Abstract:
Gas chromatography/mass spectrometry (GC/MS) analytical results of sediment samples collected by Coastal Waters Consortium researchers from 2010 to 2014. This dataset contains 3 files: (1) a master file containing all sediment sample information, total target alkane and aromatic concentrations, and qualitative oil source-fingerprinting determinations for each sample (R4.x264.000:0056_Master Oil Dataset_Sediment_2010-2014_sub1.xlsx); (2) a Windows folder (R4.x264.000:0056_Concentration Workbooks_Sediment Data_2010-2014) containing 10 excel files (organized by Principal Investigator) that provides individual concentrations of target alkane and aromatic analytes for all sediment samples listed in R4.x264.000:0056_Master Oil Dataset_Sediment_2010-2014_sub1.xlsx; (3) an excel file containing correction factor determinations for sediment samples that were contaminated by the freeze-drying process (R4.x264.000:0056_Correction Factor Documentation_sub1.xlsx).
Suggested Citation:
Ashton-Meyer, Buffy. 2017. Analytical support of the Coastal Waters Consortium: Target alkane and aromatic concentrations for sediment samples collected in 2010-2014. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7028PZZ
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: R4.x264.000-0056_Master Oil Dataset_Sediment_2010-2014_sub1.xlsx Worksheet: 2010-2014 Sediment Data “n/a” in any cell of the worksheet indicates the information was not available. Parameter Descriptions: LSU/RCAT ID#: Internal sample identifier assigned by the analytical lab; Date Sample Collected: MM/DD/YYYY or range of dates MM/DD-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, Soxhlet”, “Wet, Sonication”, “Dry, PSE”, or “Wet, PSE”); Correction Factor Applied: Indicates whether the correction factor was applied to the data (Yes/No); Latitude: Latitude where sample was collected (decimal degrees); Longitude: Longitude where sample was collected (decimal degrees); Total Alkanes (ug/g): Total of all alkane analytes in the sample; Total Aromatics (ng/g): Total of all aromatic analytes in the sample; Macondo Biomarker Pattern: (A, B, AB, Other) A, AB, and B are all indicative of relatively fresh to weathered MC252 oil; Biomarker pattern C is indicative of oil other than MC252; 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. Format and content varies with each investigator; Sample Collection Depth (cm): Target depth for sediment sample collection for oil analysis File: R4.x264.000-0056_Concentration Workbooks_Sediment Data_2010-2014 Windows folder containing 10 excel files that provide individual targeted alkane and aromatic analyte concentrations for all sediment samples listed in R4.x264.000-0056_Master Oil Dataset_Sediment_2010-2014_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). LSU/RCAT ID#; Field ID#; Initial sediment weight (mg); Final extract volume (ml); Percent moisture (%); Extraction method; Aromatic analytes (ng/g) Format and Data Parameters and Units are the same for all files: LSU/RCAT ID#: Internal sample identifier assigned by the analytical lab). If a sample was too concentrated it was diluted before analysis to minimize overloading the GC column and MS detector. Instances of dilution are indicated with a dilution factor and an “X” following the LSU/RCAT ID#. Field ID#: User defined descriptor for sample. Format and content varies with each investigator Initial Sediment Weight (mg): Weight of sample extracted Final Extract Volume (ml): Volume of extracted sample after concentration Percent Moisture: Percentage of water in each sediment sample Extraction Method: Extraction method used on the sample (“Wet, Soxhlet”, “Wet, Sonication”, “Dry, PSE”, or “Wet, PSE”) Surrogate Corrected values for 28 alkane analytes (ug/g): Alkane concentrations, including two isoprenoids, after applying surrogate recovery or extraction efficiency value. Concentrations are reported to three (3) significant figures. 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. Concentrations are reported to three (3) significant figures. Surrogate & Back 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, and after applying an average freeze-drier contamination correction factor. Values highlighted in green-colored cells indicate samples that were affected by the freeze-drier contamination discovered in 2013 (see metadata). Back corrected concentrations are reported to two (2) significant figures. Gross Oil (above the LSU/RCAT ID#): a sample that was freeze-dried, but was not back corrected. These samples had high concentrations of oil (i.e. detection of gross oil) that were orders of magnitude higher than the freeze-drier contamination, and, therefore, were not back corrected. The freeze-drier contamination greatly affected samples with trace levels of oil or background concentrations of the target aromatics Elemental Sulphur Interference: Interference from elemental sulfur, 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. File: R4.x264.000-0056_Correction Factor Documentation_sub1.doc Worksheet: ReadMe Documentation of the contamination issue of some CWC-I sediments (LSU ID# 2013234‐13 through 2013234-32, LSU ID# 2013289-01 through 2013329-45, LSU ID# 2014058-01 through 2014115-08, LSU ID# 2014153-01 through 2014303-06) discovered in 2013 including determination of a correction factor. Worksheet: Table 1 Generation of correction factors from a data set of eight sediment samples extracted using Wet and Freeze-dried methodologies Worksheet: Table 2 Final correction factors for Freeze-dried CWC-I Sediments
Methods:
GC/MS-SIM Sediment extraction (modified EPA SW-846 methods 3540C, 3550B, and 3545A): Wet, Soxhlet=sample was extracted without freeze-drying by Soxhlet extraction (SW-846 3540C); Wet, Sonication=sample was extracted without freeze-drying by ultrasonication extraction (SW-846 3550B); Dry, PSE=samples was freeze-dried and 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. Contamination of some CWC-I sediments (LSU ID# 2013234‐13 through 2013234-32, LSU ID# 2013289-01 through 2013329-45, LSU ID# 2014058-01 through 2014115-08, LSU ID# 2014153-01 through 2014303-06) was discovered in 2013. The source of contamination was determined to be the sediment freeze-drying process. Two different freeze-driers were utilized to dry sediments prior to extraction and both were contaminated by vapors that remained in the systems after heavily contaminated samples were dried. The naphthalenes, fluorenes, phenanthrenes and dibenzothiophenes were the most affected aromatic families, while compounds starting with and including anthracene were least affected. The normal alkanes and oil biomarkers in all samples were unaffected by the contamination, as were samples that contained gross amounts of oil. In an attempt to rectify the affected data, a correction factor was determined based on a ratio calculated from the average of eight (8) sediment samples that were extracted by both wet sediment and freeze-dried sediment extraction methods. By calculating the correction factor in this manner, a direct comparison between concentrations in the same sample and from each extraction methodology could be compared. See Dataset 1_Correction Factor Documentation.xls for details. All other sediment data were extracted using a wet sediment extraction procedure and were unaffected.
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