Abstract:
This dataset reports gas chromatography/mass spectrometry (GC/MS) analytical results of sediment samples collected by Coastal Waters Consortium (CWC) researchers in southeastern Louisiana inland and coastal marshes 2015-02-07 to 2018-06-27. It contains a master file containing all sediment sample collection information and total target alkane and aromatic concentrations for each sample and seven excel files (organized by Principal Investigator) that provide individual concentrations of target alkane and aromatic analytes for all sediment samples listed in the master file.
Suggested Citation:
Overton, Edward. 2019. Target alkane and aromatic concentrations for sediment samples collected in southeastern Louisiana inland and coastal marshes from 2015-02-07 to 2018-06-27. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/n7-tph2-3e25
Purpose:
In support of the Coastal Waters Consortium's effort to assess the chemical evolution, biological degradation, and environmental stresses of petroleum and dispersant within Gulf of Mexico coastal and shelf ecosystems.
Data Parameters and Units:
File: R6.x808.000-0042_Master_Sediment_2015-2018_sub1.xlsx: LSU/RCAT ID# (Internal sample identifier assigned by the analytical lab), Date Sample Collected (MM/DD/YYYY), Date Sample Received in Analytical Lab (MM/DD/YYYY), Date Sample Extracted by Analytical Lab (MM/DD/YYYY), Date Sample Analyzed (MM/DD/YYYY), Extraction Method: (Extraction method used on the sample; “Wet, PSE”), Latitude (decimal degrees), Longitude (decimal degrees), Total Alkanes (µg/L), Total Aromatics (ng/L), Macondo Biomarker Pattern: (A, B, AB are all indicative of relatively fresh to weathered MC252 oil; If field is blank, no biomarker pattern was detected), Principal Investigator (CWC Principal Investigator by which or for which the sample was collected), Sample Description (user-defined descriptor for sample), Sample Collection Depth (cm; Target depth for sediment sample collection for oil analysis), Concentration Workbook Filename (file with individual targeted alkane and aromatic analyte concentration data). N/A in any cell of the worksheet indicates the information was not available or not applicable. Samples with two extraction dates indicate samples that sat too long in the refrigerator prior to extraction, becoming contaminated. These samples were re-extracted on second indicated date and re-analyzed.
Folder R6.x808.000-0042_Concentration_Workbooks_Sediment_2015-2018: contains seven excel files that provide individual targeted alkane and aromatic analyte concentrations for all sediment samples listed in R6.x808.000-0042_Master_Sediment_2015-2018_sub1.xlsx. Data is organized by CWC Principal Investigator. Within each file, samples are grouped by LSU/RCAT ID# on different worksheets according to run batches (in other words, sequentially numbered batches of samples are on one worksheet tab). Format and Data Parameters and Units are the same for all files: LSU/RCAT ID# (Internal sample identifier assigned by the analytical lab), Field ID# (user-defined descriptor for sample), Initial Sediment Wt (mg; weight of sample extracted), Final Extract Volume (µl; volume of extracted sample after concentration), Percent Moisture (%; Percentage of water in each sediment sample), Surrogate Corrected values for 28 alkane analytes (ug/g; Alkane concentrations, including two isoprenoids, after applying surrogate recovery or extraction efficiency value), Surrogate Corrected values for 43 aromatic analytes (ng/g; Aromatic concentrations for parent aromatic compounds and alkyl homologs after applying surrogate recovery or extraction efficiency value, C30 17α,21β-Hopane (ng/g; the concentration of C30 17α,21β-Hopane (if present) in the sample, providing the option of hopane normalization of data). Elemental Sulphur Interference: Interference from elemental sulfur is reported in some of the raw data (highlighted in blue-colored cells). It is visually evident in the chromatograms and affects the integration of some analytes (mainly C-2 fluorenes, C-3 DBTs, and C-1 phenanthrenes) and in most cases, the interference prevents the integration of those compounds, so they are often 0.000. Other chromatographic interference: Chromatographic interference occurred in a few samples and is reported in the raw data (highlighted in brown-colored cells). Unlike the elemental sulfur interference, a source for this interference could not be identified.
Methods:
GC/MS-SIM Sediment extraction (modified EPA SW-846 method 3545A): Wet, PSE=approximately 10 grams of sample was centrifuged to remove excess water that was decanted and centrifuged sample was extracted by pressurized solvent extraction (SW-846 3545A) Qualitative oil source-fingerprinting (ASTM D5739-00).
Error Analysis:
The Overton lab provided sample collection and storage guidelines to all coPI's. Data quality could be affected if these guidelines were not followed. Quality control samples were analyzed with each analytical sample sequence. These QC samples had to be within ±20% of the original calibration values. Extraction efficiency was evaluated based on the percent recovery of the surrogate standard added to each sample prior to extraction. The acceptable recovery range was 70-120%. Method blanks were also extracted and quantitated every 12 samples. Any alkanes and aromatics detected in the method blanks were surrogate corrected, averaged if multiple blanks were prepared for each sample batch, and subtracted out of the surrogate corrected concentrations of alkanes and aromatics in each sediment sample. At least one laboratory duplicate was prepared and extracted for each sediment sample batch.
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