溫度及土壤含水率對揮發性有機物於土壤相/氣相間分配係數之影響

Abstract

揮發性有機物於土壤中的宿命與傳輸與其氣相吸持之行為息息相關，但大多數的研究多側重於土壤含水率對土壤吸持非極性化合物的影響。因此於本研究中發展一吸持模式，使吾人可同時考慮溫度及土壤含水率對土壤吸持揮發性有機物的影響。本研究是以批次之方式，選用乙月青、甲苯、三氯乙烯及四氯乙烯在溫度於0℃、10℃、20℃、30℃、40℃，土壤含水率於0%、1.1%、2.3%、3.4%、5.8%、11.4% 之條件下，進行氣相吸持實驗；而本研究以HP 5890配備火焰離子偵檢器之氣象層析儀進行定量分析，最後將所得之氣/固相分配係數以多變量分析之方法進行迴歸。結果顯示較高之溫度及土壤含水率對新竹土吸持揮發性有機物有負面之影響。本研究亦將氣/固相分配係數、溫度及土壤含水率進行擬合，得一相關係數大於0.955之模式，而該模式可為吾人預測揮發性有機物於不飽和層中的傳輸，提供吸持相關行為之預測。

Although the fate and transport of volatile organic compounds (VOCs) in soils heavily depend on their vapor-phase sorptive behavior, most studies involving the sorption of VOCs have focused only on soil moisture and nonpolar compounds. Therefore, this work presents a nevel sorption model that simultaneously considers temperature and soil moisture can be developed. To do so, the sorption experiments are carried out using a batch-equilibrium apparatus. Next, vapor-sorption of acetonitrile, toluene, trichloroethylene, and tetrachloroethylene are determined at five temperature conditions ranging from 0 to 40oC and six soil moisture conditions ranging from 0 to 11.4%. Additionally, a Hewlett Packard 5890 Series II GC-FID is employed in analysis of VOCs. Moreover, an ANOVA statistical evaluation of adsorption data for organic vapors on Hsinchu soil is conducted. In this study ,the results indicate that higher soil moisture and temperature affect the VOCs adsorption by decreasing the retention of these compounds on Hsinchu soil. Experimental results demonstrate that the proposed model predicts the partition coefficient of VOCs from vapor phase to soil surface within an accuracy of 0.955 for the relation coefficient value. Furthermore, the proposed model can accurately estimate the sorptive behavior, thus providing further insight into the transport of VOCs in the vadose zones.