Partitioning of aromatic and oxygenated constituents into water from regular and ethanol-blended gasolines

Variability in gasoline-water partitioning of major aromatic constituents (benzene, toluene, ethylbenzene, and xylenes (BTEX)) and methyl tert-butyl ether (MTBE) were examined for regular and ethanol-blended gasolines. By use of a two-phase liquid-liquid equilibrium model, the distribution of nonpolar solutes between fuel phase and water was related to principles of equilibrium. The models derived using Raoult's law convention for activity coefficients and liquid solubility is presented. The observed inverse log-log linear dependence of K_fw values on aqueous solubility, could be well predicted by assuming gasoline to be an ideal solvent mixture. Oxygenated additives (i.e., ethanol and MTBE), in the low percent range (below 5%), were shown to have minimal or negligible cosolvent effects on hydrocarbon partitioning. In the case of high fuel-to-water ratio (e.g., 1:1) or near contaminant source zone, the cosolvent effect of oxygenated gasoline with high content of ethanol (e.g., E85) will be environmentally significant.     

Phase partitioning modeling of ethanol, isopropanol, and methanol with BTEX compounds in water

This study investigates the equilibrium phase partitioning behavior of ethanol, isopropanol, and methanol in a two-phase liquid-liquid system consisting of water and an individual BTEX (Benzene, Toluene, Ethylbenzene, and Xylenes) compound. A previously developed computer program is enhanced to generate ternary phase diagrams for analysis of each three-component cosolvent-nonaqueous phase liquid (NAPL)-water mixture combination. The required activity coefficients are estimated using the UNIFAC (Universal Quasichemical Functional group Activity Coefficient) model. The UNIFAC-derived ternary phase diagrams generally show good agreement against published experimental data, and similar phase partitioning behavior is observed for every BTEX compound in the presence of the same cosolvent. Furthermore, a set of laboratory experiments is conducted to determine the maximum single-phase water content for every mixture combination considered in this study where the volume composition of the cosolvent and the NAPL components is a blend of 85% alcohol and 15% BTEX compound. Comparison of experimentally-derived maximum single-phase water contents against UNIFAC-derived results shows good agreement for mixtures containing ethanol and methanol, but relatively poor agreement for mixtures containing isopropanol.     

Response of a solid-liquid two-phase partitioning bioreactor to transient BTEX loadings

A two-phase partitioning bioreactor (TPPB) consisting of an aqueous phase containing a bacterial consortium and a polymeric phase of silicone rubber pellets (solid volume fraction 0.1) was used to treat a gaseous waste stream containing benzene, toluene, ethylbenzene and o-xylene (BTEX). The function of the solid polymer phase was to absorb/desorb the gaseous volatile organic compounds providing a buffering effect to protect the cells from high transient loadings and to sequester the BTEX for subsequent degradation. The TPPB was subjected to high and fluctuating inlet loadings of BTEX in the form of 4h step changes of 2, 4, 6 and 10 times the nominal inlet loading of 60 gm(-3) h(-1) total BTEX in approximately equal amounts, and removal efficiencies and elimination capacities were determined. It was found that overall removal efficiencies of greater than 95% can be achieved while obtaining overall elimination capacities of up to 282 gm(-3) h(-1) during transient operation and TPPB operation succumbs to toxic substrate levels between step changes of 6 and 10 times the nominal loading value (360-600 gm(-3) h(-1)). BTEX concentrations in the aqueous phase and the polymer phase of the TPPB were monitored throughout the imposed step changes to determine the extent to which the sequestering phase can buffer the aqueous phase from BTEX. With the polymer phase comprising only 10% of the total working volume of the reactor, the polymer beads accounted for up to 93%, 91% and 70% of the total BTEX present in the working volume for step changes of 2, 4 and 6 times the nominal loading, respectively.     

Effects of ethanol as an additive on odor detection thresholds of Alaskan gasolines at sub-arctic temperatures

This study evaluated the odor thresholds of two Alaskan unleaded gasolines, Tesoro and Mapco, and their ethanol oxyfuel blends at typical winter temperatures of −25°F, O°F, and +25°F. We found that temperature had a slight but variable effect on both odor thresholds and headspace composition. When 10% ethanol was added to Tesoro, a refined gasoline, there was a significant lowering (83%) of the odor detection threshold, i.e., an increase in human sensitivity to the odor. Vapors formulated from 10% ethanol-Mapco gasoline mixtures did not change the odor detection threshold. This study supports the hypothesis that the base gasolines interact variably with oxygenate additives. Ethanol appears to behave in a dissimilar manner when added to gasolines with different aromatic content.     

Oxygenated gasoline release in the unsaturated zone, Part 2: Downgradient transport of ethanol and hydrocarbons

In the event of a gasoline spill containing oxygenated compounds such as ethanol and MTBE, it is important to consider the impacts these compounds might have on subsurface contamination. One of the main concerns commonly associated with ethanol is that it might decrease the biodegradation of aromatic hydrocarbon compounds, leading to an increase in the hydrocarbon dissolved plume lengths. The first part of this study (Part 1) showed that when gasoline containing ethanol infiltrates the unsaturated zone, ethanol is likely to partition to and be retained in the unsaturated zone pore water. In this study (Part 2), a controlled field test is combined with a two-dimensional laboratory test and three-dimensional numerical modelling to investigate how ethanol retention in the unsaturated zone affects the downgradient behaviour of ethanol and aromatic hydrocarbon compounds. Ethanol transport downgradient was extremely limited. The appearance of ethanol in downgradient wells was delayed and the concentrations were lower than would be expected based on equilibrium dissolution. Oscillations in the water table resulted in minor flushing of ethanol, but its effect could still be perceived as an increase in the groundwater concentrations downgradient from the source zone. Ethanol partitioning to the unsaturated zone pore water reduced its mass fraction within the NAPL thus reducing its anticipated impact on the fate of the hydrocarbon compounds. A conceptual numerical simulation indicated that the potential ethanol-induced increase in benzene plume length after 20 years could decrease from 136% to 40% when ethanol retention in the unsaturated zone is considered.     

Investigation of partitioning mechanism for volatile organic compounds in a multiphase system

Laboratory experiments were performed to investigate the partitioning behavior of a set of diverse volatile organic compounds (VOCs). After equilibration at a temperature of 25 °C, the VOC concentrations were measured by headspace method in combination with gas chromatography/mass spectrometry (GC/MS). The obtained data were used to determine the partition coefficients (K_P) of VOCs in a gas-liguid-solid system. The results have shown that the presence and nature of solid materials in the working solution control the air-water partitioning of dissolved VOCs. The air/solution partitioning of BTEX and C₉-C₁₀ aldehydes was most affected in the presence of diesel soot. K_P values decreased by a factor ranging from 1.5 for toluene to 3.0 for ethylbenzene. The addition of mineral dust in the working solution exhibited greater influence on the partitioning of short aldehydes. K_P values decreased by a factor of 1.8. The experimental partition coefficients were used to develop a predictive model for partitioning of BTEX and n-aldehydes between air, water and solid phases.     

Construction and comparison of fluorescence and bioluminescence bacterial biosensors for the detection of bioavailable toluene and related compounds

Environmental pollution with petroleum products such as benzene, toluene, ethylbenzene, and xylenes (BTEX) has garnered increasing awareness because of its serious consequences for human health and the environment. We have constructed toluene bacterial biosensors comprised of two reporter genes, gfp and luxCDABE, characterized by green fluorescence and luminescence, respectively, and compared their abilities to detect bioavailable toluene and related compounds. The bacterial luminescence biosensor allowed faster and more-sensitive detection of toluene; the fluorescence biosensor strain was much more stable and thus more applicable for long-term exposure. Both luminescence and fluorescence biosensors were field-tested to measure the relative bioavailability of BTEX in contaminated groundwater and soil samples. The estimated BTEX concentrations determined by the luminescence and fluorescence bacterial biosensors were closely comparable to each other. Our results demonstrate that both bacterial luminescence and fluorescence biosensors are useful in determining the presence and the bioavailable fractions of BTEX in the environment.     

A strategy for aromatic hydrocarbon bioremediation under anaerobic conditions and the impacts of ethanol: a microcosm study

Increased use of ethanol-blended gasoline (gasohol) and its potential release into the subsurface have spurred interest in studying the biodegradation of and interactions between ethanol and gasoline components such as benzene, toluene, ethylbenzene and xylene isomers (BTEX) in groundwater plumes. The preferred substrate status and the high biological oxygen demand (BOD) posed by ethanol and its biodegradation products suggests that anaerobic electron acceptors (EAs) will be required to support in situ bioremediation of BTEX. To develop a strategy for aromatic hydrocarbon bioremediation and to understand the impacts of ethanol on BTEX biodegradation under strictly anaerobic conditions, a microcosm experiment was conducted using pristine aquifer sand and groundwater obtained from Canadian Forces Base Borden, Canada. The initial electron accepter pool included nitrate, sulfate and/or ferric iron. The microcosms typically contained 400 g of sediment, 600 approximately 800 ml of groundwater, and with differing EAs added, and were run under anaerobic conditions. Ethanol was added to some at concentrations of 500 and 5000 mg/L. Trends for biodegradation of aromatic hydrocarbons for the Borden aquifer material were first developed in the absence of ethanol, The results showed that indigenous microorganisms could degrade all aromatic hydrocarbons (BTEX and trimethylbenzene isomers-TMB) under nitrate- and ferric iron-combined conditions, but not under sulfate-reducing conditions. Toluene, ethylbenzene and m/p-xylene were biodegraded under denitrifying conditions. However, the persistence of benzene indicated that enhancing denitrification alone was insufficient. Both benzene and o-xylene biodegraded significantly under iron-reducing conditions, but only after denitrification had removed other aromatics. For the trimethylbenzene isomers, 1,3,5-TMB biodegradation was found under denitrifying and then iron-reducing conditions. Biodegradation of 1,2,3-TMB or 1,2,4-TMB was slower under iron-reducing conditions. This study suggests that addition of excess ferric iron combined with limited nitrate has promise for in situ bioremediation of BTEX and TMB in the Borden aquifer and possibly for other sites contaminated by hydrocarbons. This study is the first to report 1,2,3-TMB biodegradation under strictly anaerobic condition. With the addition of 500 mg/L ethanol but without EA addition, ethanol and its main intermediate, acetate, were quickly biodegraded within 41 d with methane as a major product. Ethanol initially present at 5000 mg/L without EA addition declined slowly with the persistence of unidentified volatile fatty acids, likely propionate and butyrate, but less methane. In contrast, all ethanol disappeared with repeated additions of either nitrate or ferric iron, but acetate and unidentified intermediates persisted under iron-enhanced conditions. With the addition of 500 mg/L ethanol and nitrate, only minor toluene biodegradation was observed under denitrifying conditions and only after ethanol and acetate were utilized. The higher ethanol concentration (5000 mg/L) essentially shut down BTEX biodegradation likely due to high EA demand provided by ethanol and its intermediates. The negative findings for anaerobic BTEX biodegradation in the presence of ethanol and/or its biodegradation products are in contrast to recent research reported by Da Silva et al. [Da Silva, M.L.B., Ruiz-Aguilar, G.M.L., Alvarez, P.J.J., 2005. Enhanced anaerobic biodegradation of BTEX-ethanol mixtures in aquifer columns amended with sulfate, chelated ferric iron or nitrate. Biodegradation. 16, 105-114]. Our results suggest that the apparent conservation of high residual labile carbon as biodegradation products such as acetate makes natural attenuation of aromatics less effective, and makes subsequent addition of EAs to promote in situ BTEX biodegradation problematic.     

The variability and intrinsic remediation of a BTEX plume in anaerobic sulphate-rich groundwater

Data from long-term groundwater sampling, limited coring, and associated studies are synthesised to assess the variability and intrinsic remediation/natural attenuation of a dissolved hydrocarbon plume in sulphate-rich anaerobic groundwater. Fine vertical scale (0.25- and 0.5-m depth intervals) and horizontal plume-scale (>400 m) characteristics of the plume were mapped over a 5-year period from 1991 to 1996. The plume of dissolved BTEX (benzene, toluene, ethylbenzene, xylene) and other organic compounds originated from leakage of gasoline from a subsurface fuel storage tank. The plume was up to 420 m long, less than 50 m wide and 3 m thick. In the first few years of monitoring, BTEX concentrations near the point of leakage were in approximate equilibrium with non-aqueous phase liquid (NAPL) gasoline. NAPL composition of core material and long-term trends in ratios of BTEX concentrations in groundwater indicated significant depletion (water washing, volatilisation and possibly biodegradation) of benzene from residual NAPL after 1992. Large fluctuations in BTEX concentrations in individual boreholes were shown to be largely attributable to seasonal groundwater flow variations. A combination of temporal and spatial groundwater quality data was required to adequately assess the stationarity of plumes, so as to allow inference of intrinsic remediation. Contoured concentration data for the period 1991 to 1996 indicated that plumes of toluene and o-xylene were, at best, only partially steady state (pseudo-steady state) due to seasonal groundwater flow changes. From this analysis, it was inferred that significant remediation by natural biodegradation was occurring for BTEX component plumes such as toluene and o-xylene, but provided no conclusive evidence of benzene biodegradation. Issues associated with field quantification of intrinsic remediation from groundwater sampling are highlighted. Preferential intrinsic biodegradation of selected organic compounds within the BTEX plume was shown to be occurring, in parallel with sulphate reduction and bicarbonate production. Ratios of average hydrocarbon concentrations to benzene for the period 1991 to 1992 were used to estimate degradation rates (half-lives) at various distances along the plume. The estimates varied with distance, the narrowest range being, for toluene, 110 to 260 days. These estimates were comparable to rates determined previously from an in situ tracer test and from plume-scale modelling.     

Biodegradability of alkylates as a sole carbon source in the presence of ethanol or BTEX

The biodegradability of alkylate compounds in serum bottles was investigated in the presence and absence of ethanol or benzene, toluene, ethylbenzene, and p-xylene (BTEX). The biomass was acclimated to three different alkylates, 2,3-dimethylpentane, 2,4-dimethylpentane and 2,2,4-trimethylpentane in porous pot reactors. The alkylates were completely mineralized in all three sets of experiments. They degraded more slowly in the presence of BTEX than in their absence because BTEX inhibited the microbial utilization of alkylates. However, in the presence of ethanol, their slower biodegradation was not related to inhibition by the ethanol. Throughout the experiments alkylates, ethanol, and BTEX concentrations did not change in the sterile controls.     

Combustion of gasolines in premixed laminar flames European certified and California phase 2 reformulated gasoline

Two gasoline qualities, European unleaded certified gasoline (EUCG) and California phase 2 reformulated gasoline (P2 RFG), were analysed. EUCG contained about twice the amount of alkyl benzenes compared to P2 RFG and a large amount of cyclohexane. As a balance, P2 RFG contained higher amounts of isooctane and MTBE. The gasolines were burned in a premixed laminar flame burner at 1 atm and at about stoichiometric fuel/air ratio. The species profiles were measured using on-line GC/MS. About 40 compounds were be detected in the gasoline flames. The EUCG resulted in formation of more reactive and toxic compounds. The combustion profiles of the fuel components showed a similar slope, which suggests that the fuel components burn quite independently of each other. Ethene and propene were the dominating species produced from the two gasolines. Commonly, substantial amounts of higher alkenes were found. Combustion of P2 RFG produced higher amounts of isobutene, propene, propyne, propadiene and methanol compared to combustion of EUCG. The high amount of isobutene is reasonably a result of high concentration of isooctane and MTBE in the fuel. The high amount of methanol formed is probably due to the MTBE present in the gasoline. EUCG produced significantly higher amounts of 1,3-butadiene, which quite likely is formed from the cyclohexane in the fuel. The benzene profiles from both gasolines shows an almost constant level up to 800 microm from the burner surface; this is probably due to formation of benzene from alkyl benzenes.     

Calculating the aquatic toxicity of hydrocarbon mixtures

For acute toxicity to aquatic organisms, individual hydrocarbons are equally toxic on the basis of their internal molar concentration within the organism. The differences in measured toxicities among hydrocarbons lies with differences in their equilibrium partitioning behavior between water and the organism. For complex hydrocarbon mixtures, an additional complication of partitioning between the bulk hydrocarbon and the water is encountered. Equations are developed for calculating the water concentration of components of complex hydrocarbon mixtures. Using gasoline as an example, a method is presented for first calculating the concentration of gasoline components in water after equilibration with different gasoline volumes and then, the component toxicities are used to estimate the gasoline volume causing 50% mortality to aquatic organisms.     

Fingerprinting of Gasoline and Coal Tar NAPL Volatile Hydrocarbons Dissolved in Groundwater

Accidental spills and chronic leaks of fuel oil or other hydrocarbon material (e.g., coal tar) often result in subsurface accumulation of nonaqueous phase liquid (NAPL), which can be a subsequent source of contamination in groundwater. Linking hydrocarbons in groundwater to a source NAPL has been difficult when using standard target analytes (e.g., BTEX) because of differences in partitioning properties of the analytes between the source NAPL and groundwater. Because aqueous solubility is predicted to be the controlling influence in the partitioning of hydrocarbons from NAPL to groundwater, a solubility-based approach to matching dissolved hydrocarbons in groundwater to their source NAPL has been developed and validated for two sites with commonly encountered types of NAPL contamination. Specifically, a gasoline LNAPL and a coal tar DNAPL from two separate sites (West Virginia and California) and groundwater interfaced with these NAPLs were analyzed for approximately 50 gasoline-range hydrocarbons consisting of paraffin, isoparaffin, (mono-) aromatic, naphthene, and olefin compounds (PIANO). Solubility characteristics of selected alkyl aromatic hydrocarbons from the PIANO analysis were used to identify a set of diagnostic hydrocarbons, expressed as hydrocarbon ratios, which were found to be useful in distinguishing the source(s) of hydrocarbons in groundwater. At the West Virginia site, the diagnostic ratios in a downgradient groundwater sample were similar to those of a gasoline NAPL at that site, indicating the source of hydrocarbons to the groundwater was the upgradient gasoline NAPL. The diagnostic ratios of the groundwater in contact with the gasoline NAPL and the remote groundwater were also similar, providing evidence that the diagnostic ratios were retained during transport in the aquifer. At the California site, diagnostic ratios in a cross-gradient groundwater sample differed from those of the coal tar NAPL at that site, indicating that the remote groundwater hydrocarbons did not originate from the coal tar contamination. Environmental factors such as selective degradation of specific isomers and various geological conditions (e.g., soil mineralogy, and organic content) may confound the application of this solubility-based fingerprinting approach. Thus, it is recommended that multiple diagnostic pairs be simultaneously evaluated when considering this fingerprinting approach for specific sites and product types.     

Gasoline Evaporation–Ethanol and Nonethanol Blends

Tests were performed to compare the evaporation rate of 10 volume percent (vol%) ethanol-blended gasoline (E10) with the evaporation rate of its base gasoline. Weight loss, temperature, pressure, and humidity were monitored as lab-blended E10 and base gasolines were evaporated concurrently from glass cylinders placed on balances located side by side under an exhaust hood. The averaged results of four tests at about 70°F showed that the E10 lost more total weight to evaporation than the base fuel, but less gasoline. The increased weight was due to ethanol, which was present in the E10 evaporative emissions at concentrations of about 13 weight percent (wt%). In two-hour tests at temperatures near 70°F, during which 4.5 to 5.3 wt% of initial fuel samples were evaporated, E10 fuels lost an average of about 5% less gasoline than their base fuels. A similar result was obtained for a one-hour test, during which about 2.4 to 2.5 wt% of the initial fuel samples were evaporated. Gas chromatography (GC) component analysis indicated that the compositions of the ethanol-free emissions from the two fuels were similar. Reid vapor pressure (RVP) measurements made using a Grabner CCA-VPS according to ASTM D5191-91 indicated that E10 fuels underwent an approximate 5% greater RVP reduction than their respective base fuels.     

Atmospheric concentrations and phase partitioning of polybrominated diphenyl ethers (PBDEs) in Izmir, Turkey

Atmospheric concentrations of 7 PBDE congeners (BDE-28, -47, -99, -100, -153, -154 and -209) were determined at four sites (i.e. Suburban, Urban 1, Urban 2, Industrial) in Izmir, Turkey and their gas/particle partitioning was investigated. Total PBDE ( summation operator(7)PBDE) concentrations ranged between 11 (Urban 1) and 149pgm(-3) (Industrial) in summer, while in winter, they ranged from 6 (Suburban) to 81pgm(-3) (Industrial). BDE-209 was the dominant congener at all sites, followed by BDE-99 and -47. Investigation of source profiles indicated that the air samples were dominated by congeners of the penta and deca-technical BDE mixtures. The measured PBDE particle fractions were compared to the predictions of the K(OA) (octanol-air partition coefficient)-based equilibrium partitioning model and to the dynamic uptake model developed by others for passive samplers, which was adapted to model gas-particle partitioning in this study. For BDE-28, good agreement was observed between the experimental particle fractions and those predicted by the equilibrium partitioning model. However, this model overestimated the particle fractions of other congeners. The predictions of the dynamic uptake model supported the hypothesis that the unexpectedly high partitioning of BDEs (except BDE-28) to the gas-phase is due to their departure from equilibrium partitioning. When congeners with very large octanol-air partition coefficients (i.e. BDE-100, -99, -154, -153, and -209) are emitted from their sources in the gas-phase, they may remain in that phase for several months before reaching equilibrium with atmospheric particles. This may also have important implications for the transport of atmospheric PBDEs. For example, in addition to particle-bound transport, the gas-phase transport of highly brominated congeners (i.e. BDE-209) may also be important.     

A physical-chemical screening model for anticipating widespread contamination of community water supply wells by gasoline constituents

Continuing modifications of fuels like gasoline should include evaluations of the proposed constituents for their potential to damage environmental resources such as subsurface water supplies. Consequently, we developed a screening model to estimate well water concentrations and transport times for gasoline components migrating from underground fuel tank (UFT) releases to typical at-risk community water supply wells. Representative fuel release volumes and hydrogeologic characteristics were used to parameterize the transport calculation. Subsurface degradation processes were neglected in the model in order to make risk-conservative assessments. The model was tailored to individual compounds based on their abundances in gasoline, gasoline-water partition coefficients (Kgw), and organic matter-water partition coefficients (Kom). Transport calculations were conducted for 20 polar and 4 nonpolar compounds found in gasoline, including methyl tert-butyl ether (MTBE) and other ether oxygenates, ethanol, methanol, and some aromatic hydrocarbons. With no calibration, the screening model successfully captured the reported magnitude of MTBE contamination of at-risk community supply wells. Such screening indicates that other oxygenates would cause similar widespread problems unless they were biodegradable. Stochastic analysis of field parameter variability concluded that community supply well contamination estimates had order-of-magnitude reliability. This indicated that such pre-manufacturing analyses may reasonably anticipate widespread environmental problems and/or inspire focused investigations into chemical properties (e.g., biodegradability) before industrial adoption of new fuel formulations.     

Solubility of volatile organic compounds in aqueous ammonia solution

The Ostwald solubility coefficient, L of 17 volatile organic compounds (VOCs) from the gas phase into water and dilute aqueous ammonia solutions was determined by the equilibrium partitioning in closed system-solid phase micro extraction (EPICS-SPME) method at 303 K and at 0-2.5 mol dm(-3) ammonia concentrations. Ammonia increased the solubility of all VOCs nearly linearly, but to a different extent. The difference in the solubility values in aqueous ammonia solutions (Lmix) compared to pure water (L) is explained on the basis of a Linear Solvation Energy Relationship (LSER) equation made applicable for solvent mixtures, logLmix - logL = x((sNH3 - sH2O)pi2H + (aNH3 - aH2O)Sigma2H + (bNH3 - bH2O)Sigmabeta2H + (vNH3 - VH2O)Vx). sNH3 - sH2O, aNH3 - aH2O, bNH3 - bH2O, vNH3 - vH2O are the differences of solvent parameters, x is the mole fraction, pi2H is the solute dipolarity-polarizability, Sigmaalpha2H is the effective hydrogen bond acidity of the solute, Sigmabeta2H is the effective hydrogen bond basicity of the solute and Vx, the McGowan characteristic volume. The most significant term was v, the phase hydrophobicity. The solubility behavior was explained by the change in structure of the aqueous solution: the presence of ammonia reduces the cavity effect. These findings show that the presence of compounds such as ammonia, frequently observed in environmental waters, especially wastewaters, affect the fugacity of VOCs, having consequences for the environmental partitioning of VOCs and having technical consequences towards wastewater treatment technologies.     

Vapor pressure response to denaturant and water in E10 blends

On December 16, 1993, the U.S. Environmental Protection Agency (EPA) released the final rule on reformulated gasoline (RFG). This rule will affect the composition of as much as 45% of the gasoline used in the United States by the summer of 1995. The acceptance of any gasoline component lies in its ability to contribute to the RFG program's environmental goals. This study was conducted to determine the effect of water and ethanol denaturant on gasoline Reid vapor pressure (RVP) for which little quantitative data are available. This paper addresses two new areas where environmental goals may be achieved while maintaining the use of ethanol-blended gasolines within ozone nonattainment areas.     

Treatment of groundwater contaminated with gasoline components by an ozone/UV process

In this paper, the treatment of real groundwater samples contaminated with gasoline components, such as benzene, toluene, ethylbenzene, and xylene (BTEX), methyl tert-butyl ether (MTBE), tert-butyl alcohol (TBA), and other gasoline constituents in terms of total petroleum hydrocarbons as gasoline (TPHg) by an ozone/UV process was investigated. The treatment was conducted in a semi-batch reactor under different experimental conditions by varying ozone gas dosage and incident UV light intensity. The groundwater samples contained BTEX compounds, MTBE, TBA, and TPHg in the ranges of 5-10000, 3000-5500, 80-1400, and 2400-20000mugl(-1), respectively. The ozone/UV process was very effective compared to ozonation in the removal of the gasoline components from the groundwater samples. For the various gasoline constituents, more than 99% removal efficiency was achieved for the ozone/UV process and the removal efficiency for ozonation was as low as 27%. The net ozone consumed per mol of organic carbon (from BTEX, MTBE, and TBA) oxidized varied in the range of 5-60 for different types of groundwater samples treated by the ozone/UV process. In ozonation experiments, it was observed that the presence of sufficient amount of iron in groundwater samples improved the removal of BTEX, MTBE, TBA, and TPHg.     

Determination of the Detailed Hydrocarbon Composition and Potential Atmospheric Reactivity of Full-Range Motor Gasolines

The quantitative data obtained with a capillary GLC method, which is used to determine the individual C₃-C₁₂ hydrocarbons in full-range motor gasolines, have been employed in a computer program to calculate the hydrocarbon composition of the vapor in equilibrium with a gasoline at 100°F, as well as the equilibrium vapor-pressure of the gasoline at that temperature. The method used for computation is similar to that previously described by McEwen, assuming the gasoline to behave as an ideal liquid. Also calculated is the potential atmospheric reactivity of this equilibrium vapor relative to that from other gasolines when specific reactivity weighting factors for the individual hydrocarbons are employed. Calculated total vapor-pressure data agree well with experimental Reid vapor-pressure data obtained for typical premium-grade gasolines. Definite differences were observed in the relative potential atmospheric reactivities calculated at 100°F for the equilibrium vapors from the test gasolines.