Abstract:

This dataset reports trace metals and minor element composition of sediments obtained from the northern Gulf of Mexico following the Deepwater Horizon marine oil blow out event from 2011-02-20 to 2017-07-28. Sediment cores were collected aboard multiple R/V Weatherbird II cruises (WB1736, WB1701, WB1602, WB1502, WB1403, WB1304, WB1114) using an Ocean Instruments MC-800 multi-corer with special care not to disturb the sediment-water interface. Cores were carefully extruded using a calibrated threaded rod at 2 mm at the surface and 5 mm resolution below 2 cm. The dataset contains the date, locations (latitude and longitude), water depth of sample collection sites, and trace metal concentrations. It includes data from 2014 to 2017, and from 2011 to 2013 that are not included in the previous dataset that is available at GRIIDC under Unique Dataset Identifier (UDI) Y1.x031.000:0006 (DOI: 10.7266/N7C24TDB).

Suggested Citation:

David W. Hastings. 2020. Trace metals and minor elements in sediment cores collected during the multiple R/V Weatherbird II cruises in the northern Gulf of Mexico following the Deepwater Horizon event from 2011-02-20 to 2017-07-28. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/n7-974t-cb83

Purpose:

Following the blowout of the Macondo well, the documented pulse in organic-rich sedimentation resulted in changes in sedimentary redox conditions. We exploit the downcore and temporal changes in the concentration of redox-sensitive metals (Mn, Re, and Cd) to demonstrate changes in sediment redox changes. Other trace and minor elements indicative of marine geochemical process and contamination are measured and presented here.

Data Parameters and Units:

Cruise ID (R/V Weatherbird II cruise ID), C-IMAGE cruise ID (the two-letter prefix of the ship (WB) followed by four digits), station ID (ID following the C-IMAGE cruise ID that used the nomenclature consistent with other C-IMAGE datasets archived in GRIIDC), Date (MM/DD/YYYY), Lat (Latitude in decimal degrees), Lon (Longitude in decimal degrees), water depth (m), length (mm), metal concentration (ppm, ppb and mg/g). Dataset also includes the cruise documentation for the R/V Weatherbird II cruises, WB1736 (2017-07-18 to 2017-08-01), WB1701 (2016-08-02 to 2016-09-09), WB1602 (2015-08-15 to 2015-08-30), WB1502 (2014-08-14 to 2014-08-29), WB1403 (2013-08-15 to 2013-08-30), WB1304 (2012-08-13 to 2012-08-25), WB1114 (2011-02-01 to 2011-02-28) led by chief scientists Steven Murawski, David Hollander, and Kendra Daly.

Methods:

Sediment cores were collected using an Ocean Instruments MC-800 multi-corer with special care not to disturb the sediment-water interface. Cores were carefully extruded using a calibrated threaded rod at 2 mm at the surface and 5 mm resolution below 2 cm. Subsamples (~0.2 g) were freeze-dried, weighed, then digested in a Milestone Ethos EZ microwave oven in closed digestion vessels with 10mL concentrated trace metal grade HNO3 at 175°C and high pressure (~25 bar) for 15 minutes according to standard methods (US EPA method 3051a). The digest was diluted 1:10 with MQ ultrapure H2O, and filtered with 0.45 µm PVDF syringe filters. Since HF is not used during the digestion, the digest does not include refractory components such as aluminosilicates but will include authigenic phases, crude oil, organic phases, FeMn oxides, and carbonates. The digested samples were analyzed using an Agilent 7500cx ICP-MS with an octopole reaction cell in helium mode for V, Cr, Mn, Fe, Co, Ni, Cu, Sr, Zn, and Cd to reduce isobaric interferences and in the no-gas mode for Mo, Ba, Re, Hg, Pb and U. Prior to analysis, samples were spiked with an internal standard containing Ge, In, and Bi in order to correct for instrumental drift during analysis. Elemental concentrations were determined using a 6-point external calibration line.

Instruments:

Sediment cores were collected using an Ocean Instruments MC-800 multi-corer. The digested samples were analyzed using an Agilent 7500cx ICP-MS with an octopole reaction cell in helium mode for V, Cr, Mn, Fe, Co, Ni, Cu, Sr, Zn, and Cd to reduce isobaric interferences and in no-gas mode for Mo, Ba, Re, Hg, Pb and U. Prior to analysis, samples were spiked with an internal standard containing Ge, In, and Bi in order to correct for instrumental drift during analysis. Elemental concentrations were determined using a 6-point external calibration line.

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