Investigation of sources of volatile organic carbon in the Baltimore area using highly time-resolved measurements

A multivariate receptor model, UNMIX, was applied to hourly volatile organic hydrocarbon concentrations measured at a Photochemical Assessment Monitoring Station, located in the Baltimore, MD area, during the summer months from 1996 to 1999. Six possible volatile organic carbon source categories were identified, and gasoline-related sources such as vehicle exhaust, gasoline vapor, and liquid gasoline contributed more than half of the total VOC concentration. Natural gas, surface coatings, and biogenic source categories accounted for 13%, 12% and 11% of the total VOC, respectively, when all hourly measurements are considered. In order to investigate possible relationships between each source category and episodes of elevated ozone concentrations, NOx, meteorological variables such as surface wind speed, and temperature as well as the hourly contribution of each source category, obtained from UNMIX, were split into high ozone days and low ozone days. Results of a comparison of diurnal patterns observed on high-ozone days with those of low-ozone days for each source category suggested that biogenic emissions may have contributed significantly to local ozone production during episodes in which the 8 h ozone standard was violated in this area. (C) 2003 Elsevier Ltd. All rights reserved.