Environmental Impact of Gasoline and other Petroleum Compounds
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Research Synopsis: Environmental Impact of Gasoline and other Petroleum Compounds
Irwin, R.J. 1997. Environmental Contaminants Encyclopedia: Gasoline. Water Resources Division, National Park Service.
- The most important hazardous components of most gasolines are PAHs, alkyl PAHs, and the BTEX compounds (benzene and alkyl substituted benzenes such as toluene, xylenes, ethyl benzene); unleaded gasoline additives such as MTBE (Methyl tertiary-butyl ether), TBE (Tertiary butyl ether), Ethanol (Ethyl alcohol), and Methanol (Methyl alcohol).
- Due to a high percentage of aromatics (generally from 25 to 50%), gasoline is associated with many potential environmental hazards, both short- and long-term:
- Short-term (acute) hazards of the some of the lighter, more volatile and water soluble aromatic compounds (such as benzenes, toluene, and xylenes) in gasoline include potential acute toxicity to aquatic life in the water column (especially in relatively confined areas) as well as potential inhalation hazards.
- Gasoline is highly volatile and soluble, and evaporates quickly. Gasolines possess high acute toxicity to biota. In the short term, spilled oil will tend to float on the surface; water uses threatened by spills include: recreation; fisheries; industrial; and irrigation.
- Long-term (chronic) potential hazards of some of the lighter, more volatile and water soluble aromatic compounds in gasoline include contamination of groundwater.
- Sublethal effects of petroleum hydrocarbons at the organismal and population levels include impairment of feeding, growth, development, energetics, and recruitment, alteration in reproductive and developmental potential of populations, and possible changes in population structure and dynamics.
- Gasoline hydrocarbons are relatively mobile and moderately persistent in most soil systems; they are more persistent in deep soils and in groundwater.
- As such, gasoline is highly volatile and soluble . The relatively lighter, more volatile, mobile, and water soluble compounds in gasoline will tend to quickly evaporate into the atmosphere or migrate to groundwater. When exposed to oxygen and sunlight, most of these compounds will tend to break down relatively quickly. However, in groundwater, many of these compounds tend to be more persistent than in surface water, and readily partition on an equilibria basis back and forth between water and solids (soil and sediment) media. Cleaning up groundwater without cleaning up soil contamination will usually result in a rebound of higher concentrations of these compounds partitioning from contaminated soils into groundwater.
Agency for Toxic Substances and Disease Registry. 1995. Toxicological profile for fuel oils. U.S. Department of Health and Human Services.
- Fuel oils are composed of a large number of different chemicals, and each fuel oil is a slightly different mixture of these chemicals.
- Some of these chemicals evaporate into the air when fuel oils are spilled onto soils or surface waters (e.g., streams, rivers, lakes, or oceans) or are stored in open containers.
- Other chemicals in the fuel oils dissolve in water following spills to surface waters or leaks from underground storage tanks. Some of the chemical constituents of fuel oils may slowly move down through the soil to the groundwater.
- Another group of chemicals in fuel oils can attach to particles in the soil or water and, in water, may sink down into the sediment.
- The chemicals that evaporate may break down in air by reacting with sunlight, e.g., photo-oxidation, or other chemicals in the air. The chemicals that dissolve in water may also be broken down by organisms (primarily bacteria and fungi) in the soil or water. However, this may take up to a year to occur, if ever, depending on the environmental conditions.
- Chemicals that attach to soil or other matter (e.g., marsh sediment) may remain in the environment for more than a decade.
McKee, J.E., F.B. Laverty, and R.H. Hertel. 1972. Gasoline in groundwater. Water Pollution Control Federation 44: 293-302.
- A large volume of gasoline was discovered in 1968 on the relatively flat groundwater table between two massive cones of drawdown. If it had moved appreciably, the gasoline would have reached one or both of these steep drawdown cones to contaminate municipal drinking water.
- The solubility of modern gasolines in water is in the range of 20 to 80 mg/l (averaging about 50 mg/l). They can be tasted by very sensitive people at only 0.005 mg/l and by most people at about 0.5 mg/l. Hence, even at concentrations of one-hundredth the average solubility, gasoline would present a taste or odor problem in a municipal water system.
- When it became apparent that much of the gasoline on a falling water table would become pellicular (form a thin skin held by molecular attraction to the soil grains), further tests were conducted to determine the effects of falling and then rising water tables. After the water level had been raised slowly to a few centimeters above the top of the soil, no free gasoline floated on the water surface. All gasoline had been en trapped within the soil.
- This experiment indicated that once gasoline had become pellicular it would not be rendered free again by a rising water table. These column studies demonstrated that free gasoline would not move far through this soil formation, vertically or horizontally, without much of it becoming pellicular, unless the gasoline saturated the pore volumes of the soil.
- These studies also explained why the removal of free gasoline by skimmer pumps and sink wells became less productive as the water table dropped by natural processes or by the drawdown cones near the sink wells. From mid-1970 to mid-1971 the water table at this location dropped 6 to 8 ft (180 to 240 cm). After the early winter rains, it recovered up to 6 ft (180 cm). Finally, the column experiments showed that pellicular gasoline could not be removed readily by water flushing or air ventilation. The question that remained was how the final cleanup could be achieved.
Petroleum Contamination of Natural Systems
Blakely, J.K., D.A. Neher, and A.L. Spongberg. 2002. Soil invertebrate and microbial communities, and decomposition as indicators of polycyclic aromatic hydrocarbon contamination. Applied Soil Ecology 21: 71-88.
- Creosote affected soil food webs and decomposition more by altering habitat of microinvertebrates and their prey, fungi and bacteria, than by direct toxicity.
- To our surprise, creosote affected soil ecosystems more by altering soil properties than direct toxicity.
- Retention and bioavailability in the environment are reduced by hydrophobicity and organic carbon contents exceeding 2%. Polycyclic aromatic hydrocarbons sorb to soil particles tightly thereby increasing the bulk density of soil.
- Greater bulk density means less oxygen and nutrient transportation through soil, thus fewer indigenous flora are able to reach contaminants to degrade them even under optimum conditions.
Lytle, D.A. and B.L. Peckarsky. 2001. Spatial and temporal impacts of a diesel fuel spill on stream invertebrates. Freshwater Biology 46:693-704.
- We assessed the effects of a 26,500 L diesel fuel spill on the macroinvertebrate fauna of a small trout stream in central New York, U.S.A.
- Immediately after the spill, invertebrate density at all three locations below the spill was significantly lower than reference density.
- Three months after the spill, density up to 5 km below the spill was still far lower (<100 individuals per sample) than reference density (800±1200 individuals per sample).
- We concluded that the diesel fuel spill significantly reduced the density of invertebrates (by 90%) and taxonomic richness (by 50%) at least 5.0 km downstream, but density recovered within a year.
- Throughout the study, however, the fauna immediately below the spill was species poor and significantly over-represented by a single dominant taxon, suggesting that 15 months was not sufficient for full community recovery from the oil spill.
Elliott, W.R. 2000. Conservation of the North American cave and karst biota. In. Wilkens, H., D.C. Culver, and W.F. Humphrey (eds). Subterranean Ecosystems. Pp. 665-689.
- Until the 1960s many cavers dumped or buried their spent carbide in caves, but the practice was discouraged.
- Peck (1969) pointed out that the calcium hydroxide in spent carbide was poisonous to cave fauna, which he demonstrated in experiments with the cave beetle Ptomaphagus hirtus.
- In 1995, a resident crustacean was decimated in Wildcat Saltpeter Cave, Virginia, by diesel fuel from a leaking underground storage tank.
Eberhard, S. 1995. Impact of a limestone quarry on aquatic cave fauna at Ida Bay in Tasmania. Proceedings of the Eleventh Australasian Conference on Cave and Karst Management. Pp. 125-137.
- The impact of the quarry operations on Bradley Chesterman Cave have been evident for more than 20 years . There are reports of sedimentation and oil pollution in the cave, also foul air, fecal contamination and sickness caused to visitors.
- Organic and inorganic poisons are particularly toxic to aquatic life, so the petroleum hydrocarbons dumped in the weighbridge sinkhole may also have been involved with elimination of the original aquatic community in Bradley Chesterman Cave.
Petroleum Toxicity and Invertebrates
Stadler, T. and M. Buteler. 2009. Modes of entry of petroleum distilled spray-oils into insects: a review. Bulletin of Insectology 62: 169-177.
- An in depth analysis of the interaction between oils and insects body surface from a physical perspective suggests that suffocation occurs only when insects are over-sprayed or dipped in oil.
- Based on this analysis, it is more likely that when petroleum oils contact the insect surface, capillary forces and complex physical interactions take place in the cuticular layer, which lead to differences in the melting point and permeability of cuticle waxes. This in turn, alters the waterproofing properties of the cuticle and also leads to penetration of spray oils that can be carried to different lipophilic tissues.
- The changes in the cuticle caused by oils, which range from changes in melting point of the cuticular wax layer to cuticle dewaxing, strongly suggest cuticular penetration as the foremost mode of entry of insecticide oils.
Trumble, J. T. and D. Vickerman. 2003. Impact of pollution on terrestrial arthropods. In:
J. Capinera, (Ed.). Encyclopedia of Entomology. Pp. 170-173.
- MTBE is a gasoline additive used to elevate the oxygenate level in gasoline. This helps the gasoline burn more completely, reducing the production of some contaminants associated with automobile exhaust.
- Unfortunately, this chemical has leaked into the groundwater at over 385,000 sites nationwide due to poorly sealed underground fuel storage tanks. MTBE has now been detected in 21% of 480 wells in regions using MTBE as a gasoline additive.
- In addition, findings from the National Water Quality Assessment Program indicate that MTBE is the second most frequently detected volatile organic compound in ground water and urban streams.
- Preliminary data suggest that this material can slow development of some arthropod species.
Freeborn, S.B. and R.F. Atsatt. The effects of petroleum oils on mosquito larvae. Journal of Economic Entomology 11: 299-308.
- Tested the toxicity of various petroleum oils (including gasoline) on mosquito (Culiseta incidens) larvae.
- There can be no doubt that the oil, no matter whether a light oil such as kerosene, or a heavy oil-like liquid petroleum does flow into the anal siphon, the main tracheae and into even the very finest subdivisions, and does this in sufficient quantity to completely block them and render the passage of air impossible.
- The vapors of the various volatile petroleum oils were toxic to mosquito larvae even in dilute quantities when there was no possibility for the oil as a liquid to come in contact with them.
Richards, G., Jr. 1941. Differentiation between toxic and suffocating effects of petroleum oils on larvae of the house mosquito (Culex pipiens L.) (Diptera). Transactions of the American Entomological Society 67: 161-196.
- As early as 1918 Freeborn & Atsatt demonstrated that oils penetrate throughout the tracheal system of mosquito larvae, that their toxicity is proportional to their volatility, and that the vapors of these oils can also kill mosquito larvae.
- Even earlier Sen (1914) and Macfie (1917) had shown that kerosene vapors alone could kill. Toxic (volatile) petroleum oils do not necessarily cause any suffocation.
- They do cause extensive degeneration of nervous tissue as shown by premortem cell separation and degeneration of nerve processes and fiber tracts.
Moore, W. 1917. Volatility of organic compounds as an index of the toxicity of their vapors to insects. Journal of Agricultural Research 10: 365-371.
- Houseflies (Musca domestica) exposed to a number of benzene derivatives (including hydrocarbons such as gasoline and kerosene) to test for mortality.
- Gasoline was 21st in toxicity in millionths of a gram-molecule killing in 400 minutes (42.0) and volatility in gram-molecules evaporating in 400 minutes (0.0520) of the 45 chemicals tested.
- The structure of the respiratory system of the insect is probably responsible for the remarkable influence of volatility on the toxicity of the vapor of volatile organic compounds.
- If the compound is very volatile, it will evaporate and readily pass out of the insect, while if very slightly volatile it will remain in the insect, and will penetrate the tissues and produce the poisonous reactions which lead to the insect’s death. In higher animals, when the compound is taken into the lungs, it is rapidly removed by the blood and carried to all parts of the body, giving it an opportunity to react chemically with the tissues. For this reason the toxicity of volatile organic compounds is more closely correlated with the chemical composition when introduced into the higher animals, while in insects toxicity is more closely associated with volatility than with chemical composition.
Importance of Cave Crickets
Taylor, S.J., J.K. Krejca, and M.L. Denight. 2005. Foraging range and habitat use of Ceuthophilus secretus (Orthoptera: Rhaphidophoridae) a key trogloxene in central Texas cave communities. American Midland Naturalist 154: 97-114.
- Though some terrestrial cave communities in central Texas are supported largely by the guano of large colonies of bats (e.g., Bracken Bat Cave, Comal County), many of the caves in this area are much smaller and lack bat colonies.
- In these smaller caves, cave crickets (Orthoptera: Rhaphidophoridae: Ceuthophilus spp.) are important in transporting energy into caves by foraging on the surface at night and roosting in caves in the daytime, depositing feces, eggs and their dead bodies in the caves.
- Even relatively small caves may harbor thousands of cave crickets and the feces they produce can form layers of energy-rich substrate. In such caves, springtails are abundant on the cricket guano and their predators, troglobitic Cicurina spp. spiders. The cave crickets deposit their eggs in the caves, and some of the eggs are depredated by cave-adapted Rhadine spp. beetles (Coleoptera: Carabidae).
- Other relationships among taxa are less well understood, but it is clear that the cave crickets play an important role in providing energy for the cave system. These taxa include several troglobitic Rhadine and Cicurina species which appear to be dependent, at least in part, on the energy brought into caves by cave crickets.
- Consequently, it follows that maintaining healthy cave cricket populations may be important in facilitating the recovery of the endangered taxa.