未飽和層土壤污染整治 - 新式現地化學氧化(ISCO)緩釋整治系統及設備操作展示

一、緣起

美國於1987年至1993年統計推估超過約130噸三氯乙烯(Trichloroethylene, TCE)可能洩漏至土壤與地下水環境中。基於TCE對於人體危害性，各國對於TCE之排放多已進行相關管制措施，台灣於《土壤污染管制標準》中TCE土壤規範濃度為60 mg/kg，《地下水管制標準》地下水規範濃度為0.05 mg/L，飲用水用途之地下水則為0.005 mg/L，美國環境保護署制定TCE飲用水管制標準最高污染容許濃度為0.005 mg/L。截至2024年，環境部環境管理署統計台灣受TCE污染之土壤與地下水污染場址共126處，其中82處污染場址仍然未解除列管，可知約有60%之TCE污染場址仍需進行相關控制與整治。

三氯乙烯屬於含氯有機溶劑的一種，屬重質非水相液體(Dense non aqueous phase liquid, DNAPL)，因此當TCE DNAPL意外洩漏進入土壤後，向下遷移的過程中會被土壤吸附，或接觸到低滲透度區土壤及不透水岩層才停止其移動或殘留於該處。台灣TCE污染土壤規範濃度為60 mg/kg，地下水規範濃度為 0.05或0.005 mg/L，儘管法規已嚴格限制，但土壤與地下水管制濃度無直接對應關係，可能導致當未飽和層土壤中殘留相TCE雖然低於土壤規範濃度(< 60 mg/kg)，但受到地表降雨滲流或豐枯水期之地下水位變化導致地下水位面抬升，產生土壤殘留相TCE淋溶作用；抑或是地下水面暴露於土壤孔隙間氣相TCE下，因氣液濃度分配的亨利定律關係，再次造成地下水中受TCE污染而濃度地下水管制濃度。

目前未飽和層土壤污染主要的整治技術包含開挖處理法(Soil excavation)與土壤氣體抽除法(Soil vapor extraction, SVE)。開挖處理法為離地(ex-situ)整治的一種方法，此技術之成本較高且受場址建築物配置的影響，若場址仍處於運作狀態則無法進行整治。SVE工法則是將土壤孔隙中氣相污染物抽出至地表上進行後端處理後排放，屬於現地(in-situ)整治技術的一種，SVE於整治後期常面臨TCE的質量傳輸限制問題，即土壤吸附相TCE傳輸至氣相之速率減緩受限，此外SVE抽取時可能會發生優勢流(Preferential flow)的現象，使氣流會選擇於高滲透度土壤中移動，反而繞過存在殘留相TCE的低滲透度土壤，導致整治成效不佳。此外，現地化學氧化法(In Situ Chemical Oxidation, ISCO)是整治飽和含水層中有機污染物的一項技術工法，其應用為將氧化劑注入場址地表下與污染物進行有效接觸，使其氧化破壞污染物達到整治的效果。然而ISCO技術較不適用於未飽和層，乃因為液態氧化劑無法停滯於土壤孔隙使氧化劑與污染土壤有效持續接觸。

此次工作坊將針對「未飽和層土壤之ISCO緩釋整治系統」之技術進行說明介紹，並展示相關控制系統及機具設備開發一應用於「未飽和層土壤之ISCO緩釋整治系統」，選用於地表下相對穩定之過硫酸鈉(Sodium persulfate, SPS)作為氧化劑，運用滴灌系統之傳輸水分方式，將ISCO過硫酸鈉氧化劑溶液以滲透管經由機電系統控制滲流頻率、水量、流速等參數緩慢傳輸氧化劑至未飽和層土壤，搭配未飽和土壤水流溶質傳輸之Hydrus軟體模擬推估，ISCO整治過程中緩釋ISCO使得SPS可以毛細力吸持停留於土壤顆粒，誘發ISCO反應得以於未飽和層土壤中進行，氧化劑液體亦可停留滲入至低滲透性土壤中，此方式可將ISCO技術應用於未飽和層土壤整治，氧化破壞殘留相污染物及克服ISCO液體輸送優勢流等問題，以降低土壤殘留相污染物，其雖低於土壤管制標準但仍會造成長期地下水污染之潛勢。

主題一 

Forever Chemicals in Soil and Groundwater: Sources, Pathways, and Risks

土壤和地下水中的永久性化學物質：來源、途徑和風險

Per- and polyfluoroalkyl substances (PFAS) have become a defining environmental challenge due to their persistence, mobility, and toxicity. This lecture will explore how PFAS are introduced into soil and groundwater through industrial activities, consumer products, firefighting foams, and agricultural applications. Their unique physicochemical properties—such as strong carbon–fluorine bonds and high resistance to degradation—make PFAS particularly difficult to manage in environmental systems. We will discuss how PFAS migrate through soils, partition into groundwater, and bioaccumulate in ecosystems and humans. Case studies from different regions will illustrate the complexity of contamination scenarios, with a focus on implications for public health and environmental sustainability. The lecture will also emphasize how understanding PFAS transport and fate in the subsurface is essential for effective site assessment and the design of remediation strategies.

主題二

Remediation of PFAS-Contaminated Sites: Emerging Technologies and Practical Applications

PFAS污染場址整治：新興技術與實際應用

The remediation of PFAS in soil and groundwater remains one of the greatest challenges in environmental engineering. This lecture will provide a comprehensive overview of current and emerging technologies being developed and deployed to manage PFAS contamination. Physical and chemical methods—including adsorption, ion exchange, high-pressure membranes, and in situ stabilization—will be presented alongside destructive technologies such as advanced oxidation processes, electrochemical degradation, and thermal or plasma treatments. Biological approaches, while still at an early stage, will also be introduced as promising future directions. Emphasis will be placed on integrated treatment trains, where separation and destruction methods are combined for greater effectiveness. Real-world examples of pilot and field demonstrations will be used to highlight key considerations such as cost, scalability, energy use, and byproduct management. Attendees will gain practical insights into both the potential and limitations of these technologies for soil and groundwater remediation.

主題三

Navigating the Evolving Regulatory Landscape for PFAS Management

應對不斷演變的 PFAS 管理法規策略

As scientific knowledge and public awareness of PFAS risks continue to grow, regulatory frameworks are rapidly adapting to address contamination in soil and groundwater. This lecture will examine the current and emerging regulatory landscape governing PFAS, including drinking water standards, soil and groundwater quality guidelines, and waste management policies. Participants will learn about the complexities of regulating a large class of compounds with varied chemistries and toxicities, as well as the challenges of balancing scientific uncertainty with the need for precautionary action. The lecture will also explore international perspectives on PFAS regulation and cleanup requirements, offering lessons on risk communication, liability, and long-term monitoring. Particular focus will be placed on how regulatory expectations influence remediation strategies and technology selection. By understanding both the science and the policy, professionals will be better prepared to design solutions that are not only technically effective but also compliant with evolving standards.