Evapotranspiration Effects On Sulfur Dioxide Dry Deposition Over A Cassava Plantation In Rayong, Thailand

摘要

Presently, SO_2 has become an important source of acid emission in East Asia region. The long term exposure to SO_2 concentrations can affect human health and environment. Approximately half of the SO_2 is delivered to the earth by the dry deposition process. Therefore, an assessment of SO_2 dry deposition is necessary for understanding its qualitative and quantitative effects. In general, the SO_2 dry deposition was studied in term of SO_2 dry deposition velocity and dry deposition velocity and related with many parameters. In this research, the relationship between the evapotranspiration and the SO_2 dry deposition were investigated. The evapotranspiration is the combined processes of evaporation (from soil and plant surfaces) and transpiration (from plant tissues). This process changes to the opening of microscopic pores on leaf surfaces, the quantity of water vapor in the atmosphere, and used energy for transferring water from liquid to gas phase. In the experiment, the SO_2 dry deposition flux and the SO_2 dry deposition velocity was determined using the Bowen ratio technique. The evapotranspiration was evaluated using the Modified Penman Equation by Pruitt and Doorenbos. All necessary parameters were measured above the cassava plantation at the site in the province of Rayong, Thailand during the period from June to September 2004. The range of significant time was from 8:00 to 17:00. The average dry deposition flux was 0.17 mg/m~2/hr, the average dry deposition velocity was 0.14 cm/s, and the average evapotranspiration was 0.31 mm. These were positively correlated with together. Thus, the results confirmed that the plant activities affect the SO_2 dry deposition. Furthermore, the solar radiation and the soil heat flux are significant factors of the SO_2 dry deposition and the evapotranspiration.