Abstract
Atmospheric deposition of ^7Be was measured at a time-series station in the southeast of China (Xiamen) from 2011 to 2013. The deposition fluxes of ^7Be ranged from 0.05 Bq m^(–2) d^(–1) to 7.42 Bq m^(–2) d^(–1), averaging 1.87 ± 0.10 Bq m^(–2) d^(–1). High fluxes occurred in months with northeast monsoon, and low values were observed in the southwest monsoon prevailing months. The significant correlations between ^7Be deposition and precipitation, existing in both northeast and southwest monsoon seasons, suggested the dominant removal of atmospheric ^7Be via precipitation. However, the correlations showed a large slope for the northeast monsoon season, indicating higher ^7Be contents in the atmosphere during the northeast monsoon prevailing months, supported by the precipitation-normalized ^7Be and the temporal variability of ^7Be/^(210)Pb ratios. Such a scenario revealed more intensive exchange of air mass between the stratosphere and troposphere during the northeast monsoon prevailing months. Together with the high pollutant concentrations in ambient air observed in these seasons, the results indicated that the pollutants in Xiamen might enter into the upper troposphere via vertical air mass exchange.
Highlights
Zhang et al, Aerosol and Air Quality Research, 16: 105–113, 2016 corresponding to its half-life
The daily deposition fluxes of 7Be varied from 0.03 Bq m–2 d–1 to 45.1 Bq m–2 d–1 with an average of 3.49 ± 0.41 Bq m–2 d–1 (Table 1 and Fig. 1)
The deposition fluxes of 7Be ranged from 0.05–7.42 Bq m–2 d–1 (Table 2), averaging 1.87 ± 0.10 Bq m–2 d–1, comparable to the values of 0.2–10.6 Bq m–2 d–1 in the low-latitude regions (e.g., Igarashi et al, 1998; Hirose et al, 2004)
Summary
Aerosol and Air Quality Research, 16: 105–113, 2016 corresponding to its half-life. In China, a few studies on 7Be have been reported in several cities, i.e., Shanghai and Guizhou (Lee et al, 2004; Du et al, 2008; Kong, 2012). One of the least polluted cities in southeastern China, experienced the hazy weather recently (Zhang et al, 2013a; Lee et al, 2014). We have little understanding of the haze diffusion in the southeast of China. A time-series station at Xiamen, located in the southeast of China, was selected to examine the deposition of 7Be and its potential application for constraining the diffusion and transport of air pollutants. Together with recorded hazy weather, 7Be could indicate potential dispersal of air pollutants in the southeast of China over a large spatial scope
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