Air quality implications of the Deepwater Horizon oil spill.

During the Deepwater Horizon (DWH) oil spill, a wide range of gas and aerosol species were measured from an aircraft around, downwind, and away from the DWH site. Additional hydrocarbon measurements were made from ships in the vicinity. Aerosol particles of respirable sizes were on occasions a significant air quality issue for populated areas along the Gulf Coast. Yields of organic aerosol particles and emission factors for other atmospheric pollutants were derived for the sources from the spill, recovery, and cleanup efforts. Evaporation and subsequent secondary chemistry produced organic particulate matter with a mass yield of 8 ± 4% of the oil mixture reaching the water surface. Approximately 4% by mass of oil burned on the surface was emitted as soot particles. These yields can be used to estimate the effects on air quality for similar events as well as for this spill at other times without these data. Whereas emission of soot from burning surface oil was large during the episodic burns, the mass flux of secondary organic aerosol to the atmosphere was substantially larger overall. We use a regional air quality model to show that some observed enhancements in organic aerosol concentration along the Gulf Coast were likely due to the DWH spill. In the presence of evaporating hydrocarbons from the oil, NO(x) emissions from the recovery and cleanup operations produced ozone.

Historic PM2.5/PM10 Concentrations in the Southeastern United States-Potential Implications of the Revised Particulate Matter Standard.

This report summarizes a PM2.5/PM10 particulate matter data set consisting of 861 PM2.5/PM10 sample pairs collected with dichotomous samplers by the Tennessee Valley Authority (TVA) from 1982 to 1991. Eight monitoring stations, ranging from urban-industrial to rural-background, were operated across three east-central U.S. states. Annual average PM2.5 concentrations ranged from 12.6 to 21.3 micrograms per cubic meter (µg/m3), with an overall mean of 15.7 µg/m3. Likewise, annual average PM10 concentrations ranged from 17.8 to 33.7 µg/m3, with an overall mean of 23.7 µg/m3. High summer-low winter seasonality was evident, particularly for PM2.5, with the highest monthly PM2.5 and PM10 concentrations in August (26.4 and 37.5 µg/m3, respectively) and the lowest in February (9.9 and 15.3 µg/m3, respectively). A strong association (r2 = 0.84) was found between PM and PM mass with PM mass contributing, on average, 67% of PM10 mass. Applying TVA's PM2 5/PM10 ratio to recent (1993-1995) regional high-volume PM10 Aerometric Information Retrieval System (AIRS) data for the east-central United States suggests that as many as 80% of monitored counties would have equaled or exceeded the level of the new annual PM2.5 metric of 15 µg/m3. A decline in average PM2.5 mass on the order of 3-5 µg/m3 from 1982 through 1991 is also suggested. Daily PM2 5 mass appears to be reasonably well associated (r = 0.47) with maximum hourly ozone during the warmer months (spring through fall). Sulfate compounds comprise a major portion of the measured PM2 5 mass, with that fraction being highest in the summer months. Viewed collectively, these data suggest that although compliance with the annual and 24-hr PM and 24-hr PM metrics should prove readily attainable, the annual PM2.5 metric will present a major regulatory management challenge for much of the east-central United States.