Scavenged (239)Pu, (240)Pu, and (241)Am from snowfalls in the atmosphere settling on Mt. Zugspitze in 2014, 2015 and 2016

Concentrations of (239)Pu, (240)Pu, and (241)Am, and atomic ratio of (240)Pu/(239)Pu in freshly fallen snow on Mt. Zugspitze collected in 2014, 2015 and 2016 were determined by accelerator mass spectrometry (AMS). For the sub-femtogram (10(−15) g) - level of Pu and Am analysis, a chemical separation procedure combined with AMS was improved and an excellent overall efficiency of about 10(−4) was achieved. The concentration of (239)Pu ranges from 75 ± 13 ag/kg to 2823 ± 84 ag/kg, of (240)Pu from 20.6 ± 5.2 to 601 ± 21 ag/kg, and of (241)Am was found in the range of 16.7 ± 5.0–218.8 ± 8.9 ag/kg. Atomic ratios of (240)Pu/(239)Pu for most samples are comparable to the fallout in middle Europe. One exceptional sample shows a higher Pu concentration. High airborne dust concentration, wind directions, high Cs concentrations and the activity ratio of (239+240)Pu/(137)Cs lead to the conclusion that the sample was influenced by Pu in Saharan dust transported to Mt. Zugspitze.