Field survey of Canadian background soils: Implications for a new mathematical gas chromatography-flame ionization detection approach for resolving false detections of petroleum hydrocarbons in clean soils.

The reference method for the Canada-wide standard (CWS) for petroleum hydrocarbons (PHCs) in soil provides laboratories with methods for generating accurate and reproducible soil analysis results. The CWS PHC tier 1 generic soil-quality guidelines apply to 4 carbon ranges/fractions: F1 (C6-C10), F2 (C10-C16), F3 (C16-C34), and F4 (>C34). The methods and guidelines were developed and validated for soils with approximately 5% total organic carbon (TOC). However, organic soils have much higher TOC levels because of biogenic organic compounds (BOCs) originating from sources such as plant waxes and fatty acids. Coextracted BOCs can have elevated F2-F4 concentrations, which can cause false exceedances of PHC soil guidelines. The present study evaluated false PHC detections in soil samples collected from 34 background sites. The list of analytes included soil type, TOC, polycyclic aromatic hydrocarbons (PAHs), F2, F3, F4, F3a (C16-C22), and F3b (C22-C34). Soils with 3% to 41% TOC falsely exceeded the CWS PHC 300 mg/kg F3 coarse soil guideline. It was previously demonstrated that clean peat had F2:F3b ratios of less than 0.10, while crude oil spiked peat and spiked sand had higher ratios of greater than 0.10. In the present background study, all of the clean organic soils with at least 300 mg/kg F3 had F2:F3b ratios of less than 0.10, which indicated false guideline exceedances. Clean inorganic soils had low F3 concentrations, resulting in high F2:F3b ratios of greater than 0.10. Validation field studies are required to determine if the F2:F3b 0.10 PHC presence versus absence threshold value is applicable to crude oil- and diesel-contaminated sites.

Is it clean or contaminated soil? Using petrogenic versus biogenic GC-FID chromatogram patterns to mathematically resolve false petroleum hydrocarbon detections in clean organic soils: a crude oil-spiked peat microcosm experiment.

The Canadian Council of Ministers of the Environment (CCME) reference method for the Canada-wide standard (CWS) for petroleum hydrocarbon (PHC) in soil provides chemistry analysis standards and guidelines for the management of contaminated sites. However, these methods can coextract natural biogenic organic compounds (BOCs) from organic soils, causing false exceedences of toxicity guidelines. The present 300-d microcosm experiment used CWS PHC tier 1 soil extraction and gas chromatography-flame ionization detector (GC-FID) analysis to develop a new tier 2 mathematical approach to resolving this problem. Carbon fractions F2 (C10-C16), F3 (C16-C34), and F4 (>C34) as well as subfractions F3a (C16-C22) and F3b (C22-C34) were studied in peat and sand spiked once with Federated crude oil. These carbon ranges were also studied in 14 light to heavy crude oils. The F3 range in the clean peat was dominated by F3b, whereas the crude oils had approximately equal F3a and F3b distributions. The F2 was nondetectable in the clean peat but was a significant component in crude oil. The crude oil­spiked peat had elevated F2 and F3a distributions. The BOC-adjusted PHC F3 calculation estimated the true PHC concentrations in the spiked peat. The F2:F3b ratio of less than 0.10 indicated PHC absence in the clean peat, and the ratio of greater than or equal to 0.10 indicated PHC presence in the spiked peat and sand. Validation studies are required to confirm whether this new tier 2 approach is applicable to real-case scenarios. Potential adoption of this approach could minimize unnecessary ecological disruptions of thousands of peatlands throughout Canada while also saving millions of dollars in management costs.