Conversations with a Really Smart Guy (RSG)

njh

This is good stuff! My experiments of course were only looking at the solubility of iron oxides in water at various pHs, but using biological action, as steve correctly points out, is a whole different approach.

Now it's good to try adding nails, but how are you going to show that your experiment actually did something. You're going to need to devise a hypothesis that you can falsify. I was using a chemical test for iron, but the problem in this system is that the iron will be removed by the plants.

So how are you going to determine whether the contraction achieves anything?

janethesselberth

Hypothesis: A Biological Iron Chelator (BIC(TM)) can be constructed such that it increases the available soluable iron in the water by biologically converting the iron in the BIC.

Well, I don't have two systems to run in parallel but one with a BIC and one without. That would be best, of course.

I do have 2 cabbages that are showing signs of deficiency. What if I spray one with a foliar spray of chelated iron, and leave the other alone? The sprayed cabbage would recover quickly, and the other would recover more slowly or not at all.

Or I could measure iron in the water before and during the BIC's operation. Even though the plants would be absorbing iron, I'd still expect to see a rise in the iron level.

Any suggestions?

njh

Can you ask your knowledgable friend what provides the energy to reduce the Iron? It's not oxygen (we removed that, and rust is already reacted with oxygen), it's not Nitrogen(we removed that). Other candidates off the top of my head are sulfur, phosphorous or some organic molecule. If it really does work it suggests an alternative approach to iron refining - reduce the oxide biologically and concentrate (somehow

Industrially, iron is reduced using carbon monoxide, which would suggest the oxidation of an organic molecule for energy. However, which organic molecules can we rely on being available in our water?

I don't know what would make for a believable experiment. I suspect you won't be able to afford a sufficiently precise test to detect the change, especially if the equilibrium is pushed a long way towards iron deficiency. Your idea of using a foliar spray is a good one. Perhaps start there and see how it goes. You should be careful about washing it off.

My iron test was to use tannic acid (which turns black in the presence of iron) and to titrate to known level. But this test is not accurate to the levels we are looking for. Tannic acid prevents uptake of iron, so you must test on a sample.

We also don't know whether steve's observation is due to rust being reduced, or in fact the metalic iron underneath reacting with another anion such as Cl or SO4. This would not change the usefulness to us, but would suggest that the bioreactor is not necessary. (on the otherhand, after civilisation collapse we may not have any iron to run our AP systems

.

steve

i'm sure a tonne of scrap metal (read car) per person would service the iron needs of an AP system for a long time

RupertofOZ

Well tell me if I'm wrong..... :wink:

Quote:

From one of the articles I linked to ...
The affinity of iron oxides and hydroxides for phosphorus is thought to contribute to phosphorus limitation to net primary productivity in humid tropical forests on acidic, highly weathered soils. Perennially warm, humid conditions and high biological activity in these soils can result in fluctuating redox potential that in turn leads to considerable iron reduction in the presence of labile carbon and humic substances. We investigated the effects of reducing conditions in combination with the addition of labile carbon substrates (glucose and acetate) and an electron shuttle compound on iron reduction and phosphorus release in a humid tropical forest soil. Glucose or acetate was added to soils as a single dose at the beginning of the experiment, and as pulsed inputs over time, which more closely mimics patterns in labile carbon availability. Iron reduction and phosphorus mobilization were weakly stimulated by a single low level addition of carbon, and the addition of the electron shuttle compound with or without added carbon. Pulsed labile carbon additions produced a significant increase in soil pH, soluble iron, and phosphorus concentrations. Pulsed labile carbon inputs also promoted the precipitation of ferrous hydroxide complexes which could increase the capacity for P sorption, although our results suggest that rates of P solubilization exceeded re-adsorption. Plant and microbial P demand are also likely to serve as an important sinks for released P, limiting the role of P re-adsorption. Our results suggest that reducing conditions coupled with periodic carbon inputs can stimulate iron reduction and a corresponding increase in soil phosphorus mobilization, which may provide a source of phosphorus to plants and microorganisms previously undocumented in these ecosystems.

From this ....

Quote:

The affinity of iron oxides and hydroxides for phosphorus is thought to contribute to phosphorus limitation to net primary productivity in humid tropical forests on acidic, highly weathered soils.

Perennially warm, humid conditions and high biological activity in these soils can result in fluctuating redox potential that in turn leads to considerable iron reduction in the presence of labile carbon and humic substances.

Given that many members systems tend to ....

Acidity....
could be described as "highly weathered" due to constant flood and drain ...
are often inside, under shade or in greenhouses - warm, humid...
and have high biological activity - the whole AP concept ...
and tend to suffer from Phosphorus defeciencies...

Then I think the results indicated within these extract are highly relevant...

Quote:

Pulsed labile carbon additions produced a significant increase in soil pH, soluble iron, and phosphorus concentrations.

Pulsed labile carbon inputs also promoted the precipitation of ferrous hydroxide complexes which could increase the capacity for P sorption, although our results suggest that rates of P solubilization exceeded re-adsorption.

Plant and microbial P demand are also likely to serve as an important sinks for released P, limiting the role of P re-adsorption.

Would suggest that the addition of carbon... (glucose and acetate were used)....

Increases pH.... Increases soluble iron and phosphorus....

Summarised ....

Quote:

Our results suggest that reducing conditions coupled with periodic carbon inputs can stimulate iron reduction and a corresponding increase in soil phosphorus mobilization, which may provide a source of phosphorus to plants and microorganisms previously undocumented in these ecosystems.

So ... is it as easy as including periodic small doses of chelated iron, or rusty nails, and some glucose and acetate?????

Wonder what sort of delivery mechanism and concentrations/solution of acetate would be safe???

NJH.... you're our scientist... along with your friend Janet..... could you both research further???

NJH... regards the actually mechanism, you mention Sulphur and "Phosphorus.... could you read this link and interpret ??

http://www.publish.csiro.au/paper/SR9930493.htm

njh

So that first paper is saying that Phosphorous is being tied to iron hydroxides (rust) which limits its bioavailability. But by switching to a reducing environment (anaerobic with enough sugar) the iron is reduced (not necessarily available for plants though) to a form which can't hold the P. Much of the P is then thought to be immediately absorbed by the roots (which is a source of P which was not realised before).

What does this mean? It means that if you have rust in anaerobic conditions and a reliable supply of a suitable sugar you will release P from your media. It doesn't directly tell us about Fe.

The second paper doesn't want to open for me (will look again tomorrow). From the abstract it sounds like acid soils have more available Sulphate ions (which is surprising as SO4 tends to be an acid). Nothing about Fe though. If I get a chance I'll read through the CSIRO stuff on Fe in soils.

RupertofOZ

In looking around to answer another post about *now Paul, stop that*, I came across this.... directly references role of iron in soils... and associated role of ethylene...

http://*now Paul, stop that*.info/fafrancis.html

if I read it right (and referring back to previous post)....and using Wiki...

http://en.wikipedia.org/wiki/Acetic_aci ... _oxidation

Then Acetate is essentially Acetic Acid.... (vinegar)....

which is corrosive to metals such as Iron, Magnesium and Zinc.... forming Hydrogen gases and "acetate" salts...

A process of "ethylene oxidation"... fundamental to *now Paul, stop that*'s theories regarding soil conditioning

So where do we get acetic acid from.....

Quote:

For most of human history, acetic acid, in the form of vinegar, has been made by bacteria of the genus Acetobacter. Given sufficient oxygen, these bacteria can produce vinegar from a variety of alcoholic foodstuffs. Commonly used feeds include apple cider, wine, and fermented grain, malt, rice, or potato mashes

Knowing some of the members on here the chances of having any leftovers for the growbeds appear pretty slim.... LOL

njh

Quote:

There is no doubt that ploughing soil does initially increase aeration and does result in intimate contact between the mineral soil and any organic residues. This stimulates microbial activity and nutrients immobilised in the organic reserves are liberated rapidly into the soil. However, unless plants are growing in the soil to take immediate advantage of these mobilised nutrients, they are leached or rapidly fixed in unavailable forms.

I believe this effect is also seen when we add inorganic fertilizers to soils - many are quite toxic to bacteria which causes a massive release of nutrients. Thus the declining usefulness of inorganic fertlizers and the steadily increasing dosage required in current farming.

janethesselberth

Nathan, Maybe it's the carbon that will oxidize. Anthony originally wrote:
"I'm not entirely
sure of all the chemistry that happens with charcoal, but in addition to
providing adsorption sites for cations (metals and ammonium) and hydrophobic
organic molecules (toxins), charcoal also catalyzes all sorts of
reduction/oxidation reactions...."

Does that sound reasonable to you? Chemistry was never my strong point in school, and it's been a long time since my one and only chemistry class.

I'm a do-er. I had to buy a foot of PVC (the guy at the store laughed, but he's used to me now). I have everything I need, and I have the day off tomorrow.

My only fear is that it will work great but stink up my house.

EffigyOfFaith

"Dissimilatory ferric iron-reducing microorganisms gain energy
from coupling oxidation of organic compounds or hydrogen to the reduction of
ferric iron(hydr)oxides," (Muller 2007)

"4Fe(OH)3 + CH3CHOHCOO- + 7H+→ 4Fe2+ + CH3COO- + HCO3- + 10H2O" (Hansel et al. 2003)

steve

So.....................who have we lost on this thread so far..................

Jaymie

slipping, too long ago since chem at uni, brain starting to hurt....

steve

we just lost YOU 'cause rupe is hinting at having to pour cider into your GB, huh?

Delgrade

me so far i think steve

i still read it but i think its gone right over the top

Jaymie

steve wrote:

we just lost YOU 'cause rupe is hinting at having to pour cider into your GB, huh?

any cider that ends up in our system is well filtered before it gets there

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Conversations with a Really Smart Guy (RSG)

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A place to discuss aquaponics