I understand how lead-lined Roman aqueducts would put lead into drinking water — there's nowhere for the lead to go but to stay in the water, since the lead lining is below the water.
But I'm unclear on how lead that had leached into groundwater would remain in groundwater. Shouldn't the lead, being heavier than water, drop out of the groundwater and get caught up in the soil? Isn't this the primary filtering function we expect of soil — the reason aggregate is used as a filtering medium in wastewater treatment?
If not, wouldn't you expect to hear about water tables that have problematically-high natural levels of this or that heavy metal? Wouldn't you expect that it'd be deadly to drink groundwater that had ever flowed through any underground ore deposits?
But I'm unclear on how lead that had leached into groundwater would remain in groundwater. Shouldn't the lead, being heavier than water, drop out of the groundwater and get caught up in the soil? Isn't this the primary filtering function we expect of soil — the reason aggregate is used as a filtering medium in wastewater treatment?
If not, wouldn't you expect to hear about water tables that have problematically-high natural levels of this or that heavy metal? Wouldn't you expect that it'd be deadly to drink groundwater that had ever flowed through any underground ore deposits?