Abstract:

These data are from beach and marsh sediment and soil samples collected partially with GOMRI CARTHE funds and partially with NSF funds. Samples were collected from Grand Isle and Barataria Bay between 2010 and 2013 (latter samples using funds from GOMRI). Samples were analyzed using the Ramped PyrOx 14C technique (Rosenheim, B. E., M. B. Day, E. W. Domack, H. Schrum, A. Benthein, J. M. Hayes (2008): Antarctic sediment chronology by programmed-temperature pyrolysis: Methodology and data treatment. Geochem. Geophys. Geosyst. 9 (4), Q04005, DOI: 10.1029/2007GC001816). Ramped PyrOx samples were sent to the National Ocean Sciences Accelerator Mass Spectrometer facility (NOSAMS) at Woods Hole Oceanographic Institution for analysis of radiocarbon and stable isotopes. This dataset reports the gas flow rates, temperature, and fraction of carbon dioxide released during pyrolysis. This dataset also reports radiocarbon dating and stable isotope analyses of ramped pyrolysis samples. Analyses took nearly two years to complete. The goal of the analyses was to observe bulk chemical transformation, degradation and mixing with the oil and byproducts. Results have been reported in Pendergraft, M. A. and B. E. Rosenheim (2014): Varying Relative Degradation Rates of Oil in Different Forms and Environments Revealed by Ramped Pyrolysis. Env. Sci. & Tech. 48 (18), 10966-10974, DOI: 10.1021/es501354c.

Suggested Citation:

Pendergraft, Matthew and Rosenheim, Brad. 2016. Marsh and Beach Sediment and Soil Ramped PyrOx 14C Data, Grand Isle and Bay Jimmy LA, June-July 2010. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7QF8QTW

Publications:

Pendergraft, M. A., & Rosenheim, B. E. (2014). Varying Relative Degradation Rates of Oil in Different Forms and Environments Revealed by Ramped Pyrolysis. Environ. Sci. Technol., 48(18), 10966–10974. doi:10.1021/es501354c

Purpose:

Assess thermochemical stability of oil in coastal LA over time

Data Parameters and Units:

The DB-... files are datafiles from the ramped pyrox analysis of sediments from coastal Louisiana. They contain the following unlabled columns: for DB-341-.... column1: timestamp column2: pCO2 - the mole fraction of CO2 in the gas leaving the ramped pyrox reactor, in umol/mol (umoles of CO2 per mole of gas) column3: pyrolysis temperature in degrees Celsius column4: smoothed/averaged pCO2 used in publications (running average smoothing) for remaining DB-... files: column1: date&time stamp column2: pCO2 - the mole fraction of CO2 in the gas leaving the ramped pyrox reactor, in umol/mol (umoles of CO2 per mole of gas) column3: pyrolysis temperature in degrees Celsius column4: main helium gas flown rate into ramped pyrox reactor, in ml/min column5: helium gas flow rate into side of ramped pyrox reactor, in ml/min column6: oxygen gas rate into side of ramped pyrox reactor, in ml/min column7: smoothed/averaged pCO2 used in publications (running average smoothing) for table es501354c_Table_S2: labeled columns: Sample - sediment sample ID number day count - sampling day count over the course of 881 days following the Macondo well blow-out RP Temp. Limit, °C - upper temperature limit at which a sample of CO2 was collected on the ramped pyrox system umol C - micromoles of carbon contained in the CO2 sample collected on the ramped pyrox system Fm - fraction of the 14C/12C ratio of the measured sample compared to that of a “modern” standard 1σ - one stadard deviation of the Fm data Δ14C - radiocarbon data using Δ convention, in ‰ 1σ - one standard deviation of Δ14C measurement Δ14Cgm - geometric mean radiocarbon value for the individual CO2 samples evolved from a single sediment sample, weighted by micromoles of carbon for individual CO2 samples, in ‰ 1σ - one standard deviation of Δ14Cgm values δ13C - stable carbon isotopic signature, in ‰ δ13Cgm - geometric mean stable carbon for the individual CO2 samples evolved from a single sediment sample, weighted by micromoles of carbon for individual CO2 samples, in ‰ foil - fraction of total acid insoluble organic matter derived from oil, calculated from radiocarbon data foil-gm - geometric mean fraction of total acid insoluble organic matter derived from oil, calculated from radiocarbon data, for the individual CO2 samples evolved from a single sediment sample, weighted by micromoles of carbon for individual CO2 samples * for radiocarbon data reporting conventions, see Stuiver, M.; Pollach, H. A. Reporting of 14C data. Radiocarbon 1977, 19(3), 355−363. ** The symbol ‰ means "per mille" or parts per thousand; 1‰ = 1/1000 = 0.001. All radiocarbon data corrected for RP ramped pyrolysis AMS Accelerator Mass Spectrometer blank; error propagated for gm geometric mean error. All δ13Cgm 1σ (one standard deviation) between 0.0 and 0.1

Methods:

Sample locations: Grand Isle (low energy site): 29.2695, -89.9552 for DB658, DB665, DB670 Grand Isle (high energy site): 29.2688, -89.9529 for DB643, DB639, DB475 Grand Isle (between the two main sites, moving daily with the tides and surf): DB646, DB649, DB653, DB654 Bay Jimmy: 29.44462 -89.89958 for DB707, DB659, DB657, DB656, DB341

Individual Files: