Geochemical characterization and rare earth elements anomalies in surface- and groundwaters of the Romagna area (Italy)

Highly industrialized and urbanized areas can be affected by microcontamination due to the inefficiency of wastewater treatment plants to remove micropollutants from effluents, with the consequence of reversing them totally or only partially undegraded in the environment. Gd, one of the rare earth elements (REE) group, can be considered as a tracer of wastewaster effluents contamination. It is commonly used as contrast agent in magnetic resonance imaging and it can be detected in hospital and wastewater discharges. In this study, surface- and groundwater quality of the Romagna area was assessed, with a particular focus on REE content in water. The efficiency of two drinking water treatment plants in removing microcontamination was also evaluated comparing REE concentrations at the entrance and exit of the plants. Chemical analyses on a large set of trace elements, as well as major ion content, were performed to geochemically characterize surface- and groundwaters and to investigate possible relations with REEs. The study revealed water chemistry of both surface- and groundwaters mainly controlled by carbonates and clay minerals contribution. As regards REEs, Gd contamination was detected only in surface waters in the northern part of the study area; in the Lamone river, this contamination was accompanied by the detection of La anomalies, reflecting a contaminated environment. The two drinking water treatment plants showed that common water treatment techniques are often inefficient to remove microcontamination.