This is a RAPID award to respond to the Deep Horizon oil spill in the Gulf of Mexico. This research applies a new methodology to assess the transformation of crude oil, over time, in coastal marine sediments. The research seeks to identify unique electromagnetic (EM) geophysical signatures that reflect specific changes in sediment physical, chemical, and microbiological characteristics. Research involves time-series measurements of geophysical signatures in oil contaminated, oil/dispersant contaminated, and uncontaminated sediments. Corresponding microbial community structure and composition, as well as corresponding geochemical characteristics of the sediments will be determined. This will be the first use of EM geophysics for biogeophysical studies in saltwater and brackish systems. Field sites and sample locations will be selected in Louisiana and Florida. Broader impacts of the work will have immediate implications for assessing the oil contamination and microbial vitality of coastal sediments impacted by the Deep Horizon oil spill. It will develop new methodology that allows the remote sensing of microbial activity in the subsurface. The project trains students in state-of-the-art molecular biology techniques and biogeophysis. It also supports two minority PIs from an institution in the EPSCoR state (Oklahoma), one of whom is from a gender under-represented in the sciences.
Intellectual Merit On April 20, 2010, oil and gas escaped from BP’s Deepwater Horizon exploratory Macondo well located 130 miles to the SE of the southern tip of the Mississippi Delta contaminating many of the coastal environments in the Gulf States. The Deepwater Horizon spill in the Gulf of Mexico was a reminder of the environmental threat of hydrocarbon contamination and the need for the development of new technologies for detecting, monitoring, and remediating oil spills. We used the BP oil spill as an opportunity to gather information on how geophysical technologies can be used to provide insights into the physical, chemical and biological processes involved in the transformation of "fresh" crude oil in saline saturated beach sediments. Most spills occur in marine and coastal environments. Understanding the fate of hydrocarbons in coastal sediments is particularly important because of their relatively high salinity. Our main goal was to conduct time-lapse geophysical investigations, integrated with microbiological and geochemical analyses of water and sediments to quantify transformations of crude oil from the BP oil spill in coastal wetlands and salt marshes. Our specific objectives were to: (1) set up a remotely operated geophysical monitoring system to investigate the changes that were occurring in the contaminated environments related to the bacterial break down of the oil (2) collect water samples and analyze then for evidence of the presence of the oil as well as provide evidence of water chemistry changes due to bacterial degradation of the oil and (3) determine the presence of indigenous microorganisms capable of degrading the oil in such coastal and beach saline environments. We chose the northern tip of Grande Terre 1, a barrier Island just north of Grande Isle, Louisiana as our study site (Figure 1). This Island was heavily contaminated by oil and we were able to observe tar balls along the shoreline. We designed an autonomous resistivity monitoring system and programmed it to take measurements twice a day- early morning and early evening. The system was installed in a weatherproof housing (Figure 2), equipped with remote communication and was powered via a solar panel bank. The system operated from January 2011 to August 2012, when hurricane Isaac damaged infrastructure and terminated the monitoring. . We processed the data to produce images (pictures) of the subsurface. Our results showed an anomalously high resistivity layer, centered at approximately 0.5 m depth (Figure 3). This high resistivity layer likely resulted from oil-contamination, as supported by direct sampling analyses performed at Oklahoma State University. Further processing of the full monitoring dataset showed a long-term, continuous decrease in resistivity at the site. Supporting datasets (e.g. specific conductance and temperature) indicate that these changes are not driven by freshwater-saltwater dynamics (e.g., tides) at the site. Instead, it appears that this long-term, continuous decrease in the electrical resistivity of the site is most likely related to processes occurring within the contaminated layer. Microbial data supports this explanation as indigenous microbial populations from the contaminated location were capable of degrading benzene and toluene whereas microorganisms from the clean background site were unable to degrade these hydrocarbon compounds. The rapid degradation of benzene and toluene in samples from the contaminated location suggests adaptation of hydrocarbon degrading bacteria at the contaminated locations, possibly due to prior exposure to a hydrocarbon source such as the BP oil spill. The resistivity data, as well as the microbial data support the conclusion that the changes in resistivity observed are likely related to oil degradation and not associated with tidal variability or changes in sea level. Broader Impact The findings from our study strongly suggest that electrical resistivity monitoring systems could be used to track the long-term biodegradation of crude oil spills in coastal and marine environments as well as in freshwater environments. Such a system could also be deployed to investigate the long term transient hydrologic changes related to climate change as well as transient changes on contaminant transformation and transport. Geophysical techniques provide a cheap, fast effective way to monitor oil spill sites. This warrants more studies to conclusively determine the application of geophysical tools for detection, monitoring, and quantifying microbial processes at crude oil contaminated high salinity environments. This site also provided an excellent learning environment for training graduate and undergraduate students at Oklahoma State University and Rutgers University, Newark. The results of this study were presented at several venues including seminars at various universities across the nation and at national and international meetings including the American Geophysical Union, the Symposium on the Application of Geophysics to Environmental and Engineering Problems and the results will be presented at the Battelle Second International Symposium on Bioremediation and Sustainable Environmental Technologies.
