Cities and industrial areas metabolize materials and energy. Urban respiration, that is the taking in of oxygen and the expulsion of gaseous pollutants and airborne particulates and aerosols, represents the direct impacts of urban metabolism on the atmosphere. These pollutants have a significant effect on both regional viability and global change issues.
A collaborative effort involving Aerodyne Research Inc., the Departments of Chemical Engineering and Urban Studies and Planning at MIT, the Department of Civil and Environmental Engineering at Washington State University, and the Complex Systems Research Center at the University of New Hampshire, is underway to couple experimental field measurements, including an extensive mobile laboratory and stationary data collection, with an urban air chemistry/dynamics model, and geographical information system (GIS) urban/industrial activity factor maps for field test cities. The integrated mobile instrument suite includes a Zeeman- infrared HeNe instrument for methane detection, Licor NDIR carbon dioxide detector, electron capture detector (ECD) SF6 instrument, a 2-color tunable diode laser system to measure between 2 and 4 trace gases such as CO, ozone, nitrogen oxides, or sulfur dioxide, a TSI condensation nuclei instrument, and a GPS for position monitoring.
We will present results of experimental field campaigns completed to date. Results from initial field measurements in Manchester, NH in Fall 1997 include maps of two important greenhouse gases, methane and carbon dioxide, and maps of canister sample data (stationary and mobile) analyzed for trace gases including various hydrocarbons and halocarbons. We have also investigated the effect of automobiles during rush hour to the build-up of trace gases in the urban environment. We will present preliminary results from more extensive campaigns to be conducted in the spring and summer of 1998. The experiments in these campaigns will be broadened to include the measurement of other trace gas species and the implementation of additional measurement strategies, such as tracer release flux measurements.
Innovative urban air quality and transport models are being developed to aid in field measurement design. The models will also be capable of inversion of the experimentally derived concentration maps and plume flux data to quantify urban area trace gas and particulate emission flux distributions. The models attempt to infer the magnitude and key features of the emissions field in the city from the in situ measurements. Initial results of the modelling effort will be presented.