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

Abstract

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 PM0.39–2.5 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.