow of elements
● water as a reagent and as a solvent
● what is seawater?
● composition
● measuring salinity
● dissolved gases
● pH and buffering
● the bicarbonate system
● trace elements
1
2
water as a solvent
● good solvent for polar and charged
substances
● not a good solvent for non-polar
substances
3
4
5
ions in seawater
elem ent/ion
klorid
sulfat
bikarbonat
brom id
borat
fluorid
natrium
m agnesium
kalsium
kalium
strontium
silisium
alum inium
jern
i sjøvann (% )
18,98
1,65
0,14
0,07
0,03
0,001
10,56
1,27
0,40
0,38
0,013
-
i jordskorpa (% )
2,4
2
4,2
2,4
28,2
8,2
5,6
ladning
+
+
+
+
+
6
measuring salinity
● drying - weighing (-)
● refractometer (-)
● titration, e.g. chlor (+)
● measure conductivity (+)
definition - salinity
● salinity is the ratio between the conductivity
of a given sample and the conductivity of a
standard KCl-solution at 15°C and 1 atm
● the concentration of KCl: 32.4356 g/kg
● almost identical to the amount of salt in the
solution
● no units to salinity, but commonly used per
mille or PSU (practical salinity units)
7
gases in seawater
● very slow molecular diffusion of gases
● divided into:
● conservative (”non-biological”): N, Ar, ..
● non-conservative (”biological”): O2, CO2
● solubility depends on:
● temperature (increase at lower
temperature)
● pressure (increase at higher depth)
oxygen
● introduced into seawater from/by:
●
● atmosphere
● photosynthesis
● mixing
consumed:
● respiration
● mixing
8
sea and rock
9
10
change 1700s-1990
particles
● separate using a filter of 0.45 µm
● riverine inputs
● dust from
● wind, atmosphere, volcanic activity,
meteorites
● biological origin
● pellets
● detritus
● aggregates (marine snow)
● remains of dead animals
11
speciation
● no binding (Na, Cl)
● ion-pairs (Fe, NO3)
● complexes, colloids
● important for bioavailability
● free, ionic form important (Cd)
● direct uptake of uncharged, nonpolar
species
12
trace elements
● all stable elements found in seawater
(probably)
● speciation
● solubility
● bioavailability/bioaccumulation
trace elements in organisms
● Fe, Cu in respiratory pigment (crustaceans,
●
●
●
●
●
molluscs, polychaetes, ..)
V accumulate in some tunicates, Nb in others
Ti accumulate in some sponges
As accumulate in some polychaetes
Po accumulate in some shrimp
Ag, Cd accumulate in scallops and some
other bivalves
13
summary
● the composition of seawater
● the definition of salinity and how it is
measured
● the solubility of gases
● the carbonate-bicarbonate buffer
system
● consequences from elevated CO2 and
decreased pH of the oceans
14
questions
● what are the most important ions in
seawater?
● how may salinity be measured?
● explain why the solubility of different
gases will vary in seawater
● describe the carbonate-bicarbonate
buffer system
● what may be biological consequences
of increased CO2 in the atmosphere
(and hence in the ocean)?
freezing point depression
15