## 6 Oil Shale Pollution Status and Preventive Measures  
Oil shale development has gained significant attention due to its potential as an energy resource. However, the extraction and utilization of oil shale can have detrimental environmental impacts, particularly in terms of pollution [61; 62]. [PERSON] examined the oil shale pollution status in Jordan comprehensively. The primary concern is the potential contamination of groundwater due to the leaching of trace elements and heavy metals from spent shale [63]. The sequential extraction procedure conducted revealed that elements like Ti, V, Cr, Co, Zn, As, Zr, Cd, Pb, and U may pose a risk. Although their concentrations were below the maximum acceptable limits, precautionary measures are necessary to prevent any future contamination. The mobilization and bioavailability of trace elements in spent shale can also lead to soil pollution. Immobilization methods using kaolin as a soil amendment showed reduced mobility for certain elements but not for Ti, V, and Cr. Further research should explore alternative amendments and evaluate their efficacy in reducing the mobility and bioavailability of these elements. To prevent water pollution, it is crucial to establish rigorous monitoring programs for groundwater quality. Regular monitoring of key pollutants should be conducted, and regulations should be implemented to ensure compliance with maximum acceptable limits. Implementing advanced oil shale extraction technologies that prioritize environmental sustainability is essential. Companies should adhere to international best practices and minimize the environmental impact of oil shale extraction. Also, prior to commencing oil shale operations, comprehensive environmental impact assessments should be conducted. These assessments should evaluate potential pollution risks and outline appropriate preventive measures to be implemented throughout the project's lifecycle. The combustion of oil shale in China, particularly notable in regions like Huadian, contributes significantly to environmental pollution through the generation of harmful emissions such as sulfur dioxide (SO\({}_{2}\)), nitrogen oxides (NO\({}_{\lambda}\)), and carbon dioxide (CO\({}_{2}\)). This is primarily due to the unique characteristics of oil shale, including its high ash content, which can reach up to 50%, and the volatile matter released during combustion. Several innovative technologies and strategies have been implemented to manage these environmental impacts. One such strategy is the use of circulating fluidized bed (CFB) combustion technology, which has been successfully deployed in a project with a handling capacity of 2.6 million tons per year of Huadian oil shale. The technology offers several advantages, including high efficiency and low emission of pollutants [64; 65]. Another adopted measure is the co-combustion of oil shale with high sulfur fuel for in-furnace desulfurization, which leverages the high molar Ca/S ratio in some oil shale types. This can reduce sulfur dioxide emissions by up to 90%. Additionally, comprehensive utilization projects have been implemented, transforming waste products from one process into inputs for another. In Huadian, China, a comprehensive utilization system has been established, including oil shale retorting, refining shale oil, burning oil shale semicoke in CFB boilers for electricity generation and heat supply, and producing building materials with oil shale ash. This integrated system significantly reduces waste and pollution, optimizing the use of resources and improving the environmental footprint of oil shale exploitation. These strategies, when used collectively, aim to create a balance between meeting China's growing energy demands and mitigating the environmental impact of oil shale combustion [66]. For in situ oil shale development, it is crucial to implement these preventive measures effectively and adhere to strict environmental regulations to minimize the potential impact on groundwater resources.