BTEX benzene, toluene, ethylbenzene

Benzene is one of a group of related aromatic monocyclic hydrocarbons (BTEX—benzene, toluene, ethylbenzene, and xylene), and since these are water soluble, there has been concern for their dissipation and persistence in groundwater under both aerobic and anaerobic conditions. Although aerobic growth at the expense of benzene was established many years ago, the pathway for its degradation was established only much later. The aerobic degradation of benzene by bacteria is... 

R. A. Deeb, H. Y. Hu, J. R. Hanson, K. M. Scow, and L. Alvarez-Cohen. Substrate interactions in BTEX [benzene, toluene, ethylbenzene, and xylene] and MTBE [methyl tert-butyl ether] mixtures by an MTBE-degrading isolate. Environ Sci Technol, 35(2) 312-317, 2001. 

BTEX Benzene, toluene, ethylbenzene, and xylenes (collectively)... 

Specific contaminants that are components of total petroleum hydrocarbons, such as BTEX (benzene, toluene, ethylbenzene, and xylene), n-hexane, jet fuels, fuel oils, and mineral-based crankcase oil have been studied and a number of toxicological profiles have been developed on individual constituents and petroleum products. However, the character of the total petroleum hydrocarbons has not been studied extensively and no profiles have been developed. Although several toxicological profiles have been developed for petroleum products and for specific chemicals found in petroleum, the total petroleum hydrocarbon test results have been too nonspecific to be of real value in the assessment of its potential health effects. 

A cost comparison between ORC, pump and treat, and air sparging with soil vapor extraction (SVE) is presented in Table 1. The costs given are for a site in Oklahoma with a plume width of 60 ft, a treatment area of 9146 ft and a treatment thickness of 11 ft. The peak BTEX (benzene, toluene, ethylbenzene, and xylenes) load was 25 parts per million (D13823I D14008Z). 

ESTD, ex situ thermal desorption VOCs, volatile organic compounds TPH, total petroleum hydrocarbons BTEX, benzene, toluene, ethylbenzene, xylene PCBs, polychlorinated biphenyls PAHs, polycyclic aromatic hydrocarbons ISTD, in situ thermal desorption. 

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). 

Distribution of contaminant subgroups at 214 sites. PAH = polynuclear aromatic hydrocarbons BTEX = benzene, toluene, ethylbenzene, and xylene. (From USEPA, Analysis of Facility of Corrective Action Data, U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response, Technology Innovation Office, Washington, D.C., January, 1994.)... 

Abbreviations 2,4,-D 2,4-dichlorophenoxyacetic acid 2,4,5-T tiichlorophenoxyacetic acid BTEX benzene, toluene, ethylbenzene, xylenes PAH polycyclic aromatic hydrocarbons. 

Some simple examples help illustrate this point. A study by Burris and MacIntyre (1984) compared the theoretical solubilities of specific chemicals in water to the solubilities of the same chemicals when they were part of such petroleum product mixtures as JP-4 jet fuel. The results are summarized in Table 5-8. Similar comparisons for all the BTEX (benzene, toluene, ethylbenzene, xylene) chemicals, based on materials presented by Potter (1993), are presented in Table 5-9. 

BTEX benzene - toluene - ethylbenzene - xy lene(s) (mixture)... 

Aromatic hydrocarbons are of special commercial importance. The benzene ring structure, with six carbons and three double bonds, is the fundamental aromatic unit. This molecule can have one or more hydrogen substitutions with side chains, resulting in alkyl benzenes (e.g. the TEX in BTEX [benzene, toluene, ethylbenzene and xylene]) or two or more aromatic rings may be fused together to form polycyclic aromatic hydrocarbons (PAHs). 

A frequently requested analytical suite is for BTEX - benzene, toluene, ethylbenzene and xylenes. This restricted suite of VOCs is widely used as an... 

Aromatic hydrocarbons are cyclic, planar compounds that are stabilized by a delocalized tt electron system. Aromatics include the mono aromatic hydrocarbons such as BTEX (benzene, toluene, ethylbenzene, and o-, m-, and p-xylenes) and other alkyl-substituted benzene compounds (C -benzenes), and polycyclic aromatic hydrocarbons (including oil-characteristic alkylated PAH homologues and the other U.S. EPA priority PAHs). Benzene is the simplest one ring aromatic compound. The commonly analyzed PAH compounds range from two ring PAHs (such as naphthalene) up through six ring PAHs (benzo g, h, i) perylene). BTEX and PAHs are of concern because of their toxic properties in the environment. 

The volatile hydrocarbons including BTEX (benzene, toluene, ethylbenzene, and 3 xylene isomers) and alkylated benzenes (C3- to Cs-benzenes), naphthenes, and volatile paraffins and isoparaffins ... 

For lightly weathered oils and refined products (for example, <15% weathered), the abundances of low end -alkanes are significantly reduced. However, the ratios of w-Cn/pristane and w-Cig/phytane are virtually unaltered. The losses of BTEX (benzene, toluene, ethylbenzene, and xylenes) and Cg-benzene compounds (8 isomers) are obvious, and the most abundant 2-ring alkylated naphthalene series appear slightly enriched. 

BTEX = benzene, toluene, ethylbenzene, xylene MTBE = methyl tert-butyl ether TCE = trichloroethylene TCA = trichloroethane PCBs = polychlorinated biphenyls. 

---