Spatial Pattern of Ground-Level Ozone Concentration in Dallas-Fort Worth Metropolitan Area

The objective of this study was to analyze spatial patterns of ground-level ozone concentration in the Dallas-Fort Worth, Texas metropolitan area. Average daily maximum eight-hour ozone concentration, number of days with concentrations exceeding 75 ppb, average outside air temperature, and resultant wind direction at 20 monitoring stations were compiled for January-December, 2013. Recent estimates of population and vehicle miles traveled were also compiled for 12 counties with ozone monitoring station(s). Ozone levels and resultant wind directions were mapped for representative months in each season. On several days from May-October, eight-hour ozone measurements exceeded 75 ppb. September, followed by August, produced the highest ozone concentrations, as well as the most observations exceeding 75 ppb. Late spring and summer months also showed the greatest range in ozone concentrations; during this time period, sustained southeasterly winds caused distinct clusters of high ozone concentration at the northern perimeter of the study area. However, ozone concentrations at individual monitoring stations were not associated with population or vehicle miles traveled in counties occupied by those stations.