Measurements of volatile organic compounds during the 2006TexAQS/GoMACCS campaign: Industrial influences, regionalcharacteristics, and diurnal dependencies of the OH reactivity

摘要

An extensive set of volatile organic compounds (VOCs) and other gas phase specieswere measured in situ aboard the NOAA RN Ronald H. Brown as the ship sailed in the Gulfof Mexico and the Houston and Galveston Bay (HGB) area as part of the Texas Air Quality(TexAQS)/Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS)conducted from July-September 2006. The magnitudes of the reactivities of CH_4, CO,VOCs, and NO_2with the hydroxyl radical, OH, were determined in order to quantify thecontributions of these compounds to potential ozone formation. The average total OHreactivity (R_(OH,TOTAL))increased from 1.01 s~(-1)in the central gulf to 10.1 s~(-1)in the HGB areaas a result of the substantial increase in the contribution from VOCs and NO_2. The increasein the measured concentrations of reactive VOCs in the HGB area compared to the centralgulf was explained by the impact of industrial emissions, the regional distribution of VOCs,and the effects of local meteorology. By compensating for the effects of boundary layermixing, the diurnal profiles of the OH reactivity were used to characterize the sourcesignatures and relative magnitudes of biogenic, anthropogenic (urban + industrial), andoxygenated VOCs as a function of the time of day. The source of reactive oxygenated VOCs(e.g., formaldehyde) was determined to be almost entirely from secondary production. Thesecondary formation of oxygenated VOCs, in addition to the continued emissions of reactiveanthropogenic VOCs, served to sustain elevated levels of OH reactivity throughout the timeof peak ozone production.