Measurement of plutonium isotopes, 239Pu and 240Pu, in air-filter samples from Seville (2001-2002)

TL;DR

This study measures and analyzes the seasonal variation of plutonium isotopes in air samples from Seville, revealing correlations with mineral dust and supporting the influence of Saharan dust intrusions.

Contribution

First temporal baseline data of 239Pu and 240Pu in Seville's atmosphere, linking plutonium levels with mineral dust and Saharan dust influence.

Findings

Maximum plutonium levels during summer months

Average 240Pu/239Pu ratio consistent with fallout plutonium

Correlation between plutonium and crustal dust tracers

Abstract

Since the last nuclear atmospheric test carried out by the People Republic of China in 1980 and since the Chernobyl accident in 1986, the plutonium hasn't been directly released into the atmosphere. However, nowadays, it is still present in the troposphere. This is due to plutonium-bearing soil particles physical resuspension processes. In this work, we study for the first time the temporal variation of plutonium isotopes, 239Pu and 240Pu, baseline concentrations on a monthly basis in surface air from Seville (Spain), and their correlation with some tracers of mineral dust, during 2001 and 2002. The Pu analyses were performed by low-energy Accelerator Mass Spectrometry (AMS). The 239Pu plus 240Pu (239+240Pu) activity levels achieved maximums during the summer period, characterized by the absence of rains, and minimums during the rainy seasons, laying in the range 1-20 nBq per cubic meter. The 240Pu/239Pu two-year average atomic ratio was 0.18(0.03), in agreement with the fallout plutonium. A good correlation with Pu and Al and Ti levels is observed. They are crustal components usually used as tracers of African dust over European countries. The hypothesis of the influence of the Saharan dust intrusions is supported as well through the study of Total Ozone Mass Spectrometer (TOMS) daily images.