When water carries sulfur from coal in a solution, we get acidic water. This is one of the major environmental concerns of the coal industry. Whether coal is mined by underground mining or strip mining (or mountaintop mining), formation is acidic water is a problem. In underground mining, not all the coal is removed and some is left in its place so as to support the mine and the soil above the mine. In strip mining, land reclamation has to be done along with the management of the pit that stored all the overburden. All these (overburden and left-over mine) contain coal and when water passes through this coal, it reacts with sulfur to form acidic water. This water reaches our surface water sources and contaminates them and potentially kills zooplankton and phytoplankton.
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