Critical Review of an Interlaboratory Forensic Dataset

Large-scale and long-term environmental investigations, like regional oil spills, typically employ multiple laboratories to prepare and analyze large numbers of samples within regulatory holding times and contractual specifications. These projects generate large quantities of quality control data for assessing method performance. In this study we compare intra- and interlaboratory variability among laboratories participating in the Deepwater Horizon Natural Resource Damage Assessment between 2010 and 2015. Results show that although interlaboratory measurements of EPA Priority Pollutant polycyclic aromatic hydrocarbons (PAHs) were consistent with environmental industry standards the concentrations of alkylated PAHs and geochemical biomarkers exhibited high variability. These observations serve as important benchmarks when designing sampling and analysis plans for source identification or other forensic purposes. As such, interlaboratory datasets generally lack the level of precision and accuracy needed to differentiate compositionally similar sources, low-level impacts from background, contaminant mobility, and natural recovery in multimedia samples.