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The Phoenix Urban Haze Study intends to determine the source contributions to light extinction during wintertime months in Phoenix, AZ. Chemical characteristics of source emissions and ambient concentrations are used as input data to models which calculate the contributions to those atmospheric constituents which are causing visibility reduction.

Aerosol, gas, visibility, and meteorological measurements are taken in different combinations at nine sites in Phoenix, three of which are elevated above ground level. One background sampling site is operated southeast of Phoenix to determine the chemical source profile of air masses transported into the urban area. Sight-path extinction measurements are taken at a downtown elevated site to relate the point measurements to atmospheric transmittance. Gaseous species which are associated with secondary aerosol formation are also measured at this elevated site …