Temporal and spatial distribution of Platinum Group Elements in rural French metropolitan territory using forest mosses.

Although emissions of platinum group elements (PGEs) have been increasing since the 1970s, their levels in rural areas are often considered negligible. We will demonstrate that there is long-distance contamination of forest ecosystems, and that palladium (Pd), platinum (Pt) and rhodium (Rh) levels are increasing over a 5-year period. PGEs levels were analyzed in mosses collected from 371 of the same forest sites in 2016 and 2021. Our results show that concentrations follow the order: Pd > Pt > Rh. Pd levels are all above the limits of quantification in 2016 and 2021, but they have increased over 5 years. Pt and Rh concentrations in mosses were respectively above the limit of quantification (LOQ) at 234 and 71 sites in 2016 and at 371 and 348 sites in 2021. We have shown that Pt is the element with the highest rate of increase, followed by Rh and Pd. This rate of change over 5 years correlates significantly with the initial concentration in 2016. A study of the Pt/Pd, Pt/Rh and Rh/Pd ratios shows a significant increase, confirming a greater increase in Pt and Rh than in Pd over the period. The study of spatial distribution tends to show that the sources of emissions of the elements are different. Nevertheless, it is necessary to work on the forms of PGEs emissions to gain a better understanding of their bioavailability and their impact on organisms, biodiversity and ecosystem functioning.