Anthropogenic gadolinium as a conservative tracer in hydrology

Surface water and in some cases also groundwaters of industrialised and hig hly populated areas show REE patterns with outstanding positive Gd anomalie s. These are formed by using gadopentetic acid (Gd-DTPA) as a contrast medi um in magnetic resonance imaging. This Gd complex is very stable under natu ral conditions. it is an anion and so not adsorbed onto clay mineral surfac es or particulate organic matter, in contrast to free rare earth element (R EE) ions. Thus, this complex is a pseudo-natural marker, and allows the stu dy of the origin of certain waters and their fate during mixing processes. (C) 2000 Elsevier Science B.V. All rights reserved.