Baseline for PAHs and metals in NW Gulf of Mexico related to the Deepwater Horizon oil spill

Abstract

As a rapid response to the massive oil spill caused by the sinking of the Deepwater Horizon (DWH) Platform in the northern Gulf of Mexico in April 2010, a baseline study was initiated. The study focused on determining the concentration of crude oil petroleum hydrocarbons and trace metals (Cr, Ni and V) in water and surface sediments from Mexico's EZZ, in the NW Gulf of Mexico. A total of 60 samples obtained from the shelf-slope regions were analyzed by GC/FID for 16 EPA priority polycyclic aromatic hydrocarbons (PAHs) and ICP/MS for Cr, Ni and V. The concentrations of PAHs in the surface water were below detection limits (<0.003–0.03 μg L−1) while in sediments, ranged from 0.01 to 0.070 μg g−1. International sedimentary quality guidelines (ERL-ERM) indicated a low probability of harmful effects to benthic organisms. Similarly, metal concentrations in sediments exhibited low concentrations (Cr 25.2–117, Ni 9.6–50.8, V 42.9–150.8 μg g−1). These metals were traced to a lithogenic source related to the heavy sediment load contributed by local rivers; no traces of anthropogenic inputs from oil related operations were identified. Significant enrichment of Ni and V was recorded in deep sediments whose ERL limits did not represent adverse conditions to benthic communities except for few sites on the upper continental slope. During the first two years of environmental monitoring of Mexico's EZZ in the NW Gulf of Mexico, no evidence of the DWH oil spill have been detected.