Coal field formation influences on water chemistry

[kzamzow]

I've been told that coal fields in Southcentral Alaska formed under conditions similar to the Powder River Basin and therefore will not have acid drainage. I also know that coal mining in BC has resulted in acid drainage.

I presume that some fields are formed in lacustrine and some in marine environments, and the difference in the level of sulfate that is sequestered and becomes sulfide is the reason for the different water chemistry. But that is just an assumption on my part.

Can anyone tell me about (or direct me to references on) the differences in how coal was formed in Southcentral Alaska, BC, and the Powder River Basin re what we need to look for as drainage chemistry?