@article {2641,
	title = {Petrocarbon evolution: Ramped pyrolysis/oxidation and isotopic studies of contaminated oil sediments from the Deepwater Horizon oil spill in the Gulf of Mexico},
	journal = {PLOS ONE},
	volume = {14},
	year = {2019},
	month = {Apr-02-2021},
	pages = {e0212433},
	abstract = {Hydrocarbons released during the Deepwater Horizon (DWH) oil spill weathered due to exposure to oxygen, light, and microbes. During weathering, the hydrocarbons{\textquoteright} reactivity and lability was altered, but it remained identifiable as "petrocarbon" due to its retention of the distinctive isotope signatures (C-14 and C-13) of petroleum. Relative to the initial estimates of the quantity of oil-residue deposited in Gulf sediments based on 2010-2011 data, the overall coverage and quantity of the fossil carbon on the seafloor has been attenuated. To analyze recovery of oil contaminated deep-sea sediments in the northern Gulf of Mexico we tracked the carbon isotopic composition (C-13 and C-14, radiocarbon) of bulk sedimentary organic carbon through time at 4 sites. Using ramped pyrolysis/oxidation, we determined the thermochemical stability of sediment organic matter at 5 sites, two of these in time series. There were clear differences between crude oil (which decomposed at a lower temperature during ramped oxidation), natural hydrocarbon seep sediment (decomposing at a higher temperature; Delta C-14 = -189 parts per thousand) and our control site (decomposing at a moderate temperature; Delta C-14 = -189 parts per thousand), in both the stability (ability to withstand ramped temperatures in oxic conditions) and carbon isotope signatures. We observed recovery toward our control site bulk Delta C-14 composition at sites further from the wellhead in similar to 4 years, whereas sites in closer proximity had longer recovery times. The thermographs also indicated temporal changes in the composition of contaminated sediment, with shifts towards higher temperature CO2 evolution over time at a site near the wellhead, and loss of higher temperature CO2 peaks at a more distant site.},
	keywords = {C-14 ANALYSES; MARINE SNOW, degradation, fractionation, organic-matter, POLYCYCLIC AROMATIC-HYDROCARBONS; MICROBIAL COMMUNITY RESPONSE, radiocarbon, STABLE CARBON, surface sediments},
	doi = {10.1371/journal.pone.0212433},
	url = {https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0212433},
	author = {Rogers, Kelsey L. and Bosman, Samantha H. and Lardie-Gaylord, Mary and McNichol, Ann and Rosenheim, Brad E. and Montoya, Joseph P. and Chanton, Jeffrey P.},
	editor = {Cooper, Lee W.}
}
@article {2721,
	title = {Sources of carbon to suspended particulate organic matter in the northern Gulf of Mexico},
	journal = {Elem Sci Anth},
	volume = {7},
	year = {2019},
	month = {May-10-2020},
	pages = {51},
	abstract = {Suspended particulate organic carbon (POCsusp) in the Gulf of Mexico is unique compared to other seas and oceans. In addition to surface primary production, isotopic analysis indicates that microbial cycling of oil and riverine inputs are primary sources of carbon to POCsusp in the Gulf. To characterize POCsusp from seep sites and non-seep north central Gulf (NCG) sites potentially affected by the Deepwater Horizon (DWH) spill, we analyzed 277 and 123 samples for δ13C and Δ1C signatures, respectively. Depth, partitioned into euphotic (300 m), was the main driver of spatial δ13C differences, with deep depths exhibiting 13C depletion. Both deep depths and proximity to sources of natural seepage resulted in 14C depletion. A two-endmember mixing model based on Δ14C indicated that sources to POCsusp were 14{\textendash}29\% fossil carbon at NCG sites and 19{\textendash}57\% at seep sites, with the balance being modern surface production. A six-component Bayesian mixing model MixSIAR, using both 13C and 14C, suggested that riverine inputs were an important carbon source to POCsusp contributing 34{\textendash}46\%. The influence of seeps was localized. Below the euphotic zone at seep sites, 46 {\textpm} 5\% (n = 9) of the carbon in POCsusp was derived from environmentally degraded, transformed oil; away from seeps, transformed oil contributed 15 {\textpm} 4\% (n = 39). We hypothesized that, at NCG sites removed from hydrocarbon seep sources, isotopic signatures would be depleted following the spill and then shift towards background-like enriched values over time. At deep depths we observed decreasing Δ14C signatures in POCsusp from 2010 to 2012, followed by isotopic enrichment from 2012 to 2014 and a subsequent recovery rate of 159{\textperthousand} per year, consistent with this hypothesis and with biodegraded material from DWH hydrocarbons contributing to POCsusp.},
	doi = {10.1525/elementa.389},
	url = {https://www.elementascience.org/article/10.1525/elementa.389},
	author = {Rogers, Kelsey L. and Bosman, Samantha H. and Weber, Sarah and Magen, Cedric and Montoya, Joseph P. and Chanton, Jeffrey P.}
}
