Toxicological and Performance Aspects of Oxygenated Motor Vehicle Fuels (1996) / Chapter Skim
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3 WATER QUALITY
3 WATER QUALITY
Pages 53-66
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From page 53... ...
The large majority of states do not have any current programs or requirements to monitor concentrations of MTBE or other fuel oxygenates in water. Yet the available data suggest that MTBE is sometimes present in precipitation, stormwater runoff, groundwater, and drinking water.
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From page 54... ...
OVERVIEW OF WATER QUALIT`( I N TH E I NTE RAG ENCY REPORT The interagency report provides a summary of major sources of fuel oxygenates in the hydrologic cycle; monitoring data on MTBE concentrations in surface water, storm-water runoff, and groundwater, including drinking-water supplies; and a review of the major processes expected to influence MTBE transport and fate in the
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From page 55... ...
Monitoring of groundwater, storm water, and drinking water have shown the presence of MTBE and have raised questions about the extent to which MTBE and possibly other oxygenates might move through the hydrologic cycle. Historically, the primary concern over oxygenate contamination In water has been associated with substantial surface spills and leakage from USTs.
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From page 56... ...
Because of the relatively low MTBE levels detected and the physical location of the wells, the report indicates that these detections were not due to releases from concentrated spills or UST leakage. The measurement of low concentrations of MTBE at scattered locations was used as an indication of diffuse contamination of shallow groundwater by contaminated precipitation or storm-water runoff.
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From page 57... ...
If EPA's recommended health-advisory concentrations were reduced considerably, substantial concerns would arise about the potential hazards of MTBE in drinking water. The impacts of storm-water and groundwater containing oxygenates on aquatic life are very poorly understood.
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From page 58... ...
For example, it is not clear whether the groundwater-monitoring data were obtained directly from the National Water Quality Assessment (NAWQA) files or from summaries prepared by Squillace et al.
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From page 59... ...
The rate of volatilization from surface water will be controlled by the concentrations in the aqueous and gas phases and the masstransfer efficiency. The interagency report should note that when the overlying atmosphere contains significant concentrations of alkyl ether oxygenates (AEOs)
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From page 60... ...
Under this scenario, soil-water AEO concentrations might increase in the wintertime due to high atmospheric concentrations and then decrease during the summer due to diffusive losses back to the surface, resulting in a very low net flux of AEOs to the water table. DISCUSSION OF INTERAGENCY REPOT RECOM M EN CATIONS The interagency report recommends that an ad hoc panel representing public and private sectors be formed to develop a comprehensive research and assessment plan to determine the impact of alkyl ether fuel oxygenates on drinking-water quality and aquatic life.
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From page 61... ...
This database could then be used in exposure assessments for AEOs in drinking water and for aquatic life in surface water. Over the short term, it is unlikely that sufficient additional information will be developed that would allow accurate exposure assessments of AEOs.
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From page 62... ...
The interagency report recommends that the available data be reviewed annually to assess the effects of AEO-use, land-use, and hydrogeologic variables on temporal and spatial variations in water quality . While a continual assessment of the effects of oxygenate use on water quality is very important, it iS not clear whether this assessment should be conducted as a separate program or should be integrated into existing water-quality assessment and management systems.
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From page 63... ...
By conducting coordinated large-scale monitoring projects, small-scale field studies, and controlled laboratory experiments, it should be possible to evaluate current theories and mathematical models of AEO fate and transport. The interagency report recommends that coordinated chronicand acute-toxicity studies of AEOs be performed with a broad range of aquatic animals and plants to assess the threat to aquatic life and form a basis for federal water-quality criteria.
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From page 64... ...
On the basis of the small amount of monitoring data, MTBE has been detected in less than 5% of the groundwater samples analyzed, suggesting that drinking water is not currently a major MTBE exposure pathway for much of the population. RESEARC H N EELS Storm-water runoff and shallow groundwater can be contaminated with low levels of MTBE (< 20 ~g/~)
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From page 65... ...
More needs to be known about the biodegradation of MTBE and other AEOs in surface water, soil, and groundwater. Biodegradation processes have the potential to substantially reduce the effects of point- and nonpoint-source releases of MTBE and other oxygenates.
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