Abstract:

This dataset covers part of the data for experiments in which oil was added to mesocosms. Data provided here are the measured concentrations of PAHs in sediment samples (surface and subsurface) and water samples of the mesocosms. Bioturbator data (including survival/recovery) and environmental data (D.O., redox, turbidity, etc.) for sediment and water in the mesocosms are provided in a separate dataset (R2.x226.000:0004). The dataset contains results for two experiments with different bioturbator species; one experiment with ghost shrimp and one with razor clams.

Suggested Citation:

Klerks, Paul and Louka, Febee. 2017. Mesocosm experiments with oil at sediment surface - PAH data. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7DV1H8X

Publications:

Klerks, P. L., Kascak, A., Cazan, A. M., Deb Adhikary, N., Chistoserdov, A., Shaik, A., … Louka, F. R. (2018). Effects of the Razor Clam Tagelus plebeius on the Fate of Petroleum Hydrocarbons: A Mesocosm Experiment. Archives of Environmental Contamination and Toxicology, 75(2), 306–315. doi:10.1007/s00244-018-0515-0

Purpose:

These experiments investigated the effects of bioturbators on the distribution and degradation of petroleum hydrocarbons in nearshore environments. This specific dataset provides data for two experiments. For the experiment with the razor clams, it provides day-30 PAH concentrations in surface sediment and subsurface sediment of the mesocosms (with or without bioturbators). For the experiment with the ghost shrimp it provides day-1 and day-15 surface sediment PAH concentrations, day-15 subsurface sediment PAH concentrations, and both day-1 and day-15 PAH concentrations in the water column. It also includes results for the PAH analyses on replicated analyses for selected sediment and water samples.

Data Parameters and Units:

The dataset has two separate excel files, with each file having different sheets for each sample type (surface sediment, surface sediment, water) for different days if mesocosms were sampled more than once. Regular spreadsheets have the following columns: sample type, mesocosm I.D., oil treatment, animal treatment, PAH concentration for each of the individual PAHs with water concentrations in μg/L and sediment concentrations in μg/kg. The final column shows the total PAH concentrations (sum of the individual PAHs). For the spreadsheet with the replicated analyses, columns are: sample type, mesocosm I.D., PAH analyzed, PAH concentration in the first replicate, PAH concentration in the second replicate, the mean for the two analyses, the coefficient of variation (C.V.) for the replicates.

Methods:

For the experiment with the razor clams, sweet petroleum crude oil (Marlin Platform Dorado oil – as a surrogate oil for the Macondo oil; BP America, Houston, that had been sparged for 48 h to imitate mild weathering) was added to the 10-gal. mesocosms by pouring 100 g of air-dried sediment (previously collected from Bay St. Louis) mixed with 1 mL of oil, on the surface sediment of each mesocosm for the treatments with oil. Control mesocosm received just the dry sediment (100 g). The experiment with the razor clam used the same methodology, except that experiments were conducted in 30-gal. tanks and received 3 mL of the sparged oil mixed with 300 g of air-dried sediment (or 300 g air-dried sediment for controls). Water samples of approximately 500 mL were collected from the mesocosms (at approximately mid-depth of the water column) using a sampling device with glass tubing and Erlenmeyer flask where air displacement from the flask resulted in water flowing through the tubing from mesocosms into flask. Samples were placed in 500-mL glass containers and transported to the lab in a cooler. Samples were stored at -4 °C for a maximum of 24 hours. Hydrocarbons were extracted using liquid-liquid extraction. Dichloromethane (DCM) was used for extraction, the organic solvent containing the extracted PAH was then evaporated using a rotary evaporator at 22°C, and the residue was dissolved in hexane. The hexane was then concentrated in a vial to a volume of 1.00 mL by purging nitrogen gas into the vial. An aliquot of the sample was then injected into an Agilent technologies 7820A gas chromatography System with a flame ionization detector (GC-FID) for quantification of the individual PAHs. Replicates of several of the samples for both treatments (with and without bioturbators) were analyzed to assess reproducibility. The collected sediment (surface and subsurface) samples were collected with a glass coring tube, transferred to the lab in a cooler, and frozen upon arrival. All samples were freeze-dried using an SP Scientific freeze dryer (Sentry 2.0). Dry samples were homogenized using mortar and pestle, and 20 g of sediment was placed in Teflon microwave tubes with 25 mL of DCM. One Touch Technology MARS microwave extraction was performed using the US EPA 3546 method. The DCM containing the extracted PAHs was then filtered by gravity filtration and the remaining sediment was then washed several times with DCM, the DCM was filtered again, and combined in order to recover all the extracted PAHs. The DCM was evaporated using a rotary evaporator. The remaining residue was then dissolved in hexane. The round-bottom flask was rinsed with hexane several times in order to maximize recovery of PAHs in the sample. All the hexane rinses were combined and concentrated in a vial to a volume of 1.00 mL by purging nitrogen gas into the vial. An aliquot of each extracted sample was injected immediately into the GC-FID or was frozen for analysis on the following day. The injections were done using the following conditions: The injector and detector temperatures were set at 250 and 300ᵒC, respectively; helium was used as the carrier gas; samples were injected in the splitless mode; the oven temperature was programmed from a 60ᵒC initial temperature to increase to 300ᵒC at a rate of 5ᵒC /min, was then decreased to 290ᵒC, and was maintained at this temperature for 25 minutes.

Instruments:

Instrumentation information is provided in the methods section.

Error Analysis:

The Gas Chromatography instrument was calibrated prior to every use. Calibration curve was obtained using Restek PAH standard with exact concentrations. An internal standard was added to all samples prior to analyses. Replicates of samples in presence and in absence of bioturbators were performed for accuracy, as were analyses of samples from mesocosms to which no oil had been added.

Provenance and Historical References:

Dataset R2.x226.000:0004 contains the experimental design and bioturbator information from these experiments, along with the environmental data for the water and sediment in the mesocosms during the experiment.

Individual Files: