R_T
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Phytoremedation

Postby R_T » Tue Mar 23, 2021 5:14 pm

Hello,
I am a student in 9th grade and I am doing research on phytoremediation. I plan to grow plants on soil contaminated with heavy metals and then harvest them. However, I am unsure how I can test the levels of heavy metals in the plants. Many research papers I read said that they ashed the plants and then conducted chemical processes to test the heavy metal content. I want to know the exact process on how to test my plants for heavy metals after I harvest. It is important to note that I have access to a high school lab ( I may be able to get access to a university lab but it is not certain) and cannot spend too much on materials.

Hope someone can help.

koneill18
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Re: Phytoremedation

Postby koneill18 » Wed Mar 31, 2021 10:06 am

Hello!

This sounds like a really interesting project! I did a bit of research, and it looks like scientists typically measure the levels of heavy metals in the plants using atomic absorption spectroscopy. This technique helps you figure how much of certain metals are present in your sample based on the wavelength of light that they absorb. Unless your high school lab is very high tech, it probably doesn't have an atomic absorption spectrophotometer. If you live close to a university, you can try contacting the chemistry department to ask if they have the technology that you need to perform your experiment. Universities are usually happy to assist students with science projects, assuming that the labs don't have restricted access now due to the pandemic.

If you can't get help from a university lab, we can try to help you modify your experiment into something that you can do without a lab. Here's an example that I found of an experiment that uses an indirect method to measure the levels of heavy metals in the plants. They grew indian mustard seeds in water containing copper and measured the amount of copper in the water over the course of the experiment. If the copper levels go down, this means the plant is absorbing the copper.
https://fcit.usf.edu/florida/teacher/science/mod1/resources/phytoremediation.pdf

I hope this helps! Feel free to ask any more questions that you have.
Katelyn

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Re: Phytoremedation

Postby R_T » Wed Mar 31, 2021 12:25 pm

Thank you for your response!

Regarding the atomic absorption spectrometer, I will ask my teacher whether we can obtain access to a university lab. I did look at the experiment that you linked and it is definitely a possibility. However, I would like to see if I can conduct an experiment with plants grown in soil. I will soon be starting the process of designing the experimental plan and I need some assistance. I plan to grow brassia juncea in soil that is contaminated with a heavy metal (not sure which metal yet) to test whether they will be able to successfully remediate the soil. One question I have is about the use of lechates, specifically EDTA to help increase metal accumulation. I was wondering whether or not they would be useful for my experiment; if yes, how I would be able to incorporate them into my experiment? . Hopefully you can help, and thanks again for your response.

Thanks,
Rohan

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Re: Phytoremedation

Postby koneill18 » Wed Mar 31, 2021 4:33 pm

Hi Rohan,

Sure, you could try adding EDTA to the soil to see if it improves heavy metal uptake by the plants. If you decide to do this, I would recommend having 3 experimental groups: one group of plants that has no heavy metals in the soil (the control), one group of plants that has heavy metals but no EDTA in the soil, and one group of plants that has both heavy metals and EDTA in the soil. This will allow you to determine the baseline level of how much metal your plant removes from the soil, and compare that to how much metal it removes when EDTA is added. Then you can report your conclusions on whether or not EDTA improves phytoremediation by Brassica juncea. It looks like Brassica juncea is pretty good at soil remediation, so I think you'll get interesting results even without the EDTA.

Let us know if you have more questions!
Katelyn

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Re: Phytoremedation

Postby R_T » Mon Apr 05, 2021 9:18 am

Thank you for your response!

I am undecided on whether or not I should use EDTA in my experiment. However, do you have any suggestions on how I should formulate my experimental plan. One big question I have is the control for my experiment. If I were to test the accumulation of heavy metals by hyperaccumulator plants, what would my control be? I am assuming that it would be a non-hyperaccumulator plant, however there are 100s of hypperaccumulator plants and I might accidentally use one of them. Do you have any suggestions for the control plant, and on the overall experimental design?

Thanks,
Rohan

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Re: Phytoremedation

Postby koneill18 » Tue Apr 06, 2021 6:45 pm

Hi Rohan,

To make your experimental plan, you should start by writing out what exactly your research question is and what your independent and dependent variables are going to be. From what you’ve said so far, it sounds like the question you’re trying to answer is something along the lines of, “Can brassica juncea remediate soil contaminated with heavy metals?” In this case, the dependent variable will be the heavy metal levels in the plant. Now, for the independent variable, you have a lot of options for things you can change to observe what effect it has on the dependent variable.

The simplest experiment would be to just put the plants in the soil and test if they’re able to remove any of the heavy metals. Since so many studies have already reported that brassica juncea is good at phytoremediation, I would recommend adding an extra variable that would make your experiment a little more unique. For example, you can add different concentrations of metal to each of the planters to test how well your plants can perform phytoremediation at different levels of soil contamination. Another option would be adding EDTA to some of the plants to see if those plants are better at phytoremediation than the plants that didn’t get EDTA in the soil. If you have access to a university lab, they will definitely have EDTA that you can use. You could also test out 2 different plants and compare them to find out which one is better at phytoremediation.

There are plenty of different options for things you can test. It all depends on which option sounds the most appealing and feasible for you. For all of these experiments, I would recommend using a plant with no heavy metals in the soil as your control. I think trying to find a non-hyperaccumulator plant would be too hard because, as you said, there are hundreds of hyperaccumulator plants. Even if there are no sources saying that a plant is a hyperaccumulator, that could just be because no one has tested it yet. A plant with no heavy metals in the soil would work perfectly fine as your control. The point of this control would be to tell you if the results that you’re seeing in your experimental groups are due to the heavy metals in the soil or to something else. For example, if your experimental plants died but the control plants didn’t, then you could confidently attribute the death to the heavy metals and not something else. Also, when you’re testing the heavy metal levels in your plants, it’s good to have normal plant samples without heavy metals that you can compare those results to.

Once you decide exactly what you want to test, we can help you fine tune all of the details of your experimental plan.

I hope this helps!
Katelyn

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Re: Phytoremedation

Postby R_T » Mon Apr 12, 2021 6:55 am

Thank you so much for your response!

Thank you for clarifying what I should use as a control. I am beginning the process of narrowing down what I want to test.I would like to either use multiple plants or EDTA to make my experiment more complex. I have decided to use brassica juncea as one of my plants, but do you have any recommendations for other plants I can use? Additionally, I would need to test a specific heavy metal in my experiment. I am leaning towards either copper or nickel. Are these safe to use in a high school lab? I am working on finding the materials required for the experiment because my school requires a list to make sure they are safe to use.

Thanks again for your response!

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Re: Phytoremedation

Postby koneill18 » Tue Apr 13, 2021 7:54 am

Hello,

I think copper would be a good metal for you to use. It's safe to use in a high school lab- as long as you wear gloves and eye protection- and it should be pretty easy for you to obtain. I've seen a lot of reports where people added copper sulfate to the soil for their phytoremediation experiments. Another option would be zinc. You could add zinc chloride to your soil and use that as your source of zinc contamination. In terms of what plants you could use, you have plenty of options! You could choose another plant from the Brassicaceae genus like Brassica napus or Brassica rapa. Micranthemum umbrosum is a type of decorative plant that is also used as a hyperaccumulator. Some other plants that I've seen people use are grasses like vetiver grass; vegetables like radishes, alfalfa, and lettuce; and beans like soybeans. You could do an internet search for "list of hyperaccumulators" and see which ones are available in your area.

I hope this helps!
Katelyn

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Re: Phytoremedation

Postby R_T » Thu Apr 15, 2021 1:22 pm

Thanks for your suggestions!

My teacher has just informed me that the school has a mass spectrometer. Would this work for my project? I tried to do some research on the types of spectrometers but was pretty confused. If not, do you think there is any way to modify my project so that I don't need to use a spectrometer? Hope you can help.

Thanks!

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Re: Phytoremedation

Postby koneill18 » Fri Apr 16, 2021 9:28 am

Hello,

Wow, it’s really cool that your school has a mass spectrometer! Do you know what type of mass spectrometer you have? You can measure heavy metals in plants using inductively coupled plasma (ICP) mass spectrometry. This is a technique especially suited to analyzing trace metals in a sample. But I'm guessing that your school just has a normal mass spectrometer and not an ICP-MS device. The problem with using a mass spectrometer for your experiment is that these devices are not quantitative. That means that a mass spectrometer could tell you whether or not a heavy metal is present in your sample, but it can’t tell you how much of the metal there is. So, if you wanted to compare the levels of heavy metals in each of your plants, you probably wouldn’t be able to do that. Atomic absorption spectroscopy is usually used to measure heavy metal concentrations in plants because this technique is quantitative. I’m not aware of a technique that would let you measure heavy metals in the plants or in the soil that doesn’t involve some sort of spectrophotometer. I do know that farmers sometimes send their soil samples to soil testing labs in their area to get them tested for heavy metal content. You might be able to send your soil samples to a lab for analysis, but it could be expensive.

I think the easiest way for you to modify your project would be to grow the plants in water and use copper test strips to measure the copper levels in the water. This is something you could do at home or at your school and it wouldn’t involve any complex machinery. The test strips are easy to find and not too expensive. I know you wanted to grow your plants in soil, but I don’t know of a way to measure copper levels in soil that doesn’t involve analyzing the samples in a lab. I’m sorry I can’t be of more help in that regard!

Katelyn

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Re: Phytoremedation

Postby R_T » Mon Apr 19, 2021 12:35 pm

Thanks for your response!

I had researched ICP-MS, and will contact my teacher on whether or not we have that type of mass spectrometer. I agree that growing aquatic plants is probably the most feasible option for my project. I plan on using duckweed, and possibly another aquatic plant for my experiment. However, when growing plants in water, is there a chance that the heavy metals could evaporate along with the water? Thank you once again for all the help you have provided, I will keep you posted on any questions I have, and on the progress of my experiment.

Thanks,
Rohan

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Re: Phytoremedation

Postby koneill18 » Tue Apr 20, 2021 8:32 am

Hi Rohan,

You definitely want to prevent the water from evaporating so you don't have to add more water throughout the experiment and mess up your metal concentrations. You can put a plastic cover over your aquarium, or whichever type of container you use to grow your plants, and that should prevent evaporation. I'm looking forward to hearing about your progress and any other questions you have along the way. It sounds like you're off to a great start!

Katelyn


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