Chemistry data associated with submerged sediment samples collected in the Gulf of Mexico from April 2010 through December 2011

The focus of this data posting is chemistry data associated with submerged sediment samples collected in both federal and state jurisdictional waters in the Gulf of Mexico from April 2010 through December 2011. Additionally, sediment-associated water samples (e.g., pore water, supernatant, floc, and slurp2) are also provided in this data posting. More than 20,000 submerged sediment and associated water samples with associated chemistry analyses are included in this data posting. These samples were collected at more than 10,200 sampling stations during 48 studies, using more than 100 sampling cruises and/or surveys. These studies can be classified into four general categories: NRDA Cooperative—Studies conducted as part of the NRDA which were agreed to and executed cooperatively by the National Oceanic and Atmospheric Administration (NOAA), U.S. Department of Interior (DOI), and/or other Trustees, and BP. BP NRDA Independent—Studies conducted by BP independently to develop data to support and inform the NRDA. Trustee Independent—Studies conducted by NOAA, DOI, and/or other Trustees independently to develop data to support and inform the NRDA. Response (non-NRDA)—Studies conducted by BP and/or government representatives under the direction of the Unified Area Command and in association with activities performed in response to the DWH accident (the Response). The chemical parameters provided in this data posting include: Parent and alkylated polycyclic aromatic hydrocarbons (PAHs), Saturated hydrocarbons (SHC), Total petroleum hydrocarbons (TPH), including parameters reported as total extractable material (TEM) and total extractable hydrocarbon (TEH), Benzene, toluene, ethyl benzene, and xylenes (BTEX) and other volatile hydrocarbons classified as paraffins, isoparaffins, aromatics, naphthenes, and olefins (PIANO), Geochemical biomarkers (sterane and triterpane), where available, Metals, Total Organic Carbon (TOC), Percent moisture or percent solids, Grain size parameters. This dataset includes data associated with natural field samples, along with the associated field-collected quality control samples, such as field replicates, equipment blanks, field blanks, and trip blanks. No other laboratory quality control samples (e.g., laboratory blanks and spike samples) are included in this data posting. The Trustees developed an approach for screening sediments for the potential presence of oil using analysis by gas chromatography/flame ionization detection (GC/FID) and visual inspection of the resulting chromatograms. Through this visual inspection of the chromatograms, screened samples were categorized by comparing the amount of oil (of any source) present in the sample, if any, to the abundance of naturally-occurring organic matter (NOM) as determined by the chromatographic character of the extractable hydrocarbons. The Trustees developed the following four classification levels: A = Oil is present in excess of NOM, B = Oil is present in comparable abundance to NOM, C = Trace oil is present but is exceeded by NOM, D = No obvious oil, overwhelmingly comprised of NOM. All samples classified by Trustee representatives in the preliminary screening phase as Category A, B, or C were sent for further laboratory analysis. The Sediment Chemistry Sample Summary associated with this data release [see Version History] provides Trustee’s “TPH Category from Chromatogram” classification level in Column S. Within this Sediment Chemistry Data Posting of approximately of 20,350 analytical samples: 7,800 samples have TPH screening classification levels available on the Trustees website, 1,473 (19% of total screened) samples were assigned to classification levels of A, B, or C, 6,327 (81% of total screened) samples were assigned to classification levels of D. Of the 6,327 samples classified by Trustee representatives as Category D samples (no obvious oil), 845 (13%) were further analyzed for the PAH, SHC, and biomarker parameters; thus, leaving 5,482 samples in this data posting with chemistry data limited to TPH or TPH and SHCs and a Trustee assigned screening classification of “no obvious oil”.