現場底泥電學性質感測貫入器研發

Abstract

由於國內各主要河川於相關法令公告後，每年應至少於豐水期及枯水期各進行底泥定期檢測及品質狀況調查，建立「底泥品質基線資料檔」，以便適時更新河川水體底泥的基線資料檔。相關底泥調查與量測需求，除現有規定之相關取樣標準作業可能受限於取樣空間代表性以及其作業效率，國內外研究計畫均初步建議配合地球物理調查方法，以可大範圍輔助底泥範圍、厚度，甚至汙染潛勢等相關特性之調查，但目前其技術限制因子為探測深度以及實際量化(Quantifying)方法。由於底泥土壤基本物理行為與電學特性，影響電流或電磁波在底泥內傳輸而產生異常，為地球物理探測的電學方法應用提供了探測與量化前提。因此，有必要對於底泥的電學特性進行探討，以增進對電流或電磁波信號測定底泥範圍、厚度以及相關特性的認識與研究。本研究的目的在於發展一現地可直接貫入底泥之感測桿，該量測系統具備容易組裝及操作的特性，有助於探討底泥厚度與對應之電學特性，並配合時域反射技術(Time Domain Reflectometry, TDR)於時域的介電度、導電度量測優勢，以及寬頻介電頻譜量測方法研擬，據以作為電學探測結果解讀與量化分析的依據，並延伸至地球物理試驗結合，提供其電學性質參數率定與驗證使用，以可充分達到快速檢測底泥範圍、厚度與對應可能汙染潛勢調查。

According to recent regulations, sediment properties of major rivers should be conducted at least once during wet season and dry season to establish the sediment quality data base and update the baseline for each major river. Current standard practice of sediment sampling may be limited in terms of spatial representativeness and working efficiency. Geophysical methods are often suggested to complement sampling for investigation of sediment coverage, thickness, and even pollution potential in large scale. However, current geophysical practice has limited investigation depth and lacks quantification approach. The difference in physical and electrical properties of sediment affects electrical current flow and electromagnetic wave propagation in sediment, providing the basis for the application of geophysical methods in sediment investigation. Therefore, there is a need to better understand the electrical properties of sediments to improve interpretation of geophysical methods. The objective of this study is to develop a field measurement penetrometer that is easy to assemble and operate for measuring sediment thickness and profiling electrical properties. The measurement will take advangate of time domain reflectometry (TDR) technique to simultaneously provide apparent dielectric constant and electrical conductivity estimatin by time domain analysis. Wide-band dielectric spectroscopy method will also be developed based on TDR measurement. Penetrometer measurements developed in this study will serve the basis for quantitative interpretation of electrical geophysical method and facilitate fast investigation of sediment coverage, thickess, and pollution potential.