Sulphur dioxide dry deposition flux and velocity in Northern Thailand

摘要

Measurement of dry deposition of atmospheric sulphur species has been conducted recently in the Mae Moh thermal power plant area in Northern Thailand. In this study, a circular water surface sampler (WSS) and a knife-leading edge surrogate surface (KSS) were used to measure directly the sulphate and sulphur dioxide (SO_2) dry deposition loads and fluxes. Sampling was carried out on a daily basis during the dry season. The dry deposition velocity of SO_2 has been calculated using on-site measured sulphate flux and ambient SO_2 concentration data. The average dry deposition flux for sulphate was 57.60 mg/m~2/day; for particulate sulphate, it was 12.76 mg/m~2/day; and for SO_2 gas, it was 34.27 mg/m~2/day. The average dry deposition velocity of SO_2 calculated from the measured flux and concentration was 0.07 cm/s. Results in this study area reveal that the gas phase deposition contributed significantly more than the particulate phase to the overall deposition of sulphur compound.