The role of iron in sea water to store carbon dioxide
The 2004 EIFEX experiment re****ted a carbon dioxide to iron
fixation ratio of nearly 300,000 to 1.
Advocates say that using this technique to restore ocean plankton to
recent known levels of health would help solve half the climate change
problem, revive major fisheries and cetacean populations, and
alleviate several other urgent ocean crises
About 70% of the world's surface is covered in oceans, and the upper
part of these (where light can penetrate) is inhabited by algae. In
some oceans, the growth and/or reproduction of these algae is limited
by the amount of iron in the seawater. Iron is a vital micronutrient
for phytoplankton growth and photosynthesis that has historically been
delivered to the pelagic sea by wind-driven dust storms from arid
lands. This Aeolian dust contains 3~5% iron and its deposition has
fallen nearly 25% in recent decades[16] due to modern changes in land
use and agricultural practices as well as increased greening of dry
regions thanks to increasing levels of atmospheric CO2. (Arid zone
gr***** and vegetation now lose less water va**** through their stomata
to absorb the same amount of carbon dioxide, and thus stay greener
longer, reducing dust storm frequency and the amount of iron reaching
the deep seas. Increasing sand desertification does little to
compensate for this shortfall since sand is primarily silica with
relatively low iron content.)
The Redfield ratio describes the relative atomic concentrations of
critical nutrients in plankton biomass and is conventionally written
"106 C: 16 N: 1 P." This expresses the fact that one atom of
phosphorus and 16 of nitrogen are required to "fix" 106 carbon atoms
(or 106 molecules of CO2). Recent research has expanded this constant
to "106 C: 16 N: 1 P: .001 Fe" signifying that in iron deficient
conditions each atom of iron can fix 106,000 atoms of carbon[17], or
on a mass basis, each kilogram of iron can fix 83,000 kg of carbon
dioxide. The 2004 EIFEX experiment re****ted a carbon dioxide to iron
fixation ratio of nearly 300,000 to 1. Assuming that data is on a mass
basis, then the normalized atomic ratio would be approximately:
"380,000 C: 58,000 N: 3,600 P: 1 Fe".
In "desolate" HNLC zones, therefore, small amounts of iron (measured
by mass parts per trillion) delivered either by the wind or a planned
restoration program can trigger large responsive phytoplankton blooms.
Recent marine trials suggest that one kilogram of fine iron particles
may generate well over 100,000 kilograms of plankton biomass. The size
of the iron particles is critical, however, and particles of 0.5~1
micrometre or less seem to be ideal both in terms of sink rate and
bioavailability. Particles this small are not only easier for
cyanobacteria and other phytoplankton to incor****ate, the churning of
surface waters keeps them in the euphotic or sunlit biologically
active depths without sinking for long periods of time.
http://en.wikipedia.org/wiki/Iron_fertilization
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