Identifying gravitational settling by combining Chorine and Bromine isotopes: a new method to detect isolated aquifers.

It is becoming more and more important to identify isolated aquifers. Here we show that the combination of chlorine and bromine isotopes have the potential to identify them. In an isolated and immobile aquifer, the main transport processes that can be expected are diffusion and gravitational settling. Both processes are expected to produce non-detectable changes in anion concentration while producing significant isotope variations. We then show that these patterns are indeed found in a case study of a presumably relatively well isolated aquifer .