Oil fate and mass balance for the Deepwater Horizon oil spill

Based on oil fate modeling of the Deepwater Horizon spill through August 2010, during June and July 2010, ~89% of the oil surfaced, ~5% entered (by dissolving or as microdroplets) the deep plume (>900 m), and ~6% dissolved and biodegraded between 900 m and 40 m. Subsea dispersant application reduced surfacing oil by ~7% and evaporation of volatiles by ~26%. By July 2011, of the total oil, ~41% evaporated, ~15% was ashore and in nearshore (10 m (including 1.5% after August 2010). Volatile and soluble fractions that did not evaporate biodegraded by the end of August 2010, leaving residual oil to disperse and potentially settle. Model estimates were validated by comparison to field observations of floating oil and atmospheric emissions. [Display omitted] •Complete mass balance and oil budget for the Deepwater Horizon oil spill•Oil budget: ~41% evaporated, ~15% ashore, ~3% burned, 41% subsea and degraded•Model validated by field observations of floating oil and atmospheric emissions•Subsea dispersant injection reduced surfacing oil by 7%, volatile emissions by 26%.•Subsea dispersant effectiveness was limited by dispersant amounts applied.