Resolving Chernobyl vs. global fallout contributions in soils from Poland using Plutonium atom ratios measured by inductively coupled plasma mass spectrometry

Plutonium in Polish forest soils and the Bór za Lasem peat bog is resolved between Chernobyl and global fallout contributions via inductively coupled plasma mass spectrometric measurements of ²⁴⁰Pu/ ²³⁹Pu and ²⁴¹Pu/²³⁹Pu atom ratios in previously prepared NdF₃ α spectrometric sources. Compared to global fallout, Chernobyl Pu exhibits higher abundances of ²⁴⁰Pu and ²⁴¹Pu. The ratios ²⁴⁰Pu/²³⁹Pu and ²⁴¹Pu/²³⁹Pu co-vary and range from 0.186 to 0.348 and 0.0029 to 0.0412, respectively, in forest soils (²⁴¹Pu/ ²³⁹Pu=0.2407×[²⁴⁰Pu/²³⁹Pu]-0.0413; r ²=0.9924). Two-component mixing models are developed to ap portion ^239+240Pu and ²⁴¹Pu activities; various estimates of the percentage of Chernobyl-derived ^239+240Pu activity in forest soils range from <10% to >90% for the sample set. The ²⁴⁰Pu/ ²³⁹Pu-²⁴¹Pu/²³⁹Pu atom ratio mixing line extrapolates to estimate ²⁴¹Pu/²³⁹Pu and the ²⁴¹Pu/^239+240Pu activity ratio for the Chernobyl source term (0.123±0.007; 83±5; 1 May 1986). Sample ²⁴¹Pu activities, calculated using existing alpha spectrometric ^239+240Pu activities, and the ²⁴⁰Pu/²³⁹Pu and ²⁴¹Pu/ ²³⁹Pu atom ratios, agree relatively well with previous liquid scintillation spectrometry measurements. Chernobyl Pu is most evident in locations from northeastern Poland. The ²⁴¹Pu activities and/or the ²⁴¹Pu/²³⁹Pu atom ratios are more sensitive than ²⁴⁰Pu/²³⁹Pu or ²³⁸Pu/^239+240Pu activity ratios at detecting small Chernobyl ^239+240Pu inputs, found in southern Poland. The mass spectrometric data show that the ²⁴¹Pu activity is 40-62% Chernobyl-derived in southern Poland, and 58-96% Chernobyl in northeastern Poland. The Bór za Lasem peat bog (49.42°N, 19.75°E), located in the Orawsko-Nowotarska valley of southern Poland, consists of global fallout Pu.