> wouldn't you expect to hear about water tables that have problematically-high natural levels of this or that heavy metal? Where I live, I get periodic water

> wouldn't you expect to hear about water tables that have problematically-high natural levels of this or that heavy metal? Where I live, I get periodic water quality reports in the mail, with the test results for all kinds of different contaminants. The reports always list the typical source of contaminants; and naturally-occurring metals in the ground is very common. Interesting artifact: A well near my childhood home has unusually high levels of chromium for the town. It's believed to be from when someone was running a car repair shop near the watershed; and they left some brake drums or similar car parts outside.