Assessment of Hydrocarbon Carryover Potential for Six Field Cleaning Protocols

Sample collection in the field faces many challenges including, but not limited to, the equipment and materials that can be brought safely into the field. Field teams will often reuse sample collection gear by cleaning it between sampling sites to prevent cross-contamination. Decontamination protocols for equipment used to collect samples for organic contaminant analysis range from a simple water rinse with scrub brush application to more involved measures that include soap and/or the use of various organic solvents. The efficacy of six different field cleaning protocols for sediment sampling tools was evaluated in a controlled laboratory setting using two different sediments (predominantly sand and silt) that were dosed with weathered Deepwater Horizon oil (i.e. “Slick B oil”; collected from surface slicks on June 19, 2010). Percent (%) residual total extractable hydrocarbons (TEH) and percent residual polycyclic aromatic hydrocarbons (PAH) were measured to evaluate the relative effectiveness of the various protocols in removing oiled sediment from the stainless steel materials. Cleaning protocols encompass scenarios where decontamination is limited by resources, supplies, and time, as well as scenarios where resources, supplies, and time are not a factor. Key findings from this study are that the measured % residual TEH and PAH values from all protocols in this study were within the range of values that would be indistinguishable from expected sampling, laboratory, or instrumental variability; thus, regardless of decontamination protocol, all were effective at hydrocarbon removal, cleaning protocols that used organic solvents as a step had less % residual TEH and % residual PAH than protocols that didn’t use solvent as a step and the highest % residual TEH and % residual PAH value (0.032% and 0.029% respectively) were obtained from the cleaning protocol that only used site water and a scrub brush.