| 摘要: | 地球物理探勘方法係協助土壤及地下水污染問題進行場址評估的可行技術，已經常應用在整治前的污染分布與水文地質調查，更逐漸延伸應用在整治中、後的研究。惟不同的場址、技術與設備均有其限制與瓶頸，地球物理方法不應在缺乏專業素養與詳細規劃，對污染問題認知不足的情況下隨意施測，武斷解釋，而是必須在調查研究前充分瞭解場址環境與污染物特性，因地置宜交互使用各式地物技術，並妥善與環工、地質、地下水、土木、生物化學等其他領域共同整合，完備融入在調查或整治系統中，才能取得有效之成果。
本文藉由數值模擬與真實案例研析，探討地電阻影像法、透地雷達法與頻率域電磁法交互應用於各類型土壤及地下水污染場址之適當時機與方式及所能解決之問題，以提昇運用地球物理方法協助解決土壤及地下水污染問題的價值與正確性，並擴大應用層面。本研究之具體成果為：
一、提出在棄置掩埋型場址與工廠型場址污染調查時各技術應用時機、作業流程與污染判釋邏輯。一般而言，固態廢棄物、純相有機溶劑電阻率偏高，易在透地雷達呈現強反射訊號；重金屬污泥則多具有高導電率的性質，易使透地雷達反射訊號衰減。但地下污染牽涉許多複雜的現象，爐石與飛灰含水時電阻率會下降；油品類可能因生化作用造成電性改變，導電率上升；高導電率的垃圾水與廢污水則可能隱蔽其他污染物的反應。
二、地表地電阻影像法不同電極排列之解析能力及受雜訊干擾影響程度不同。為取得較高解析度的成果，建議在土壤及地下水問題調查時，電極間距應小於3 m，且測線長度應超過目標測深4 ~ 5倍以上，同時應以兩種以上的排列調查成果綜合研判。跨孔式地電阻影像法則須依據場址現況設計並反覆調整排列法，應用在地下水污染場址時，井內電極建議應以小於1 m，時間序列分析時應特須特別維持資料品質與一致性。
三、將跨孔式地電阻影像法有效融入在地下水整治規劃設計之中，採用自行改良設計跨孔式地電阻影像法電極排列，並妥善應用時間序列分析，發展出一套藥劑流布評估系統，以接近4D影像形式描繪整治藥劑在灌注過程中的主要傳輸範圍，配合採樣分析，研判地層中尚待加強改善的區域，並依評估成果規劃次階段改善方式，更能達到精確整治的目標，大幅提升地下水整治的效益。
本研究含附錄共計探討17個台灣真實場址之案例，牽涉之污染問題包含垃圾廢棄物、爐石、土壤重金屬、油品與含氯有機溶劑。另整彙百餘篇地物技術於土壤及地下水污染相關研究之國際發表文獻，以利檢索。期望本研究能作為未來類似場址調查應用之參酌。
;Geophysical exploration methods are used to assist to assess the soil and groundwater contaminated sites, and they have not only been often used to survey the pollution distribution and hydrogeological investigation in pre-remediation, but also extended their applications into the during and post remediation analyses. However, there are limitations and bottlenecks subject to different sites, techniques and equipment. Geophysical methods results should not be randomly and arbitrarily interpreted without sufficient professionalism and detailed planning. Instead a comprehensive understand of the environment and pollutant characteristics of sites before the investigation is a must. Carefully map the properties and the qualities of the contaminated sites to the features of each technology, and then prudently hand-picked out the appropriate technology/ies to evacuate the remediation. At the same time, in order to obtain valid results, all the way from the pre-remediation investigation to the post-remediation evaluation, it is curtail to closely work with professionals from other areas such as from environmental engineering, geology, groundwater, civil engineering, biochemistry and so forth.
By numerical simulation and real case analysis, this present study explores the appropriate timing and manner of applying ERT，GPR，EM interactively onto various types of soil and groundwater contaminated sites, and what problems can be best resolved by using what kind of configuration. Therefore, the value and correctness of geophysical methods in solving the soil and groundwater contamination can be enhanced, and the application level of the methods can be promoted. The actual results of this study are:
First, to propose the best timing of applying each technology, the processes, and the pollution interpretation logic for sites with buried disposal, and factories. In general, solid wastes, and pure organic solvents are with high resistivity, and strong reflection signals often show in GPR, while heavy-metal sludge is with high electrical conductivity properties, and often cause signal attenuations in GPR.
However, underground contamination involves complex phenomena, when the hearthstone is moist, the resistivity drops, where there are biochemicals, oil products can change in electrical properties, and reactions of other pollutants can be concealed by sewage.
Second, in different ERT electrode arrangements, the degree of influence by noise interference varies. Therefore, to achieve higher resolution results, it is suggested that when investigating the soil and groundwater, the electrode spacing be less than 3 m, the survey lines be 4 to 5 times longer than the target sounding, and two or more configurations be arranged for comprehensive judgments. Cross-hole resistivity imaging needs to be designed in accordance with the features of the site, and repeatedly rearrange the setting. For example, at groundwater contaminated sites, in-well ERT electrodes should be less than 1 m, while it is important to specially maintain the data quality and the consistency when applying time-lapse analysis.
Third, an improved array, the cross-hole resistivity imaging method is integrated effectively into the groundwater remediation plan designs. Additionally, a drug spreading evaluation system is developed by using 4D image depicting to outline the major transmission after the agent injection, and with the sampling and analysis methods to locate the formations where need to be enhanced, and according to the assessment results to plan the following remediation stage to achieve the goal of accurate remediation, and improve the groundwater remediation effectiveness.
This study including its appendix contains a total of 17 cases in Taiwan. Contaminations discussed include wastes, hearthstones, soil with heavy metals, and oil and chlorinated organic solvents. Another feature is incorporating more than one hundred of internationally published literature of research in the soil and groundwater contamination for reference. Hope this study can shad light on investigation into sites with similar compositions. |
