Science Seminars

1/14/2011 – Deepwater Horizon atmospheric emissions constrain air-water partitioning, hydrocarbon fate, and leak rate

Speaker: T.B. Ryerson (Chemical Sciences Division, NOAA Earth System Research Laboratory, Boulder, CO)
Date: Friday, Jan 14, 2011
Time: 4:00 PM
Location: Duane D-142

Seminar Abstract:

The fate of deepwater releases of gas and oil is initially determined by solubility and volatility of individual hydrocarbon species; these attributes determine partitioning between air and water. Quantifying this air-water partitioning is necessary to constrain simulations of gas and oil transport, to predict marine bioavailability of different fractions of the gas-oil mixture, and to develop a comprehensive picture of the fate of leaked hydrocarbons in the marine environment. Here we show massive amounts (exceeding 226,000 kg/day) of hydrocarbons evaporating from the Deepwater Horizon spill; these data collected during two research flights constrain air-water partitioning, thus bioavailability and fate, of the leaked fluid. Our analysis quantifies the fraction of released hydrocarbons that dissolves in the water column (~33% by mass), the fraction that does not dissolve, and the fraction that is removed promptly by evaporation after surfacing (~14% by mass). This study provides a lower limit to the leak rate of 24,000 to 37,200 barrels of fluid per day, depending on reservoir fluid composition information, and demonstrates an effective new approach for rapid-response airborne assessment of future oil spills.