Dry deposition of metal elements on surrogate surfaces in the ambient air of central Taiwan

Abstract

Different surrogate surface were used to measure the atmospheric dry deposition flux of total‐particle mass and metals. Three different surrogate surface (overhead projection, T60A20 and Teflon) and two absorbent grease (Apenzion L grease and silicone grease) were compared and investigated. The results of this study indicated that using the Teflon filter coated with the silicone grease yielded the minimum background interference and high reproducibility for metal dry deposition analysis. Dry deposition and particle concentration were sampled simultaneously among three sampling sites (THU, JES and SES) with several dry deposition plates and TSP (total suspended particle) samplers from October 1994 to December 1995 at the central Taiwan. Six individual metals (Ca, Fe, Zn, Pb, Cu and Cd) were analyzed primarily with an AA‐680/G flame atomic absorption spectrophotometer. The results showed that the highest dry deposition flux, concentration of total particle‐mass and metals occurred in the SES sampling site which had the highest mean wind speed. In general, the crustal metals (Fe, Ca) had higher dry deposition velocities, while the anthropogenic metals (Zn, Pb, Cu, Cd) had lower dry deposition velocities for all three sampling sites. The mean dry deposition velocities of total particle‐mass. Fe and Ca were 9.32, 1.93 and 1.67 cm/sec, respectively. The mean dry deposition velocities of Zn, Pb, Cu and Cd were 0.51, 0.32, 0.11 and 0.26 cm/sec, separately. The results also indicated that the deposition velocities were overestimated for mass, Fe and Ca during high wind speed for these three sampling sites compared to previous studies. A suitable sampling device to collect coarse particles is needed to verified this result. In addition, re‐suspension phenomena are significant for these three sampling sites.

Keywords:

• Concentration
• Dry deposition
• Deposition velocity

Notes

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