[NatureNS] Fundy gypsum

Date: Wed, 16 Nov 2011 23:37:36 -0400
From: "Stephen R. Shaw" <srshaw@dal.ca>
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text-transform: none; white-space: normal; widows: 2; wor
The comments below seem puzzling at first sight.

Reflecting DW's comment (who seems to be knowledgeable about soil  
chemistry), how is it that CaSO4.2H2O (gypsum) could act as a buffer  
for anything?  Calcium sulphate dihydrate is slightly soluble in  
water, and neither the completely dissociated Ca or SO4 ions produced  
from the salt in solution would be expected to have buffering  
properties, or am I missing something?  Is it that the calcium  
releases something from its interaction with some soil component, and  
that this indirect effect can then produce some buffering?  Gypsum  
apparently has been used, in the past at least, to enhance crop growth  
(wheat), but I'm guessing that this effect could be due to fertilizing  
supplementation of either low calcium or low sulphate (calcium is  
involved in lots of cell functions) -- something other than buffering.

It would be interesting to hear some detail on both counts: how any  
buffering effect from dissolved gypsum is thought to come about, and  
how agricultural application of gypsum can sometimes increase crop  
yield.  Maybe someone knows?
Steve, Halifax
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Quoting Doug Linzey <doug.linzey@gmail.com>:
> On 15/11/2011 7:38 PM, Dusan Soudek wrote:
>>   As minerals go, gypsum is probably environmentally the most  
>> benign one there is. It even neutralizes the acid rain that is  
>> ruining our Atlantic salmon, speckled trout, and other fish  
>> populations.
>
(& Doug Linzey wrote) If you have to have a mine in your back yard,  
gypsum would be a good choice. It's a pretty benign mineral. The walls  
of our houses are made of it. It's in some of the food we eat. It's a  
common soil additive. And to address Dusan's last point, it is a salt  
with buffering properties: it can raise the pH of acidic soils and  
lower the pH of alkaline soils...


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