Soils are extremely important parts of every ecosystem. They are a home to many microbes and provide vital nutrients to the plants that live in them. pH is the measure of acidity or alkalinity of a solution, and most organisms have a very small range of pH values in which they can survive. 7 is considered neutral, lower than 7 is acidic (lemon juice, rain water) and above 7 is basic (bleach, soap).
Lots of urban areas are dependent on car transportation, and at the present time, most of our cars run on gasoline. It has already been documented that burning gasoline produces greenhouse gases that contribute to warming in our atmosphere, and byproducts have been linked to asthma and cancer. Do gas stations also pollute the soil around them?
Do gas stations affect the pH of surrounding soil?
Form a hypothesis on whether or not the presence of gas stations in your area affects the soil by observing plant life.
- Sterile lab dishes, small
- Labeling tape
- Universal pH indicator and color table
- Plastic zip-top bags
- Plastic dropper
- Collect 1-tablespoon soil samples from the immediate area surrounding 4 different gas stations. Store the samples in separate plastic bags and label the location where you collected them.
- Collect 1-tablespoon soil samples from areas away from gas stations. Try to get soil samples from urban, suburban and rural areas. For this experiment, the more samples, the better.
- Put a pea-sized portion of each sample into a separate lab dish. Label the samples carefully.
- Use the plastic dropper to add drops of water until the sample is barely covered.
- Add 2 to 3 drops of universal pH indicator to each sample.
- Observe your samples and use the color table that comes with the indicator to record the pH of each sample.
The results of your test will depend on the environmental regulations of your state, city or town, and on how well gas stations comply. Newer gas stations should not have any effect on the soil, but older gas stations may have an effect.
Science and governmental regulation have come a long way in protecting the environment. A compound that has been found to contaminate soil as well as water near gas stations is called MTBE, or methyl tert-butyl ether. Oil companies used to add MTBE to gasoline to give it higher oxygen content (which gives better combustion in your car engine). While it isn’t listed as a cancer-causing chemical, it affects the taste of the water, and its potential health effects have not been widely studied. The US government began to phase out MTBE usage in the year 2000 in favor of adding ethanol. Cleaning up pollution like MTBE costs hundreds of millions of dollars and takes a long time. Other evidence of pollution you may have found could also have been caused by gasoline leakage and unknown spills. If you notice a large difference in pH of soils surrounding gas stations, report your results to a local government representative.