Enhanced polonium concentrations in aerosols from the gulf oil producing region and the role of microorganisms

This study provides the first data set of²¹⁰ Po and²¹⁰ Pb activity concentrations in the organic and inorganic components of several particle size classes of aerosols collected at two sampling stations in Kuwait. The²¹⁰ Po 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 PM_{0.39–2.5 µm}, most of the²¹⁰ Po activity was carried by this aerosol fraction. At the two sampling stations, the²¹⁰ Po/²¹⁰ Pb 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 in²¹⁰ Po 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 the²¹⁰ Po concentration in the organic component was one order of magnitude higher than the²¹⁰ Po concentration in the inorganic component, in contrast with²¹⁰ Pb, which displayed similar concentrations in both organic and inorganic aerosol components. The²¹⁰ Po 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 atmospheric²¹⁰ Po carried out by microorganisms, which underlies the²¹⁰ Po enrichment process in the organic component of aerosols. This bioconcentration of polonium in bioaerosols was unknown.