some refs to al to ph etc
Hi Mick
Ok. I have some interest in what you're discussing here, and would descibe my knowledge of it as 'passing'. I've had a little look around and getting more familiar with the subject.
With regard to the Al/ph content I can say this: It's really not enough to say: 'It was perhaps a bit broad to say that adding more aluminum will not change anything..' when the answer to that, if you take it to its logical conclusion, must be the opposite. Adding aluminum in many of its different forms, will change a lot of things - toxicity is one of them; ph can be another. Here's an example: from:
http://www.scribd.com/doc/52830869/4/Acidity-alkalinity-pH
Aluminum sulphate (alum)
Aluminum sulphate (code FAS - common names Alum or Sulphate of Alumina) can be obtained inliquid or granulated forms and is commonly used as a coagulant. The granular form (chemicalformula - Al2 (SO4)3.n H2O with n typically between 14-18) is most commonly used by Oxfambecause it is relatively easy to freight (as it is not classified as a hazardous chemical), simple totransport by land in sacks and is widely available in all but the remotest areas of the world. It can beadded to water and shaken or stirred vigorously to produce a solution which is suitable for dosing intothe raw water in treatment processes. It does, however, have some detrimental health effects whenused in the long term and its prolonged use is not recommended.Aluminum sulphate coagulates best in a pH range between 6.5 and 7.5 as its solubility depends on thepH of the raw water and is lower outside this range. pH adjustment can be made to improvecoagulation. The addition of acid, usually sulphuric, would be required to reduce the pH, while theaddition of lime or soda ash will increase the pH. Aluminum ions combine with hydroxide ionsduring flocculation, and the addition of alum decreases the pH of the water. The addition of lime (analkaline) will increase the pH and is useful to keep the pH within the optimum range.The dose of aluminum sulphate required for coagulation of any surface water will vary, but willprobably be in the range of 25 - 150mg/litre or 25 - 150g/m
3
(this is the weight of alum, of which only25% of this weight is aluminum sulphate, the rest is water). The correct dose of alum will flocculatesuspended solids in the water together into large "fluffy" lumps. These will then be heavy enough tosettle out the water naturally within an hour or two. The settled water at the top should then be veryclear, i.e. <5 NTU to permit effective chlorination.Under or over dosing can result in inefficient flocculation and lead to aluminium residuals in theproduct water which exceed current WHO quality recommendations (WHO recommend aluminium<0.2 mg/l). For this reason and to ensure the use of an economical dose, it is normal practice to carryout a series of jar tests to determine the optimum dose. A simplified version of this test has beendesigned for Oxfam work in the field, where the normal "laboratory" support will not be available.// end quote
So, here we can see that Al sulfate is used help reach the desired ph in water (and soil, btw). That is unequivocal. It also states: Aluminum ions combine with hydroxide ions during flocculation, and the addition of alum decreases the pH of the water. end//
So you were partially right about the Al ions being part of the problem for plants in Al rich, acid soils.
I don't think it's a good argument to say that it's the sulfate part that makes the change - Al is the primary constituent and Al is toxic, period. Write it out in as many different forms as you like; different manifestations have differing toxicities. I think the previous papers linked showed very clearly the toxic effects of Al on aquatic/plant/bacterial organisms. The same is true of all human and animal life - there are many papers about detrimental effects of Al - even the industry admit it's a problem.
Like this: From:
http://www.ncbi.nlm.nih.gov/pubmed/11130287/
The toxicology of aluminum in the brain: a review.
Yokel RA.
Source
College of Pharmacy and Graduate Center for Toxicology, University of Kentucky Medical Center, Lexington, USA.
ryokel1@pop.uky.edu
Abstract
Aluminum is environmentally ubiquitous, providing human exposure. Usual human exposure is primarily dietary. The potential for significant Al absorption from the nasal cavity and direct distribution into the brain should be further investigated. Decreased renal function increases human risk of Al-induced accumulation and toxicity. Brain Al entry from blood may involve transferrin-receptor mediated endocytosis and a more rapid process transporting small molecular weight Al species. There appears to be Al efflux from the brain, probably as Al citrate. There is prolonged retention of a fraction of Al that enters the brain, suggesting the potential for accumulation with repeated exposure. Al is a neurotoxicant in animals and humans. It has been implicated in the etiology of sporadic Alzheimer's disease (AD) and other neurodegenerative disorders, although this is highly controversial. This controversy has not been resolved by epidemiological studies, as only some found a small association between increased incidence of dementia and drinking water Al concentration. Studies of brain Al in AD have not produced consistent findings and have not resolved the controversy. Injections of Al to animals produce behavioral, neuropathological and neurochemical changes that partially model AD. Aluminum has the ability to produce neurotoxicity by many mechanisms. Excess, insoluble amyloid beta protein (A beta) contributes to AD. Aluminum promotes formation and accumulation of insoluble A beta and hyperphosphorylated tau. To some extent, Al mimics the deficit of cortical cholinergic neurotransmission seen in AD. Al increases Fe-induced oxidative injury. The toxicity of Al to plants, aquatic life and humans may share common mechanisms, including disruption of the inositol phosphate system and Ca regulation. Facilitation of Fe-induced oxidative injury and disruption of basic cell processes may mediate primary molecular mechanisms of Al-induced neurotoxicity. Avoidance of Al exposure, when practical, seems prudent.
Re: your assessment of quantity
I think you're making a basic error here. You seem to be suggesting that simply adding more Al wouldn't matter as there is already lots there naturally. Well, if you added a very small amount of salt (there naturally) to water (also natural) then you would affect a great change in the qualities of both elements, particularly the water, to the point that you wouldn't want to drink it (also changes conductivity etc etc). So, you see, it's not as simple as you make it sound. It is right to say that Al (in certain forms) plays havoc with ph levels - it makes them go down, dramatically; and then, in that environment it's more likely Al would be taken up by plants at those more acidic levels; so it's a symbiosis in some cases. Also on quantities: if you keep adding more, then there is more available to take up. It's logical to conclude that in those circumstances - more available - that more can be taken up, therefore increasing the likelihood of toxicity. A vicious cycle leading to lethality.
I'm having a closer look at this argument as it's not as clear cut as you might think, in my opinion. I think there might be another point to that as well - there is one other thing that stands out in your disagreement with unreg (I'll stand up a bit for the other as they're not here): the elements to this argument encompass many 'disciplines', science is only one. I do agree with that. If I think I have anything more to say, then I'll come back to you. In meantime, hope that's helped to clear up some misconceptions on the sub-matter discussed here.
If - and I mean if - there is some sort of 'aerosol operation' going on? Well, I'm sure I don't need to tell you there are also thousands of epidemiological reports on the effects of particulates on health. All particulates are harmful, toxic or not (depends on size, but toxic is worse, ofcourse). So if any are being released, it's a very bad idea.
best
Dave