Concentrations, Sources, and Fate of the Gasoline Oxygenate Methyl tert-Butyl Ether (MTBE) in a Multiple-Use Lake

Abstract

Discovery of the fuel additive methyl tert-butyl ether (MTBE) in drinking water supplies is of concern to public health officials, water suppliers, and the public. Despite recent policy decisions, few published studies exist on the concentrations, sources, and fate of MTBE in surface waters. The purpose of this study was to determine (1) the relative contribution of motorized watercraft as a source of MTBE, (2) its seasonal distribution, (3) loss from the water column, (4) the extent of vertical transport, and (5) its persistence between years; this work was done in Donner Lake, California, a multiple-use lake in the Sierra Nevada Mountains. MTBE measurements were made at 9 individual depths from surface to bottom on 16 dates. Recreational boating was the most important source of MTBE. Statistically, 86% of the change in MTBE was explained by variation in motorized watercraft use. Neither highway runoff nor precipitation contributed significantly. MTBE concentration ranged from <0.1 µg‚L -1 to a high of 12 µg‚L -1 . Between July 1 and 7, 1997, MTBE content rose dramatically from 115 to 365 kg. By January, levels had declined to a minimum of 15 kg, suggesting little interannual persistence. The major loss of MTBE appeared to be volatilization at the air-water interface characterized by two distinct periods. During the boating season, MTBE decline was 1.2 kg‚day -1 (193 day half-life). At the end of the boating season, MTBE loss increased to 8.1 kg‚day -1 (14 day halflife). Thermal stratification acted to retard MTBE transport to deeper depths.

Seasonal and daily variations in concentrations of methyl-tertiary-butyl ether (MTBE) at Cranberry Lake, New Jersey

“…This rate is smaller than that observed on Donner Lake by Reuter et al [8], which was 8 kg/day, and is similar to that observed on Perris Lake [9], which was 1.6 kg/day. The surface areas of the lakes differ, however, and Perris Lake has the highest rate when its surface area is accounted for.…”

“…As part of the National Water Quality Assessment (NAWQA) program conducted by the US Geological Survey (USGS), Squillace et al [3] found that MTBE was the second most frequently detected volatile organic compound (VOC) in ground water in nine areas across the country. MTBE also has been found in urban storm runoff and streams [4], lakes [5][6][7][8][9], and improper disposal of used motor oil [10]. MTBE in the atmosphere over southern New Jersey was monitored from 1996 to 1998 [11,12].…”

“…MTBE occurrence has been documented in lakes in Nevada and California [6][7][8][9] and in northern New Jersey [5]. Concentrations of MTBE in Lake Tahoe, Nevada (500 km 2 or 123,000 acre), ranged from 0.18 to 4.2 mg/L, and the compound was found throughout the 30-m vertical profile [6].…”

“…Concentrations of MTBE in Lake Tahoe, Nevada (500 km 2 or 123,000 acre), ranged from 0.18 to 4.2 mg/L, and the compound was found throughout the 30-m vertical profile [6]. Reuter et al [8] found that 86% of the variation in MTBE concentration in Donner Lake (3.9 km 2 or 950 acre) in California could be attributed to monitored variations in boat traffic, on the basis of sampling approximately monthly from March 1997 to January 1998. Concentrations increased from 2 to 12 mg/L on July 4, holiday.…”

MTBE Ambient Water Quality Criteria Development: A Public/Private Partnership

“…Reports of MTBE in freshwater lakes and reservoirs indicated that detected MTBE concentrations ranged from <1 µg/L to as high as 88 µg/L and were typically associated with watercraft activity both spatially (e.g., marinas) and temporally (summer season/holiday weekends; 3,4,5). MTBE was also documented to occur in stormwater runoff at a low frequency of detection but ranging in concentration from 0.2 to 8.7 µg/L (6).…”