Assessing soil ecotoxicity of methyl tert-butyl ether using earthworm bioassay; closed soil microcosm test for volatile organic compounds

An earthworm bioassay was conducted to assess ecotoxicity in methyl tert-butyl ether (MTBE)-amended soils. Ecotoxicity of MTBE to earthworms was evaluated by a paper contact method, natural field soil test, and an OECD artificial soil test. All tests were conducted in closed systems to prevent volatilization of MTBE out of test units. Test earthworm species were Perionyx excavatus and Eisenia andrei. Mortality and abnormal morphology of earthworms exposed to different concentrations of MTBE were examined. MTBE was toxic to both earthworm species and the severity of response increased with increasing MTBE concentrations. Perionyx excavatus was more sensitive to MTBE than Eisenia andrei in filter papers and two different types of soils. MTBE toxicity was more severe in OECD artificial soils than in field soils, possibly due to the burrowing behavior of earthworms into artificial soils. The present study demonstrated that ecotoxicity of volatile organic compounds such as MTBE can be assessed using an earthworm bioassay in closed soil microcosm with short-term exposure duration.     

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.     

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.     

Determination and impact of volatile organics emitted during rush hours in the ambient air around gasoline stations

This study analyzes the volatile organic compounds (VOCs) in the ambient air around gasoline stations during rush hours and assesses their impact on human health. Results from this study clearly indicate that methyl tertiary butyl ether (MTBE), toluene, and isobutane are the major VOCs emitted from gasoline stations. Moreover, the concentrations of MTBE and toluene in the ambient air near gasoline stations are remarkably higher than those sampled on surrounding roads, revealing that these compounds are mainly released from gasoline stations. The concentration of VOCs near the gasoline stations without vapor recovery systems are approximately 7.3 times higher than those around the gasoline stations having the recovery systems. An impact on individual health and air quality because of gasoline station emissions was done using Integrated Risk Information System and Industrial Source Complex Short Term model.     

Determination and Impact of Volatile Organics Emitted during Rush Hours in the Ambient Air around Gasoline Stations

Abstract

This study analyzes the volatile organic compounds (VOCs) in the ambient air around gasoline stations during rush hours and assesses their impact on human health. Results from this study clearly indicate that methyl tertiary butyl ether (MTBE), toluene, and isobutane are the major VOCs emitted from gasoline stations. Moreover, the concentrations of MTBE and toluene in the ambient air near gasoline stations are remarkably higher than those sampled on surrounding roads, revealing that these compounds are mainly released from gasoline stations. The concentration of VOCs near the gasoline stations without vapor recovery systems are ～7.3 times higher than those around the gasoline stations having the recovery systems. An impact on individual health and air quality because of gasoline station emissions was done using Integrated Risk Information System and Industrial Source Complex Short Term model.     

Water quality at five marinas in Lake Texoma as related to methyl tert-butyl ether (MTBE)

Water quality in five marinas on Lake Texoma, located on the Oklahoma and Texas border, was monitored between June 1999 and November 2000. Focus was to evaluate lake water associated with marinas for methyl tert-butyl ether (MTBE). Lake water was collected at locations identified as marina entrance, gasoline filling station, and boat dock. Occurrence of MTBE showed a direct seasonal trend with recreational boating activity at marina areas. There was a positive correlation with powerboat usage ratio, which was directly related to the gallons of gasoline sold. Sampling before and after the high boat use holiday weekends determined the apparent influence of powerboat activity on MTBE contamination. Boat dock locations were the most sensitive sites to MTBE contamination, possibly due to gasoline spillage during engine startup. The most common compound of the BTEX series found with MTBE was toluene and co-occurrence was most frequent at gasoline filling stations.     

Effects of carbaryl, chlorpyrifos and endosulfan on growth, reproduction and respiration of tropical epigeic earthworm, Perionyx excavatus (Perrier)

Effects of sub-lethal doses of carbaryl (1-Naphthyl-methylcarbamate), chlorpyrifos (O,O-diethyl O-3,5,6-trichloro-2-pyridinyl-phosphorothioate) and endosulfan (6,7,8,9,10,10-Hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,4,3-benzodioxathiepin-3-oxide), respectively a carbamate, an organophosphate and an organochlorine insecticide on growth, reproduction and respiration of the tropical earthworm, Perionyx excavatus (Perrier) were investigated under laboratory conditions. The results showed significant reduction in biomass, production and hatching of cocoon and production of juveniles of the worms exposed to 0.75 to 3.03 mg/kg soil of carbaryl, 0.91 to 3.65 mg/kg soil of chlorpyrifos and 3.75 to 15.0 μg/kg soil of endosulfan corresponding to 12.5 to 50 % of LC(50) value of the respective insecticide for P. excavatus. Endosulfan was found most dangerous among the three insecticides followed by carbaryl and chlorpyrifos. There was no hatching of the worms at endosulfan treatment 5.0 μg/kg soil (25 % LC(50)) or above while the highest dose of carbaryl and chlorpyrifos (50 % of LC(50)) rendered respectively 87.13 and 24.84 % reductions in hatching as compared to control. Chlorpyrifos produced no change in respiration of the worms except at the highest dose, while the worms showed an increase in evolution of CO(2) at all doses of carbaryl and endosulfan. Based on the recommended agricultural dose of each insecticide, it was concluded that application of endosulfan and carbaryl was potentially dangerous to earthworms.     

Using the Gasoline Additive MTBE in Forensic Environmental Investigations

A variety of additives are used in gasoline, and they can sometimes be used to help identify the source, timing, or number of gasoline spills at a site. The physicochemical characteristics of the additive MTBE, and its historical use pattern in the United States since 1979, make it a key compound to study when conducting forensic investigations of gasoline spills. MTBE's low octanol: water distribution coefficient and high solubility cause it to dissolve into groundwater more readily than other gasoline components. Thus, the initial appearance of MTBE in the groundwater is often a good indicator of a recent gasoline spill. MTBE's very low retardation and minimal biodegradation in groundwater can be used with transport rate calculations to establish relatively accurate estimates of spill timing. Because MTBE moves faster in groundwater than BTEX compounds, if a gasoline spill site has a BTEX plume that is longer than the MTBE plume, it is certain that at least two distinctly different gasoline releases have occurred. This allows for the identification of new gasoline spills, even when substantial subsurface petroleum contamination already exists. An example application is reviewed to demonstrate the use of MTBE data in forensic investigations.     

甲基叔丁基醚的污染治理技术研究进展

甲基叔丁基醚(MTBE)是一种无铅汽油添加剂,其广泛使用造成了土壤和地下水污染;同时对人类有可疑致癌作用,因此成为人们关注的焦点.对近年来国外MTBE的污染治理技术研究进展进行了综述,并对主要方法进行了对比.在适宜的微生物存在条件下,MTBE的生物降解是可以发生的;植物修复技术可用于地下水和土壤污染治理;物理化学方法种类繁多,包括吸附和高级氧化等,其处理效率高成本也较高;新的处理技术如渗透性活性障壁PRB、膜分离/催化技术等也在研究之中.     

Laboratory evidence of MTBE biodegradation in Borden aquifer material

Mainly due to intrinsic biodegradation, monitored natural attenuation can be an effective and inexpensive remediation strategy at petroleum release sites. However, gasoline additives such as methyl tert-butyl ether (MTBE) can jeopardize this strategy because these compounds often degrade, if at all, at a slower rate than the collectively benzene, toluene, ethylbenzene and the xylene (BTEX) compounds. Investigation of whether a compound degrades under certain conditions, and at what rate, is therefore important to the assessment of the intrinsic remediation potential of aquifers. A natural gradient experiment with dissolved MTBE-containing gasoline in the shallow, aerobic sand aquifer at Canadian Forces Base (CFB) Borden (Ontario, Canada) from 1988 to 1996 suggested that biodegradation was the main cause of attenuation for MTBE within the aquifer. This laboratory study demonstrates biologically catalyzed MTBE degradation in Borden aquifer-like environments, and so supports the idea that attenuation due to biodegradation may have occurred in the natural gradient experiment. In an experiment with batch microcosms of aquifer material, three of the microcosms ultimately degraded MTBE to below detection, although this required more than 189 days (or >300 days in one case). Failure to detect the daughter product tert-butyl alcohol (TBA) in the field and the batch experiments could be because TBA was more readily degradable than MTBE under Borden conditions.     

Speciated hydrocarbon and carbon monoxide emissions from an internal combustion engine operating on methyl tertiary butyl ether-containing fuels

In the present work, engine and tailpipe (after a three-way catalytic converter) emissions from an internal combustion engine operating on two oxygenated blend fuels [containing 2 and 11% weight/weight (w/w) methyl tertiary butyl ether (MTBE)] and on a nonoxygenated base fuel were characterized. The engine (OPEL 1.6 L) was operated under various conditions, in the range of 0-20 HP. Total unburned hydrocarbons, carbon monoxide, methane, hexane, ethylene, acetaldehyde, acetone, 2-propanol, benzene, toluene, 1,3-butadiene, acetic acid, and MTBE were measured at each engine operating condition. As concerns the total HC emissions, the use of MTBE was beneficial from 1.90 to 3.81 HP, which were by far the most polluting conditions. Moreover, CO emissions in tailpipe exhaust were decreased in the whole operation range with increasing MTBE in the fuel. The greatest advantage of MTBE addition to gasoline was the decrease in ethylene, acetaldehyde, benzene, toluene, and acetic acid emissions in engine exhaust, especially when MTBE content in the fuel was increased to 11% w/w. In tailpipe exhaust, the catalyst operation diminished the observed differences. Ethylene, methane, and acetaldehyde were the main compounds present in exhaust gases. Ethylene was easily oxidized over the catalyst, while acetaldehyde and methane were quite resistant to oxidation.     

Enhancing bioremediation of diesel oil and gasoline in soil amended with an agroindustry sludge

This paper presents a study of the bioremediation of diesel oil and gasoline by a series of controlled laboratory tests. Sludge from an agroindustry was used to enhance bioremediation of both gasoline and diesel oil mixed with a soil mass to compare its efficiency with that of a mineral fertilizer. Effects of soil microbiology and soil mixtures were investigated by means of evolution of CO2, microorganism populations at 90 days, pH at 65 and 95 days, mineral nitrogen, and gas chromatographic analysis of the benzene, toluene, methyl tertiary butyl ether, C8, and C9+total aromatics at the end of the experiments. Treatments containing sludge showed better soil conditions after 170 days of treatment (inorganic nitrogen and microbiota activity) compared with gasoline and diesel oil without amendments. Samples had no detectable traces of the measured hydrocarbons at 170 days of treatment.     

Oxygenated gasoline release in the unsaturated zone - Part 1: Source zone behavior

Oxygenates present in gasoline, such as ethanol and MTBE, are a concern in subsurface contamination related to accidental spills. While gasoline hydrocarbon compounds have low solubility, MTBE and ethanol are more soluble, ethanol being completely miscible with water. Consequently, their fate in the subsurface is likely to differ from that of gasoline. To evaluate the fate of gasoline containing oxygenates following a release in the unsaturated zone shielded from rainfall/recharge, a controlled field test was performed at Canadian Forces Base Borden, in Ontario. 200L of a mixture composed of gasoline with 10% ethanol and 4.5% MTBE was released in the unsaturated zone, into a trench 20cm deep, about 32cm above the water table. Based on soil cores, most of the ethanol was retained in the source, above the capillary fringe, and remained there for more than 100 days. Ethanol partitioned from the gasoline to the unsaturated pore-water and was retained, despite the thin unsaturated zone at the site (~35cm from the top of the capillary fringe to ground surface). Due to its lower solubility, most of the MTBE remained within the NAPL as it infiltrated deeper into the unsaturated zone and accumulated with the gasoline on top of the depressed capillary fringe. Only minor changes in the distribution of ethanol were noted following oscillations in the water table. Two methods to estimate the capacity of the unsaturated zone to retain ethanol are explored. It is clear that conceptual models for sites impacted by ethanol-fuels must consider the unsaturated zone.     

Toxicological and biochemical responses of the earthworm Lumbricus rubellus to pyrene, a non-carcinogenic polycyclic aromatic hydrocarbon

The effects of the polycyclic aromatic hydrocarbon (PAH) pyrene on earthworms were investigated in contact and soil tests. In addition to measuring toxic effects on survival and reproduction, Ethoxyresorufin-o-deethylase (EROD) activity and catalase activity were also studied as possible biomarkers of toxic stress. The survival data indicated that LC₅₀ values were 0.0068 mg/ml for the contact test, and 283 mg/kg in the soil test. Cocoon production rate was significantly reduced compared to controls at 160, 640 and 2560 mg/kg in the soil test. No EROD activity could be detected in preliminary studies using control and exposed animals from the contact test, so this assay was not used to the soil test. Catalase activity was shown to be significantly lower at 640 mg/kg in the soil test compared to all other treatments and the control. When compared to toxicological data for other soil invertebrates, Lumbricus rubellus has an intermediate sensitivity in respects of survival and a lower sensitivity for reproductive effects, although the soil used in this study had a higher organic content than previous studies, meaning that the sensitivity of this species may be underestimated in comparison to previous published data for other soil invertebrates.     

Using the Gasoline Additive MTBE in Forensic Environmental Investigations

A variety of additives are used in gasoline, and they can sometimes be used to help identify the source, timing, or number of gasoline spills at a site. The physicochemical characteristics of the additive MTBE, and its historical use pattern in the United States since 1979, make it a key compound to study when conducting forensic investigations of gasoline spills. MTBE's low octanol : water distribution coefficient and high solubility cause it to dissolve into groundwater more readily than other gasoline components. Thus, the initial appearance of MTBE in the groundwater is often a good indicator of a recent gasoline spill. MTBE's very low retardation and minimal biodegradation in groundwater can be used with transport rate calculations to establish relatively accurate estimates of spill timing. Because MTBE moves faster in groundwater than BTEX compounds, if a gasoline spill site has a BTEX plume that is longer than the MTBE plume, it is certain that at least two distinctly different gasoline releases have occurred. This allows for the identification of new gasoline spills, even when substantial subsurface petroleum contamination already exists. An example application is reviewed to demonstrate the use of MTBE data in forensic investigations.     

Speciated Hydrocarbon and Carbon Monoxide Emissions from an Internal Combustion Engine Operating on Methyl Tertiary Butyl Ether-Containing Fuels

ABSTRACT

In the present work, engine and tailpipe (after a three-way catalytic converter) emissions from an internal combustion engine operating on two oxygenated blend fuels [containing 2 and 11% weight/weight (w/w) methyl tertiary butyl ether (MTBE)] and on a nonoxygenated base fuel were characterized. The engine (OPEL 1.6 L) was operated under various conditions, in the range of 0-20 HP. Total unburned hydrocarbons, carbon monoxide, methane, hexane, ethylene, acetaldehyde, acetone, 2-propanol, benzene, toluene, 1,3-butadiene, acetic acid, and MTBE were measured at each engine operating condition. As concerns the total HC emissions, the use of MTBE was beneficial from 1.90 to 3.81 HP, which were by far the most polluting conditions. Moreover, CO emissions in tailpipe exhaust were decreased in the whole operation range with increasing MTBE in the fuel.

The greatest advantage of MTBE addition to gasoline was the decrease in ethylene, acetaldehyde, benzene, toluene, and acetic acid emissions in engine exhaust, especially when MTBE content in the fuel was increased to 11% w/w. In tailpipe exhaust, the catalyst operation diminished the observed differences. Ethylene, methane,and acetaldehyde were the main compounds present in exhaust gases. Ethylene was easily oxidized over the catalyst,while acetaldehyde and methane were quite resistant to oxidation.     

NAPL migration and ecotoxicity of conventional and renewable fuels in accidental spill scenarios

Fuels derived from non-petroleum renewable resources have raised interest due to their potential in replacing petroleum-based fuels, but information on their fate and effects in the terrestrial and aquatic environments in accidental spill scenario is limited. In this study, migration of four fuels (conventional diesel, conventional gasoline, renewable diesel NExBTL, and ethanol-blended gasoline RE85 containing maximum 85 % ethanol) as non-aqueous phase liquids (NAPL) in soil was demonstrated in a laboratory-scale experiment. Ecotoxicity data was produced for the same fuels. There was no significant difference in migration of conventional and renewable diesel, but gasoline migrated 1.5 times deeper and 7–9 times faster in sand than diesel. RE85 spread horizontally wider but not as deep (p?Eisenia fetida followed by ethanol-blended gasoline (LC50 1,643 mg/kg THC) and conventional diesel (LC50 2,432 mg/kg THC), although gasoline evaporated fast from soil. For comparison, the toxicity of the water-accommodated fractions (WAF) of the fuels was tested with water flea Daphnia magna and Vibrio fischeri, also demonstrating groundwater toxicity. The WAF of conventional gasoline and RE85 showed almost similar toxicity to both the aquatic test species. EC50 values of 1:10 (by volume) WAF were 9.9 %WAF (gasoline) and 9.3 %WAF (RE85) to D. magna and 9.3 %WAF (gasoline) and 12.3 %WAF (RE85) to V. fischeri. Low solubility decreased toxicity potential of conventional diesel in aquatic environment, but direct physical effects of oil phase pose a threat to organisms in nature. Renewable diesel NExBTL did not show clear toxicity to any test species.     

Summer and winter nonmethane hydrocarbon emissions from on-road motor vehicles in the Midwestern United States

On-road vehicle emission rates of nonmethane hydrocarbons (NMHCs) were measured in two tunnels in Milwaukee, WI, in summer 2000 and winter 2001. Seasonal ambient temperatures in the Midwestern United States vary more widely than in locations where most studies of NMHC emissions from vehicle fleets have been conducted. Ethanol is the added fuel oxygenate in the area, and, thus, emissions measured here are of interest as other regions phase out methyl tertiary butyl ether and increase the use of ethanol. Total emissions of NMHCs in three types of tunnel tests averaged 4560 +/- 800 mg L(-1) fuel burned (average +/- standard error). To investigate the impact of cold start on vehicle emissions, samples were collected as vehicles exited a parking structure in subzero temperatures. NMHC emissions in the subzero cold-start test were 8830 +/- 190 mg L(-1) fuel-nearly double the tunnel emissions. Comparison of ambient data for the Milwaukee area with tunnel emissions showed the impact of seasonal differences in fuels and emissions on the urban atmosphere. Composition of fuel samples collected from area gas stations in both seasons was correlated with vehicle emissions; the predominant difference was increased winter emissions of lighter hydrocarbons present in winter gasoline. A chemical mass balance model was used to determine the contributions of whole gasoline and gasoline headspace vapors to vehicle emissions in the tunnel and cold-start tests, which were found to vary with season. Results of the mass balance model also indicate that partially combusted components of gasoline are a major contributor to emissions of aromatic compounds and air toxic compounds, including benzene, toluene, xylenes, napthalene, and 1,3-butadiene, whereas air toxics hexane and 2,2,4-trimethylpentane are largely attributed to gasoline and headspace vapors.     

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.     

The Use of Stable Isotopes to Differentiate Specific Source Markers for MTBE

The recent controversy over the use of MTBE within gasoline to boost oxygen content and decrease carbon monoxide emissions to the atmosphere has led to a proposed phase-out of this compound by 2002. This paper is a preliminary investigation into the use of gas chromatography isotope-ratio mass spectrometry (GCIRMS) to determine both carbon and hydrogen isotopic compositions of MTBE as a means of differentiating sources of MTBE. Three pure MTBE samples were purchased from chemical distributors. Little variation of the δ¹³C values were observed although the samples had isotopically distinct δ-D values. Four different methods of obtaining carbon isotope ratios of neat MTBE, MTBE in gasoline, and MTBE in water are described, and the precision and accuracy of each is discussed. The carbon isotopic compositions of MTBE within 10 gasoline samples from three different areas of the United States show a wide range of carbon isotope compositions. This novel method of MTBE analysis could be valuable in forensic investigations.