The use of moss as an indicator of rare earth element deposition over large area

Nowadays, rare earth elements (REEs) represent a group of emerging pollutants due to their growing application in industry and agriculture, hence, the environmental and human exposures undergone a steady spread. Since REEs can be a part of airborne particulate matter (PM), moss biomonitoring could be a tool for the assessment of their atmospheric deposition. In 2015, moss samples of Hypnum cupressiforme Hedw. were collected at 212 sites across Serbia, and 16 REEs, including Lanthanides (La to Lu), Sc and Y, were determined in the samples by inductively coupled plasma mass spectrometry (ICP-MS). The measured element concentrations were normalised according to different natural reference systems searching for the REE enrichment in the studied environmental samples, and their possible anomalies. The ratios of REEs, specified in the literature, were used to reveal the element origin. In this study, the order of REE abundance in the moss samples was similar to that found in other environmental compartments, which together with the obtained strong correlations among the elements imply their similar origin, probably geogenic. Nevertheless, the ratio La/Sm (5.1) entered the range that characterised coal combustion. In addition, the median enrichment factors (EFs) of the elements calculated according to typical crustal elements, Al and Sc, were not exceeded the value 5 which suggests slightly anthropogenic stake. However, high values of EF REEs (≈40) were obtained in the moss samples from certain regions of Serbia (south and northeast) characterised by the extensive exploitation of coal and mineral deposits, and their further manufacturing or combustion. The results of this study found that the moss is a sensitive tool reflecting the presence of REEs in atmospheric deposition even those in traces (Ho, Er, Tm, Yb, Lu)