Sulfur (S) is the key component of atmospheric acid deposition on ecological system. This study, S components were collected by a four-stage filter pack over a tropical forest from July 2011 to June 2012 at Sakearat Environmental Research Station. The experiment was operated under conditional sampling technique or relaxed eddy accumulation (REA) method. This method was deployed to sample concentration of aerosol particulates and gases over the forest canopy. The REA system consisted of a 3D sonic anemometer, a flow controlling device, a software for switching valve controller and a chemical collecting equipment. Concentration and continuous micrometeorological data were measured on a tower height of 36 meter. The S components were analyzed by an ion chromatography. Deposition fluxes of S components were computed by F = βσ w (C̅ up -C̅ dn). The empirical coefficient value (β) for the REA equation was evaluated to be 0.50±0.04. The deposition flux of S over the forest canopy was determined to be 57.2 and 1.7 ng m-2 s-1, for the dry and the wet season, respectively. The annual mean value for the flux was determined to be 20 ng m-2 s-1. The deposition velocities were evaluated to be 0.7 and 1.0 cm s¯¹, for the dry and the wet season, respectively. The annual mean deposition velocity of S was 0.9 cm s-1.
Phuvasa Chanonmuang, Thailand Institute of Scientific and Technological Research, Thailand
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