GoMRI
Investigating the effect of oil spills
on the environment and public health.
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Funding Source: Year 8-10 Research Grants (RFP-VI)

Project Overview

Radium Isotope Release from Oil Degradation: Development of an ‘Oil Clock’

Principal Investigator
Coastal Carolina University
Department of Coastal & Marine Systems Science

Abstract:

Time is the central theme of this proposal – specifically, the residence time that hydrocarbons spend in the marine environment and therefore exposure time related to the kinetically- and microbially-controlled processes of natural attenuation. Many studies interpreting results of the Deepwater Horizon blowout attempted to infer exposure time based on potentially misleading timelines (e.g., the blowout timeline), but few, if any, have proposed methods for age-dating the material once released. Fewer still have the specialized tool set to do so both in the deep sea and at the surface. The radioisotope approach proposed here is well established for coastal and continental shelf settings, and applying those geochemical tracers to hydrocarbon dynamics in the open ocean would be of immense value in understanding the complex evolution of hydrocarbon degradation within an oceanic plume. These efforts do not duplicate any existing efforts in the Gulf of Mexico, but may certainly augment the interpretations of various ongoing studies.

 

Published studies regarding microbial respiration dynamics in a deep, laterally-spreading hydrocarbon plume months after the Deepwater Horizon blowout report contradictory findings because they lacked a tool to unambiguously constrain the amount of time that in-situ microbial communities were exposed to the hydrocarbons. These contradictory findings have led to uncertainties regarding the potential rates of natural remediation of hydrocarbons in the marine environment from the Deepwater Horizon event, and perhaps more importantly, for future oil spill scenarios. Time is the central theme of this proposal – specifically, the residence time that hydrocarbons spend in the marine environment and therefore exposure time related to the kinetically- and microbially-controlled processes of natural attenuation. Many studies interpreting results of the Deepwater Horizon blowout attempted to infer exposure time based on potentially misleading timelines (e.g., the blowout timeline), but few, if any, have proposed methods for age-dating the material once released. Fewer still have the specialized tool set to do so both in the deep sea and at the surface. The radioisotope approach proposed here is well established for coastal and continental shelf settings, and applying those geochemical tracers to hydrocarbon dynamics in the open ocean would be of immense value in understanding the complex evolution of hydrocarbon degradation within an oceanic plume. These efforts do not duplicate any existing efforts in the Gulf of Mexico, but may certainly augment the interpretations of various ongoing studies.

 

Published studies regarding microbial respiration dynamics in a deep, laterally-spreading hydrocarbon plume months after the Deepwater Horizon blowout report contradictory findings because they lacked a tool to unambiguously constrain the amount of time that in-situ microbial communities were exposed to the hydrocarbons. These contradictory findings have led to uncertainties regarding the potential rates of natural remediation of hydrocarbons in the marine environment from the Deepwater Horizon event, and perhaps more importantly, for future oil spill scenarios.

 

This proposal is based on exciting new data demonstrating that as hydrocarbons degrade within a water parcel, radium isotopes (specifically 224Ra and 228Ra) are released into the surrounding water. The ultimate goal of this proposal is to use this characteristic to develop an ‘oil clock’ geochronometer of hydrocarbon residence time in the marine system based on this released radium isotopic signature. The objectives of this proposal include: (1) collect and geochemically characterize discharged hydrocarbons from natural seep vents at Green Canyon lease block 600 (GC-600) to assess the degree of hydrocarbon source homogeneity across a Gulf of Mexico lease block; (2) use these collected hydrocarbons to perform a series of time-course radium release experiments, in which natural and dispersant-influenced degradation processes under conditions simulating deep water and surface hydrocarbon plumes will be used to determine the radium isotopic release signatures; and (3) create and validate a conceptual model of hydrocarbon residence time in the marine environment based on these isotopic release signatures.

 

These objectives and final deliverable of the project (i.e., the geochronometer conceptual model) meet the goal of Theme #2: Chemical Evolution and Biological Degradation of the Petroleum/Dispersant System and Subsequent Interactions with Coastal, Open-Ocean, and Deep- Water Ecosystems. The experimental approach of this project aims to simulate real-world conditions at the ocean surface as well as at depth to allow these degradation processes to occur such that the radium isotopic release signatures can be assessed as a function of hydrocarbon degradation. The goal of this project is not to examine the specific mechanisms, rates, or processes by which microbial and/or photodegradation of petroleum hydrocarbons occur, but rather how the chemical evolution of the degrading petroleum releases the radiotracers of interest. These results will ultimately produce a much needed tool available to the broader research and management communities that will constrain exposure times of oceanic microbial communities to hydrocarbons, and therefore allow a more comprehensive assessment of the efficiency of natural remediation processes in the event of another significant spill.

 

This project is led by an early career scientist at Coastal Carolina University and benefits from a strong collaboration with the ongoing GoMRI consortium on Ecosystem Impacts of Oil & Gas Inputs to the Gulf (ECOGIG). Valuable graduate and undergraduate student involvement will be incorporated into this project, as well as public educational components via blogs-from-sea. The fundamentally significant results from this work will be disseminated to oil spill researchers and managers via presentations at the GoMRI annual meetings, as well as to the broader scientific community through peer-reviewed journal publications and presentations at a national conference.


This research was made possible by a grant from The Gulf of Mexico Research Initiative.
www.gulfresearchinitiative.org