TRACKING OIL FROM DEEPWATER HORIZON OIL SPILL IN BARATARIA BAY SEDIMENTS
One and a half year after this incident, a set of oiled marsh samples (2 grab samples) coupled with nearby subtidal and intertidal cores (12 cores) were collected from Barataria Bay, Louisiana to determine the probable source of petroleum residues present and to characterize the chemical composition of oil. Total aliphatic and polycyclic aromatic hydrocarbons (PAHs) concentrations and weathering rate were determined from GC-MS and GC-FID analyses. Surface total petroleum hydrocarbons (TPH) range from 93 to 3,000 ug/g in the area with the exception of samples collected nearest the source (Area “A”: average = 410,000 ug/g). Similarly, concentrations of aromatic hydrocarbons (PAHs) in the surface samples range from 39 to 490 ng/g contrast with the average concentration encountered for samples in area “A” (21,000 ng/g). Most cores collected in the area showed a nearly homogeneous distribution with depth while concentrations in area “A” decreased from a surface value of 30,000 ng/g to 430 ng/g at a depth of 9 cm.
Although a direct connection between the detected and spilled Macondo oils is complicated due to confounding factors (e.g., already present hydrocarbons and weathering processes), our preliminary data indicates that both oils have similar signature, and the impact of the Macondo Mc252 Oil Spill in Barataria Bay appears to be limited to certain areas where more oil was deposited. The oil has undergone moderate weathering and appears to have penetrated the top 5 cm sediments. Additionally, sedimentation rate was estimated as 0.39 cm/year, from 137Cs inventories. Using the sedimentation rate, there is a concordance with the amount of onshore oil and gas production, the loss of wetlands in Barataria Bay and down TPH concentrations.