"A three-year baseline sampling and analysis study of petroleum pollutants in Coastal Louisiana"

Abstract

The Louisiana Oil Spill Coordinator's Office (LOSCO) conducted a three-year study of baseline levels of oil spill constituents in South Louisiana as mandated by Act 740 of the Louisiana Legislature. The act mandated an environmental inventory concentrating on areas with a high probability of oil spills. The main goal of the project was to streamline restoration efforts in Coastal Louisiana, the Mississippi River, major tributaries and reduce associated risks to habitat. The study consisted of 3,540 composite sediment samples collected at 1,180 sites each year from 1997 through 1999. Results indicate that the mean level of total unresolved petroleum hydrocarbons (TUPH) in coastal Louisiana and major rivers during 1997 to 1999 was 44,608ng/g based on dry weight sediment. The mean total saturated hydrocarbons n-alkanes level (nC9-nC35) was 5,444ng/g. and mean total polynuclear aromatic hydrocarbons (PAH) level was 587ng/g. Results indicate chronic/degraded and recent input of petroleum contamination in coastal areas and the Mississippi river. These results indicated that petroleum constituents in Louisiana sediments are bio-available reservoirs of polynuclear aromatic hydrocarbons posing some risk to the ecosystem. Approximately 5% of the sites investigated have TPAH levels more than 1,000ng/g in three consecutive years while 51% of the samples have TPAH levels less than 100ng/g indicating low pollution. More than 98% of the samples were below NOAA sediments quality guidelines ERL (Effects Range - Low) values for PAHs. About 159 hot spots in 17 parishes (counties) were identified where all TUPH, TPAH and T-Sat exceeded the average concentration in at least one sampling year. The data suggests that current concentrations of contaminants in Louisiana are basically not in the toxic range to produce biological effects. However efforts would be necessary to monitor, control, and alleviate contaminants of concern especially in hotspot areas.