Total petroleum hydrocarbons from marine sediments sampled for the Davis STP project

Brief description

This metadata record contains an Excel file containing total petroleum hydrocarbon data from analysis of marine sediments collected at Davis Station from December 2009 to March 2010. Refer to the Davis STP reports lodged under metadata record Davis_STP for the full Davis Sewage Treatment Project methods and result details.

Davis STP - Total petroleum hydrocarbons
Hydrocarbons were extracted from a 10g sub-sample of homogenised wet soil by tumbling overnight with a mixture of 10 mL of deionised water, 10 mL of dichlormethane (DCM), and 1 mL of DCM spiked with internal standards: 254 mg/L bromoeicosane; 55.2 mg/L 1,4 dichlorobenzene; 51.2 mg/L p-terphenyl; 52.2 mg/L tetracosane-d50; and 255 mg/L cyclo-octane. Samples were then centrifuged for 5 minutes at 1000 rpm, this was repeated a further 3 times to ensure complete separation of the organic and aqueous fractions. The DCM fraction was then extracted and placed into GC-vials.
Extracts were analysed for total petroleum hydrocarbons (TPH) by gas chromatography using flame ionisation detection (GC-FID; Agilent 6890N with a split/splitless injector) and an auto-sampler (Agilent 7683 ALS). Separation was achieved using an SGE BP1 column (25 m x 0.22 mm ID, 0.25 µm film thickness). 1 µL of extract was injected (5:1 pulsed split) at 310° C and 17.7 psi of helium carrier gas. After 1.3 minutes, the carrier gas pressure was adjusted to maintain constant flow at 3.0 mL/min for the duration of the oven program. The oven temperature program was started at 36 °C (held for 3 minutes) and increased to 320 °C at 18 °C/min. Detector temperature was 330 °C.
TPH concentrations were determined using a calibration curve, generated from standard solutions of special Antarctic blend diesel (SAB), and standard diesel. TPH was measured using the ratio of the total detector response of all hydrocarbons to the internal standard peak response.
List of compounds analysed
- C8-C28 individual hydrocarbon components
- Naphthalene
- Biomarkers (phytanes)
- Total signal and area, and resolved compounds from C8 to C40, over specific ranges (e.g. C9-C18, SAB)
Reporting limit
- 0.3 mg.kg-1 on a dry matter basis (DMB) for individual components
- 2.5-160 mg.kg-1 on a dry matter basis (DMB) for various calculated ranges
Analytical uncertainty
- Analytical precision: (a) 3 samples extracted and analysed in triplicate, (b) 3 extracts analysed by GC-FID in duplicate; only 1 of each set greater than RL (160): (a) RSD = 2%, (b) RSD = 0.4%
- Site heterogeneity: reproducibility (RSD) of mean data from site replicate samples (mostly duplicates) was 24% (mean, SD 20%, range 4-60%, n=8)
- From the limited data on reproducibility summarised above, it can be concluded that site heterogeneity contributes most to the uncertainty of the TPH data for the site locations.


Background of the Davis STP project

Refer to the Davis STP reports lodged under metadata record Davis_STP.