Temporal variations, sources and tracer significance of Polonium-210 in the metropolitan atmosphere of Beijing, China

In the present study, Polonium-210 (210Po) is studied in TSP and coal combustion samples for its potential application in tracing air pollutants. A significant seasonal variation of atmospheric 210Po in Beijing was observed: winter > autumn > summer > spring. During the combustion of coal, 210Po was highly enriched in fly ash but was depleted in bottom ash. Using selenium (Se) as an indicator of coal combustion, significantly positive correlation between 210Po and Se in TSP samples (r2 = 0.705) revealed that coal combustion was a primary source of atmospheric 210Po in Beijing. The mean emission factor of 210Po from industry sector was found to be the highest (1.15 Bq kg−1), followed by the residential (0.308 Bq kg−1) and coal-fired power plant (0.0776 Bq kg−1) sectors. The annual emission inventories of 210Po from three coal consumer sectors (residential, coal-fired power plant, and industry) in 2016 in Beijing were estimated to be 1.49, 0.0729, and 1.36 GBq, respectively. The ratio of radioactive 210Po and stable element Se (210Po/Se) was creatively used as a combined indicator or fingerprint of coal combustion emission, which will contribute to the development of radioisotope tracer technology based on nuclide fingerprint database in the source identification of air pollutants.