Tracing the Impact of Aviation on the Atmospheric Nitrate With Oxygen Triple Isotopes

Abstract:

The aviation industry is responsible for ~ 5% of anthropogenic climate change. Jet emission affects ~ in 25 mile radii from airports produce fine particles and concomitant pulmonary and cardio-vascular diseases. These unregulated emissions are of particular concerns for the health of local residents and environment in general due to rapid increase in worldwide air travel in 21^st century. The accurate measurement of emissions from airports therefore requires development of new tools that quantification of aviation related emissions against other road traffic and hence to assess its local and global impacts and provide deeper understanding of nitrate in the environment in general, including the stratosphere where contrails are inadequately detailed

Triple oxygen isotopic analysis of particulate nitrate from a DC 8 engine during a controlled experiment in Palmdale, CA documented the emission of nitric acid (~31 ng.m^-3) at ~ 1m. The oxygen triple isotopic composition of nitrate emitted directly from the jet had δ¹⁸O values (22±1‰) identical to air O₂ (δ¹⁸O = 23.5‰) with a mass dependent isotopic signature (Δ¹⁷O = 0), thus providing a unique isotopic signature of jet nitrate. A year long sampling campaign at one of the world’s busiest airports, the Los Angeles International airport showed the contribution of NO₃ varies from 60 to 90% in summer and winter with variations largely attributed to the change in road traffic as air traffic remains fairly constant throughout the year at LAX. The next step in this is to detect these contributions at distal sites and use this as a signal carrier of atmospheric nitrate and its transport in general in the global biogeochemical system. These aspects will be discussed in the presentation.