Petroleum hydrocarbons volatilization

Total Recoverable Petroleum Hydrocarbons Volatile PAHs Less Volatile PAHs Organochlorine Pesticides PCBs... 

Many useful lipid oils are extracted from a variety of plant seeds including rapeseed, soybeans, sunflowers, and com. In addition to their food uses, these oils are used in a large variety of applications including raw materials for making other chemical products, lubricants, and as biodiesel fuels. Part of the usefulness of lipid oils in many applications is due to their similarity to petroleum hydrocarbons. Volatile solvents, most commonly the 6-carbon straight-chain alkane n-hexane, CgHj4, are used to extract oils from plant sources. In this process, the solvents are distilled off from the extract and recirculated through the process. 

In the wood rosin process, rosin is isolated from aged pine stumps that have been left in fields cleared for farming or lumbering operations. The stumps are cut and shredded to pieces the size of matchsticks. The wood chips are then extracted with an appropriate solvent, eg, aUphatic or aromatic petroleum hydrocarbons or ketones. The extract is fractionally separated into nonvolatile cmde rosin, volatile extractibles, and recovered solvent. The dark rosin is usually refined further to lighter-colored products using selective solvents or absorption. 

Pure M-hexane is widely used in laboratories as an extractant for nonpolar compounds and in calibrating instruments for analyses of volatile organic compounds (VOC) or total petroleum hydrocarbons (TPH) (Kanatharana et al. 1993). Since such analyses may require very high levels of purity, laboratories sometimes carry out their own fractional distillation or other pretreatment-purification procedures to remove petroleum hydrocarbon impurities found in commercially available grades of M-hexane (Kanatharana et al. 1993). See Chapter 6 for more information about testing for -hexane. 

Yang Yu, Hawthorne B, Miller DJ. 1995. Comparison of sorbent and solvent trapping after supercritical fluid extraction of volatile petroleum hydrocarbons from soil. J Chromatogr A 699 265-276. 

Yang et al. [2] have compared sorbent trapping with solvent trapping after the supercritical fluid extraction of volatile petroleum hydrocarbons in soil. Sorbent trapping yielded quantitative collections of n-alkanes as volatile as n-hexane, while solvent trapping effectively collected w-alkanes as volatile as n-octane. 

Organic compounds such as the chlorinated solvents also include a wide range of compounds and do not easily fit into the structural classification as described for petroleum hydrocarbons. Chlorinated hydrocarbons are commonly discussed in terms of their relative density (i.e., LNAPL or DNAPL) or degree of halogenation and degree of volatility (i.e., volatile, semi-volatile). 

Current EPA analytical methods do not allow for the complete speciation of the various hydrocarbon compounds. EPA Methods 418.1 and 8015 provide the total amount of petroleum hydrocarbons present. However, only concentrations within a limited hydrocarbon range are applicable to those particular methods. Volatile compounds are usually lost, and samples are typically quantitated against a known hydrocarbon mixture and not the specific hydrocarbon compounds of concern or the petroleum product released. By conducting EPA Method 8015 (Modified) using a gas chromatograph fitted with a capillary column instead of the standard, hand-packed column, additional separation of various fuel-ranged hydrocarbons can be achieved. 

FIGURE 10.18 Graphs of total volatile petroleum hydrocarbons concentration with time at... 

Two methods, EPA SW-846 8015 and 8015A, were, in the past, often quoted as the source of gas chromatography-based methods for measurement of the total petroleum hydrocarbons in a sample. However, the original methods were developed for nonhalogenated volatile organic compounds and were designed to measure a short target list of chemical solvents rather than petroleum hydrocarbons. Thus, because there was no universal method for total petroleum hydrocarbons, there were many variations of these methods. Recently, an updated method... 

A gas chromatography-mass spectrometry system is used to measure concentrations of target volatile and semivolatile petroleum constituents. It is not typically used to measure the amount of total petroleum hydrocarbons. The advantage the technique is the high selectivity, or ability to confirm compound identity through retention time and unique spectral pattern. 

Rather than quantifying a complex total petroleum hydrocarbon mixture as a single number, petroleum hydrocarbon fraction methods break the mixture into discrete hydrocarbon fractions, thus providing data that can be used in a risk assessment and in characterizing product type and compositional changes such as may occur during weathering (oxidation). The fractionation methods can be used to measure both volatile and extractable hydrocarbons. 

The assessment of health effects due to exposure to the total petroleum hydrocarbons requires much more detailed information than what is provided by a single total petroleum hydrocarbon value. More detailed physical and chemical properties and analytical information on the total petroleum hydrocarbons fraction and its components are required. Indeed, a critical aspect of assessing the toxic effects of the total petroleum hydrocarbons is the measurement of the compounds, and the first task is to appreciate the origin of the various fractions (compounds) of the total petroleum hydrocarbons. Transport fractions are determined by several chemical and physical properties (i.e., solubility, vapor pressure, and propensity to bind with soil and organic particles). These properties are the basis of measures of teachability and volatility of individual hydrocarbons and transport fractions (Chapters 8, 9, and 10). 

Because of the relative complexity of the analytical methods for total petroleum hydrocarbons, there is a need for devising methods for the determination of total petroleum hydrocarbons. But the major problem lies in the range of compounds covered by the term hydrocarbons. Again, the most notable variation is in the relative volatility and other properties of the hydrocarbons under investigation. Although instrumental detection methods are available (Sadler and Connell, 2003), another approach involves collection of the contaminated soil and sealing it in a container, where the soil gas can accumulate. This gas is then analyzed by one of several reliable instrumental procedures. 

Producing relatively accurate dry-weight values for heavy petroleum hydrocarbons but questionable dry weight values for lighter, more volatile compounds. Note Different labs dry the samples in different ways and a sample with lots of lighter-fraction hydrocarbons is more prone to hydrocarbon loss the variable loss of volatile hydrocarbons in a drying step is therefore an additional area of lab and data variability). 

Fig. 8.13 Concentration of selected petroleum hydrocarbons (mL / 100 g soil) during volatilization of kerosene from air dry vertisol. Reprinted from FineP, Yaron B (1993) Outdoor experiments on enhanced volatilization by venting of kerosene components from soil. J Contam Hydrol 12 335-374. Copyright 1994 with permission of Elsevier...

Dror I, Gerstl Z, Prost R, Yaron B (2000a) Behavior of neat and enriched volatile petroleum hydrocarbons mixture in the subsurface during leaching. Land Contam Reclam 8 341-348... 

Turpentine is a mixture of CioHie volatile terpenes (hydrocarbons made of isoprene units). There are actually four different types and methods of making turpentine, including steam distillation of wood. The two pinenes, a and P, are major components of turpentine. Other compounds found in abundant amounts are camphene, dipentene, terpinolene, and A -carene. Although it has been replaced by petroleum hydrocarbons as paint thinners (lower price, less odor), turpentine is still a good solvent and thinner in many specialty applications. The use pattern for turpentine is as follows synthetic... 

Bioventing technology is applicable to contaminants in the vadose zone as well as contaminated regions just below the water table. It is applicable for any contaminant that degrades more readily aerobically than anaerobically. Most applications have targeted the less volatile petroleum hydrocarbons, although the technology has also remediated mixtures that include acetone, benzene, toluene, biphenyl, phenol, methylphenol, naphthalene, and polycyclic aromatic... 

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