theory of arsenic contamination in the groundwater?

Answer 1

Well. Arsenic is a naturally occuring toxin. And actually groundwater can be naturally contaminated by arsenic, but it's more of a problem in poor underdeveloped regions where they still export the natural resources they mine, and then drink groundwater nearby. This disturbance of the ground causes more loose arsenic to get into to the groundwater.

Answer 2

Arsenic was used to get gold and silver out of the rocks in the old mining towns. Since the mines were usually situated next to rivers and streams, arsenic was leached into the streams and eventually the groundwater, causing problems for anyone downstream.

Answer 3

I seem to remember that there was a number of natural minerals that contain arsenic. The most common one i remember was Wolfenite. it occurs with blue-john feldspar and Galena (lead ore). It was used as a natural rat poison for years. Not sure if it is water soluble though. Another common cause of ground water contamination is from flooding of old mines. This is especially relevant with old coal mines. Once abandoned they flood and this water can react with minerals that had sat for millions of years in impermeable rock. This water then seeps into the water table. Sorry i know it's a bit vague but I'm sure you can use it as a start. Research the old lead mining minerals and process.