Varying Relative Degradation Rates of Oil in Different Forms and Environments Revealed by Ramped Pyrolysis

Degradation of oil contamination yields stabilized products by removing and transforming reactive and volatile compounds. In contaminated coastal environments, the processes of degradation are influenced by shoreline energy, which increases the surface area of the oil as well as exchange between oil, water, sediments, microbes, oxygen, and nutrients. Here, a ramped pyrolysis carbon isotope technique is employed to investigate thermochemical and isotopic changes in organic material from coastal environments contaminated with oil from the 2010 BP Deepwater Horizon oil spill. Oiled beach sediment, tar ball, and marsh samples were collected from a barrier island and a brackish marsh in southeast Louisiana over a period of 881 days. Stable carbon (¹³C) and radiocarbon (¹⁴C) isotopic data demonstrate a predominance of oil-derived carbon in the organic material. Ramped pyrolysis profiles indicate that the organic material was transformed into more stable forms. Our data indicate relative rates of stabilization in the following order, from fastest to slowest: high energy beach sediments > low energy beach sediments > marsh > tar balls. Oil was transformed most rapidly where shoreline energy and the rates of oil dispersion and exchange with water, sediments, microbes, oxygen, and nutrients were greatest. Still, isotope data reveal persistence of oil

Supplement 1. R scripts for conducting clear sky PAR simulations described in the main text.

<h2>File List</h2><div> <p><a href="Clear Sky PAR Model.txt">Clear Sky PAR Model.txt</a> (MD5: 487aee68581be90fc60476a2c3af1b2d)</p> </div><h2>Description</h2><div> <p>The code included in <i>Clear Sky PAR Model.R</i> allows conducting the model of clear sky PAR used for calibration of PAR sensors as described in the methods section of the main text.</p> </div