Atmospheric rare earth elements in a southeastern China metropolis: photoelectric source and associated health risk assessment

Abstract

Rare earth elements (REEs) are commonly used to trace sources and geochemical processes due to their coherent chemical properties and systematic variations. However, with the rapid expansion of their industrial applications, REEs have increasingly become emerging atmospheric pollutants, while their anthropogenic sources and associated health risks remain poorly understood. In this study, a year-long observation (April 2021–March 2022) of total suspended particles (TSP) and size-segregated aerosol was conducted in Nanchang, a major Chinese REE industry city. We found the average annual concentration of total REEs (ΣREE) was in the order of spring > winter > autumn > summer. Most REEs showed low enrichment factors (EFs), suggesting a primarily crustal origin. However, the elevated Ce and Eu EFs, combined with positive Ce and Eu anomalies pattern, indicated anthropogenic influence. A significant positive correlation of Ce and Eu EFs across both TSP and size-segregated samples further suggests a common anthropogenic source. Photoelectric industry emissions were identified as the primary contributors to the observed anomalies, accounting for 39 % ± 18 % of Ce and 24 % ± 11 % of Eu annually. Notably, both Ce and Eu anomalies showed comparable degree across fine and coarse PM, demonstrating the unique particle size distribution characteristics of photoelectric Ce and Eu. While Ce inhalation showed no significant non-carcinogenic health risks in Nanchang, concerns should be raised for workers and residents near photoelectric industry sites due to high Ce exposure levels. Furthermore, the urgent establishment of threshold values for REEs, particularly Eu, is necessary given its notable enrichment.