A new model for the biodegradation kinetics of oil droplets: application to the Deepwater Horizon oil spill in the Gulf of Mexico

Geochemical Transactions

Research Article

Susan S Hubbard¹  Javier Vilcáez²  Li Li³ 

[1] Earth Sciences Division, Lawrence Berkeley National Laboratory, 94720, Berkeley, CA, USA;John and Willie Leone Family Department of Energy and Mineral Engineering, The Pennsylvania State University, 16802, University Park, PA, USA;EMS Energy Institute, The Pennsylvania State University, 16802, University Park, PA, USA;Currently at the University of Tokyo, Tokyo, Japan;John and Willie Leone Family Department of Energy and Mineral Engineering, The Pennsylvania State University, 16802, University Park, PA, USA;EMS Energy Institute, The Pennsylvania State University, 16802, University Park, PA, USA;Earth and Environmental Systems Institute (EESI), The Pennsylvania State University, 16802, University Park, PA, USA;

关键词: Modeling;    Biodegradation;    Oil droplets;    Size distribution;    Shrinking core model;    Gulf of Mexico oil spill;    Deepwater horizon oil spill;   

DOI  :  10.1186/1467-4866-14-4

 received in 2012-12-20, accepted in 2013-10-09,  发布年份 2013

来源: Springer

【 摘 要 】

Oil biodegradation by native bacteria is one of the most important natural processes that can attenuate the environmental impacts of marine oil spills. Existing models for oil biodegradation kinetics are mostly for dissolved oil. This work developed a new mathematical model for the biodegradation of oil droplets and applied the model to estimate the time scale for oil biodegradation under conditions relevant to the Deepwater Horizon oil spill in the Gulf of Mexico. In the model, oil is composed of droplets of various sizes following the gamma function distribution. Each oil droplet shrinks during the microbe-mediated degradation at the oil-water interface. Using our developed model, we find that the degradation of oil droplets typically goes through two stages. The first stage is characterized by microbial activity unlimited by oil-water interface with higher biodegradation rates than that of the dissolved oil. The second stage is governed by the availability of the oil-water interface, which results in much slower rates than that of soluble oil. As a result, compared to that of the dissolved oil, the degradation of oil droplets typically starts faster and then quickly slows down, ultimately reaching a smaller percentage of degraded oil in longer time. The availability of the water-oil interface plays a key role in determining the rates and extent of degradation. We find that several parameters control biodegradation rates, including size distribution of oil droplets, initial microbial concentrations, initial oil concentration and composition. Under conditions relevant to the Deepwater Horizon spill, we find that the size distribution of oil droplets (mean and coefficient of variance) is the most important parameter because it determines the availability of the oil-water interface. Smaller oil droplets with larger variance leads to faster and larger extent of degradation. The developed model will be useful for evaluating transport and fate of spilled oil, different remediation strategies, and risk assessment.

【 授权许可】

Unknown   
© Vilcáez et al.; licensee BioMed Central Ltd. 2013. This article is published under license to BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.