ABSTRACT
The Louisiana Oil Spill Coordinator's Office (LOSCO) has conducted a 3-year study of baseline petroleum pollutant levels in South Louisiana. The project collected a total of 3,540 composite sediment samples from 1,180 sites. Each site was sampled three times, once a year from 1997 through 1999. Samples were collected within four zones; each zone was assigned to a different contractor. The zones were located primarily along the Louisiana coast, with additional sampling points along the Mississippi River, Atchafalaya Navigation Channel, Red River, and Ouachita-Black River. LOSCO emphasized areas at high risk of sustaining oil spills. The project required a 10 parts-per-billion detection limit for 65 analytes, including parent and alkylated polynuclear aromatic hyrdrocarbons (PAHs), saturated hydrocarbons (up to 35 carbon units), pristane, phytane, hopanes, and steranes. The targeted analytes provide a sample profile that can be used to both classify contaminant sources (crude, heavy fuel oil, combustion sources, etc.) and identify crude oil sources.
To standardize analytical results between contract laboratories and to ensure data quality, LOSCO funded development of an analytical standard operating procedure (SOP). The SOP describes a tumbling method of sample extraction and gas Chromatograph mass spectrometer (GC-MS) selected ion mode (SIM) analysis. This method is similar to procedures used to assess the environmental impacts of the Exxon Valdez oil spill, as well as other spills. SOP appendices describe identification and standardization procedures for quantifying alkylated PAH. Extraction and quantitative analysis of a reference-contaminated sediment supplied by LOSCO was required for every 30 samples.
The review process included: (1) a review of electronic spreadsheets to pinpoint incorrect or invalid results, and (2) an examination of hardcopy laboratory documents and electronic data files to determine if the analysis and data processing were performed correctly.
Baseline Sampling and Analysis Monitor Point Locations data sets1, in Geographic NAD83 (LOSCO, 1999a) for each of the sampling years, have been compiled in a geographical information system (GIS) format. Analytical results will be provided via the Internet or CD-ROM. The linking of field and analytical results allows examination and spatial analysis of study results.