|M.Sc Student||Dinerman Efrat|
|Subject||Modeling MTBE in Lake Kinneret as a Tool for the Assessment|
of the Risk to the Water Quality in the Lake
|Department||Department of Civil and Environmental Engineering||Supervisor||Professor Eran Friedler|
|Full Thesis text - in Hebrew|
MTBE (Methyl tert-Butyl Ether) is a fuel additive that replaced lead due to its high toxicity. This replacement significantly improved air quality. However, few years later MTBE started to be detected in water sources. MTBE has a very low organoleptic threshold and is categorized as a potential carcinogen. Recreational boating is believed to be a major source of MTBE to lakes.
Lake Kinneret is a warm monomictic lake, undergoing summer stratification. It is a multiple use lake, serving both recreational boating and as a source of potable water. In 2007 about 1,500 motorized watercrafts (boats & jet-skis) were active in the lake.
The objective of this research was to develop a simulation model for the prediction of MTBE concentrations in Lake Kinneret. The research consisted of a sampling campaign and boating survey, followed by development of a model for assessment of possible future scenarios.
Samples were taken from the main rivers feeding the lake, the marinas along its shores and from its waterbody. Surprisingly, MTBE concentrations in the lake were found to be higher in winter, probably due to higher volatilization during summer which results from the region's unique winds regime.
The boating survey revealed that May-September is the main recreational season, although boating continues throughout winter. A boat is active 23 d/y (average), most during weekends and holidays, it stays in water for 4.5 h/d, and consumes 16 L/h of gasoline.
A one-dimensional simulation model was developed. It considers thermal stratification in summer, main rivers discharges, mass transfer between water layers and MTBE losses due to volatilization and degradation. It examined two groups of scenarios: the first examined the effects of variations in the characteristics of boating activity, and the second the effects of variations in the watershed contribution.
The model demonstrated that watercrafts cause great daily variations of MTBE concentrations in the lake. Thus, if the nature of the activity would change, MTBE may exceed the recommended limits much more often. Positive relationships were found between MTBE in the lake and increase of watercrafts number or watershed contribution.
The research pointed out that recreational boating is the main MTBE source to Lake Kinneret, contributing 65% of its annual load, while the watershed contributes 35%. At present of MTBE concentrations are lower than the recommended values and do not exert health or aesthetic problem. However, on certain days and in specific locations (marinas) its concentrations can be problematic.