Practice exam #3 - QUESTION 2

a)These soils contain iron sulfides, which when dried react with oxygen and form sulfuric acid. Release of this sulfuric acid from the soil can in turn weather other constituents (like clay minerals containing Fe/Al) in the soil and release iron and aluminum (amongst other things). Via reactions with these compounds many excess H+ ions are released, lowering soil acidity.

b)Lime the soil, or do something to contribute to it’s buffering capacity?

I am particularly bad at explaining this stuff…..but I get it! I think….

b) Could you also add organic matter or a clay with high SSA like montmorillonite that would increase the CEC, creating a bigger buffering capacity. Also not sure how you would do it but could you increase the base forming cations (such as Ca, maybe that's what lime does)?

Bennett, increasing the buffering capacity would have minimal impact on the extreme acidity produced by the oxidation of Fe-sulfides (e.g., acid mine drainage). See Blaise's suggestion below.