Abstract:
Mesocosm experiments were performed with seawater collected from the NGOM and enriched with coastal plankton collected from Galveston Bay. The four treatments in triplicate were 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 (DCWAF). The oil composition data presented here are EOE (estimated oil equivalence using fluorescence), PAH (polycyclic aromatic hydrocarbons), and Total PAH. Additionally, nutrients for these treatments are also included. Solid-state 13C NMR spectroscopic analysis data are available in GRIIDC dataset UDI: R4.x263.000:0022.
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 and nutrients for the COAST mesocosm study, COASTal water with added coastal microbial concentrate. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7PK0D64
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
Schwehr, K. A., Xu, C., Chiu, M.-H., Zhang, S., Sun, L., Lin, P., … Santschi, P. H. (2018). Protein: Polysaccharide ratio in exopolymeric substances controlling the surface tension of seawater in the presence or absence of surrogate Macondo oil with and without Corexit. Marine Chemistry, 206, 84–92. doi:10.1016/j.marchem.2018.09.003
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. Also, to track the change in nutrients during the same time course.
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); nutrient data are given in 2 conc. or concentration formats: micromoles/L (umol/L) and mg/L with respect to the listed standard. NO3- is nitrate, N is nitrogen, HPO4= is hydrogen phosphate, P is Phosphorus, HSIO3- is hydrogen silicate, SiO3 refers to silicate, NH4+ is ammonium, NO2- is nitrite, Time (hr), Volume (L)
Methods:
The seawater was collected from the same location as that used in TeCOAST Mesocsom, but was collected 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. The EOE mean concentration of the three for the control, WAF, DCEWAF and CEWAF mesocosms after 72 hours were 0 mg/L, 0.06 mg/L, 1.03, and 17.3 mg/L, respectively. 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.
View Metadata