Regional distribution and sources of Au, Pd and Pt in moss and O-,B- and C-horizon Podzol samples in the European Arctic

A cost-effective analytical method for analysing various terrestrial sample materials for noble metals at detection limits in the sub-ppb range has been developed. The method has been used to analyse c. 600 samples of moss, O-, B- and C-horizon samples collected from a large area (188,000 km (super 2) ) in the European Arctic at a sample density of 1 site/300 km (super 2) . For the first time reliable analytical data for Au, Pd and Pt for a large, statistically representative number of samples from four different sample materials can be reported. The regional distribution of Au, Pd and Pt in moss and O-horizon samples provides clear evidence that the Russian nickel industry on the Kola Peninsula is emitting Au and platinum group elements (PGEs). However, maps and profiles for moss and the O-horizon also demonstrate that the emissions of one of the very few and largest Pd emission sources on earth cannot be traced further than 200 km on the ground before reaching background values. The predominant natural geochemical characteristics of the study area are visible in the maps of the B- and C-horizon samples even when using such low-density sampling. Furthermore, the data allow estimation of realistic "background values" for these three elements in the four sample materials. By collecting four interrelated sample materials from a large area it is possible to detect unusual processes leading to the enrichment of certain elements in specific compartments of the ecosystem. Most dramatic is a greater than four-fold higher Pt concentration in the B-horizon of arctic podzols compared to all other media. Platinum concentrations are also slightly higher in the O-horizon than in the C-horizon. Palladium shows a tendency to organic binding. Moss is actively enriching Pd and shows even higher Pd concentrations than in the O-horizon. The highest Au values can be found in the deepest soil layers (C-horizon). Natural, geogenic sources influence Au concentrations measured in moss and the O-horizon as much as industrial emissions.