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RE: Photoreduction of iron and other elements

Paul Sears asked for the references Diana Walstad used for her comments on
photoreduction of iron..... here they are:

Re: Free iron (Fe++ and Fe+++) being the only two forms of iron used by
- Anderson MA and Morel FMM. 1982. The influence  of aqueous iron chemistry
on the uptake of iron by the costal diatom Thalassiosira weissflofii.
Limnol. Oceanogr. 27:789-813.

Re: [photoreduction], which also aplies to manganese and copper, is greatly
accellerated by DOC. - Morel FMM. 1983. Principles of Aquatic Chemistry.
John Wiley & sons (NY), p.371.
- Sunda WG, Huntsman SA, and Harvey GR. Photoreduction of manganese oxides
in seawater and its geochemical and biological implications. Nature
- Brezonik PL, 1994. Chemical Kinetics and Process Dynamics in Aquatic
Systems. Lewis Publishers (Ann Arbor MI), pp 688-697.

Re: UV and blue light sources inducting the most photoreduction because
wavelengths below about 500 mn are energetic enough to break the chemical
bonds. [the 280 - 400 nm portion of the light energy spectrum encompasses UV
(ultraviolet) light, while the 400 - 500 nm range consists of violet and
blue light.]
- Morel FMM. 1983. Principles of Aquatic Chemistry. John Wiley & sons (NY),

Re: [rooted] aquatic plants readily take up iron from the water, even when
planted in iron containing substrates.
- Basiouny FM, Garrard LA and Haller WT. 1977. Absorption of iron and growth
of Hydrilla verticillata (L.F.) Royle. Aquat. Bot. 3:349-356.
- Cooley TN, Dooris PM, and Martin DF. 1980. Aeration as a tool to improve
water quality and reduce the growth of Hydrilla. Water Res. 14:188-194.
- DeMarte JA and Hartman RT. 1974. Studies on absorption of 32P, 59Fe, and
45Ca by Water-Milfoil (Myriophyllum exalbedescens fernald). Ecology

Greg Morin wrote:

"...I didn't say anything about this reaction taking place or not taking
place in my
conversation with Ryan."

I know that you didn't make that claim - I realized that it was Ryan
connecting the dots....

"Since we are still selling quite a lot of Flourish and Flourish Iron,
I would have to conclude that people are not having massive algae
outbreaks using these products ;-). Thus it follows that the algae
are not able to utilize the gluconate bound iron and the plants are
(or that the plants are able to use it many orders of magnitude more
rapidly then algae)."

Mmmmmm...... I don't know how scientifically valid it is to claim that algae
cannot use gluconate bound iron based upon the sales volume of a product....
in my mind, it doesn't follow at all (even though the supposition that algae
cannot use gluconate bound iron may very well be true). The sales figure for
the product say more for the effectiveness of the advertising behind it than
they do for anything else. <g>

In ALL of this discussion regarding iron and the possible effects of actinic
light upon it, will everyone please remember that I'm quoting from Diana
Walstad's book, not making these claims personally. The way things get cut
and pasted around here, it can be quite easy for things to be taken out of
context and attributed to the wrong source. I didn't know such a thing could
happen but figured that the beat way to find out for sure would be to post
the idea here and let some real experts have a go at it.


James Purchase