Sulfides (pyrite, other sulfides) oxidize (give away electrons) to electron donors (oxygen, iron), in this process, water hydrolyses and releases H+/H3O+ into water in vicinity of the reacting material.

Smaller grains have a higher surface area to volume ratio and thus will react faster.

AMD is not something that you usually quantify or assess by quality - however, you can characterize by 'water quality'.

"Good" water quality in terms of AMD will mean pH 4-5, and low to moderate metal content.

"Poor" water quality will be anything between about 1.8-3.4 pH and have significantly increased metal and sulphate concentration.

Effect of limestone is difficult to predict. In some cases the actual limestone gets coated in secondary precipitate, which forms an insulting barrier between the acidic water and the neutralizing material.

Usually, however, if limestone is present where the sulphide oxidation is taking place in sufficient quantities and well enough mixed, it can inhibit the acidification.

In this type of environment, partial pressure of CO2 and availability of neutralizing material will be the primary controlling factors on the pH - which should remain circa-neutral as long as NP is sufficient.

If the system remains mostly neutral, using thermodynamic equilibration software such as phreeqci on water samples that have been analyzed using ICP-MS will give you indicative mineralogical controls in your system.

Thank you very much for the explanation, but do you have any books or links or journal about it? If you do that would be very helpful.

My geochemistry bible is "Geochemistry, groundwater and pollution" by Appelo and Postma.

Second edition.

http://www.amazon.com/Geochemistry-Groundwater-Pollution-Second-Edition/dp/0415364280

However, it's difficult to get everything you need out of one book. I'd suggest attending some environmental chemistry, aquatic chemistry, and applied low temperature geochemistry courses at your local university.

Standard second and third year chemistry courses in college are a good starting place to learn fundamental chemical relationships, electron transfer, ion interaction, Ksp functions and how to build and understand chemical formulas and half reactions.

With that as a basis, I'd definitely delve into mine water and mine waste publications. Each year there are several conferences, from the self explanatory "Acid Mine Drainage" to the more vague "Water in mining" or "Mine Closure" conferences. I'm sure there will be some useful papers available in their publication journals - however, many will not be related to your specific subject. Regardless, they will often contain current research reports and will often contain applications of modeling or new ways of tackling/solving problems and may shed light on your specific problem.

There are also some very well regarded online resources hosted by MDAG http://www.mdag.com/

I also have to highly recommend Bill Price's "Guidelines For Metal Leaching and Acid Rock Drainage at Mine sites in British Columbia" , one of the most comprehensive guides for everything from sampling densities, to suggested laboratory testing methods, standardized testing procedures for static (ABA) tests, and even reporting and interpretation.

This guide is available online here:

http://www.empr.gov.bc.ca/Mining/Permitting-Reclamation/ML-ARD/Pages/Guidelines.aspx

Hope that helps. 

The Global Acid Rock Drainage Guide (GARD Guide) is a good online resource atwww.gardguide.com. It has an explanation of the basic geochemistry of acid drainage and chapters on methods for characterization, prevention, and treatment.