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

Publication date: Available online 17 October 2017
Source:Journal of Environmental Radioactivity
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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