Award: OCE-1058448

The Deepwater Horizon oil spill introduced millions of gallons of crude oil, natural gas, and dispersants into the Gulf of Mexico. Understanding the fate of these materials is paramount to ensuring ecosystem recovery. Our lab participated in the scientific response to this catastrophe by applying a sensitive detector to Gulf water samples to find the components of oil and dispersants that dissolved in seawater. Our detector, an ultrahigh resolution mass spectrometer, determines the mass of individual molecules with high precision and accuracy, and can resolve thousands of molecules within complex mixtures. We coupled this detector to a quantitative tool, the triple-quadrupole mass spectrometer (TSQ-MS). This mass spectrometer was acquired with this funding. The TSQ-MS is housed within the WHOI FT-MS facility, a multi-user multi-instrument facility established in October 2007. The other instruments in our facility are an ultrahigh resolution mass spectrometer (a 7T FT-ICR MS, purchased with NSF funds) and a low-resolution ion-trap mass spectrometer (LTQ-MS, purchased with private foundation funds), both from Thermo-Fisher Scientific. The FT-ICR MS is used to screen complex mixture samples and to determine their molecular composition. However, it is not suitable for routine quantification of specific target compounds. For that purpose, we use the LTQ-MS and the TSQ-MS. The triple quadrupole mass spectrometer gives much higher selectivity of target compounds than the ion-trap, and therefore is the gold-standard for quantitative analysis. As anticipated, the TSQ -MS has integrated smoothly into the FT-MS facility due to software and other similarities between the mass spectrometers. The TSQ-MS has been utilized for both training and research over the past year. We have used this instrument to analyze water samples taken from the Gulf of Mexico in the aftermath of the Deepwater Horizon oil spill for dispersants and polar petroleum products . Our data show components of the dispersant, namely the surfactant dioctyl sodium sulfosuccinate (DOSS). Levels of DOSS are highest at water depths between 1100 and 1200 m, coincident with deepwater hydrocarbon plumes identified at those depths. Our results also indicate that other sulfur containing water soluble oil components such as sulfonic acids are present. We are in the process of identifying these compounds and assessing their viability as tracers of oil. We have also taken the opportunity to use the instrument for other unique applications. These applications are yielding interesting results regarding the cycling of specific molecules in seawater, such as steroidal estrogens and small metabolites produced by bacteria and phytoplankton. The instrument will be an integral part of our future research program, as we identify additional molecules in both natural and contaminated waters that can be used to trace different environmental processes and sources. Last Modified: 04/03/2013 Submitted by: Melissa Soule