Abstract:
Mesocosm experiments were performed with seawater collected from the NGOM and enriched with coastal plankton collected from Galveston Bay. The four treatments analyzed for oil composition were 1) Control, 2) Water accommodated oil fraction (WAF), 3) Chemically enhanced (Corexit 9500) water accommodated fraction (CEWAF), and 4) 10-fold diluted CEWAF (DCEWAF). The oil composition data presented here are EOE (estimated oil equivalence using fluorescence), PAH (polycyclic aromatic hydrocarbons), and Total PAH. Dissolved organic matter FTICR-MS data can be found in GRIIDC dataset UDI: R4.x263.000:0020.
Suggested Citation:
Terry L. Wade, Anthony H. Knap, Dawei Shi, Gerardo Gold-Bouchot, Maya E. Morales-McDevitt, Stephen T. Sweet, Peter H. Santschi and Antonietta Quigg. 2017. Oil Composition for the TeCOAST mesocosm study, Test of COASTal water with coastal microbial concentrate. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7TB14ZW
Publications:
Wade, T. L., Morales-McDevitt, M., Bera, G., Shi, D., Sweet, S., Wang, B., … 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
Morales-McDevitt, M. E., Shi, D., Knap, A. H., Quigg, A., Sweet, S. T., Sericano, J. L., & Wade, T. L. (2020). Mesocosm experiments to better understand hydrocarbon half-lives for oil and oil dispersant mixtures. PLOS ONE, 15(1), e0228554. doi:10.1371/journal.pone.0228554
Purpose:
To determine the concentration of oil constituents and dispersant and their degradation with time in four different mesocosm treatments from coastal waters.
Data Parameters and Units:
EOE (Estimated Oil Equivalence, mg/L); PAH (Polycyclic Aromatic Hydrocarbons, ng/L); Total PAH (ng/L);WAF (Water Accommodated Fraction); CEWAF (Chemically Enhanced Water Accommodated Fraction); DCEWAF (Diluted Chemically Enhanced Water Accommodated Fraction); Time (hr); WAF maker EOE (mg/L); CEWAF maker EOE (mg/L); Control tank EOE (mg/L); WAF Tank EOE (mg/L); DCEWAF Tank EOE (mg/L); CEWAF Tank EOE (mg/L); WAF Bottle EOE (mg/L); DCEWAF Bottle EOE (mg/L); CEWAF Bottle EOE (mg/L); Volume (L)
Methods:
The seawater used in the TeCOAST Mesocsom studies was collected on July 30, 2015 from 8 kilometers off shore south of Galveston (TX) in the Gulf of Mexico. The salinity was 34. The seawater was processed through a charcoal filter to remove large particles and debris. 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. This seawater was also used to fill 130 L recirculating glass flumes (Knap et al. 1986; Knap et al. 2016 in preparation) to make water accommodated fraction (WAF) and a chemically enhanced water accommodated fraction of oil (CEWAF). The WAF was prepared by mixing a total of 24 mL (2 ml to start, 2 ml after 1 hr, then 5 ml at ~ 2, 3, 4 and 5 hrs total of 24 ml) of Macondo surrogate Marlin oil into 130 L of the seawater. Total mixing time from the start of oil addition to transfer to the mesocosms was 18 hrs. The WAF (79 L) 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 (79 L) was transferred to the WAF mesocosm tank and mixed. In addition a dilute CEWAF (DCEWAF) mesocosum treatment was produced by adding 9 L of CEWAF to 70 L of the original seawater for a total volume of 79 L. Light dark bottles were also filled from the WAF and CEWAF. Plankton (≥63 µm) samples were collected using a net and transferred into polycarbonate bottles. This concentrated plankton mass was introduced to each mesocsom and stirred (2 L to each tank for a final volume 81 L) immediately prior to starting the experiments. No plankton was added to the light or dark bottles. The EOE concentration for the control, WAF, DCEWAF and CEWAF at the start of the experiments were estimated as 0 mg/L, 3.4 mg/L, 3.6 mg/L and 36 mg/L, respectively. The EOE concentration of the control, WAF, DCEWAF and CEWAF mesocosms averaged for samples taken during the first 74 hours were 0 mg/L , 1.21 mg/L, 4.28 and 43.4 mg/L, respectively. All mesocosms had loses of EOE from 88 to 100%, while the bottles had losses of 56 to 74%. Estimated Oil Equivalence (EOE) The estimated oil equivalents (EOE) were determined by fluorescence (Wade et al. 2011) using Macondo surrogate oil as a standard to produce calibration curves at 5 to 7 concentrations. Water samples (5 to 20 ml) were extracted with 5 ml of dichloromethane. An aliquot of the extract was placed in a cuvette for fluorescence analyses (Horiba Scientific Aqualog Fluorometer). The EOE were determined from the calibration curve (Wade et al. 2011). Samples with florescence responses that exceeded the calibration curve were diluted so that their florescence was within the calibration range. Samples were taken at the beginning and end of the experiment and at intervals in between and at the same time point as measurements of other parameters during the experiment. PAH (polycyclic aromatic hydrocarbons) and Total PAH extraction of the sample with dichloromethane. The samples are then purified using silica/alumina columns. analyzed. The analysis is performed with gas chromatography to separate the individual aromatic compounds and with a mass selective detector in the selected ion mode for identification and quantification. The parent PAH (e.g. naphthalene) and its alkylated homolog’s (e.g. C-1, C-2, C-3 and C-4) are also determined. These analyses can be used to distiquish between petroleum and combustion sources or a mixture of these sources. The individual PAH compounds and their alkylated homologs are reported.
Instruments:
EOE fluorescence analyses was carried out using a Horiba Scientific Aqualog Fluorometer. Total PAH were determined by gas chromatography (GC) with a flame ionization detector (GC/FID) and PAHs by GC with a mass selective detector [Short et al., 1996].
Provenance and Historical References:
Short, J. W., T. J. Jackson, M. L. Larsen, and T. L. Wade (1996), Analytical methods used for the analysis of hydrocarbons in crude oil tissues, sediments, and seawater collected for the natural resources damage assessment of the Exxon Valdez oil spill, in Proceedings of the Exxon Valdez Oil Spill Symposium, edited by S. D. Rice et al., pp. 140–148, Am. Fish. Soc., Bethesda, Md. Wade, T. L., S. T. Sweet, J. N. Walpert, J. L. Sericano, J. J. Singer, and N. L. Guinasso Jr. (2011), Evaluation of possible inputs of oil from the Deepwater Horizon spill to the Loop Current and associated eddies in the Gulf of Mexico, in Monitoring and Modeling the Deepwater Horizon Oil Spill: A Record-Breaking Enterprise, Geophys. Monogr. Ser., doi:10.1029/2011GM 001095.
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