Abstract:

The concentration of redox sensitive metals (Mn, Re, and Cd) and a suite of other metals (V, Cr, Mn, Fe, Co, Ni, Cu, Sr, Cd, Mo, Ba, Re, and U) was analyzed in bulk sediments following the blowout event. These are metals extracted with concentrated HNO3 at high temperature and pressure.

Suggested Citation:

Hastings, David. 2014. Trace metals and minor elements in Northern Gulf of Mexico Sediments baseline and following the DWH oil spill, Jan 2009, May 2010, and August 2010 to 2013. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7C24TDB

Publications:

Hastings, D. W., Schwing, P. T., Brooks, G. R., Larson, R. A., Morford, J. L., Roeder, T., … Hollander, D. J. (2014). Changes in sediment redox conditions following the BP DWH blowout event. Deep Sea Research Part II: Topical Studies in Oceanography. doi:10.1016/j.dsr2.2014.12.009

Schwing, P. T., Romero, I. C., Larson, R. A., O’Malley, B. J., Fridrik, E. E., Goddard, E. A., … Mulhollan, J. (2016). Sediment Core Extrusion Method at Millimeter Resolution Using a Calibrated, Threaded-rod. JoVE, (114). doi:10.3791/54363

Hastings, D. W., Bartlett, T., Brooks, G. R., Larson, R. A., Quinn, K. A., Razionale, D., … Hollander, D. J. (2019). Changes in Redox Conditions of Surface Sediments Following the Deepwater Horizon and Ixtoc 1 Events. Deep Oil Spills, 269–284. doi:10.1007/978-3-030-11605-7_16

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

Data Parameters and Units:

Units are those normally used in trace and minor element analysis: Either ppm or ppb for trace elements; mg/g for Mn and Fe. Hastings_GRIIDC_Data.xlsx-- [Sed Trap 2009, Fisk Basin July 2007, Garrison Basin July 2007, June 2011 NT1200, Aug 2010 DSH10, Dec 2010 DSH08, Dec 2010 DSH10, Dec 2010 PCB06, Feb 2011 DSH08, Feb 2011 DSH10, Feb 2011 PCB06, Sept 2011 DSH08, Sept 2011 DSH10, Sept 2011 PCB06, Apr 2012 SW01, Apr 2012 SW02, Aug 2012 SW03, Aug SL1040, Aug 2012 DWH01, Aug 2012 DSH08, Aug 2012 DSH10, Aug 2012 PCB06, Aug 2012 SW01, Aug 2013 DSH08, Aug 2013 PCB06, Aug 13 DSH10]: Point Latitude and Longitude (decimal degrees), one water depth (meters), Sample ID, Depth(mm), trace and Minor elements (ppm) [V, Cr, Mn, Fe, Co, Ni, Cu, Sr, Mo, Cd-111, Ba, Re, U].

Methods:

Sediment cores were collected in the NE GoM on a series of cruises from August 2010 to August 2013. Cores were carefully extruded using a calibrated threaded rod at 2 mm resolution in the top 20 mm, and at 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.

Instruments:

The 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, and Cd to reduce isobaric interferences and in no-gas mode for Mo, Ba, Re, 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.

Error Analysis:

Triplicate samples were typically measured for one or two depth intervals in each core with an average relative precision of ±2.5%, ±4.5%, ±4%, and ±4% (1 σ) for Mn, Re, Cd and Ba, respectively. Long-term analytical precision based on analyzing the same sample 3 times each run over 1.5 years of ICP MS analyses is ±3%, ±5%, ±5%, and ±2% (1 σ) for Mn, Re, Cd and Ba, respectively.

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