Abstract:

Mesocosm experiment was conducted in June 2018 as part of ADDOMEx-2 program funded through the Gulf of Mexico Research Initiative (GoMRI). Marine oil snow samples were collected during the mesocosm experiments and analyzed using gas chromatography (GC) with flame-ionization detection (FID) and two-dimensional gas chromatography and time-of-flight mass spectrometry (GCXGC-TOFMS). Here, a highly advanced analytical tool, comprehensive two-dimensional gas chromatography (GC x GC) was employed to investigate the chemical composition of oils and their degradation by microbial activities. Alkanes and oxidized polycyclic aromatic hydrocarbons (PAH) were quantified and their changes were tracked along with the mesocosm experiments.

Suggested Citation:

Chen, Hongmei; Waggoner, Derek; Hatcher, Patrick. 2020. Molecular level characterization of oil and aggregate oxidation products: MICROX, a mesocosm for studying microbial oxidation and degradation of oil, two-dimensional gas chromatography-mass spectrometry (GCxGC-MS) data. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/n7-gfqj-xx35

Purpose:

Quantitative examination on the degradation of oil in mesocosm simulations of the Deepwater Horizon oil spill event using gas chromatography coupled with mass spectrometry.

Data Parameters and Units:

Dataset contains comprehensive two-dimensional gas chromatography (GCxGC) and gas chromatography–flame ionization detection (GC-FID) analysis of DCM-soluble components of marine oil snow. The dataset contains GC-FID result reports and GCxGC raw data that will be used in manuscripts to be submitted during 2020~2021. For GC-FID results, data file naming convention includes the mesocosm experiment number (M6), treatment (control, dilute chemically enhanced water accommodated fraction of oil = DCEWAF, water accommodated fraction = WAF), time since the start (in days), and replicate filter IDs. Note: GC = Gas chromatography, FID = Flame ionization detector, TOF = Time of fight.

Methods:

Mesocosm 6 bottom Particle samples were taken from the tanks at Days 0, 1, and 3, as well as a Control. Marine snow from control samples and marine oil snow (MOS) from dilute chemically enhanced water accommodated fraction of oil (DCEWAF) samples were freeze-dried prior to analysis. Due to limited amounts of particles resulting from mesocosm 6, only approximately ~10 mg of particulate matter of each sample was soaked in 2mL of dichloromethane (DCM) solvent, and placed on a New Brunswick Scientific Classic Series C24 Incubator Shaker (at 125 rpm) overnight. The DCM-insoluble components were removed by filtering through a 21 mm, 0.7 µm pore Glass Fiber Filter (GF/F). The filtrate was re-concentrated by a factor of 5 to 10 through evaporating out excess DCM under pure nitrogen gas, followed by gas chromatography–flame ionization detection (GC–FID) and two-dimensional gas chromatography-mass spectrometry (GCxGC-MS) analysis. Macondo Surrogate Oil was diluted by using 1 µL to mix with 2 mL Dichloromethane (DCM), and analyzed by GC-FID and GCxGC-MS to obtain reference oil features for comparison. A GC–FID analysis was performed with an Agilent Technologies 7890A gas chromatography using a Restek RTX-5: 350°C: 30 m x 250 µm x 0.25 µm column. The parameters were set to start at 35° C and to ramp up 10° C/min to 100°C and then ramp up 20° C/min to 300° C and hold there for 10 minutes. Samples were injected in the splitless mode. Samples were analyzed by GC-MS and GC x GC- MS using an Agilent 6890 2D GC coupled to Leco Pegasus IV Time of Flight Mass Spectrometer (TOFMS). Leco ChromaTOF software was employed to operate the GC x GC – MS system. DCM extracts were analyzed following previously established methods (Reference 1, Hatcher et al., 2018). The seawater used in the Test of Coastal water with coastal microbial concentrate (TeCOAST) mesocosm studies was collected in June 2018 from the Gulf of Mexico near Galveston, Texas and processed through a charcoal filter to remove large particles and debris. A plankton concentrate was collected nearby in Galveston Bay using a mesh size of 63 µm plankton net; 2 L of this “concentrate” was added to all mesocosm treatments, immediately prior to the start of the experiment. Four mesocosm tanks were treated in the following way. The control tank was filled with the seawater directly from the storage tank of filtered seawater plus the added plankton concentrate. This seawater was also used to fill recirculating glass flumes (References 2, 3, & 4) to make water accommodated fraction (WAF) and a chemically enhanced water accommodated fraction of oil (CEWAF). The WAF was prepared by mixing a Macondo surrogate Marlin oil into the seawater. Total mixing time from the start of oil addition to transferring to the mesocosms was 18 hrs ~ 24 hrs. The WAF was transferred to the WAF mesocosm tank and mixed. In order to make CEWAF, Corexit 9500 was mixed with Macando Surrogate oil in a ratio of 1:20 (Corexit to oil) and 24 mL of this mixture (2 ml to start, 2 ml after 1 hr, then 5 ml at ~ 2, 3, 4 and 5 hrs total of 24 ml) of surrogate oil plus Corexit was added to 130 L of seawater and mixed for 18 hrs. The CEWAF was transferred to the WAF mesocosm tank and mixed.

Provenance and Historical References:

[1] Hatcher, P. G., Obeid, W., Wozniak, A. S., Xu, C., Zhang, S., Santschi, P. H., & Quigg, A. (2018). Identifying oil/marine snow associations in mesocosm simulations of the Deepwater Horizon oil spill event using solid-state 13 C NMR spectroscopy. Marine Pollution Bulletin, 126, 159–165. doi:10.1016/j.marpolbul.2017.11.004 [2] Wozniak, A. S., Prem, P. M., Obeid, W., Waggoner, D. C., Quigg, A., Xu, C., … Hatcher, P. G. (2019). Rapid Degradation of Oil in Mesocosm Simulations of Marine Oil Snow Events. Environmental Science & Technology, 53(7), 3441–3450. doi:10.1021/acs.est.8b06532 [3] Knap, A. H., Burns, K. A., Dawson, R., Ehrhardt, M., & Palmork, K. H. (1986). Dissolved/dispersed hydrocarbons, tarballs and the surface microlayer: Experiences from an IOC/UNEP Workshop in Bermuda, December, 1984. Marine Pollution Bulletin, 17(7), 313–319. doi:10.1016/0025-326x(86)90217-1 [4] Wade, T. L., Morales-McDevitt, M., Bera, G., Shi, D., Sweet, S., Wang, B., Gold-Bouchot, G., Quigg., A. & Knap, A. H. (2017). A method for the production of large volumes of WAF and CEWAF for dosing mesocosms to understand marine oil snow formation. Heliyon, 3(10), e00419. doi:10.1016/j.heliyon.2017.e00419

Individual Files: