The Effect of Chromium on Algal Populations Peter Chekan Central Catholic High School Pittsburgh

Surface Runoff Flow of water from rain or melting snow Soil's saturation level is filled to capacity Water might pick up dangerous chemicals Pesticides, insecticides, and chromium Surface water runoff might untimely enter rivers, lakes, or other bodies of water

Chromium 24 th element in the periodic table. Heavy metal Soluble in water Breaks up into ions Hexaaquachromium or [Cr(H2O)6]3+. Potassium Chromate

K 2 CrO 4 Yellow Powder form Soluble in water Used as a solution in experiment

Chromium Runoff Because of its solubility, it poses a threat to aquatic life. It is often used in paints, dyes, and chrome plating.

Chromium Effect on Pittsburgh Used to give steel polished silvery coating Used as an alloy for stainless steel Many rivers in Pittsburgh

Euglena Single celled protists Lives in fresh water Oval shaped Between μm long Bottom of the food chain Used as an experimental algal model

Purpose Determine if chromium inhibits the growth of aquatic life To estimate the minimum concentration of potassium chromate detrimental to euglena

Hypothesis Null Hypothesis The potassium chromate concentrations will not significantly affect euglena population growth The potassium chromate concentrations will significantly affect euglena population growth

Materials Spectrophotometer Test Tubes Test Tube Rack Potassium Chromate Euglena sp. Macro Pipettes Micro Pipettes Pipette tips Spring Water

Procedure 1. The following experimental tubes were created

Procedure Continued 2. The test tubes were placed in a dark room with a controlled source of light for 12 hours 3. All tubes were mixed by inversion prior to spectrophotometry 4. The absorbance of algae was measured everyday by a spectrophotometer using a wavelength of 430nm 5. Absorbance was recorded everyday for 20 days

P= P<0.01

Conclusion The statistical analyses allow a REJECTION of the null hypothesis, indicating that potassium chromate can significantly effect euglena population growth All tested potassium chromate concentrations resulted in significant changes in the euglena populations

Limitations/Extensions Use lower concentrations of chromium Use larger sample sizes Test different types of algae Test natural aquatic systems

References elements/Cren.htm elements/Cren.htm overview/runoff.html overview/runoff.html omium.html m