Quantitative assessment of the spatial distribution of^(239+240)Pu inventory derived from global fallout in soils from Asia and Europe

Due to the atmospheric nuclear weapon tests carried out,terrestrial environments have been extensively contaminated by global fallout of plutonium(Pu)worldwide.The^(239+240)Pu inventories in soil profiles from undisturbed and flat forest or grasslands(reference sites)mainly from Europe and Asia are considered as important background for evaluating soil erosion.Thus,we conducted a literature survey over an area extending from 2.6°W to 148.9°E and from 53.2°S to 76.6°N,with the purpose of analyzing the spatial distribution of^(239+240)Pu inventories and possible controlling factors.The aim of this work was to derive an empirical model of^(239+240)Pu inventory based on currently available^(239+240)Pu data,precipitation and latitude.The results show that,in general,the latitudinal distribution of^(239+240)Pu inventory was consistent with the UNSCEAR reports.However,the^(239+240)Pu inventories are higher than the UNSCEAR data,especially in the Northern Hemisphere.In addition,close relationships(at the 0.01 significance level)were identified between^(239+240)Pu inventories and annual precipitation and latitude.An empirical formula was therefore developed to estimate^(239+240)Pu inventories in soils based on latitude and precipitation data.However,future research may require more data of measured^(239+240)Pu inventories in soil profiles that can be used to compare,validate and improve upon the accuracy of the inferred empirical equation.