Sensitivities of Atmospheric Composition to High-Altitude Vehicles Emissions
This thesis explored the environmental implications of high-altitude transportation, with a focus on civil supersonic transport (SST) emissions. The potential atmospheric impacts of these emissions, including changes in atmospheric composition and air quality, are examined in detail. Previous studie...
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Massachusetts Institute of Technology
2023
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| Online Access: | https://hdl.handle.net/1721.1/151561 https://orcid.org/0000-0001-6672-910X |
| Summary: | This thesis explored the environmental implications of high-altitude transportation, with a focus on civil supersonic transport (SST) emissions. The potential atmospheric impacts of these emissions, including changes in atmospheric composition and air quality, are examined in detail. Previous studies have evaluated global ozone changes and radiative forcing resulting from aviation emissions. However, they have sometimes neglected the variability due to altitude, latitude, and species, which are needed to understand the impacts of these emissions. This study addressed the research gap concerning surface air quality impacts, specifically surface ozone and particulate matter (PM₂.₅) concentrations.
We used the GEOS-Chem chemistry-transport model to quantify the atmospheric sensitivities linked to civil supersonic transport, specifically evaluating the consequences of four distinct supersonic emission inventories on surface ozone, global column ozone, and PM₂.₅ concentrations via forward sensitivity analyses. Under scenario A, the established ceiling altitude of 21 km and a total fuel burn of 122 Tg corresponded with a decrease of 0.48 ppbv in population-weighted mean (PWM) surface ozone. This change is attributable to contributions from NOₓ (-0.22 ppbv) and SOₓ (-0.20 ppbv). Additionally, we observed a decline of 14.1 DU in global column ozone, with NOₓ and SOₓ contributing -11.2 DU and -2.8 DU, respectively. In contrast, population-weighted mean (PWM) PM₂.₅ levels rosed by 0.12 μg/m³, with the major contribution coming from NOₓ emissions, accounting for an increase of 0.092 μg/m³, while SOₓ added 0.004 μg/m³. Under scenario B1, where the ceiling altitude was 17 km and the total fuel burn was 43.1 Tg, we estimated a 0.058 ppbv increase in PWM surface ozone. This increase was primarily due to a 0.057 ppbv rise from NOₓ emissions, while black carbon and organic carbon caused a reduction of 0.0005 ppbv. Additionally, we noted an increase in global column ozone (0.14 DU), with NOₓ and water vapor contributing 0.20 DU and -0.026 DU, respectively. PWM PM₂.₅ increased by 0.006 μg/m³, where NOₓ was responsible for 0.0054 μg/m³ and black carbon and organic carbon offset it by 0.00013 μg/m³.
The composition of PM₂.₅ was found to be influenced by the altitude of emissions. In the higher altitudes ranging from 20 to 22 km, sulfate composed 97% of PM₂.₅, and a 15% reduction in PM₂.₅ is linked to nitrate. However, the sulfate proportion decreased, while the nitrate proportion correspondingly increased with the decrease in altitude. For example, in the altitudes bracket between 10 to 12 km, nitrate became the dominant constituent, making up 92% of PM₂.₅, while a 15% reduction in PM₂.₅ was attributed to sulfate.
The Linear Sensitivity Combination (LSC) method was developed and applied, achieving a strong correlation with the GEOS-Chem results (coefficients of determination above 0.96 and 0.99 for scenarios A and B1, respectively). The LSC method was employed to evaluate the implications of fuel composition, illustrating that the selection of fuel – such as a transition to hydrogen fuel, Ultra-Low Sulfur (ULS) fuel, or biofuel – impacts atmospheric composition and overall environmental effects. In scenario A, the population-weighted mean (PWM) surface ozone demonstrated shifts from -0.48 ppbv to -0.30 ppbv with hydrogen, -0.28 ppbv with ULS fuel, and -0.29 ppbv with biofuel. PWM PM₂.₅ concentration showed shifts from an initial 0.12 μg/m³ to 0.013 μg/m³ when hydrogen was used, 0.090 μg/m³ with ULS fuel, and 0.092 μg/m³ with biofuel. This comprehensive study offers understandings into the environmental implications of supersonic transportation. |
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