Field Observations of Regional and Urban Impacts on NO sub(2), Ozone, UVB, and Nitrate Radical Production Rates in the Phoenix Air Basin

In May and June 1998, the Phoenix Air Quality Study was undertaken to assess the processes controlling the photochemical production of ozone. During the study, nitrogen dioxide, PANs, O sub(3), UV-B (UVB) radiation, and air temperature data were collected over a period of four weeks. The data were used to examine the lower pollution transport from the Phoenix air basin into the Usery Pass Recreation Area and to assess the contributions from long-range transport of pollutants from California. Analysis of the data showed that nocturnal boundary-layer chemistry led to the production of NO sub(2) plumes that were transported over the User Pass Recreation Area, resulting in variable nitrate-production rates. During the latter part of the monitoring period, high levels of carbon monoxide and PAN were observed that were attributed to long-range transport of air masses from southern California, while lower observed concentrations of O sub(3) and lower UVB levels were attributed to smoke from a biomass-burning event that occurred in Mexico during the study period. The overall results indicated clearly that air quality in the Phoenix air basin was influenced both by plumes from the urban center and by long-range transport of O sub(3), its precursors, and aerosols.