2000 Progress Report: Effects of Air Pollution on Water Quality: Emission of MTBE and Other Pollutants From Motorized Watercraft

EPA Grant Number: R825433C024
Subproject: this is subproject number 024 , established and managed by the Center Director under grant R825433
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: EERC - Center for Ecological Health Research (Cal Davis)
Center Director: Rolston, Dennis E.
Title: Effects of Air Pollution on Water Quality: Emission of MTBE and Other Pollutants From Motorized Watercraft
Investigators: Reuter, John E. , Allen, Brant C. , Goldman, Charles R.
Current Investigators: Reuter, John E. , Allen, Brant C. , Goldman, Charles R. , Jassby, Alan D.
Institution: University of California - Davis
EPA Project Officer: Hahn, Intaek
Project Period: October 1, 1996 through September 30, 2000
Project Period Covered by this Report: October 1, 1999 through September 30, 2000
RFA: Exploratory Environmental Research Centers (1992) RFA Text |  Recipients Lists
Research Category: Center for Ecological Health Research , Targeted Research


To investigates sources, fate and transport of MTBE in surface water bodies used as drinking water sources.

Progress Summary:

Background - Methyl tertiary-butyl ether, or MTBE, is an oxygenate added to gasoline to reduce air pollutant emission; ethanol is another oxyfuel. U.S. use of MTBE has been estimated at 10.5 million gallons a day. MTBE accounts for 10-15% of gasoline by volume; the potential for contamination surface and groundwater resources is wide spread.

Cause for Concern - U.S. EPA classifies MTBE as a possible human carcinogen. Groundwater contamination is related to underground gasoline storage systems. Emission of unburned fuel from marine watercraft engines is the primary source of MTBE to lakes and reservoirs. On the basis of scientific data, both the California and the U.S. EPA have called for a phase-out of MTBE from fuels.

Focus of Previous Investigations - Our research on MTBE in lakes and reservoirs, has focused on (a) extent of MTBE in surface waters, (b) sources of MTBE, (c) understand the fate and transport, and (d) management plans.

California's MTBE Public Health and Environmental Protection Act of 1997 directed the University of California to assess human health and environmental impacts of MTBE. One goal was a survey of MTBE in the state's drinking water reservoirs and lakes. Data was available for 105 waterbodies. 75% of these had =10 samples. Our understanding of MTBE in surface waters comes from a few heavily monitored sites (e.g. Donner Lake, Lake Tahoe, Lake Perris). 59 of the 105 waterbodies did not contain MTBE and the remaining 46 had MTBE greater than detection at least once. 26 contained MTBE at levels above the California taste & odor standard (5 µg/L), with 13 above the public health goal (13 µg/L). State-wide data clearly showed MTBE in waterbodies allowing motorized watercraft.

The Donner Lake Case Study on sources, fate and transport of MTBE was the first comprehensive published study on MTBE in a lake. Over 500 individual samples for MTBE analysis were made at depths from surface to bottom on 16 dates. 86% of the change in MTBE was explained motorized watercraft use. Neither highway runoff nor precipitation were contributors. MTBE concentration ranged from <0.1 µg/L to a high of 12 µg/L. Between July 1-7, 1997, whole-lake MTBE content rose dramatically as a direct result of motorized watercraft activity. Minimum levels in January suggested little inter-annual persistence. Major loss of MTBE appeared to be volatilization at the air-water interface. In the absence of boating, MTBE half-life was 14 days. Thermal stratification acted to retard MTBE transport to deeper depths. Upon turnover, MTBE was able to reach deeper depths, but only temporarily.

MTBE was detected at a number of nearshore locations in Lake Tahoe resulting from emission of unburned fuel. Concentrations at an open-water sampling station (mid-lake) were near or below detection. Complete depth sampling from the surface to 450 m, gave no indication that MTBE was either transporting to depth or accumulating in the lake. Concentrations dropped at the end of the summer boating. For MTBE, 2-stroke outboard engines were the least efficient. Over 30% of the MTBE was deposited into the water during operation. Similarly, 10% of the MTBE in fuel used by PWCs was released. Carbureted 2-stroke engines contributed a disproportionate load of MTBE, benzene, and toluene. They added over 90% of the MTBE to Lake Tahoe, while only utilizing about 11-12% of the total fuel.

Effective June 1, 1999, the Tahoe Regional Planning Agency imposed a ban on certain 2-stroke marine engine technologies. Previous studies had shown that 2-stroke carbureted engines were responsible for approximately 90% of the MTBE emissions to the lake. Lake Tahoe was monitored in late August and over the Labor Day weekend in 1999 to determine if concentrations of MTBE and BTEX were affected by implementation of the new marine engine policy. Samples were taken on three dates, (1) mid-week, (2) weekend, and (3) following Labor Day; peak boating activity traditionally occurs at this time of the year. Samples were taken from a mid-lake (open water locations), a series of 10 stations located around the perimeter of the lake, and at 10 "hot spots" along the south shore where boating and boating related activities are high. The results showed an approximate 10-fold decline in both MTBE and BTEX compounds between 1997-1998 and 1999 (Figure 1). Many of the 1999 concentrations were below the 0.06 µg/L limit of analytical detection, whereas much fewer were this low in previous years. High levels of MTBE were still found at certain "hot spots" which were attributed to isolated boating actions not related to overall boating intensity.

On the whole, fuel constituent concentrations in Lake Tahoe are down dramatically from previous years. This could be the result of the TRPA regulation banning certain two cycle engine technologies or as a byproduct of some service stations within the Tahoe basin selling MTBE-free fuel. A comparison of the decreases in ambient MTBE and toluene concentrations was done to determine which corrective action was having the greatest impact on Tahoe water quality. If the MTBE-free fuel was having the greatest impact, the ambient MTBE concentrations would be expected to decrease while toluene concentrations in the lake remained near the levels recorded in 1997 and 1998. If the new boating regulations were having the greatest impact, both MTBE and toluene concentrations could be expected to drop. Indeed both mean MTBE and mean toluene concentrations drop significantly (95.8% and 88.3% respectively) indicating that the elimination of the highly polluting two cycle engines is having a clear impact on water quality. The data strongly suggests that the ban on certain types of 2-stroke engines at Lake Tahoe was very successful in reducing both MTBE and BTEX.

Figure 1.

Figure 1. Reduction in MTBE at both nearshore and mid-lake locations following the ban on most 2-stroke carbureted marine engines in 1999 in Lake Tahoe.

Future Activities:

This series of research projects on MTBE has contributed to a number of policy decisions regarding MTBE, including banning of 2-stroke marine engines on Lake Tahoe and other waterbodies, and the call by Governor Gray Davis of California to phase-out the use of MTBE. At this time, our CEHR-related MTBE work is largely complete. Working with colleagues from other institutions (Jim Oris - Miami University, Ohio and Glenn Miller - University of Nevada, Reno), we are planning to continue the study of PAH emission and possible aquatic toxicity in Lake Tahoe. In joint cooperation with Dr. Geoff Schladow (U.C. Davis and CEHR member), we are using newly collected field data to calibrate and verify a model written to predict MTBE concentrations in lakes and reservoirs which allow motorized watercraft. This model will be the cornerstone for a guidance manual for water distribution agencies and other lake managers.

Supplemental Keywords:

RFA, Scientific Discipline, INTERNATIONAL COOPERATION, Water, Ecosystem Protection/Environmental Exposure & Risk, Aquatic Ecosystems & Estuarine Research, Environmental Chemistry, Aquatic Ecosystem, Biochemistry, Environmental Monitoring, Ecology and Ecosystems, Drinking Water, fate and transport, human health effects, watershed management, watersheds, ecosystem monitoring, MTBE, source water, air pollution, aquatic ecosystems, environmental stress, water quality, drinking water contaminants, ecosystem stress, hydrologic modeling

Progress and Final Reports:

Original Abstract
  • 1997
  • 1998
  • 1999 Progress Report
  • Final Report

  • Main Center Abstract and Reports:

    R825433    EERC - Center for Ecological Health Research (Cal Davis)

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R825433C001 Potential for Long-Term Degradation of Wetland Water Quality Due to Natural Discharge of Polluted Groundwater
    R825433C002 Sacramento River Watershed
    R825433C003 Endocrine Disruption in Fish and Birds
    R825433C004 Biomarkers of Exposure and Deleterious Effect: A Laboratory and Field Investigation
    R825433C005 Fish Developmental Toxicity/Recruitment
    R825433C006 Resolving Multiple Stressors by Biochemical Indicator Patterns and their Linkages to Adverse Effects on Benthic Invertebrate Patterns
    R825433C007 Environmental Chemistry of Bioavailability in Sediments and Water Column
    R825433C008 Reproduction of Birds and mammals in a terrestrial-aquatic interface
    R825433C009 Modeling Ecosystems Under Combined Stress
    R825433C010 Mercury Uptake by Fish
    R825433C011 Clear Lake Watershed
    R825433C012 The Role of Fishes as Transporters of Mercury
    R825433C013 Wetlands Restoration
    R825433C014 Wildlife Bioaccumulation and Effects
    R825433C015 Microbiology of Mercury Methylation in Sediments
    R825433C016 Hg and Fe Biogeochemistry
    R825433C017 Water Motions and Material Transport
    R825433C018 Economic Impacts of Multiple Stresses
    R825433C019 The History of Anthropogenic Effects
    R825433C020 Wetland Restoration
    R825433C021 Sierra Nevada Watershed Project
    R825433C022 Regional Transport of Air Pollutants and Exposure of Sierra Nevada Forests to Ozone
    R825433C023 Biomarkers of Ozone Damage to Sierra Nevada Vegetation
    R825433C024 Effects of Air Pollution on Water Quality: Emission of MTBE and Other Pollutants From Motorized Watercraft
    R825433C025 Regional Movement of Toxics
    R825433C026 Effect of Photochemical Reactions in Fog Drops and Aerosol Particles on the Fate of Atmospheric Chemicals in the Central Valley
    R825433C027 Source Load Modeling for Sediment in Mountainous Watersheds
    R825433C028 Stress of Increased Sediment Loading on Lake and Stream Function
    R825433C029 Watershed Response to Natural and Anthropogenic Stress: Lake Tahoe Nutrient Budget
    R825433C030 Mercury Distribution and Cycling in Sierra Nevada Waterbodies
    R825433C031 Pre-contact Forest Structure
    R825433C032 Identification and distribution of pest complexes in relation to late seral/old growth forest structure in the Lake Tahoe watershed
    R825433C033 Subalpine Marsh Plant Communities as Early Indicators of Ecosystem Stress
    R825433C034 Regional Hydrogeology and Contaminant Transport in a Sierra Nevada Ecosystem
    R825433C035 Border Rivers Watershed
    R825433C036 Toxicity Studies
    R825433C037 Watershed Assessment
    R825433C038 Microbiological Processes in Sediments
    R825433C039 Analytical and Biomarkers Core
    R825433C040 Organic Analysis
    R825433C041 Inorganic Analysis
    R825433C042 Immunoassay and Serum Markers
    R825433C043 Sensitive Biomarkers to Detect Biochemical Changes Indicating Multiple Stresses Including Chemically Induced Stresses
    R825433C044 Molecular, Cellular and Animal Biomarkers of Exposure and Effect
    R825433C045 Microbial Community Assays
    R825433C046 Cumulative and Integrative Biochemical Indicators
    R825433C047 Mercury and Iron Biogeochemistry
    R825433C048 Transport and Fate Core
    R825433C049 Role of Hydrogeologic Processes in Alpine Ecosystem Health
    R825433C050 Regional Hydrologic Modeling With Emphasis on Watershed-Scale Environmental Stresses
    R825433C051 Development of Pollutant Fate and Transport Models for Use in Terrestrial Ecosystem Exposure Assessment
    R825433C052 Pesticide Transport in Subsurface and Surface Water Systems
    R825433C053 Currents in Clear Lake
    R825433C054 Data Integration and Decision Support Core
    R825433C055 Spatial Patterns and Biodiversity
    R825433C056 Modeling Transport in Aquatic Systems
    R825433C057 Spatial and Temporal Trends in Water Quality
    R825433C058 Time Series Analysis and Modeling Ecological Risk
    R825433C059 WWW/Outreach
    R825433C060 Economic Effects of Multiple Stresses
    R825433C061 Effects of Nutrients on Algal Growth
    R825433C062 Nutrient Loading
    R825433C063 Subalpine Wetlands as Early Indicators of Ecosystem Stress
    R825433C064 Chlorinated Hydrocarbons
    R825433C065 Sierra Ozone Studies
    R825433C066 Assessment of Multiple Stresses on Soil Microbial Communities
    R825433C067 Terrestrial - Agriculture
    R825433C069 Molecular Epidemiology Core
    R825433C070 Serum Markers of Environmental Stress
    R825433C071 Development of Sensitive Biomarkers Based on Chemically Induced Changes in Expressions of Oncogenes
    R825433C072 Molecular Monitoring of Microbial Populations
    R825433C073 Aquatic - Rivers and Estuaries
    R825433C074 Border Rivers - Toxicity Studies