Abstract
The atmospheric signature and potential sources of rare earth elements (REEs) in ambient particulate matter (PM) collected at urban (ZH) and background sites (ZWY) between February 2011 and January 2012 in the Yangtze River Delta region were investigated in this study. The average total concentrations of REEs for TSP, PM_(10) and PM_(2.5) were measured to be 11.98, 9.37, 2.24 ng m^(-3) in ZH, which were 1.9, 1.8, 1.3 times higher than those measured in ZWY. The size distribution pattern of the REEs shows that they are significantly fractionated into coarse particles (e.g., approximately 50% in PM_(2.5-10)). However, La, Ce and Sm are even more enriched in PM with respect to each other and other REEs. It is also shown that Ce contamination is prevalent throughout the study area, which is particularly exemplified in the finer particulate matter fraction; this significant Ce contamination could be primarily attributed to vehicle emissions. Additionally, the REEs' pollution events during the sampling campaign were identified by the time series of the REE ratios. And the contaminations of La, Sm and Ce show clearly wind-induced variations. The enrichment factors for REEs indicate that La, Ce, Nd and Sm originated from a mix of anthropogenic and natural emission sources with small EF values.
Highlights
Ambient particulate matter (PM) pollution is a serious environmental problem in developing countries that are experiencing rapid industrialization and urbanization
The aims of this study are to (1) measure the concentration levels and size distribution patterns of rare earth elements (REEs) in size-resolved particles collected in China and make a global comparison of those data reported in previous studies; (2) describe the geochemical characteristic of REEs in three size fractions; (3) identify REE pollution events during the sampling campaign; and (4) analyze potential sources that may contribute to REE pollution
The ratios of light” rare earth elements (LREE)/heavy” rare earth elements (HREE) in this study are lower than those found in northern China (e.g., Baotou and Beijing), which is consistent with the geographic distribution pattern of REEs in crust in China
Summary
Ambient particulate matter (PM) pollution is a serious environmental problem in developing countries that are experiencing rapid industrialization and urbanization. The measurement of the chemical constituents of ambient PM is critical to evaluate its environmental impact and potential sources (Villalobos et al, 2015). China has the largest proved rare earth reserve of the world and is a major contribution country of REEs for the world’s rare earth market (Zhao et al, 2008). Along with the rapid and widespread application of REEs in industry, agriculture and medical materials in previous decades (Pang et al, 2001; Wang et al, 2001; Zhao et al, 2008), it is necessary to measure their levels in ambient air
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