Biogeochemical Processes Affecting the Fate of Discharged Deepwater Horizon Gas and Oil: New Insights and Remaining Gaps in Our Understanding

John Farrington,Edward Overton,Uta Passow

doi:10.5670/oceanog.2021.118

Abstract

Research funded under the Gulf of Mexico Research Initiative provided new insights into the biogeochemical processes influencing the fate of petroleum chemicals entering the Gulf of Mexico from the Deepwater Horizon (DWH) accident. This overview of that work is based on detailed recent reviews of aspects of the biogeochemistry as well as on activities supported by the US Natural Resource Damage Assessment. The main topics presented here are distribution of hydrocarbons in the water column; the role of photo-oxidation of petroleum compounds at the air-sea interface; the role of particulates in the fate of the DWH hydrocarbons, especially marine oil snow (MOS) and marine oil snow sedimentation and flocculent accumulation (MOSSFA); oil deposition and accumulation in sediments; and fate of oil on beaches and in marshes. A brief discussion of bioaccumulation is also included. Microbial degradation is addressed in a separate paper in this special issue of Oceanography. Important future research recommendations include: conduct a more robust assessment of the mass balance of various chemical groupings and even individual chemicals during specific time intervals; seek a better understanding of the roles of photo-oxidation products, MOS, and MOSSFA and their relationships to microbial degradation; and determine the fates of the insoluble highly degraded and viscous oil residues in the environment.

Highlights

This article provides an up-to-date overview of some of the important research findings of the past five years related to the biogeochemical processes influencing the immediate and longer-term fate of chemical constituents from the Deepwater Horizon (DWH)–Macondo accident that took place April 20, 2010
In the research and assessments for the DWH oil spill, the issues of marine snow interacting with oil and becoming marine oil snow, or MOS, and accumulating, flocculating, and sinking to the seafloor in the marine oil snow sedimentation and flocculent accumulation (MOSSFA) process were identified as important subjects for extensive research because of their apparent major roles in the biogeochemistry and fate of oil chemicals in the water column (Passow and Ziervogel, 2016; Daly et al, 2016)
This research has documented that photo-oxidation was a significant process acting on the surface oil slick very early in the spill, and that it played a significant role in the fate of the spilled oil

Summary

Introduction

This article provides an up-to-date overview of some of the important research findings of the past five years related to the biogeochemical processes influencing the immediate (minutes to months) and longer-term (years to a decade or longer) fate of chemical constituents from the Deepwater Horizon (DWH)–Macondo accident that took place April 20, 2010. These processes result in the dilution of the input, potentially in microbial degradation of gas and oil hydrocarbons (Weiman et al, 2021, in this issue), and in sorption-desorption to various particles in the water column.

Results

Conclusion