Abstract:

Mesocosm experiments were performed as part of the ADDOMEx GOMRI funded program with seawater collected from the NGOM and “seeded” with microbial populations collected from coastal Texas (in Galveston Bay). Aggregate materials that formed between days 2 and 4 of the experiment in control, WAF, DCEWAF, and CEWAF treatments and sunk to the bottom of mesocosm tanks were collected at the end of the experiment. The particles were extracted using dichloromethane. Dichloromethane extracts were diluted with methanol and analyzed using one dimensional and two dimensional gas chromatography mass spectrometry (GC-MS). Only DCEWAF treatment particles produced spectra with sufficient GC-MS signal to noise to archive here. The GC-MS data contained in the .csv file datasets represent the time elapsed after sample injection and the corresponding spectral response at the mass (or mass range) of interest that were obtained directly from the ChromaTOF software. The .jpeg files represent the spectral response (as generated by the ChromaTOF software) for the one-dimensional and two-dimensional GC-MS runs.

Suggested Citation:

Pat Hatcher and Andrew Wozniak. 2017. GC MS data for bottom particle dichloromethane extracts from the COAST, a COASTAL water mesocosm experiment amended with microbial concentrate. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7765CJ8

Publications:

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

Purpose:

To investigate molecular level differences in sinking aggregate organic matter (OM), sinking aggregates OM impacted by oil, and sinking aggregates OM impacted by oil and dispersant mixtures.

Data Parameters and Units:

Sample – the identification of the sample being analyzed Scan – mass spectrometer scan number Time – time elapsed since sample injection measured in seconds Spectral Response – mass spectral response for the given ion mass (or sum of the response at the given mass range)

Methods:

The seawater was collected from the same location as that used in TeCOAST Mesocsom, but on October 17 2015, from 8 kilometers off shore south of Galveston (TX) in the Gulf of Mexico. The salinity was 31. The seawater was processed through a charcoal filter to remove large particles and debris. Four treatments were prepared in triplicate. Control tanks were filled with seawater and a plankton mixture. Water accommodated fraction (WAF) of oil was prepared by mixing 25 mL (5 ml ~ every 30 min for 2.5 hrs) of Macondo surrogate oil into 130 L of seawater then mixing for 12 to 24 hrs (Knap et al. 1986; Knap et al. 2016 in preparation). The WAF was then introduced into the WAF mesocosm tanks and filled to 87 L and mixed. From these WAF tanks 6 L was removed for other experiments and analyses (2L for roller tables, 2 L dark/light, 4 L hydrocarbon analyses). In order to make chemically enhanced water accommodated fraction (CEWAF), Corexit was mixed with oil in a ratio of 1:20 and 25 mL of this mixture (5 ml every 30 min for 2.5 hrs) of surrogate oil plus Corexit was added to 130 L of seawater which was mixed for 8 to 24 hrs prior to being transferred to the mesocosm tanks. The CEWAF was then introduced into the CEWAF mesocosm tanks and filled to 96 L and mixed. From these CEWAF tanks 15 L was removed for other experiments and analyses (9 L for the DCEWAF mesocosms, 2L for roller tables, 2 L dark/light, 4 L hydrocarbon analyses). Diluted CEWAF (DCEWAF) was prepared by mixing 9 L of CEWAF with 78 L of the original seawater for a total volume of 87 L. From these DCEWAF tanks 6 L was removed for other experiments and analyses (2L for roller tables, 2 L dark/light, 4 L hydrocarbon analyses). Plankton (≥63 µm) were collected using a net and transferred into polycarbonate bottles. This concentrated plankton mass was introduced to the tanks and stirred (2 L to each final volume 83 L) immediately prior to starting the experiments. The EOE mean concentration of the three mesocosms for the control, WAF, DCEWAF and CEWAF at the start of the experiments were 0 mg/L, 0.26 mg/L, 2.74 mg/L and 41.5 mg/L, respectively. Methylene chloride extracts of marine oil snow 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 used to operate the GC x GC MS system. For GC x GC-MS analysis, methylene chloride extracts were injected into a heated (280 °C) split/splitless injector using a 1 µL injection volume in splitless injection mode. A nonpolar Restek Rtx-5 (30m x 0.25 mm x 0.25 µm 5% phenyl-95% dimethyl polysiloxane) column was used for the first dimension column using helium as a carrier gas at a rate of 1 mL min-1. The sample was held at 40 °C for 2 min before being ramped at 10 °C min-1 for 24 min to 280 °C then being held at 280 °C for 10 min. A quad jet-dual stage cryogenic modulator focused compounds eluted from the first column prior to separation on the second column. The modulator used a cold jet of dry N2. The hot jet air temperature was offset from the main oven by 15 °C throughout the run. The hot pulse lasted 1.3 s, and the cold pulse lasted 0.7 s. The second dimension column was a polar Restek Rxi-17 (1.1 m x 0.1 mm x 0.1 µm 50% diphenyl-50%dimethyl polysiloxane) held at a constant temperature of 290 °C. The TOFMS transfer line temperature and MS ion source temperatures were held at 280 °C and 200 °C, respectively. The electron ionization was set at -70 eV, and the MS detector voltage was set at 1550 V. Data was acquired at a rate of 200 spectra min-1 over a mass range of 45-650. ChromaTOF software implemented a signal to noise of 40 for peak detection, and compounds were identified using a NIST spectral database. For one-dimensional GC-MS analyses of methylene chloride extracts, the modulator time was set to 0 to eliminate separation in the second dimension. The injection volume was set to 3 µL, and the signal to noise for peak detection was set at 100. The remaining sample analysis parameters for one-dimensional GC-MS analyses were the same as those for the GC x GC MS analyses.

Instruments:

Agilent 6890 2D GC coupled to Leco Pegasus IV Time of Flight Mass Spectrometer (TOFMS)

Individual Files: