HR: 09:48h
AN: A31D-09    [Abstracts]
TI: Spatial distribution of gases emitted from large urban areas derived from SF6 measurements
AU: * Santella, N
EM: santella@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, Columbia University, 61 route 9w, Palisades, NY 10964-8000 United States
AU: Ho, D
EM: david@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, Columbia University, 61 route 9w, Palisades, NY 10964-8000 United States
AU: Schlosser, P
EM: schlosser@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, Columbia University, 61 route 9w, Palisades, NY 10964-8000 United States
AU: Stute, M
EM: martins@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, Columbia University, 61 route 9w, Palisades, NY 10964-8000 United States
AB: A 6 year (1998-2003) long, high-resolution, time series of atmospheric SF6 from Lamont Doherty Earth Observatory (LDEO), ~ 25 km north of New York City (NYC), has shown that SF6 mixing ratios are highly variable and elevated above remote atmosphere values. Subsequent measurements in soil air (which functions as a low-pass filter) around the New York metropolitan area demonstrate that elevated SF6 levels are widespread. Mapping of the elevated SF6 levels caused by local emissions in NYC allows us to determine the region influenced by emissions from this urban area. To determine if such elevated SF6 levels are typical for large US cities, soil air measurements were repeated in five major urban areas in the US. In each case, significant elevation of SF6 mixing ratios above remote atmosphere values was observed. SF6 emissions from the electrical industry in NYC are particular high, resulting in average mixing ratios within the city in excess of remote atmosphere values by up to 200 %, with elevated levels persisting out to ca. 200 km. Emissions from Boston, Philadelphia, Washington DC/Baltimore, and Tucson appear average for large cities in the U.S.A. with maximum mixing ratios 50-100% above background, and elevated levels detected over tens of kilometers. Using a simplistic atmospheric dispersion model and emissions records, the observed distribution of average SF6 mixing ratios around NYC can be reproduced. This indicates that studies using similar methods, with higher spatial resolution, coupled with modeling of atmospheric transport may allow independent estimates of emissions of SF6, or other inert gases. Observed distributions of SF6 are indicative of average atmospheric transport patterns, and elevated levels of SF6 in remote areas demonstrate significant influence of air masses from urban areas. Comparison of SF6 timeseries at LDEO and Harvard Forest, 205 km to the northeast, demonstrate transport of individual pollution events.
DE: 9360 South America
DE: 0368 Troposphere--constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting