Organic aerosol formation downwind from the Deepwater Horizon oil spill.

A large fraction of atmospheric aerosols are derived from organic compounds with various volatilities. A National Oceanic and Atmospheric Administration (NOAA) WP-3D research aircraft made airborne measurements of the gaseous and aerosol composition of air over the Deepwater Horizon (DWH) oil spill in the Gulf of Mexico that occurred from April to August 2010. A narrow plume of hydrocarbons was observed downwind of DWH that is attributed to the evaporation of fresh oil on the sea surface. A much wider plume with high concentrations of organic aerosol (>25 micrograms per cubic meter) was attributed to the formation of secondary organic aerosol (SOA) from unmeasured, less volatile hydrocarbons that were emitted from a wider area around DWH. These observations provide direct and compelling evidence for the importance of formation of SOA from less volatile hydrocarbons.

Airborne measurements of ethene from industrial sources using laser photo-acoustic spectroscopy.

A laser photoacoustic spectroscopy (LPAS) instrument was developed and used for aircraft measurements of ethene from industrial sources near Houston, Texas. The instrument provided 20 s measurements with a detection limit of less than 0.7 ppbv. Data from this instrument and from the GC-FID analysis of air samples collected in flight agreed within 15% on average. Ethene fluxes from the Mt. Belvieu chemical complex to the northeast of Houston were quantified during 10 different flights. The average flux was 520 +/- 140 kg h(-1) in agreement with independent results from solar occultation flux (SOF) measurements, and roughly an order of magnitude higher than regulatory emission inventories indicate. This study shows that ethene emissions are routinely at levels that qualify as emission upsets, which need to be reported to regional air quality managers.

Observations of air composition in Brazil between the Equator and 20°s during the dry season

Field measurement programs in Brazil during the dry season months of August and September in 1979 and 1980 have demonstrated the great importance of the continental tropics in global air chemistry. Especially in the mixed layer, the air composition over land is much different from that over the ocean and the land areas are clearly longe scale sources of many inportant trace gases. During the dry season much biomass, burning takes place especially in the cerrado regions leading to substantial emission of air pollutants, such as CO, NOx, N2O, CH4 and other hydrocarbons. Ozone concentrations are alsoenhanced due to photochemical reactions. Biogenic organic emissions from tropical forests play likewise an important role in the photochemistry of the atmosphere. Carbon monoxide was found to be present in high concentrations in the boundary layer of the tropical forest, but ozone concentrations were much lower than in the cerrado.

Programa de medidas de campo no Brasil nas estações secas de 1979 e 1980, durante os meses de agosto e setembro, demonstraram a grande importância das regiões tropicais continentais na química atmosférica global. Especialmente na camada de mistura, a composição do ar sobre o continente e oceano é muito diferente e as regiões terrestres são fontes de produção em grande escala de muitos gases-traço importantes. Queimas de blomassa ocorrem durante a estação seca, especialmente nos cerrados, causando emissões substanciais de poluentes atmosféricos tais como CO, HOx, H2O, CH4, e outros hidrocarbonetos. Concentrações de ozônio são tombém aumentadas devido a reações fotoquímicas. Emissões orgânicas biogênicas de florestas tropicais tem um papel importante na fitoquímica da atmosfera. O monóxido de carbono mostrou-se presente em altas concentrações na camada limite da floresta tropical e as concentrações de ozônio foram muito inferiores no cerrado.