Arsenic in groundwater is not static. It mobilises, migrates and re-deposits as redox conditions, abstraction patterns and recharge change — which is why a well that tested safe once cannot be assumed safe indefinitely, and why depth-aware siting tools such as the Sediment Colour Tool matter so much in the field.
The original article was unreachable when the site was rebuilt. This placeholder preserves the item in the news archive; please restore the full text.