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

Keywords: Chernobyl; Contamination; Plutonium; Poland; Soils; Isotopic ratios; Inductively coupled plasma, mass spectrometry

Abstract: 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; r²=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.

URL: http://www.sciencedirect.com/science/article/pii/S0265931X03002522