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chenhongxia
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chenhongxia
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The part carbon dioxide plays in environmental processes
Carbon dioxide is one of the most abundant gasses in the atmosphere. Carbon dioxide plays an important part in vital plant and animal process, such as photosynthesis and respiration. These processes will be briefly explained here.Green plants convert carbon dioxide and water into food compounds, such as glucose, and oxygen. This process is called photosynthesis.
The reaction of photosynthesis is as follows:
6 CO2 + 6 H2O --> C6H12O6 + 6 O2
Plants and animals, in turn, convert the food compounds by combining it with oxygen to release energy for growth and other life activities. This is the respiration process, the reverse of photosynthesis.
The respiration reaction is as follows:
C6H12O6 + 6 O2 --> 6 CO2 + 6 H2O
Photosynthesis and respiration play an important role in the carbon cycle and are at equilibrium with one another.Photosynthesis dominates during the warmer part of the year and respiration dominates during the colder part of the year. However, both processes occur the entire year. Overall, then, carbon dioxide in the atmosphere decreases during the growing season and increases during the rest of the year.Because the seasons in the northern and southern hemispheres are opposite, carbon dioxide in the atmosphere is increasing in the north while decreasing in the south, and vice versa. The cycle is more clearly present in the northern hemisphere; because it has relatively more land mass and terrestrial vegetation. Oceans dominate the southern hemisphere.
Influence of carbon dioxide on alkalinity
Carbon dioxide can change the pH of water. This is how it works:
Carbon dioxide dissolves slightly in water to form a weak acid called carbonic acid, H2CO3 , according to the following reaction:
CO2 + H2O --> H2CO3
After that, carbonic acid reacts slightly and reversibly in water to form a hydronium cation, H3O+, and the bicarbonate ion, HCO3-, according to the following reaction:
H2CO3 + H2O --> HCO3- + H3O
This chemical behaviour explains why water, which normally has a neutral pH of 7 has an acidic pH of approximately 5.5 when it has been exposed to air.


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...deja vu....

Hiya Chen,
This probably is a better forum for your Topic.
On your original post (Gen.Sci.Forum) I responded:
Originally Posted By: #27313
"The cycle is more clearly present in the northern hemisphere; because it has relatively more land mass and terrestrial vegetation. Oceans dominate the southern hemisphere." -chenhongxia

This is what give the characteristic sawtooth shape to the rising CO2 curve, I think.

If the "downstroke" were just slightly larger than the "upstroke," then the CO2 curve would start descending, wouldn't it?

Changing agricultural and forestry practices could shift that balance (as well as would restoring productivity to the oceans).


People focus so much on emissions, but the planet exchanges over 100 gigatonnes/year. There is a large pool of carbon cycling, of which emissions are only a small part of the equation.


Originally Posted By: **
In its Second Assessment Report the IPCC, 1996 estimated that it might be possible, over the next 50 to 100 years, to sequester 40-80 Gt of C in cropland soils (Cole et al., 1996; Paustian et al., 1998; Rosenberg et al., 1998).

...agricultural soils alone could capture enough Carbon to offset any further increase in the atmospheric inventory for a period lasting between 12 and 24 years.

...there is also a very large potential for Carbon storage in the soils of degraded and desertified lands.

Soil Carbon sequestration alone could make up the difference between expected emissions and the desired trajectory in the first three or four decades of the 21st century, buying time for development of the new technological advances...[emission reduction/recycling].


40-80 Billion Tonnes of Carbon (just in cropland soils) + even larger potential sequestration by restoring "the soils of degraded and desertified lands" would be enough to return CO2 to pre-industrial levels within a few decades.

Why isn't this solution being implemented?

Originally Posted By: **
This mitigation option was set-aside in the Kyoto negotiations ostensibly because of the perceived difficulty and cost of verifying that Carbon is actually being sequestered and maintained in soils.


**Storing Carbon in Agricultural Soils: A Multi-purpose Environmental Strategy
Edited by:
Norman J. Rosenberg and Roberto C. Izaurralde
Reprinted from Climatic Change, Vol.51, no.1, 2001
Kluwer Academic Publishers
ISBN 0-7923-7149-6

...and this isn't the high-cost, high-tech "carbon capture" CO2 sequestration schemes that energy companies are researching.

It's very low cost, requiring mainly organization and a change in culture and behaviour.
===

Chen, are you familiar with "bio-char" supplementation of soils to enhance sequestration, resilience, and productivity?
...see:
http://www.scienceagogo.com/forum/ubbthreads.php?ubb=showflat&Number=8943#Post8943

What do you think? Could a small percentage shift in agricultural practices counteract all of our current emissions?

Could we change the shape of that sawtooth curve?

Thanks,
~ smile


Pyrolysis creates reduced carbon! ...Time for the next step in our evolutionary symbiosis with fire.

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