CORPUS CHRISTI, Texas – A new method for detecting oil degradation in the water long after the spill has disappeared from the surface provides another tool for researchers studying long-term environmental impacts.
Xinping Hu, Assistant Professor of Chemistry at Texas A&M University-Corpus Christi, and his team looked at subsurface Gulf of Mexico coastal waters, using samples collected from 2006 to 2012. The team was able to focus on comparing water samples near the site of the 2010 Deepwater Horizons oil spill.
The first-of-its-kind research provides a new indicator for detecting oil in subsurface water, and could be used to determine the spread of impact from spills once the oil has disappeared from the surface.
“If this type of incidence occurs again, we can go out and use this method to study the subsurface water and see if the oil degradation signal is present in the water even after it can no longer be seen by the naked eye,” Hu said. “Oil in the water can do a lot of damage to sea life. If you know it is there, you have to study the consequences.”
Under normal circumstances, marine microbes release carbonate dioxide (CO2) as they feed on oxygen from decomposing phytoplankton. This produces a known ratio of CO2 production and oxygen (O2) consumption.
Hu said that ratio changes when microbes are consuming petroleum.
“We can tell if microbes are using oxygen from plankton-derived carbon or from the carbon in petroleum,” he said.
The researchers published their study online in the January 2014 issue of Deep Sea Research Part II: Topical Studies in Oceanography. It was also featured in June at the Gulf of Mexico Research Initiative.
Analysis of samples showed four sites at 20-50 meter depth to the west of the Mississippi River mouth in 2010 that had different CO2:O2 ratios. The same spots in both 2011 and 2012 suggested the area was likely free from oil influence.
But Hu cautions that oil residue may still be present in the sediments, something other scientists are studying.
“It is all part of the study of the environmental impact of the disaster,” he said.
The research, done in partnership with colleagues from the University of Delaware, Louisiana Universities Marine Consortium, and University of Texas Marine Science Institute, was funded by the Gulf of Mexico Research Initiative and the National Oceanic and Atmospheric Administration.
Hu plans further research in this area, examining the carbon cycle in the Gulf, how quickly carbon is put in and removed from the water; and the carbon connection between fertilizer and the growing hypoxia zone seen every summer in the northern Gulf of Mexico.