Analyses of airborne 7Be concentrations in Hong Kong using back-trajectories

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

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Author(s)

  • L. Y L Lee
  • R. C W Kwok
  • Y. P. Cheung
  • K. N. Yu

Detail(s)

Original languageEnglish
Pages (from-to)7033-7040
Journal / PublicationAtmospheric Environment
Volume38
Issue number40 SPEC.ISS.
Publication statusPublished - Dec 2004

Abstract

A total of 71 air samples were collected in Hong Kong area from November 2001 to February 2003 using a high-volume air sampler and a high-volume cascade impactor with five atmospheric pressure stages. The 7Be radioactivity on each stage was measured using a high-efficiency germanium gamma-ray spectrometer. From the radioactivity of stages, the total airborne 7Be radioactivity was determined. The activity median aerodynamic diameter (AMAD) of 7Be-associated atmospheric aerosols was found to be 0.22-1.11 μm and the geometric standard deviation (GSD) was found to be 1.2-10.5. With the assumed mean growth rate (MGR) of atmospheric aerosols of 0.004-0.005 μm h -1 and the size of Aitken nuclei of 0.015 μm, the residence times of 7Be-associated atmospheric aerosols were also found from the AMAD. Three-dimensional 4-day back-trajectories were obtained using the HYSPLIT model from NOAA Air Resources Laboratory. These trajectories were used with the measured 7Be radioactivity to construct regional 7Be intensity fields for four different altitude levels (less than 1000, 1000-2000, 2000-3000 and above 3000 m) with a Geographic Information System (GIS). Low 7Be intensities were found to have advected from low altitudes (less than 1000 m) and oceanic areas. The 7Be intensities increased for the higher intensity field layers. By comparing the time taken for air masses to come from the 7Be source to Hong Kong and the residence time determined from the AMAD of 7Be-associated atmospheric aerosols, good agreement was found if the mean growth rate of 0.005 μm h -1 for atmospheric aerosols was used, and the use of back-trajectories was shown to be satisfactory even up to about 6.5 d. By using the residence time with a MGR of 0.005 μm h -1, the 7Be source was found to be relatively well confined in the areas of Mongolia and southeastern Siberia, which further supported that the association of 7Be source with the Siberian anticyclone. © 2004 Elsevier Ltd. All rights reserved.

Research Area(s)

  • 7Be, AMAD, Anticyclone, Back-trajectories, Geographic Information System, HYSPLIT, Residence time

Citation Format(s)

Analyses of airborne 7Be concentrations in Hong Kong using back-trajectories. / Lee, L. Y L; Kwok, R. C W; Cheung, Y. P.; Yu, K. N.

In: Atmospheric Environment, Vol. 38, No. 40 SPEC.ISS., 12.2004, p. 7033-7040.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review