Dry and wet deposition of elements in Hong Kong

Abstract

Inductively coupled plasma-mass spectrometry (ICP-MS) was used to characterize fourteen major and trace elements including Al, Fe, Na, K, Mg, Ti, Ba, Cu, Mn, Pb, Sb, Sr, V, and Zn, in dry and wet deposition samples collected in Hong Kong. Calculated model deposition velocities for various elements showed that marine elements such as Na, Mg, and Sr exhibited the highest deposition velocities (from 1.0 cm s − 1 to 1.2 cm s − 1), while pollution elements including V, Sb, and Pb had the lowest deposition velocities (0.2 cm s − 1). The positive correlation of deposition velocities between crustal and marine elements suggests that the deposition velocities were influenced by the particle size in addition to other factors such as wind speed and humidity. A comparison between modeled dry fluxes (the indirect method) and measured dry fluxes (the direct method) showed that modeled dry fluxes were slightly higher for marine and crustal elements while measured dry fluxes were higher for the pollution elements. Comparisons of measured dry and wet deposition fluxes for various elements in Hong Kong indicated that dry and wet removal processes were of similar significance for crustal and marine elements. However, wet removal was dominant for the pollution elements (93% V, 86% K, 81% Sb, and 75% Pb).