Plutonium Marker for the Great Acceleration by Intensified Human Activities

Abstract

There has been a sharp rise in the extent and scale of human activities since the mid-20th century, termed the “Great Acceleration”, and nuclear activities are one of the defining technological processes for this period. ^239,240Pu released by atmospheric nuclear weapons tests provides an ideal chronostratigraphic marker for labeling this change due to its global fallout feature, temporal mutation, and long half-lives. However, the accumulation dynamics of plutonium from atmospheric deposition to preservation in the sediment is still controversial. Three sediment cores collected from two maar lakes with high-quality chronology were analyzed for ^239,240Pu. The first high-yield thermonuclear test (31st October 1952) and the highest global tests in 1961–1962 were identified, respectively, as the first rapidly increased ^239,240Pu in 1953 and peaked in 1963. In anoxic Lake Sihailongwan (SHLW), scavenging Pu from the water to sediment was accelerated due to the major particulate associated forms of Pu(III) and Pu(IV) and rapidly elevated dust flux when ice-melting occurred in every spring. The desorption of Pu from beneath sediment to the lake water and resorption by sediment particles were stronger in shallow and oxic Lake Huguangyan. Therefore, the first rapid increase of ^239,240Pu in 1953 and peak in 1963 accompanied by rapid scavenging and well preservation of plutonium provide a robust time marker for the “Great Acceleration”, and this marker nearly permanently exists in such kind of lake sediment similar to Lake SHLW.