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Environmental occurrence and fate of ethanol and MTBE gasoline oxygenates in surface water and shallow groundwater in Nebraska

Yi Zhang, University of Nebraska - Lincoln


Contaminations of fuel oxygenates pose a threat to the environment and human health. Oxygenates are more mobile in groundwater than other fuel components. It has put an increased emphasis on early detection and response to fuel leaks and spills. An innovative method using solid phase microextraction and gas chromatography/mass spectrometry (SPME-GC/MS) was developed to detect ethanol and TBA in low microgram per liter concentrations and MTBE, ETBE, TAME at nanogram per liter concentrations in water. SPME is sensitive for oxygenate analysis in water but its usage for alcohols may be affected in samples containing free product due to fuel matrix interfering effects on SPME fiber. Samples containing oxygenates should be stored at 4°C and analyzed within 3 mo. HCl or HgCl2 properly preserves ethanol, TBA MTBE, ETBE, and TAME in water samples. ^ Fuel oxygenate pollution results from point and nonpoint sources. Shallow groundwater from 10 sites along Instate-80 (I-80) in Nebraska was analyzed using SPME-GC/MS for oxygenates and young groundwater ages were profiled by the CFC dating technique. Oxygenate concentrations in groundwater along I-80 were compared to 3 sites in agricultural areas with limited atmospheric deposition of oxygenates and those in surface water in urban areas (Lincoln, NE). Nonpoint sources of oxygenates from vehicle emissions does not appear to affect the quality of shallow groundwater and urban surface waters even in high traffic areas in Nebraska. In groundwater from leaking underground storage tank sites in Nebraska, MTBE, ETBE, TAME, and TBA were detected at various concentrations but ethanol was below 10 mg/L. The decreasing trend of occurrence frequencies of 4 oxygenates was: MTBE >> TAME > TBA > ETBE. ^ A pulse of 220 mg L−1 ethanol and 15.8 mg L −1 bromide was injected into a shallow aquifer and monitored for 2.5 mo to estimate the persistence and transport of ethanol. Breakthrough curves were fit to the advection-dispersion model. First-order degradation constants ranged from 0.23 to 0.57 d−1 and its half-life values ranged from 1.29 to 3.24 d. Ethanol was not retarded (retardation factor, 0.99∼1.01). How ethanol impacts behavior of BTEX plumes in groundwater needs further study. ^

Subject Area

Chemistry, Analytical|Environmental Sciences|Engineering, Environmental

Recommended Citation

Zhang, Yi, "Environmental occurrence and fate of ethanol and MTBE gasoline oxygenates in surface water and shallow groundwater in Nebraska" (2003). ETD collection for University of Nebraska - Lincoln. AAI3092610.