I doubt it matters, but do you actually need a strong base? Wouldn't a pK in the range of 9.4 to 12 be almost as good as one above 12? As long as the pK is a unit or two above the pH of the water it's in, it will be mostly dissociated. It's probably a distinction without a difference, since as far as I know there isn't any plausible substance with a pK in that range. The closest thing I can think of is iron(II) hydroxide, which precipitates in the neutral range according to the CRC handbook. It may be that iron will be of some use in the most acidic areas of ocean, as those become more acidic.
That raises the question of whether iron provides any fertilization benefit at all when it's not limiting. It seems as though it should: the more of a concentration gradient an organism has to work against to bring an ion across its cell membrane, the more energy it takes to do so. I would expect the effect to be minor, and the limiting- nutrient concept to be fairly robust, but even a minor effect might be worthwhile if it's cheap to get. More realistically, extra iron after it's no longer limiting might have an effect on ecology: some organisms may be worse than others at getting iron out of the water, and find a niche only in especially high-iron areas. Pure speculation here, though: I don't actually know anything about it. On Apr 4, 5:27 pm, Ken Caldeira <[email protected]> wrote: > One way of looking at the CO2 problem is that you are introducing a (weak) > acid (CO2) into the environment. > > (Recall that Arrhenius's famous 1896 paper was called "On the Influence of > Carbonic Acid in the Air upon the Temperature of the > Ground".http://www.globalwarmingart.com/images/1/18/Arrhenius.pdf). > > The partitioning of CO2 between the ocean and the atmosphere is controlled > by the oceanic acid-base balance. > > Rather than thinking in terms of sequestering CO2, we could think in terms > of either sequestering an acid away from the system or adding a base > (loosely, negative acidity) to the system. > > So, instead of injecting CO2 underground we could, say, add CO2 to the ocean > and remove HCl from the ocean and inject the HCl underground -- this would > have a similar effect on atmospheric CO2 content. Alternatively, you can add > strong bases (i.e., alkalinity) to the ocean, which is chemically very > similar to removing an acid. Any strong base will do, NaOH, Mg(OH)2, etc, > etc. > > Finding a source of this alkalinity is a well recognized problem. House et > al (2007) and Lackner et al (1995, 1997) have both proposed ways of getting > this alkalinity from silicate rocks and Rau and Caldeira (1999) and Rau et > al (2007) have proposed getting this alkalinity from carbonate rocks > (however this would require oceanic disposal of the resulting CO2-enriched > fluid). > > Kheshgi (1995) has also thought about ways to add alkalinity to the ocean. > > In contrast, Calera in their public documents show only seawater and CO2 as > inputs to their process, with the implication that they will obtain their > alkalinity from seawater. > > Best, > > Ken > > ----------------------- > > references > > *House, K.Z., House, C.H, Schrag, D.P., Aziz, M.J. Electrochemical > acceleration of chemical weathering as an energetically feasible approach to > mitigating anthropogenic climate change. Environ. Sci. Technol., 41(24): > 8464-8470, 2007. > > Kheshgi, H. S., 1995. Sequestering atmospheric carbon dioxide by increasing > ocean alkalinity. Energy, 20: 915-922. > > Lackner et al., 1995 K.S. Lackner, C.H. Wendt, D.P. Butt, E.L. Joyce and > D.H. Sharp, Carbon dioxide disposal in carbonate minerals, Energy 20 (1995) > (11), pp. 1153–1170. > > Lackner et al., 1997 K.S. Lackner, D.P. Butt and C.H. Wendt, Progress on > binding CO2 in mineral substrates, Energy Conversion and Management 38 > (1997), pp. S259–S264 > > Rau, G.H., and Caldeira, K. Enhanced carbonate dissolution: A means of > sequestering waste CO2 as ocean bicarbonate. Energy Conversion and > Management 40, 1803-1813, 1999. > > Rau, G.H., K.G. Knauss, W.H. Langer AND K. Caldeira. 2007. Reducing > energy-related CO2 emissions using accelerated weathering of limestone. > Energy, 32:1471-1477. > > * > ___________________________________________________ > Ken Caldeira > > Carnegie Institution Dept of Global Ecology > 260 Panama Street, Stanford, CA 94305 USA > > [email protected]; > [email protected]http://dge.stanford.edu/DGE/CIWDGE/labs/caldeiralab > +1 650 704 7212; fax: +1 650 462 5968 > > On Fri, Apr 3, 2009 at 10:45 AM, concernedcitizen <[email protected]> > wrote: > > > > > Ken - Wanted to follow up on your statement re: needing strong bases. > > What type of bases are needed and what strength. Is this just a scale > > and cost issue or is there a fundamental roadblock here? Cheers: > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en -~----------~----~----~----~------~----~------~--~---
