Determination and Assessment of Transuranic Isotopes (Pu, Np, Am) Activities and Isotopes Ratios in Antarctic Marine Sediments

Abstract

Due to the nuclear testing in the 20th century, a considerable amount of anthropogenic transuranic isotopes (237Np, 239, 240Pu, and 241Am) was produced, spread, and deposited in the natural environment including Antarctica. Here, activities of 239+240Pu, 237Np, and 241Am in Antarctic marine sediments are determined by ICP-SF-MS, ranging from 0.008 to 0.293 Bq/kg for 239+240Pu, from 0.057 to 0.926 mBq/kg for 237Np, and from 0.027 to 0.277 Bq/kg for 241Am. The dominant source of 237Np, 239, 240Pu, and 241Am in the study marine sediments is global fallout. 240Pu/239Pu atom ratio is measured to be 0.179 ± 0.010 (n = 17) on average, which is consistent with the global fallout of the nuclear weapons tests. Average 237Np/239Pu atom ratio for global fallout is suggested as 0.221 (n = 58), which may be used as a new characteristic index to indicate the current source of Np in a certain region. Due to the different fractionations of Pu and Am by seawater and the enrichment efficiency of marine particles, 241Am/239+240Pu activity ratios in these samples (mean, 2.037 ± 0.040; n = 17) are much higher than global fallout. In addition, 237Np/239Pu atom ratio and 241Am/239+240Pu activity ratio are found to be positively correlated with the sampling depth. Furthermore, the correlation between organic matter and eight heavy metals with transuranic activities is revealed. The cold climate, latitude, and sediment properties have an important influence on the distributions of Np, Pu, and Am in these marine sediments of Antarctic.

Migration of Fallout Radionuclides and Soil Erosion of Hongsongwa Mountainous in China

“…The result was in good agreement with the global fallout standard value of atmospheric nuclear testing, which is 0.18 ± 0.02. Notably, it deviates significantly from the values associated with the Chernobyl source (0.42), nuclear weapons (0.007–0.01), and nuclear reactors (0.23–0.67). − Comparable findings were observed in other regions located at the same latitude . It is evident that the plutonium isotopes observed in the study area originate from global fallout.…”

Sequential Extraction of 239+240Pu and the Vertical Distribution of 239+240Pu, 137Cs, and Heavy Metals in Chang-Bai Mountains’ Grassland Soil

“…Soil is a natural carrier of the terrestrial productivity and the earth’s historical memory, but it is essentially a nonrenewable resource for the human time scale . Yet, this valuable resource is being threatened by anthropogenic production activities such as agricultural production and industrial activities. , These activities released large amounts of heavy metals (e.g., Co, Cr, Fe, Cu, Pb, Cd, and Zn) into the environment in China since early 20th century. − Additionally, human nuclear activities in 1954–1986 released huge amounts of 239+240 Pu (10.87 PBq) and 137 Cs (910 PBq) into the environment. − They were transported into the soil by rainfall or air currents, etc. Some radionuclides will be absorbed by the organic matter or particulate matter, affecting the safety of human food. , In addition, the heavy metals will enter underground water as well as affect the safety of human drinking and food safety. − Therefore, it is very important for the safety of human life to monitor the contents of radionuclides and heavy metals in the environment.…”