# Investigating Effects of Landfill Soil Gases on Landfill Elevated Subsurface Temperature
## 5 Results
### Effect of Variable Combinations on Temperature  
Although different documents or regulations regarding landfill operation suggest safe ranges for the mentioned parameters, it is essential to study how well these safe ranges corresponding with the subsurface temperature. We studied how the SET is influenced by various gas parameter combinations with a boxplot of temperature versus different events shown in Figure 6, where 0 is denoted as safe and 1 as unsafe. The observations from the figure are as follows:  
* In four cases, i.e., (temperature = 0, CH\({}_{4}\) = 1, CH\({}_{4}\):CO\({}_{2}\) = 1, O\({}_{2}\) = 0, RN\({}_{2}\) = 0), (temperature = 0, CH\({}_{4}\) = 1, CH\({}_{4}\):CO\({}_{2}\) = 1, O\({}_{2}\) = 0, RN\({}_{2}\) = 1), (temperature = 0, CH\({}_{4}\) = 1, CH\({}_{4}\):CO\({}_{2}\) = 1, CH\({}_{2}\) = 1, RN\({}_{2}\) = 0), and (temperature = 0, CH\({}_{4}\) = 1, CH\({}_{4}\):CO\({}_{2}\) = 1, O\({}_{2}\) = 1, RN\({}_{2}\) = 1), the temperature ranges were wide. The widest interquartile temperature ranges were noticed in the events with \(<\)45% and \(>\)60% CH\({}_{4}\), (CH\({}_{4}\):CO\({}_{2}\)) ratio \(<\)1, RN\({}_{2}\)\(<\)20% or \(>\)20%, O\({}_{2}\)\(<\)5% or \(>\)5% and temperature \(<\)80 \({}^{\circ}\)C. These combinations resulted in temperatures ranging from safe to almost unsafe, although some parameters were in the unsafe range. * The highest positive quartile value for temperature was observed for (temperature = 1, CH\({}_{4}\) = 1, CH\({}_{4}\):CO\({}_{2}\) = 1, O\({}_{2}\) = 0, RN\({}_{2}\) = 1), which represents events with \(<\) 45% and \(>\)60% CH\({}_{4}\), (CH\({}_{4}\):CO\({}_{2}\)) ratio \(<\) 1, RN\({}_{2}\)\(>\) 20%, O\({}_{2}\)\(<\) 5%, and temperature \(>\)80 \({}^{\circ}\)C. Here, the combination resulting in the highest SET did not include an unsafe O\({}_{2}\) range, which contradicts the suggested safe O\({}_{2}\) range. * Only one data point was noticed for the (temperature = 0, CH\({}_{4}\) = 1, CH\({}_{4}\):CO\({}_{2}\) = 0, O\({}_{2}\) = 1, RN\({}_{2}\) = 1) combination, which indicates that the events with \(<\) 45% and \(>\)60% CH\({}_{4}\), (CH\({}_{4}\):CO\({}_{2}\)) ratio \(>\) 1,  
Figure 5: Conditional inference trees on the distribution of four temperature ranges. RN\({}_{2}\) \(>\) 20%, O\({}_{2}\) \(>\) 5%, and temperature \(<\) 80 \({}^{\circ}\)C may be rare. This combination requires more historical data to confirm its rare occurrence. * Four of the combinations (temperature = 1, CH\({}_{4}\) = 1, CH\({}_{4}\):CO\({}_{2}\) = 1, O\({}_{2}\) = 0, RN\({}_{2}\) = 0), (temperature = 1, CH\({}_{4}\) = 1, CH\({}_{4}\):CO\({}_{2}\) = 1, O\({}_{2}\) = 0, RN\({}_{2}\) = 1), (temperature = 1, CH\({}_{4}\) = 1, CH\({}_{4}\):CO\({}_{2}\) = 1, O\({}_{2}\) = 1, RN\({}_{2}\) = 0), (temperature = 1, CH\({}_{4}\) = 1, CH\({}_{4}\):CO\({}_{2}\) = 1, O\({}_{2}\) = 1, RN\({}_{2}\) = 1) representing events with \(<\) 45% and \(>\)60% CH\({}_{4}\), (CH\({}_{4}\):CO\({}_{2}\)) ratio \(<\) 1, RN\({}_{2}\) \(<\) 20% or \(>\) 20%, O\({}_{2}\) \(<\) 5% or \(>\)5%, and temperature \(>\) 80 \({}^{\circ}\)C showed temperatures higher than 176 \({}^{\circ}\)F, whereas the other combinations produced safe temperatures (under 80 \({}^{\circ}\)C) with a probability of more than 75%. * Similar gas parameter combinations were noticed in three combination pairs. For example, the (temperature = 0, CH\({}_{4}\) = 1, CH\({}_{4}\):CO\({}_{2}\) = 1, O\({}_{2}\) = 0, RN\({}_{2}\) = 0) and (temperature = 1, CH\({}_{4}\) = 1, CH\({}_{4}\):CO\({}_{2}\) = 1, O\({}_{2}\) = 0, RN\({}_{2}\) = 0) combinations demonstrate same gas combinations with temperature in both safe and unsafe ranges, which indicates that temperature is insignificantly affected by gas parameters in the gas combination of (CH\({}_{4}\) = 1, CH\({}_{4}\):CO\({}_{2}\) = 1, O\({}_{2}\) = 0, RN\({}_{2}\) = 0). We observed a similar outcome for the gas combination of (CH\({}_{4}\) = 1, CH\({}_{4}\):CO\({}_{2}\) = 1, O\({}_{2}\) = 0, RN\({}_{2}\) = 1) and (CH\({}_{4}\) = 1, CH\({}_{4}\):CO\({}_{2}\) = 1, O\({}_{2}\) = 1, RN\({}_{2}\) = 0).