Atmospheric emissions from the Deepwater Horizon spill constrain air-water partitioning, hydrocarbon fate, and leak rate

Thomas B Ryerson ,J S Holloway,D A Lack,D W Fahey,L A Watts,I B Pollack,A M Middlebrook,C Warneke,J Peischl,F C Fehsenfeld,A E Perring,C A Brock,J P Schwarz,A R Ravishankara,J R Spackman,D M Murphy,W M Angevine,J A De Gouw,J M Roberts,D D Parrish,K C Aikin,John B Nowak ,R Lueb ,Simone Meinardi ,Elliot L Atlas ,Donald R Blake ,R S Gao ,Harald Stark ,J Andrew Neuman

doi:10.1029/2011gl046726

Abstract

[1] The fate of deepwater releases of gas and oil mixtures is initially determined by solubility and volatility of individual hydrocarbon species; these attributes determine partitioning between air and water. Quantifying this 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. Analysis of airborne atmospheric data shows massive amounts (∼258,000 kg/day) of hydrocarbons evaporating promptly from the Deepwater Horizon spill; these data collected during two research flights constrain air-water partitioning, thus bioavailability and fate, of the leaked fluid. This analysis quantifies the fraction of surfacing hydrocarbons that dissolves in the water column (∼33% by mass), the fraction that does not dissolve, and the fraction that evaporates promptly after surfacing (∼14% by mass). We do not quantify the leaked fraction lacking a surface expression; therefore, calculation of atmospheric mass fluxes provides a lower limit to the total hydrocarbon leak rate of 32,600 to 47,700 barrels of fluid per day, depending on reservoir fluid composition information. This study demonstrates a new approach for rapid-response airborne assessment of future oil spills.

Highlights

[1] The fate of deepwater releases of gas and oil mixtures is initially determined by solubility and volatility of individual hydrocarbon species; these attributes determine partitioning between air and water
[4] In this study we present airborne in situ measurements of Deepwater Horizon (DWH) emissions taken from an instrumented P‐3 research aircraft showing massive amounts of spill‐related hydrocarbons evaporating promptly to the atmosphere
The atmospheric plume volatile organic carbon (VOC) composition sampled on both flights (Figure 2) corresponds to that of the leaking reservoir fluid modified by partial or complete removal of soluble species in the water column

Summary

Introduction

[1] The fate of deepwater releases of gas and oil mixtures is initially determined by solubility and volatility of individual hydrocarbon species; these attributes determine partitioning between air and water. A significant, but previously undefined, fraction of leaked hydrocarbon mass at the ocean surface evaporated [National Research Council, 2003], resulting in emission of a wide range of volatile organic carbon (VOC) compounds to the atmosphere.

Results

Conclusion