United States Department of Transportation
i
Use of Isotopic Measurement and Analysis Approach to Uniquely Relate Aircraft Emissions to Changes in Ambient Air Quality
-
2011-06-01
[PDF-1.06 MB]
Details:
-
Creators:
-
Corporate Creators:
-
Corporate Contributors:
-
Subject/TRT Terms:
-
Publication/ Report Number:
-
Resource Type:
-
Geographical Coverage:
-
Corporate Publisher:
-
Abstract:Airports around the nation are considering expansion plans in order to meet increasing demand for aviation transport. There are increasing concerns, as well, about how and to what extent air pollutant emissions from airports contribute to local and regional air quality degradation and hence to negative impacts on human health and welfare. However, it is difficult to quantify the amount, transport, and secondary conversion processes of aircraft emissions, which usually comprise the bulk of airport-attributable emissions. This is due to four reasons: 1. Difficulty of determining the actual amounts of emissions from aircraft and characterizing the chemical speciation. 2. Difficulty of determining, at the particle level, the secondary chemical transformations that occur. 3. Difficulty in detection of the species and identification of the aircraft contribution in a region where air quality degradation is a consequence of emissions from multiple sources, both natural and anthropogenic. For the project described in this report, the technique of stable isotopic measurements was utilized in an attempt to develop and assess the impact of aircraft emissions in a region. The theme was, “Are the aircraft emissions recognizable at the isotopic level in a region and are they separable from other sulfates?” To explore this theme, the project team performed three measurement campaigns at Los Angeles International Airport (LAX) to sample aerosol sulfate and characterize the isotopic composition of oxygen atoms in the sulfate particles. It was hoped that aerosol sulfate from jet engines would be shown to have a distinct isotopic character in comparison to sulfate from other sources such as diesel engines, aiding attribution of degraded air quality to jet aircraft sources. The premise that the oxygen isotopic composition of aerosol sulfate could be used to define jet contributions to a region was ultimately not conclusively supported by the study presented in this report. It appears that at low humidity an isotopic anomaly is preferentially created, as observed in the first Aviation Alternative Fuels Experiment (AAFEX), thus identifying a jet aircraft engine. At the humidity of LAX however, the presence of excess water on the aerosol surfaces dilutes the anomaly. Hence, for assessment of the potential of the technique to be broadly applied, it is likely that only low-humidity areas would be capable of providing the signature, based upon the experiments conducted to-date. Furthermore, unexpectedly low sulfate concentrations were observed in the study, suggesting that jet engine exhaust SO2 oxidation occurs further away from LAX and optimal sampling sites in future studies would need to be done at further distances. However, it is unlikely that increased distance between the source sulfur and the sampling monitors at LAX will show much isotopic anomaly in high humidity conditions (60+ %). Conceptually, the potential remains for isotopic analysis to quantitatively address the contributions from aircraft jet engines to degraded air quality near airports. If future research is performed on this technique, an airport in a dry environment must be selected as an initial candidate so that the methods initially explored in this report can be retried. Monitors may need to be located further away from the airport environment so that engine SO2 has more opportunity to become sulfate.
-
Format:
-
Collection(s):
-
Main Document Checksum:
-
Download URL:
-
File Type:
