Monitoring of 7Be in surface air of varying PM10 concentrations

In this study, beryllium-7 (7Be) concentrations of surface air were monitored throughout a span of 23 years (1992-2012) in the Taiwanese cities Yilan, Taipei, Taichung, and Kaohsiung. During this period, particulate matter (PM) concentrations, in terms of PM10, were collected monthly from the nearest air-quality pollutant monitoring stations and compared against 7Be concentrations. Seasonal monsoons influenced 7Be concentrations in all cities, resulting in high winter and low summer concentrations. In addition, the meteorological conditions caused seasonal PM10 variations, yielding distinct patterns among the cities. There was no correlation between 7Be and PM10 in the case cities. The average annual 7Be concentrations varied little among the cities, ranging from 2.9 to 3.5 mBq/m3, while the PM10 concentrations varied significantly from 38 μg/m3 in Yilan to 92 μg/m3 in Kaohsiung depending on the degree of air pollution and meteorological conditions. The correlation between the 7Be concentration and gross-beta activities (Aβ) in air implied that the 7Be was mainly attached to crustal PM and its concentration varied little among the cities, regardless of the increase in anthropogenic PM in air-polluted areas.