2004 Fairfax County Regional Science and Engineering Fair

The abstract below was written by the student. The Northern Virginia Soil and Water Conservation District made no editorial changes.

Abstract

The purpose of this experiment was to see if D. sagittaria and A. caroliniana would have a more positive effect on the nitrate, pH, and ammonia levels of fertilizer-polluted water alone or in separate tanks.

Nine tanks (each with a capacity of 3.8 L) were used: 3 with Azolla plants, 3 with Dwarf plants, and 3 with both. Gravel was placed on the bottom of each tank along with the D. sagittaria in the "Dwarf" and "Both" tanks. Then 2.5 L of spring water was added to all nine tanks along with 50 mL of Pokon 5-5-5 fertilizer. The floating Azolla plants were then added to the 3 "Azolla" and "Both" tanks. Using liquid Aquarium Pharmaceutical testers, initial data was taken. All the tanks had a pH of 6, 6ppm of Ammonia, and 160 ppm of nitrate. Data was taken and recorded every other day for 25 days.

The final results were the "Azolla" tanks with a neutral pH of 7, an ammonia level of 0ppm, and 40 ppm for nitrate. The "Dwarf tanks had a pH of 6.8, an ammonia level of 0.5 ppm, and 20ppm of nitrate. The "Both" tanks, with an ending result of 7 for pH, oppm for ammonia, and 20ppm for nitrate, had similar data as the other tanks but they also reached those results first. By the 19th day, before the other tanks, the three containers with both plants neutralized its pH, ammonia, and lowered its nitrate level to 20ppm and maintained those numbers for the duration of the experiment.

The original hypothesis, "If A. caroliniana and D. sagittaria are placed in the same tank of fertilizer-polluted water, then they will have a more positive effect on the pH, nitrate, and ammonia levels than if they were separate," was supported by the data because the "Both" tanks lowered the ammonia and nitrate levels and neutralized the pH before the other 6 tanks.