Rare Earth Elements in Moss in Sweden Spatial Patterns and Temporal Comparisons

Abstract

Rare earth elements (REEs) are increasingly used in modern technologies such as wind turbines, electric vehicles and electronics. Despite their growing importance, there is still limited knowledge about how these elements spread and behave in the environment. Mosses are often used as biomonitors of air pollution due to their ability to accumulate elements directly from atmospheric deposition. This thesis investigates temporal and spatial patterns of REEs in Swedish moss between 2015 and 2025, compares Swedish concentrations with those reported in international studies and evaluates correlations between REEs and selected metals in order to assess potential sources. The work was based on concentration data from moss samples collected within the Swedish national environmental monitoring programme. Samples from 2015 and 2025 were analysed using descriptive statistics, temporal comparisons and GIS-based spatial analysis. In addition, enrichment factor calculations and correlation analyses with aluminium (Al), lead (Pb) and antimony (Sb) were carried out to support interpretation of REE sources and behaviour. The results showed that REE concentrations in Swedish moss were generally low and followed the natural abundance pattern of the Earth's crust, with light REEs (LREEs) occurring at higher concentrations than heavy REEs (HREEs). Similar spatial distributions were observed in both 2015 and 2025, with somewhat elevated concentrations mainly in southern and central Sweden. Most REEs showed modest increases in concentration between 2015 and 2025, while the overall spatial patterns remained similar. Strong correlations between REEs and aluminium indicated that crustal material is an important contributor to the observed concentrations. However, local hotspots and enrichment patterns suggested that anthropogenic influences may occur in specific areas. Overall, the results suggest that REEs in Swedish moss are predominantly influenced by natural background sources, although the observed temporal increases and local enrichment indicate that continued environmental monitoring remains important.