Urban emissions measured with aircraft

Area of Science:

• Atmospheric Chemistry
• Environmental Science
• Air Quality Monitoring

Background:

• Accurate urban emission inventories are crucial for atmospheric models predicting pollutant transport.
• Aircraft measurements offer a method for quantifying urban emission fluxes.

Purpose of the Study:

• To assess the capabilities and constraints of aircraft measurements for determining urban emission fluxes.
• To deduce relative emission ratios of key air pollutants in the Athens urban area.

Main Methods:

• Analysis of aircraft measurement data collected in and around Athens, Greece, in September 1994.
• Utilizing ground-based measurements in a street canyon to support aircraft data.
• Determining emission ratios for nitrogen oxides (NOx), sulfur dioxide (SO2), and volatile organic compounds (VOCs) relative to carbon monoxide (CO).

Main Results:

• Aircraft measurements can quantify urban emission fluxes with acceptable precision (better than a factor of 2) only under very favorable meteorological conditions (homogeneous flow, well-mixed boundary layer).
• Ensemble averaging of repeated measurements can improve accuracy.
• High-precision emission ratios were determined: NOx/CO, SO2/CO, and 34 individual VOCs/CO.
• Non-traffic VOC emissions were found to be of similar magnitude to traffic-related emissions in Athens.

Conclusions:

• Aircraft measurements are valuable for assessing urban air pollution, but limitations exist regarding meteorological conditions.
• The study provides crucial data for validating and refining existing emission inventories.
• The significant contribution of non-traffic sources to VOC emissions highlights the need for comprehensive emission control strategies.