ALUMINUM TOXICITY IN AGRICULTURE- How it works and how to reverse it;implications in irrigation.

The fact that aluminum is toxic to living arganisms is well documented. What has not been understood is the method of action and how to reverse it. The ability of any aqueous solution including water, blood and urine to carry material in suspension without settling out is a function of a minute, electrical charge on small particles in the solution. These particles (colloids) are usually one micron or less in size and not visible to the naked eye. As long as the particles carry an negative charge of -20 millivolts (Mv) or greater, the solution is stable.
Aluminum is a trivalent cation (three positive electrons) which destroys the electronegative charge on the particles in suspension.A substance with three posive electrons has 6000 times more effect on suspension stability than a substance with one positive electron making aluminum very destructive of supension stability..

As the negative charge on particles is reduced, the small particles begin to clump together and either settle out or look for a receptor with the appropriate charge to attach themselves. Scale in pipes.is a classic example of the principle at work as is biofilm corrosion in pipes and condensers. Algae and biofilms are caused by the same mechanism. Any air conditioner with an aluminum drip pan will have a problem with algae growth in the discharge line though few realize it is the aluminum that causes it.

When the abiltiy of the water.to carry material in solution is destroyed, plants are being fed by water that has almost the same characteristics as distilled water.The water is unable to carry nutrients into the plant and disease will flourish not only from undernourished plants but also from the clumping of other materials in suspension.Many potenially toxic materials are handled in living systems without a problem as small colloids and may even contribute to the vitality of the system. When the charge on the entire system drops below about -10mv., they become toxic to the system. Implications is agriculture.

There are several other principles that affect suspension stability that are germane to irrigation.

1. Lowering the pH, lowers the electronegative charge. Aeration lowers the pH due to the ineraction with atmospheric carbon dioxide (0.03%)
2. Depth of the water in the reservoir has an effect as the top one third will contain about 0.03 carbon dioxide;below thirty feet carbon dioxide may be as high as as 40-50 ppm..
3. Electromagnetic radiation, 60 cycle AC, as from a motor on a pump reduces the charge.
4. Any colloidal system can be "salted out" by the addition of too much salt regardless of the source.

Reversal
The obvious solutions of eliminating salt and aluminum are not, at present, practical. Whats works is this;
1.. For normal irrigation, there are devices which impart a high electronegative charge on water and cause about a 20% drop in surface tension. The effect of the reduction in surface tension is the water will dissolve more nutrients from the soil and carry them to the plant.(.System cost about $3000.00 with almost no maintainence; uses about seven cents of electricity per day.)
2. Coupled with the above, the addition of a small amount of eitherof two mineralized rock dusts in small quantities into the water will stabilze the colloidal solution. (Cost less than $100.00 for most systems) Also a trivalent anion like potassium citrate can be added which has three negative ions.
3. In severe salted out situations, there is a product used in oilfield remediation which may be necessary. Information for products for particular applications is available from esystems@flash.net  or from the author. This is a over-simplification of the whole area of colloidal chemistry dealing with this subject which is little understoood. Most of the more recent texts deal with the more esoteric aspects of Zeta potential, surface charge and colloidal chemistry rather than what I call practical Zeta Potential.

For those interested in a better understanding the following are recommended:
1. Zeta Potential- the complete course in 5 minutes available from Zeta Meter- fax 540 886-3728; sales@zetameter.com .
2.Intoduction to Colloidal Chemistry-Mysels-Wiley/Interscience 1959 edition
3.Control of Colloidal Stabilty through Zeta Potential - Thomas Riddick.available on interlibrary loan as it is out of print. C 1997

by Frank H.

Regarding a recent posting on Alumimum:

> 1.. For normal irrigation, there are devices which impart a high electronegative charge on water and cause about >a 20% drop in surface tension. The effect of the reduction in surface tension is the water will dissolve more >nutrients from the soil and carry them to the plant.(.System cost about $3000.00 >with almost no maintainence; >uses about seven cents of electricity per day.)

First of all, what is surface tension? I have never heard of this as a chemical phenomena. Secondly, we've already gone through several discussions on electro charging water..doesn't seem to be any merit in this. Please check out:
- http://www.mif.org/ion.html on the Microirrigation Forum web site.

Don't mean to sound too skeptical, but I am yet to be convinced of such a technology. Why isn't 'Control of Colloidal Stabilty through Zeta Potential' by Thomas Riddick in a Scientific Journal? or is it? I need more objective facts.

by Richard Mead

Lets see if I can answer your questions one at a time.
1. Surface tension is what holds a drop of water together. Normal water in the US is about 75 dynes/cm as it comes from the tap. (using a Fisher Ring tensionometer). Surface tension is the quality of water that allows a water spider to walk on the surface or allows one to float a needle on the surface. Surface tension is decreased by surfacants, or by increasing Zeta Potential i.e. electronegative charge on colloids in suspension. The water becomes wetter, feels like soft water but without the calcium/sodium exchange from a water softener. Raising water to a boil decreases surface tension to about 55 dynes/cm which causes water to dissolve better. In essence, it is wettter water.
2. As to the comments on ionized water- As with most things, until we understand the mechanism by which things work, results are spotty. The ionization site focuses on magnetic water treatment. The ASHRAE works in keeping down scale in Heating and AC units as do studies by NASA, DOD and the Air Force. The problem is that magnetic treatment will not work consistently and, when it doesn't, and the mechanism of action isn't understood, what do you do then.Looking at the comments on the site, it appears that this is what happened. This has been the case for many of the non-chemical devices for water treatment and we have experimented with at least 20 different ones.
3.There is no magic or mystery in what was described and the science of surface charge and Zeta Potential has been around for 100 years. The practical implications have not been recognized because the frame of reference for most people is ionic chemistry not colloidal. Al toxicity is a colloidal problem that cannot be solved with ionic chemistry.
4. Ridddicks work is a book of 370 pages and it is considered a seminal work in ZP. It will be an eye opener. The implications of this go far beyong agriculture.I would suggest getting the first reference from Zeta Meter on the five minute course. Hope this answers some of your questions.

by Frank H

Frank, Excellent rebuttal.
Now that I've gone through my soil physics memory banks, I do recall studying water surface tension (Hillel: Soil and Water). Thus, I didn't mean to lie when I said I've never heard of this chemical phenomena when actually it's more physical. Nevertheless, I'm puzzled how any of this has relevance to normal irrigated agriculture.

Specifically to:
>The practical implications have not been recognized because the frame of reference for most people is ionic >chemistry not colloidal. Al toxicity is a colloidal problem that cannot be solved with ionic chemistry.

My questions here is; does the plant respond to colloidal chemistry or ionic chemistry? I would think ionic due to the ionic exchange at the soil-root interface. It seems when the pH of a soil is too low, Al ions are toxic to plants, even as low as 1 ppm. Thus, are we to measure and correct this problem using colloidal thinking via changing the zeta potential? What's the difference if its colloidal or ionic if we just need to add lime [CaCO3] to the acid/Al toxic soil?

This is all very interesting and I would like to continue, but let's focus on how drip irrigation per se would implement then contribute to enhancing the soil from such technology. I guess what I'm saying is, this is NOT Zeta-potential-L. So, what would be needed to change the zeta potential of irrigation water which consequently would change the zeta potential of soil-water?

Thanks again Frank for reminding me of my physical chemistry (blush) and enlightening us with an interesting yet curious concept. Any other physical chemist out there yearning to respond?

by Richard Mead

Great! lets stick to the practical.
The effect of impressing a electronegative charge on irrigation water is the following:

1. Elimination of scale and algae in the line although at first there may be an increase as scale formed inside the pipe goes back into suspension.
2. major increase in plant vitality and disease resistance as nutrients including trace chemicals locked up in soil are freed by the change in surface temsion which disolves them..
3. Reduction or elimination of the need for supplemental feeding as the plant can now take up the nutrients that have been unlocked from the soil.

By reducing the artificial feeding, salting out of soils from fertilizer salts is eliminated.
This part I don't understand unlesss Professor Phil Callahan is right about insects being drawn to less healthy plants.In adjacent rows of corn and lima beans (treated vs untreated0 no bean beetle damage and very minor corn borer on the treated without pesticides and normal damage on the untreated using pesticide. Go figure?
A lot of what has been done in the past is treating symptoms. Addressing Zeta potential treats the cause.
When cause is understood, treatment becomes simple. Ocam's razor. I hope this clears some of this up.
PS I am using a new version of netscape and clicking " return to sender" not sender and all recipients. If this isn't going to where it should let me know .

by Frank H.

Zeta Potential of a particle suspended in water can be measured; it is the chemical potential at the boundary between the water which moves with the particle (hydration shell) and the rest of the water. The water itself does not have a zeta potential.
Aluminum (Al) toxicity: This is very dependent on the pH of the soil. Al forms complexes with hydroxyls (OH ions) and the degree of complex formation depends on pH. At a pH of 3, Al is not associated with hydroxyls, consequently it is a simple, hydrated ion in water, with a charge of plus 3. This form is toxic to plants. At higher pH's, the aluminum hydroxide complexes begin to form, and the charge of the complexes varies. It decreases from plus 2.9 to near zero as the pH increases from 3 to about 8. What all this means in terms of flocculation (adding alum (aluminum sulfate)) to enhance flocculation and remove suspended colloids in water and Al toxicity to plants is an interesting subject. I will pose a generalization: The addition of alum to flocculate suspended solids will not cause a problem with Al toxicity unless the pH of the soil solution, to which the treated water is applied, is less than 5.
by J.D. Oster

Thanks for the reply. I agree with your generalization on pH and aluminum toxicity but if we look at that as a symptom and look to the change in zP as the cause the picture changes.. All the studies have focused on ionic changes in solution when unsuccessfully trying to understand the method of aluminum toxicity.

Given that reduction of ph reduces the Zeta potential and the solution is in the -15 to -25mv range, the reduction in zP drops the solution past the threshold of agglomeration; so nutrients are no longer carried as colloids in solution.
This is something for the research guys to determine.

From a practical standpoint, when an electronegative charge is induced artificially on the solution say by electrostatics, aluminum toxicity disappears. No change in pH,; no change in chemistry. Plants suddenly thrive and material like calcium and algae which caused a prolem with clogging of nozzles disappear. There may be an initial period of higher clogging unless the system is flushed. This is due to the material like scale which has adhered to pipe in the past breaking free from the pipe wall. After the initial period, the water will remain clear with no scale or algae.

So If we look at aluminum toxicity as a pure zP problem, a different picture emerges. Even where aluminum toxity is not a problem, the same results occur. In part, the increase in growth and reduction in feeding requirements may be from two factors:

1. By keeping small particles in suspension, they are more bioavailable to the plant. As a corollary, toxic materials such as metals seem to lose their toxicity as colloids. Another one for the research guys.
2. Why surface tension decreases as ZP rises isn't clear but, it clearly does. If you have an explanation for that, it would be appreciated. The reduced surface tension of the water produces wetter water which dissolves material from the soil and makes it bio avaiialble.
All this started 7 years ago when changing the zP of aqueos solutions with no chemisrty change caused impressive effects which didn't fit the ionic model.The zP model accounts for a whole series of analmous effects that have been observed by various experimenters.

by Frank H.