Background petroleum pollution before Hurricane Katrina in southeastern Louisiana (USA) coastal sediments was evaluated at 320 locations in three consecutive years for polycyclic aromatic hydrocarbons (PAHs), saturated alkanes (nC₉–nC₃₅), and petroleum biomarker compounds (hopanes, steranes, pristane, and phytane). Approximately 90% of the sample locations had a total PAH concentration of less than 2.0 μg/g and total saturated alkane concentration of less than 17 μg/g, with 50% indicating a total PAH concentration of less than 200 ng/g. Upper limit or baseline high concentration for total PAHs was 1.5 μg/g, comparable to the 2.18 μg/g reported for the National Status and Trends (NST) Program of the National Oceanic and Atmospheric Administration (NOAA). Thus, 85% of sites were below the baseline high concentration. Baseline high total PAHs at 6% of the sites (described as land) was 5.1 μg/g, comparable to the 4 μg/g benchmark calculated for NST. The three-year average total PAH concentration for 95% of the sites was less than 7.5 μg/g, a defined limit of fivefold the baseline high concentration. Samples indicated petrogenic, pyrogenic, and natural/biogenic hydrocarbon inputs. Contaminant levels exceeded the state soil screening limits at only 3% of the 320 locations. Federal screening limits proposed by the NOAA for ecological effects were exceeded at only 18% of the sites (including those sites exceeding the state limit). Only 4% of the sites had concentrations exceeding the NOAA effect range-low (ER-L) in more than one collection year. At least 61% of the analytes exceeding the ER-L were pyrogenic source indicators. Source-fingerprint analysis of these selected samples showed 10 samples with notable petroleum contamination, whereas six indicated pyrogenic input. Of all samples collected, only one site showed relatively fresh/lightly weathered petroleum.

Keywords: Hurricane Katrina, Polycyclic aromatic hydrocarbons, Effect range-low, National status/trend program, Sediment-quality benchmarks