鹽度對感潮人工溼地中螢光染料發光與衰減特性之影響

Salinity Effects on Light Emission and Decay of Fluorescent Dyes in Tidal Freshwater Constructed Wetland

本研究為能瞭解於感潮人工溼地進行追蹤劑水力實驗時，鹽度對追蹤劑於溼地質傳過程中干擾其守恆特性環境因素之影響，其探討之環境因素包括溫度、日照之光解作用、礫石固定生物膜、懸浮質等，本研究選用螢光染料為Rhodamine WT （RWT）與Rhodamine B （RB）進行比較探討鹽度之效應，由其結果顯示於無鹽水體中，RWT與RB之螢光釋放強度均隨溫度上升而下降，而鹽度對RWT與溫度間特性關係之影響甚為微小，惟對RB而言，其線性斜率將由-0.2798降為-0.6921，影響頗大。至於RWT與RB受日光照射後，因受光解作用而分解，由此造成螢光強度隨時間成指數型態下降，由本研究之實驗結果可知二者之光解衰減係數（k）頗為相近，然鹽度對二者之影響迥異，RWT之k值由3.1×10^（-3）降為2.2×10^（-3），而RB則由3.0×10^（-3）升為5.4×10^（-3）。另由礫石生物膜及懸浮質之結果可知，前者之吸附效應造成RWT及RB之衰減，後者則不甚明顯，鹽度因改變RWT之表面特性而有促進吸附之效應，而RB則未受明顯影響。因此，以螢光染料Rhodamine WT於感潮人工溼地進行追蹤劑實驗時，鹽度對其螢光釋放特性影響較小，惟有促進吸附之效應。而鹽度對RB則大幅改變其螢光釋放特性並提升光解作用之效應。

To investigate the salinity effects on the hydraulic tests of tidal freshwater constructed wetland by dye tests, the fluorescent dyes, Rhodamine WT （RWT） and Rhodamine B （RB） were employed to explore the mechanisms affecting the conservation processes of the dye tracers. They included temperature, photolysis, fixed biofilm and suspended solid. From the results obtained, in fresh water, the fluorescent intensity released decreased as the temperature increased. For RB, the slope of linear relation would decrease from -0.2798 to -0.6921 when in saline environment. It implied that the calibration relation would be strongly dependent on the salinity. As for RWT, the connection was comparatively weak. In the tests of photolysis, both of RWT and RB were affected and the decay coefficients （k） were similar. In the saline water, it would decrease from 3.1×10^（-3） to 2.2×10^（-3） for RWT and increase from 3.0×10^（-3） to 5.4×10^（-3） for RB. The reduction of RWT and RB resulted from the adsorption was observed in the tests of fixed biofilm without salinity effects. However, it was not so obvious in the tests of suspended solid. In the saline water, the surface characteristics of RWT were changed and the adsorption between fixed biofilm and suspended solid was also enhanced. It resulted in an additional loss of RWT in the saline water. As for RB, it was not affected by the salinity and the adsorption behavior was similar to the one without salinity effects.