Enhanced Polonium Concentrations in Aerosols from the Gulf Oil Producing Region and the Role of Microorganisms.

Montaha Behbehani,Nazima Habibi,Fernando Piedade Carvalho,Saif Uddin

doi:10.3390/ijerph182413309

Abstract

This study provides the first data set of 210Po and 210Pb activity concentrations in the organic and inorganic components of several particle size classes of aerosols collected at two sampling stations in Kuwait. The 210Po concentrations in the aerosols (Bq/g) were similar in all of the particle size classes, but as most (91%) of the aerosol load was made of fine fraction particles of PM0.39–2.5 µm, most of the 210Po activity was carried by this aerosol fraction. At the two sampling stations, the 210Po/210Pb activity concentration ratios in the aerosols were similar, stable around the year, and averaged 1.5 (range 1.2–1.9), much higher than the typical activity concentration ratios of these radionuclides in unmodified (background) aerosols, with Po/Pb < 0.1. The aerosol enrichment in 210Po was likely originated from the oil industry, specifically by gas flaring and oil refining in the Gulf region. Radionuclide analysis in the organic and inorganic components of aerosols showed that the 210Po concentration in the organic component was one order of magnitude higher than the 210Po concentration in the inorganic component, in contrast with 210Pb, which displayed similar concentrations in both organic and inorganic aerosol components. The 210Po carrying organic component of aerosols was investigated and it was found to be largely composed of microorganisms with high microbial and fungi diversity, with the phyla Proteobacteria, Ascomycota, and Basidiomycota being dominant among the bacteria and with Zygomycota being dominant among the fungi. Therefore, we are facing an active concentration process of the atmospheric 210Po carried out by microorganisms, which underlies the 210Po enrichment process in the organic component of aerosols. This bioconcentration of polonium in bioaerosols was unknown.

Highlights

This study focused on polonium (210Po) and radioactive lead (210Pb) distribution in Thisparticle study focused on polonium
The aerosol samples collected between February 2019 and February 2020 at the two locations are listed in Table 1, with information on the weight of the particulate material collected in each particulate grain size class and the weight of the organic and inorganic components of the aerosols
At the two sampling stations, the activity concentrations of 210 Pb in the aerosols were comparable in the three particulate size classes and in both the organic and inorganic components, with a mean organic/inorganic ratio of 1

Summary

Introduction

Polonium (210 Po, T1/2 = 138.4 d) and radioactive lead (210 Pb, T1/2 = 22.3 a) are naturally occurring radionuclides that belong to the uranium radioactive decay series. Under the environmental conditions that prevail at the surface of our planet, both radionuclides exist in the solid state, and their presence in the atmosphere is primarily related to the radioactive decay of airborne radon gas (222 Rn; T1/2 = 3.8 d) [1]. In contrast to radon, which is a noble gas with atoms that carry a neutral electric charge, all of the radon daughters are positive ions that are highly particle reactive and, once formed, they become rapidly attached to particles. Polonium-210 ions become attached to aerosol particles within 40 to 180 s after its formation from the radioactive decay of the precursor radon daughters [2]. Dry and wet atmospheric depositions continuously scavenge radon daughter ions from the atmosphere, preventing the formation of a secular radioactive equilibrium between radon and radon progeny and maintaining a very significant radioactive disequilibrium between 210 Pb and 210 Po, with 210 Po/210 Pb ratios that are generally much lower than 0.1 [3]

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Results

Conclusion