Δευτέρα 19 Μαρτίου 2018

Evaluation of mean transit time of aerosols from the area of origin to the Arctic with 210Pb/210Po daily monitoring data

Publication date: August 2018
Source:Journal of Environmental Radioactivity, Volume 188
Author(s): Weihua Zhang, Baki Sadi, Christopher Rinaldo, Jing Chen, Norman Spencer, Kurt Ungar
In this study, the activity concentrations of 210Pb and 210Po on the 22 daily air filter samples, collected at CTBT Yellowknife station from September 2015 to April 2016, were analysed. To estimate the time scale of atmospheric long-range transport aerosol bearing 210Pb in the Arctic during winter, the mean transit time of aerosol bearing 210Pb from its origin was determined based on the activity ratios of 210Po/210Pb and the parent-progeny decay/ingrowth equation. The activity ratios of 210Po/210Pb varied between 0.06 and 0.21 with a median value of 0.11. The aerosol mean transit time based the activity ratio of 210Po/210Pb suggests longer mean transit time of 210Pb aerosols in winter (12 d) than in autumn (3.7 d) and spring (2.9 d).Four years 210Pb and 212Pb monitoring results and meteorological conditions at the Yellowknife station indicate that the 212Pb activity is mostly of local origin, and that 210Pb aerosol in wintertime are mainly from outside of the Arctic regions in common with other pollutants and sources contributing to the Arctic. The activity concentration ratios of 210Pb and 212Pb have a relatively constant value in summer with a significant peak observed in winter, centered in the month of February. Comparison of the 210Pb/212Pb activity ratios and the estimated mean 210Pb transit time, the mean aerosol transit times were real reflection of the atmosphere transport characteristics, which can be used as a radio-chronometer for the transport of air masses to the Arctic region.



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