Total petroleum hydrocarbons in soil

Freon-extractable material is reported as total organic material from which polar components may be removed by treatment with silica gel, and the material remaining, as determined by infrared (IR) spectrometry, is defined as total recoverable petroleum hydrocarbons (TRPHs, or total petroleum hydrocarbons-IR). A number of modifications of these methods exist, but one particular method (EPA 418.1 see also EPA 8000 and 8100) has been one of the most widely used for the determination of total petroleum hydrocarbons in soils. Many states use or permit the use of this method (EPA 418.1) for identification of petroleum products and during remediation of sites. This method is subject to limitations, such as interlaboratory variations and inherent inaccuracies. In addition, methods that use Preon-113 as the extraction solvent are being phased out and the method is being replaced by a more recent method (EPA 1664) in which n-hexane is used as the solvent and the n-hexane extractable material (HEM) is treated with silica gel to yield the total petroleum hydrocarbons. 

A superior approach to determination of total petroleum hydrocarbons in soil is the summation of areas for specific ranges of hydrocarbons. This allows a better profiling of the contaminants and also confers the ability to trace the source of the pollutant. Typical ranges for the hydrocarbon profiles are n-Cio to n-Ci4, n-Cis to n-C2o, n-C2i to n-C26, and n-C2i to n-Css. However, one must be cautious in the application of statistical methods to the determination, insofar as such methods are only as good as the information and assumptions used. Recall Garbage in, garbage out ... 

Fitzpatrick MG, Tan SS. 1993. Recent advances in the determination of total petroleum hydrocarbons in soil. Chemistry in New Zealand, 22. 

TPHCWG. 1997a. A risk-based approach for the management of total petroleum hydrocarbons in soil. Total petroleum hydrocarbon criteria working group. March 1997. http //www.aehs.com. 

Heath JS, Koblis K, Sager SL, et al. 1993. Risk assessment for total petroleum hydrocarbons. In Kostecki PT, Calabrese EJ, eds. Hydrocarbon contaminated soils and groundwater. Vol. 3,267-301. Chelsea, MI Lewis Publishers. 

Once the sample preparation is complete, there are several approaches to the analysis of petroleum constituents in the water and soil (1) leachability or toxicity of the sample, (2) the amounts of total petroleum hydrocarbons in the sample, (3) petroleum group analysis, and (4) fractional analysis of the sample. These methods measure different petroleum constituents that might be present in petroleum-contaminated environmental media. 

On the other hand, gas chromatographic methods may overestimate the concentration of total petroleum hydrocarbons in a sample due to the detection of nonpetroleum compounds. In addition, cleanup steps do not separate petroleum hydrocarbons perfectly from biogenic material such as plant oils and waxes, which are sometimes extracted from vegetation-rich soil. Silica gel cleanup may help to remove this interference but may also remove some polar hydrocarbons. 

For petroleum and petroleum product releases in a sensitive area, the preferred analytical method to determine concentrations of total petroleum hydrocarbons in environmental media is the standard EPA test method (EPA 418.1). To determine concentrations of benzene, toluene, ethylbenzene, and xylenes in environmental media, other methods (EPA SW-846, SW-846 8021B, SW-846 8260) are preferred, provided that the detection limits are adequate for soil and for groundwater protection. 

Analysis for total petroleum hydrocarbons (EPA Method 418.1) provides a one-number value of the petroleum hydrocarbons in a given environmental medium. It does not, however, provide information on the composition (i.e., individual constituents) of the hydrocarbon mixture. The amount of hydrocarbon contaminants measured by this method depends on the ability of the solvent used to extract the hydrocarbon from the environmental media and the absorption of infrared light (infrared spectroscopy) by the hydrocarbons in the solvent extract. The method is not specific to hydrocarbons and does not always indicate petroleum contamination, since humic acid, a nonpetroleum material and a constituents of many soils, can be detected by this method. 

The analysis for the total petroleum hydrocarbons (TPHs) in a sample as a means of evaluating petroleum-contaminated sites is also an analytical method in common use. The data are used to establish target cleanup levels for soil or water by regulatory agencies in the United States and in many other countries. 

Therefore, for infrared spectroscopic methods, the total petroleum hydrocarbons comprise any chemicals extracted by a solvent that are not removed by silica gel and can be detected by infrared spectroscopy at a specified wavelength. The primary advantage of the infrared-based methods is that they are simple and rapid. Detection limits (e.g., for EPA 418.1) are approximately 1 mg/L in water and 10 mg/kg in soil. However, the infrared method(s) often suffer from poor accuracy and precision, especially for heterogeneous soil samples. Also, the infrared methods give no information on the type of fuel present in the sample, and there is little, often no information about the presence or absence of toxic molecules, and no specific information about potential risk associated with the contamination. 

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 soil or sediment data which cannot be compared directly with other total petroleum hydrocarbons data or guidelines because one is expressed in dry weight and the other in wet weight. 

The total petroleum hydrocarbons represents a summation of all the hydrocarbon compounds that may be present (and detected) in a soil sample. Because of differences in product composition between, for example, gasoline and diesel, or fresh versus weathered fuels, the types of compounds present at one site may be completely different from those present at another. 

Accordingly, the total petroleum hydrocarbons at a gasoline spill site will be comprised of mostly Cs to Cu compounds, while total petroleum hydrocarbons at an older site where the fuel has weathered will likely measure mostly Cg to Cn compounds. Because of this inherent variability in the method and the analyte, it is currently not possible to directly relate potential enviromnental or health risks with concentrations of total petroleum hydrocarbons. The relative mobility or toxicity of contaminants represented by total petroleum hydrocarbons analyses at one site may be completely different from that of another site (e.g., Ce to Cn compared to Cio to C25). There is no easy way to determine if total petroleum hydrocarbons from the former site will represent the same level of risk as an equal measure of the total petroleum hydrocarbons from the latter. For these reasons it is clear that the total petroleum hydrocarbons value offers limited benefits as an indicator measure for cleanup criteria. Its current widespread use as a soil cleanup criterion is a function of a lack of understanding of its proper application and... 

In New York and Massachusetts where PCB contamination is always a possibility, the laboratory tests required by the state environmental protection agencies for analysis of a petroleum-contaminated soil are as follows (a) flash point (b) total petroleum hydrocarbon (TPH) (c) PCB screening (d) total organic halides (TOH) (e) reactivity of cyanide and sulfide (f) BTEX or equivalent (g) eight metals under TCLP (Toxicity Characteristics Leaching Procedure) for USTs and (h) full range of tests under TCLP for ASTs and spills. 

Franl ort, Indiana. This project involved full-scale remediation of an leaking underground storage tank (LUST) site. The site contained 1238 tons of soil contaminated with total petroleum hydrocarbons (TPH). The area of contaminated soil was 27 by 55 ft across and 15 ft deep. TPH concentrations were reduced from 1200 parts per million (ppm) to nondetectable levels in 82 days. The cost of the project was 13,600. This cost included mobilization, demobilization, and in situ BIO-INTEGRATION treatment (D17796C, p. 1). This breaks down to approximately ll/ton of soil treated. 

DO-IT has been used at several sites to treat benzene, toluene, ethyl benzene, and xylene (BTEX), methyl ferf-butyl ether (MTBE), and total petroleum hydrocarbons (TPH). According to the vendor, this technology may also be applied or modified to clean up any aerobically biodegradable contaminants in soil. 

Mycova mycoremediation and mycofiltration are ex situ treatment technologies that use mushrooms to destroy total petroleum hydrocarbons (TPH), polycyclic aromatic hydrocarbons (PAHs), and pathogens in contaminated soil, wood debris, wastewater, and surface water. The mushrooms are specially selected, cultured, screened, and preconditioned to treat a specific site s target contaminants. The mushrooms may be added directly to contaminated soil or used as a filter in wastewater and surface water applications. 

The PetroClean bioremediation system treats biodegradable contaminants (i.e., gasoline, diesel fuel, aviation fuel, solvents, polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), semivolatile organic compounds (SVOCs), total petroleum hydrocarbons (TPH), and other organic compounds in soils and groundwater. 

Seymour Recycling Site in Seymour, Indiana Cost ranged from 50 to 100/yd to remediate 190,000 yd of soil (in situ) in a full-scale cleanup where the site was contaminated with total petroleum hydrocarbons (TPH) (D10003E, pp. 8-12). 

The in situ HRUBOUT process was used to treat a lO-ft-by-20-ft area to a depth of 20 ft. Soil at the site was contaminated with total petroleum hydrocarbons (TPH). According to the vendor, the cost of the remediation activities was approximately 75/yd of contaminated soil (D10050L, p. 15). 

Natural attenuation, often called intrinsic remediation, intrinsic bioremediation, bioattenuation, or monitored natural attenuation (MNA) is an in situ treatment technology for soil, sediment, or groundwater. The technology has been used for full-scale remediation of sites contaminated with volatile organic compounds (VOCs), total petroleum hydrocarbons (TPH), chlorinated solvents, explosives, inorganics, and metals. 

As part of a pilot study, the biopile technology was tested at the Marine Corps Mountain Warfare Training Center in Bridgeport, California. The site was contaminated with total petroleum hydrocarbons (TPH) at concentrations of 1200 parts per million (ppm). After 2 months of treatment using biopile, TPH concentrations were reduced to 120 ppm. Costs for this project were 80 per ton of soil treated (D21224Y, p. 23). 

According to the vendor, the cost to remediate 7000 yd of soil contaminated with total petroleum hydrocarbons (TPH) at a service station in South Carolina was less than 45/yd. At a wood preserving site in New Jersey, remediation activities cost a total of 1,300,000 or an average of 50/yd (D10335V, p. 10, 20). 

At a salvage yard in Anchorage, Alaska, the cost of treating 250 kg of lead- and polychlorinated biphenyl-contaminated soil was 22,000. At a underground storage tank site at the Boston Central Arterial, 10 kg of soil contaminated with total petroleum hydrocarbon was treated at a cost of 45 per ton (D10328W, pp. 8-16). 

Sohdification/stabihzation technology was used at an existing metal recycling facility in Sun Valley, Cahfomia, to treat 20,000 tons if soil contaminated with lead and total petroleum hydrocarbons (TPH). The vendor stated that the treatment reagents and the on-site technical services for this project cost 9.00 per ton (D113382, p. 10). 

The vendor claims that asphalt emulsion stabilization can treat soils with up to 60,000 parts per million (ppm) total petroleum hydrocarbons (TPH). In New York and New Jersey, permitting of the asphalt emulsion process is not allowed for sites where TPH levels are above 30,000 ppm. U.S. Environmental Protection Agency (EPA) regulations allow for the technology to be applied to soils with polychlorinated biphenyl (PCB) concentrations of 10 ppm for controlled-access sites and 25 ppm for uncontrolled-access sites. 

Biodegradation can be accelerated in a prepared bed reactor with forced aeration. These reactors (Figure 1.2) are used at many Superfund sites for bioremediation of PAHs and BTEX (benzene, toluene, ethylbenzene, and xylene) (Alexander, 1994). This method, with recirculating leachate, was used to reduce the average total petroleum hydrocarbon concentration in a diesel-contaminated soil from 6200 mg/kg dry soil to 280 mg/kg in approximately 7 weeks (Reynolds et al., 1994). A bed reactor with forced aeration was also used to treat 115 000 m3 of soil contaminated with bunker C fuel oil (Compeau, Mahaffey Patras, 1991) and 23 000 m3 of soil contaminated with gasoline and fuel oil (Block, Clark Bishop, 1990). 

Various workers [36-39] have discussed various aspects of the determination of total petroleum hydrocarbons and benzene, toluene, ethyl benzene and xylene in soils. 

A common problem at public utilities is soil that becomes contaminated with PCBs near and around transformers. There still are a number of such sites with this problem in the United States. Table 9 gives data from a soil cleanup project from a site in New York State. The soil contained approximately 1200 ppm of PCB (Aroclor 1260) prior to treatment with SET . After treatment, the PCB level was reduced to 1.4 ppm (Table 9). Aroclor 1260 is particularly hard to bioremediate, so this result is significant. Small quantities of PAHs (pyrene and phenanthrene) were also remediated. The total petroleum hydrocarbons increased, which is what should be expected because the initial... 

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