The effect of gasoline fumes on plants
The hypothesis that longer periods of exposure to gasoline fumes, at higher temperatures will result in quicker death of plants. Gasoline contains aromatic hydrocarbons like benzene that are carcinogenicand harmful to living organisms. Therefore, the occurrence of gasoline leaks are a big threat to public health and the environment. Gasoline is also extremely volatile and will evaporate more quickly at higher temperatures. Many safety factors must be taken into consideration to prevent leakage when designing and building gasoline storage tanks and transportation piping.
Repeat the science fair project to study the effect of gasoline vapor on insects.
Alternatively, you could also try to ascertain if certain species of plants are more resilient in the presents of gasoline fumes
Gasoline - http://en.wikipedia.org/wiki/Gasoline
Environmental affects of ethanol and gasoline - http://www.sentex.net/~crfa/ethaenv1.html
Avoid evaporating gas - http://planetgreen.discovery.com/tech-transport/avoid-evaporating-gas-shade.html
Extreme care and caution required to ensure that the gasoline does not ignite and to prevent inhalation. The assistance of adults is required and the experiment must be conducted in a properly equipped laboratory which is well ventilated. Fire safety gear and equipment required.