ANTHROPOGENIC GADOLINIUM IN TRIANGLE AREA WATERS, NC: A CASE STUDY OF WASTEWATER TREATMENT PLANTS

The development of modern technologies has contributed to the increasing release of rare earth elements (REE) into the environment. Large positive anomalies of the REE gadolinium (Gd) were first observed in natural waters in the 1990’s and have since been reported in developed regions across the world. These Gd anomalies are anthropogenic in origin and have been determined to be primarily caused by gadolinium-based contrast agents used in magnetic resonance imaging (MRI). This dissolved gadolinium enters wastewater treatment plants (WWTPs) where it is largely untreated and then released in natural waters. This study analyzes gadolinium concentration of waters in the Triangle area of North Carolina with particular attention to WWTPs. Two WWTPs were selected and sampled for their influent and effluent. Samples from before and after the location of these WWTPs as well as one additional WWTP were also taken. These samples were then analyzed for REE concentrations. Normalization of the measured concentrations show large gadolinium spikes in the samples from the influent, effluent, and downstream samples, but not samples upstream of WWTPs. This is consistent with other observations in developed regions and emphasizes the anthropogenic origin of the Gd from wastewater effluent. Flux calculations show that over half of the riverine Gd is due to WWTP effluent contribution. While the observed concentrations of gadolinium are currently at nontoxic levels, the element is still an emerging microcontaminant to be monitored.