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Gasoline Additive in Water Will Be a Key Topic At American Chemical Society Meeting in San Francisco
Released: 4/15/1997

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Methyl tert-butyl ether (MTBE) in the nation’s ground waters and surface waters will be the subject of papers and poster presentations by U.S. Geological Survey scientists at the American Chemical Society annual meeting, April 16-17, in San Francisco, Calif.

MTBE is a volatile organic compound (VOC) derived from natural gas that is added to gasoline either seasonally or year round in many parts of the U.S. to increase the octane level and to reduce carbon monoxide and ozone levels in the air. It is the most commonly used oxygenate in the United States.

MTBE is one of 60 VOC’s being measured in ground water and surface water samples collected across the nation as part of the USGS National Water-Quality Assessment Program. This contaminant is of interest because of its widespread use as an oxygenate, numerous past releases of gasoline from storage tanks and other point sources--some of which have contained MTBE--,and instances of impact to some drinking water wells. The U.S. Environmental Protection Agency has classified MTBE as a possible carcinogen and has established a draft lifetime drinking water health advisory of 20 - 200 micrograms per liter. This advisory is currently being updated by the EPA. MTBE imparts taste and odor to water, which can be detected by many persons at levels beginning at 40 - 130 micrograms per liter.

Selected papers and poster presentations on MTBE by USGS scientists include:

Distribution of MTBE in Ground Water in New England by Aquifer Type and Land Use, by S. J. Grady, USGS-Hartford, Conn.

MTBE was the most frequently detected volatile organic compound in ground-water samples collected from 1993 to 1995 in New England. Ninety-seven percent of the MTBE detections were found in Connecticut and Massachusetts, where reformulated gasoline that often contains MTBE is used year round. MTBE was present in 26 of 103 (25%) monitoring wells screened in near-surface aquifers and in 7 of 30 (23%) water-supply wells in fractured bedrock. Most MTBE detections were in areas where the human population exceeds 1,000 residents per square mile. Concentrations of MTBE were low and suggest that nonpoint sources such as atmospheric deposition and recharge of urban runoff are the likely sources of MTBE in ground water. (Grady, telephone 860-240-3060, email sgrady@usgs.gov, poster session - Wed., April 16, 5-7 p.m. - Grand Ballroom B, Ballroom Level)

Occurrence of MTBE in Surface and Ground Water, Long Island, New York and New Jersey, by Paul E. Stackelberg, Anne K. O’Brien, USGS-West Trenton, New Jersey; Stephen A. Terracciano-USGS, Coram, N.Y.

MTBE is one of the most frequently detected volatile organic compounds in streams and aquifers of Long Island, New York and New Jersey. Although concentrations and detection frequencies were higher in samples collected from heavily populated and urbanized areas, MTBE was detected in all types of land-use settings. Concentrations, however, are generally low and rarely exceed the draft lifetime health advisory. MTBE was detected more frequently in surface-water samples collected during winter months than in summer months. Low median concentrations in both streams and ground water, and increased detection frequencies in streams during winter months, indicate that nonpoint sources of contamination such as precipitation or stormwater runoff may play important roles in the frequent low-level detection of MTBE. Point sources of contamination may augment nonpoint sources in more highly urbanized areas resulting in more frequent detections and larger concentrations. (Stackelberg, telephone 609-771-3951, email pestack@usgs.gov, poster session - Wed., April 16, 5-7 p.m., Grand Ballroom B)

MTBE in Water from Fractured-Bedrock Aquifers, Southcentral Pennsylvania, by Bruce D. Lindsey, Kevin J. Breen and Matthew J. Daly, USGS-Lemoyne, Pa.

A study of the occurrence of MTBE in the Lower Susquehanna River Basin in southcentral Pennsylvania showed that land use is an important factor affecting the occurrence of MTBE in ground water and that bedrock type had little or no effect on the compound’s occurrence. For 20 monitoring wells in each of adjacent urban and rural areas, both underlain by limestone, MTBE was detected in 10 of 20 wells (50%) in the urban areas and in only 1 of 20 wells (5%) in the rural area. Similar to findings from studies in New York, New Jersey, and New England, concentrations of MTBE, were generally low. The MTBE concentration in only one monitoring well exceeded the draft EPA lifetime health advisory. This well was not used for drinking water purposes. (Lindsey, telephone 717-730-6964, email blindsey@usgs.gov, poster session - Wed., April 16, 5-7 p.m., South Grand Ballroom B- Ballroom Level)

Occurrence of MTBE and Tert-butyl Alcohol in a Gasoline Contaminated Aquifer, by James E. Landmeyer, USGS, Columbia, S.C., James F. Pankow and Clinton D. Church, Dept. Of Environmental Science and Engineering, Oregon Graduate Inst. Of Science and Technology, Portland, Ore.

Methyl tert-butyl ether (MTBE) was measured between 1993 and 1997 in a shallow aquifer contaminated by the release of gasoline from an underground storage tank. Since 1993, when the tank was removed, MTBE values have decreased in some wells by up to 3 orders of magnitude. To determine if this decrease in MTBE was related to natural attenuation processes (such as dilution or biodegradation), concentrations of tert-butyl alcohol (TBA), a proposed biotransformation intermediate, were measured in 1996 and 1997. In 1996, ratios of TBA to MTBE increased with increasing distance from the former underground storage tank area. This increase may reflect (1) the microbial production of TBA, a proposed MTBE biotransformation intermediate, or (2) the preferential dissolution and transport of more soluble TBA over less soluble MTBE. Although scenario 1 cannot yet be corroborated with laboratory studies, the presence of TBA in unsaturated-zone source-area sediments suggests that TBA may have been in the fuel spilled and scenario 2 may be a more plausible explanation for the observed field data. However, it is possible that both of these processes have occurred at this site. (Landmeyer, telephone 803-750-6128, email: jlandmey@usgs.gov, Thurs., April 17 (9:25 a.m., Franciscan B, Ballroom Level).

(Note to Editors: Reporters are encouraged to attend the paper presentations and view the poster sessions on MTBE at the national meeting of the American Chemical Society in San Francisco, Calif., April 13-17, 1997, at the San Francisco Marriott, 55 Fourth St. ACS will hold a media advisory on MTBE on Wed., April 16, at 12:30 p.m. in Pacific Suite C. The ACS press room telephone number at the Marriott is 415-284-8008.)

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