Characterization and degradation of petroleum hydrocarbons following an oil spill into a coastal environment of south Texas, USA
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abstract
Petroleum hydrocarbons were characterized at eleven sites within the sediments of a coastal stream in south Texas, U.S.A. following a medium sized crude oil spill. Bank and open-water (deep) sediments were collected at each site. Hydrocarbons targeted for analysis included 22 aliphatic hydrocarbons (C-11 to C-34) and 16 polynuclear aromatic hydrocarbons. Sediment concentrations were measured at intervals of 1, 2, 3, 4, 6, and 12 months post-spill. Higher hydrocarbon concentrations were observed for a longer duration within the deep sediments than bank sediments. Initial hydrocarbon constituents in impacted sediments matched the crude oil fingerprint accurately with the exception of the lighter-end hydrocarbons. The lighter-end aliphatic hydrocarbons are affected immediately by evaporation and dissolution processes during the spill event and were found below the detection levels at most of the sites. Total hydrocarbon concentrations in sediments within each hydrocarbon group returned to background levels by the end of the study period. Observed decreases in high molecular weight polycyclic aromatic hydrocarbons (PAH) concentrations exceeded known environmental degradation rates which suggests the influence of a sediment transport process. Overall, the fate of petroleum hydrocarbons within this type of environment were likely related to both degradation and sediment transport processes. By the end of the study period, most individual PAH constituent concentrations were below threshold concentrations thought to produce toxic effects in marine and estuarine organisms. PAH constituents concentrations remaining above threshold concentrations included benz(a)anthracene, chrysene, and benzo(a)pyrene.
