tph analysis theory and practice

1. TPH Analysis

2. Subjects Covered Chemistry of TPH and PAH Sample preparation

3. Definition of Petroleum Hydrocarbons Gasoline Range C5 - C15 aliphatic hydrocarbons, cycloalkanes (volatile) (C5 - C10 typical analysis range) BTEX + other monoaromatics (20 - 50% of fresh petrol) Diesel Range C8 - C30 alkanes and aromatic hydrocarbons, polar aliphatics and aromatics (contain N, O or S) (C10 - C30 typical analysis range) The 16 EPA PAHs included in this range Mineral Oil Range C21 - C45+ hydrocarbons Mainly aliphatic, but 20 - 30% complex aromatics

4. GC trace of TPH

5. TPH confuser! EPH = Extractable Petroleum Compound DRO=Diesel Range Organics GRO=Gasoline Range Organics TPH=Total Petroleum Hydrocarbon (GRO+DRO) EDRO=Extended Diesel Range Organics SVOCs=Semi Volatile Organic Compounds Numerous methods used Each gives a very different result for the same sample Indiscriminate use of TPH data can create poor risk assessments!

6. TPH - What is it really? TPH is a measure of the sum of the aliphatic and aromatic hydrocarbons derived from refined petroleum products or crude oils TPH should not include naturally occurring organics TPH should not include polar compounds (substances containing N, O or S) The majority of the toxicity of TPH is derived from the C6 - C21 aromatic content

7. TPH Analysis Each method generates a different set of information Some of the information generated will contradict information from another method No single method can really provide a definitive concentration of petroleum derived hydrocarbons in a sample TPH values should be used as guidance only and not a hard and fast �real� value

8. Gasoline Range Organics C5 - C10 hydrocarbons BTEX (20 - 50%) Aliphatics (octane etc) Parrafins Cycloalkanes Polyaromatics (Naphthalenes) Petrol includes components in both GRO and DRO fraction

9. Weathering of GRO Aliphatics easier for microbes to metabolise Aliphatics have much lower boiling points and volatilise very easily Aromatics and cyclic alkanes more stable towards bacterial degradation Benzene very soluble, TEX less so, but monoaromatics dissolve appreciably in water Weathering of gasoline retains more of the aromatic fraction, except benzene Weathered petrol is approx 60% TEX

10. Weathering of GRO

11. BTEX

12. GRO v BTEX BTEX is just 6 compounds. GRO is several hundred, including many aliphatic compounds However, weathered petrol is approx 60 - 80% BTEX, mainly TEX The GRO analysis will give results from diesel samples. In this case the GRO result will be considerably higher than the BTEX result

13. BTEX Recovery Purge and Trap standard method used by labs in UK The poor recovery is why many lab results significantly under estimate the BTEX fractions Modified purge and trap is still not very efficient

14. Sample Collection for GRO The hydrocarbons are very volatile For best results place sample into extraction methanol at sample location Transferring sample to a normal lab sample jar and then taking a sub sample for the analyser will cause as much as 80% of the GRO hydrocarbons to be lost Shipping samples in containers where soil in the cap or on the jar thread stops the cap from sealing allows BTEX to escape

15. Headspace analysis of GRO/TPH Volatile Hydrocarbons are very labile, especially in clays and light soils. Removing a sample from the ground can cause over 50% of the pollutant to be lost to the air. Small concentrations of gasoline or slightly weathered diesel can give strong odours especially when a sample has been placed in a sample jar and the jar is subsequently opened. A soil sample weighing 850g with a contamination level of 100mg/kg of petrol contained in a 500 ml sample jar contains 85 mg of petrol. If all this volatilises into the headspace, this will give an effective concentration of 85 mg/50ml (assuming 50 ml of headspace is present). This is the same as 1,700 ppm in the headspace. In practice, only 10 � 20% will volatilise, but this still gives around 170 � 340 ppm of petrol in the headspace and this will have a very strong odour and high reading on the PID/FID 25 microlitres (a drop) of petrol or diesel in a 100 ml jar smells very strongly of fuel. This is equivalent to 175 parts per billion and indicates the sensitivity of the human nose to petroleum hydrocarbons. This is why headspace analysis with PID or FID detectors can give misleading data when used as a simple screening tool.

16. Diesel Range Organics Includes, Diesel, Kerosene, Heating Oil, Jet fuel C8 - C30 aliphatics, paraffins and cycloalkanes C10 - C22 polyaromatics Complex heterocyclics (benzothiophenes, pyrroles, anilines) Complex aliphatics (Pristane, Phytane) Diesel contains appreciable amounts of GRO range hydrocarbons (monoaromatics)

17. Composition of #2 Diesel BTEX present 2 - 3 ring PAHs make up >1% of the total 5 ring + PAHs form a very low % of the total

18. DRO GC Trace

19. Diesel Standard - Aliphatics

20. Diesel Standard - Aromatics

21. DRO Diesel contains very little hydrocarbon above C21, both for aliphatic and aromatic fractions. It is unlikely that a diesel or heating oil spill will create high concentrations of >C21 hydrocarbons, even when recently spilled Most DRO analyses by GC cannot see the BTEX range as the solvent used to dissolve the diesel masks these compounds

22. Diesel Weathering Diesel predominantly aliphatic hydrocarbons. Bacteria quickly eat these chains reducing their length. The light end hydrocarbons such as naphthalenes, monoraomatics and C8-C10 aliphatics are volatile and will evaporate quickly The remaining hydrocarbons are less volatile and soluble than petrol hydrocarbons Polyaromatic hydrocarbons remain as these are less soluble and more resistant to microbial activity Main route of weathering is bacteria

23. Weathering of Diesel

24. DRO Interpretation Weathered diesel predominantly in the range C14 - C22. PAHs the predominant compound For EPH lab results, DRO should have the majority of the hydrocarbon in the C14 - C16 and C17 - C21 bands Lab results showing >70% of the EPH result in the >C21 bands are detecting compounds not from the Diesel Range

25. Laboratory Reporting Many labs now report TPH bands C6-C7 aromatics C10 - C12 aliphatics etc These are useful for identifying the hydrocarbon type. For EPH analysis, the method requires air drying at 350C. This drives off the most of the C6 - C10 hydrocarbons so they are under estimated

26. EPH v DRO Interpretation Last sample is from soil containing free product spilled 8 years ago This shows the expected DRO banding pattern Others have the majority of their EPH value outside the DRO range 2nd to last sample is predominantly DRO, but high C21+ aromatics shows presence of bitumens Most samples classified as hazardous using EPH, but many not when looking at DRO range

27. EPH v DRO Interpretation Check the % contribution of each of the aliphatics and aromatics bands to the total values >C21 values above 400% indicate that the hydrocarbons are not all in the DRO range DRO fuel hydrocarbons should predominantly be in the C14 - C21 range Low % of C10 - C12 does not mean they were absent from the sample at the point of sampling

28. What Hydrocarbons are >C21 Bitumens (Ashphaltenes and Heterocyclic compounds) Ashphaltenes from coal Lubricating oils Waxes and greases Humic Acids Waxes from leaf surfaces Pristanes, Phytanes, Hopanes, Steranes etc

29. Chromatogram of TPH?

30. TPH - Organic Compost

31. Chromatograms Obtaining the chromatograms is essential to aid interpretation of the data. In most cases, the classic patterns of diesel, lubricating oils, bitumens and naturally occurring plant debris can be seen

32. Biomarkers-naturally occurring

33. Biomarkers These compounds are present in diesel range compounds, but also in naturally occurring plant material The presence of Pristane and Phytane at specific ratios are good indicators that the hydrocarbon is from a petroleum source

35. PAH Sources coal tar coal carbonisation residue creosote fuel oils, diesel bitumen/asphalt general combustion of organic matter

36. PAH Structures

37. Poly Aromatic Hydrocarbons Majority of the 16 EPA target PAHs detected. (C2 - C21 aromatics) 7 ring+ PAHs (asphaltenes) not detected. (C22+ aromatics) Ability to differentiate between high naphthalene content (coal and wood tars) and coal carbonisation residues. Gives biotreatability indication when 3 filter analysis used.

38. Identification of PAH Type PAH from coal carbonisation residue Low % naphthalene, acenaphthene, fluorene (<20%) Majority 3 rings + Coal Tar over 30% can be naphthalene Analysis using the standard A filter ignores fluorescence of naphthalene, fluorene etc Samples with little change between analysis using the A and D filter set is usually, coal carbonisation residue. A higher result from the D filter indicates Naphthalenes are present