Anthropogenic gadolinium sources and remediation in highly urbanized river in the Beijing-Tianjin-Hebei (BTH) region, China: Insights from buffer zone and three-dimensional tracer system

Abstract

As a newly emerging microcontaminant, rare earth elements (REEs), especially gadolinium (Gd) in surface water, are attracting great environmental concern in large urban cities. The Beijing-Tianjin-Hebei (BTH) region stands as the preeminent urban agglomeration in northern China, whereas the riverine Gd characteristics and environmental impacts on this region remain inadequate. This study analyzed 27 river water samples in BTH, all of which displayed evidently positive Gd anomalies ranging 1.44–290.75. Spearman correlation indicated the positively correlated REEs concentrations in river water with urban land and cultivated land. A three-dimensional tracing system was established involving anthropogenic Gd (Gdanth) and conventional ion ratios (NO3−/Na+, Cl−/Na+). This system effectively discerned the influences originating from sewage treatment plants, wastewater treatment plants, hospitals, and factories within the BTH region. Gd-based contrast agents (GBCAs) manifest notable potential ecological toxicity and adverse health effects when getting exposed. However, traditional wastewater treatment methods demonstrate limited efficacy in removing these pollutants completely from urban water. To deal with this challenge, this study proposed a new method by combining the latest GBCAs remediation technology with mixing membrane wastewater treatment. This technology may shed light on the potential of an economical and operational procedure of handling medical wastewater specifically in urban water.