Data Parameters and Units:
Worksheet - materials and treatments: Description; sample time in days (Day0, Day5, Day10, Day17, Day24, Day34, Day44); experimental treatments [S=seawater (light), SO=seawater+ oil (light), SOP=seawater+ oil+ 13C-phenanthrene (light), SOPD=seawater+ oil+ 13C-phenanthrene (dark)].
Worksheet - weight of SARA: Description; treatment (Seawater+Oil, Seawater+Oil+C13, Seawater+Oil+C13+Dark); sample time in days (Day0, Day5, Day10, Day17, Day24, Day34, Day44); Mean of Saturate, Aromatic, Resin, and Asphaltene (%); standard deviation of Saturate, Aromatic, Resin, and Asphaltene (%). Note: Saturate, Aromatic, Resin, and Asphaltene fractions were separated from DCM-extracted oil samples. Asphaltene fraction was hexane-insoluble. The hexane-soluble part was fractionated by column chromatography using solvents with different polarity.
Worksheet - PAHs in aromatic fraction: Description; ug/g oil added (concentration was normalized to the weight of oil added); ug/g aromatic (concentration was normalized to the weight of aromatic fraction); treatments (SO=seawater+ oil, SOP=seawater+ oil+ 13C-phenanthrene, SOPD=seawater+ oil+ 13C-phenanthrene), time in days (0, 5, 10, 17, 24, 34, 44), mean of all PAHs, 16 PAHs+DBT+Biphenyl, alkyl PAHs; standard deviation of all PAHs, 16 PAHs+DBT+Biphenyl, alkyl PAHs; DBT=Dibenzothiophene.
Worksheet - delta 13C of SARA and DIC: Description; saturate (5 saturate samples for days 0 and 44); delta 13C for saturate. Aromatic - treatments (SO=seawater+ oil (light), SOP=seawater+ oil+ 13C-phenanthrene (light), SOPD=seawater+ oil+ 13C-phenanthrene); time in days (0, 5, 10, 17, 24, 34, 44); mean of aromatic, standard deviation of aromatic. Resin - treatments (SO=seawater+ oil, SOP=seawater+ oil+ 13C-phenanthrene, SOPD=seawater+ oil+ 13C-phenanthrene); time in days (0, 5, 10, 17, 24, 34, 44); mean of Resin, standard deviation of Resin. Asphaltene - treatments (SO=seawater+ oil, SOP=seawater+ oil+ 13C-phenanthrene, SOPD=seawater+ oil+ 13C-phenanthrene); time in days (0, 5, 10, 17, 24, 34, 44); mean of Asphaltene, standard deviation of Asphaltene. DIC (Dissolved Inorganic Carbon) - treatments (SO=seawater+ oil, SOP=seawater+ oil+ 13C-phenanthrene, SOPD=seawater+ oil+ 13C-phenanthrene); time in days (0, 5, 10, 17, 24, 34, 44); mean of DIC, standard deviation of DIC. Note: only five saturate samples were analyzed for delta 13C; 13C values were determined using an elemental analyzer coupled to a Finnegan isotope ratio mass spectrometer. The 13C values are reported relative to the Vienna Peedee Belemnite (PDB) standard. The precision was 0.2‰ or better.
Worksheet - 13C-phen in fractions: Description; sample (asphaltene, aromatic, resin); treatment (SOP=seawater+ oil+ 13C-phenanthrene, SOPD=seawater+ oil+ 13C-phenanthrene); time in days (0, 5, 10, 17, 24, 34, 44); mean of samples (%); standard deviation of samples. Note: 13C-phen was not analyzed in saturate fractions; values were normalized to the concentration of 13C-phen added at the beginning of the experiment. For asphaltene samples- only SOP-0, SOP-44, and SOPD-44 were analyzed.
Worksheet - pyrolysis of asphaltene: Description; Name (PAHs, alkylated PAHs and n-alkanes C6-C37); time in days (day 0, day 5, day 44, day 44 dark); six thermal slices (50-90, 90-170, 170-290, 290-370, 370-530 and 530-650 in degree Celsius); area/mg asphaltene.
Worksheet - NMR of asphaltene: Description; structure description (structural parameters, lattice parameters); symbol; Direct Polarization (mole % of total carbon); Cross Polarization (mole % of total carbon); NMR=Nuclear Magnetic Resonance.
Methods:
Surface seawater (2 m) collected from the Deepwater Horizon site was filtered (0.2 μm), and autoclaved. The LLS crude oil (~100 ml) used was pre-heated in glass beakers at 180°C in an oven for overnight to remove volatile components. The experiment included 4 treatments in duplicate: (1) S: 100 ml seawater; (2) SO: 100 ml seawater plus ~100 mg crude oil; (3) SOP: 100 ml seawater plus ~100 mg crude oil and 20 μg 13C-phenanthrene (10 μl 2000 ppm in DCM) in pre-combusted 120-ml quartz glass bottles; (4) SOPD: the dark treatment of SOP with same bottles but wrapped with aluminum foil. The experiment was conducted under the natural sunlight/dark cycle at the Pier Laboratory of the University of Texas Marine Science Institute in Port Aransas, Texas. All bottles, capped and sealed with Parafilm, were put in pump-driven flowing seawater, and manually shaken lightly for about 10 s each day. The experiment lasted from July 25, 2015, to September 7, 2015, sampling on day 0, 5, 10, 17, 24, 34 and 44 with individual bottles sacrificed at each time point. During the experiment, the water temperature was 30~32 degree Celsius and the average irradiance was ~2000 µmol photons/m2/s at noon. To obtain enough materials of Nuclear Magnetic Resonance (NMR) analysis, another experiment was conducted with the same protocols and conditions but the dose of oil six times higher. The experiment consisting of 3 treatments (SO, SOP, and SOPD), lasted 30 days, from August 13 to September 11, 2015. For NMR analysis - Direct-polarization (DP) spectra were generated by applying 90o excitation pulse at the 13C frequency (75 MHz), followed by a rotor synchronized refocusing pulse, to eliminate baseline distortions. Cross-polarization (CP) was conducted under a 90o 1H excitation pulse and a variable-amplitude contact pulse of 2 ms. The Hartman-Hahn matching conditions for 1H-13C polarization transfer was optimized using crystalline glycine as an external standard. Dipolar–dephasing (non-quaternary suppression) spectral editing experiments were conducted for both CP and DP experiments with a total dephasing delay of 70 µs. All signals (CP and DP) were acquired under conditions of composite pulse proton decoupling. Time-domain NMR signals were each exponentially-multiplied, zero filled to 16,384 data points, and Fourier transformed with 60 Hz line broadening.
View Metadata