Source Apportionment of Rare Earth Elements in PM2.5 in a Southeast Coastal City of China

In order to study the geochemical characteristics and sources of rare earth elements (REEs) in the PM2.5 in Quanzhou City, 116 PM2.5 samples were collected from three functional areas in the city during each season. The REE compositions and distribution patterns were then analyzed, together with ternary diagrams, to investigate the main provenance of these elements. Additionally, the sources of PM2.5 were traced using a diagram of the Nd isotope ratio versus REE characteristics. The concentrations of the total rare earth elements (FREE), total light rare earth elements (Sigma LREE) and total heavy rare earth elements (Sigma HREE) in the PM2.5 vary across both the four seasons (summer > spring > winter > autumn) and different functional areas (residential and industrial area > residential and commercial area > scenic area). There are significant correlations between FREE in the PM2.5 and the PM2.5 mass concentration in spring, summer and winter but none in autumn. The chondrite-normalized REE patterns in the PM2.5 and potential-source samples are all rightward inclined, with the enrichment of LREE relative to HREE, and display obvious negative Eu anomalies. Results of the La-Ce-Sm diagram demonstrate that the REEs in the PM2.5 of all functional areas are mainly derived from sources other than soil dust. The sources of REEs in the PM2.5 across the four seasons and the reasons for spatial differences in the REEs across various functional areas can be determined via the La-Ce-V ternary diagram. The diagram of Nd-143/Nd-144 versus LREE/HREE suggests that the levels of REEs in the PM2.5 in Quanzhou City are mainly affected by vehicle exhaust, followed by coal combustion and construction dust, and less influenced by soil dust and steelworks emissions.