Report – ENVR206B – Phytoremediation

Biology 206B, Biotechnology – Phytoremediation Report

Allanah Greenham, Alex Carota, Stefan Martensson, Brianne Smith

December 3, 2009

Purpose

The reason for this experiment was to determine if water hyacinths are able to successfully absorb contaminants such as Zinc and Copper from an aqueous solution and also possible methods to improve results in the experiment for future classes.

Process

We placed water hyacinths is solutions of known concentrations and molarities of Zinc and Copper over a six week period. 10ml samples were taken every week along with root samples. The plants were replaced each week to ensure maximum absorption of the elements. At the end of the 6 week period we performed an EDTA titration of the water and root samples to determine the presence of Zinc and a colorimetric assay was conducted to determine the presence of copper.

Results

The plants appeared to be taking in both metals due to the fact that the plants either died or were dying after each week. This hypothesis is supported by the steady drop in molarity of both metals from week to week as was determined by titration and colorimeter and is shown on figure 1 and 2 below.

The root data is also supports this fact in the case of Copper as is indicated in figure 1. The molarity of the root samples saw a sharp increased from the first sample to the second indicating an absorption of Copper. The root data for the Zinc was not as conclusive and is visible in figure 2. The presence of Zinc is noted in the roots but does not change significantly from week to week.

Figure 1. Notice the consistent drop in PPM of Copper water samples from week to week. Also note the sharp increase in root sample absorption from the first to the second sample.

Figure 2. Not the drop in molarity of Zinc in the water samples from week 1 to the end of the study. Also note the presence of Zinc in the root samples.

Compare and Contrast

The plants appear to absorb Zinc and Copper effectively however they were able to absorb Copper much more consistently from week to week. In reference to roots the Copper showed up much more in testing than did Zinc.

Effectiveness of Water Hyacinths as Phytoremediators

According to the results of the experiment it is reasonable to conclude that Water Hyacinths are effective phytoremediators of both Zinc and Copper due to the consistent drop in concentration of both metals from week to week in water samples. The inconsistencies in root data should not take away from the fact that these plants effectively removed heavy metals from water. In real world practices the whole point of phytoremediation is to remove pollutants from a water source and this experiment showed that Water Hyacinths are excellent remediators of Zinc and Copper.

Sources of Error

The sources of error in this experiment were compounded due to the number of steps involved. Some possible sources could include but are not limited to:

  • Errors in measurement, The scales were limited to one decimal place
  • Root samples were taken from different areas of the roots each time
  • The combination of Data between more than one lab bench
  • Differences in root length and age in plants
  • Dripping of water from leaky greenhouse into water/root samples diluting concentrations
  • Errors during titrations, colorimetry

Figure 3. Week 1 Results.

Figure 4. Week 2 Results.

Figure 5. Week 3 Results.

Figure 6. Week 4 Results.

Figure 7. Week 5 Results.

Recommendations

Since the root samples were not very accurate in determining concentrations of the element in the plant, it would be worth testing the leaves. Considering that roots did not represent the life of the plant, and the leaves did, the results may be more accurate. Determining whether root size makes a difference would make the lab more accurate. Having a consistent root size would be important in controlling Cu and Zn concentration in the plant. We only took 0.1 g of a root sample, recommending that more than one sample be taken off each plant in order to determine differing concentrations within the roots on the entire plant. We also believe that one lab bench should do its own Zinc and Copper concentrations to avoid unnecessary error when combining data.

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