Seasonal variations of dissolved rare earth elements and anthropogenic gadolinium in the highly urbanized river basin, Busan, Korea

Abstract

Anthropogenic gadolinium (Gdanth) has been reported in rivers as a result of magnetic resonance imaging. We collected seasonal water samples from the Suyeong River Basin, to investigate seasonal variations in dissolved rare earth elements (REEs) and Gdanth in highly urbanized areas. The post-Archean Australian shale-normalized REE patterns indicate a significant influence of terrestrial source inputs during the summer. Although higher concentrations of dissolved REEs were measured in summer than in winter, the Gdanth concentrations exhibited similar levels. During winter, the concentrations of Gdanth showed conservative mixing trends downstream of the wastewater treatment plant (WWTP), whereas no clear trend was observed in summer. Moreover, the estimated daily discharge of Gdanth accounts for approximately 11–22% of the number of MRI tests performed, when the WWTP treats only 6% of Busan area size. Our results suggests that the elevated Gdanth level in the highly urbanized river basin is a major concern.