Chemistry data associated with water column samples collected in the Gulf of Mexico from May 2010 through July 2012

This report contains water chemistry data, and provides additional context for the posted dataset, including information about the collection, analysis, and organization of the data. This data posting differs from other recently published datasets relating to the Gulf of Mexico in several respects: This Water Chemistry dataset focuses only on information related to petroleum-related chemical constituents in water samples. Chemical compounds that are not present in oil (such as polychlorinated biphenyls, pesticides, and halogenated volatiles) are not included in this dataset. This dataset includes data from independent studies performed by BP consultants. BP has been working to produce and organize these independent data, and has engaged outside consultants to perform quality assurance and quality control (QA/QC) checks. These data were initially made publically accessible in November 2013 and are updated with additional results in this publication to reflect the results of further QA/QC. This dataset combines results from fifty-four NRDA studies and thirteen Response studies to create a unified data file. Certain Response data have been reprocessed with lower analytical method detection limits (MDLs) than originally reported, and other data have been adjusted for surrogate recoveries as described in the documentation. The focus of this data posting is chemistry data associated with water column samples collected in both federal and state jurisdictional waters in the Gulf of Mexico from May 2010 through July 2012. More than 20,000 water samples with associated chemistry analyses collected at more than 6,300 sampling stations are included in this posting. These samples were collected during 67 studies, using more than 100 sampling cruises and 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. The chemical analyte lists are generally consistent between studies for the standard PAH, SHC, and BTEX compounds. However, portions of the dataset also include analysis of the extended PIANO volatile hydrocarbon list, TPH, or geochemical biomarkers. Additionally, NRDA PAH analyses include an extended list of parent and alkylated decalins, benzothiophenes, naphthobenzothiophenes, and several other PAHs and related chemicals that were not included in Response analyses. This dataset includes data associated with natural field samples for whole water and for Payne filter and filtrate pairs (Payne et al. 1999), along with the associated field-collected quality control samples, such as field replicates, equipment blanks, field blanks, and trip blanks. Laboratory duplicate sample data are provided, where available. Mississippi Canyon lease block 252 (MC252) control oils analyses associated with water chemistry analyses are provided separately from this data posting (see Version History). No other laboratory quality control samples (e.g., laboratory blanks and spike samples) are included in this data posting. Before posting, extensive work was done to verify some aspects of the posted information (e.g., positional coordinates and field data).