Department of Civil, Construction and Environmental Engineering, University of Alabama at Birmingham (UAB), Birmingham, AL, USA.
Department of Civil, Construction and Environmental Engineering, University of Alabama at Birmingham (UAB), Birmingham, AL, USA; Department of Environmental Health Sciences, University of Alabama at Birmingham (UAB), Birmingham, AL, USA.
Sci Total Environ. 2021 Aug 15;782:146831. doi: 10.1016/j.scitotenv.2021.146831. Epub 2021 Mar 29.
Subsurface elevated temperatures (SETs) often occur in landfills and pose great threats to their structural and environmental integrity. Current landfill gas monitoring practices only recommend maintaining certain soil gases percentages, with no integrated strategy for predicting subsurface temperature. As a solution, this paper proposes a comprehensive risk assessment framework specific to SET mitigation. The risk model (R) was constructed by incorporating independent gas variables (methane, carbon dioxide, oxygen, residual nitrogen, and temperature) identified in the existing literature as SET indicators, and analyzing gas-well data from the Bridgeton Landfill. Upon identifying these gas indictors and their safety thresholds, we found a significant association (p-value < 0.05) between safe-unsafe ranges of gas variables and subsurface temperature. Temperatures above 80 °C were found to be associated with 100%, 92.3%, and only 4% of the unsafe ranges of methane, residual nitrogen, and oxygen, respectively. As the correlation between gases and temperature seemed to vary for different gas combinations, we developed the R by incorporating into these correlation coefficients event intensities specific to certain gas combinations, and then normalizing the R scale over a 0-10 range. Over the study period, we identified 22.29% of cases as medium risk at the Bridgeton Landfill and 17.7% as high risk. SETs are governed by different combinations of safe-unsafe ranges of parameters rather than any individual parameters alone. Subsequently, we used a decision tree algorithm to assess the risk types associated with R values. The proposed R can serve as a monitoring and decision-making tool for landfill authorities for managing and preventing SET incidents.
地下温度升高（SET）在垃圾填埋场中经常发生，对其结构和环境完整性构成了巨大威胁。目前的垃圾填埋场气体监测实践仅建议维持某些土壤气体百分比，而没有针对地下温度进行预测的综合策略。为此，本文提出了一种针对 SET 缓解的综合风险评估框架。风险模型（R）通过将独立气体变量（甲烷、二氧化碳、氧气、残余氮气和温度）纳入其中来构建，这些气体变量在现有文献中被确定为 SET 指标，并分析了布里奇顿垃圾填埋场的气体井数据。在确定了这些气体指标及其安全阈值后，我们发现气体变量的安全-不安全范围与地下温度之间存在显著关联（p 值<0.05）。发现 80°C 以上的温度分别与甲烷、残余氮气和氧气的不安全范围的 100%、92.3%和 4%相关。由于气体和温度之间的相关性似乎因不同的气体组合而异，因此我们通过将特定气体组合的事件强度纳入这些相关系数中来开发 R，然后将 R 范围归一化为 0-10 范围。在研究期间，我们确定了布里奇顿垃圾填埋场中有 22.29%的情况为中等风险，17.7%为高风险。SET 受不同的安全-不安全参数组合而不是任何单个参数的控制。随后，我们使用决策树算法评估与 R 值相关的风险类型。所提出的 R 可以作为垃圾填埋场管理当局的监测和决策工具，用于管理和预防 SET 事件。
