need help designing an experiment on phytoremediation - (Aug/31/2014 )
We have to do a research project for my college Bio 1 class and I would really like to do something dealing with phytoremediation but I'm having some difficulty. Since I have not been able to find a description of the materials and procedure for such a project on the internet I'm trying to figure it out on my own but obviously with my lack of experience there are many things I am unsure of. Any help would be greatly appreciated.
Okay, so what I want to test is the rate of accumulation of a contaminant from the soil into a specific plant. For the contaminant I'm thinking of using either lead or copper. For the plant I'm thinking sunflowers, indian mustard, or water hyacinths (though these would be grown in water instead of soil). All I really know is that I'm going to have to mix the soil with the contaminant, put it in pots, grow the plants in them until they're big enough to take samples from, then begin collecting samples every 7 days or so to be dried and tested for contaminant content.
So here come the questions;
How much contaminant should I mix into the soil? I figure something around the amount you would find in naturally contaminated soil but I can't find any numbers on this.
Which plant should I use? Which can I grow faster and healthier in a tropical climate (I live in Miami, Florida)? I imagine any of these will grow here but I don't know anything about gardening and I don't want the entire experiment to fail because the plants die or don't grow fast enough. I have until the end of November to complete this project, by the way.
And finally, how do I analyze the samples? I'm sure it's a fairly complicated procedure, and a detailed description isn't neccessary, but is it the kind of thing that's possible to do with the resources available in an average university laboratory? And if not, is there like a lab or something that could do it for me?
Note: I don't do phytoremediation, so take this advice with a bit of scepticism.
Basically, as I see it, you seem to want to test which plants accumulate metal contaminants best or the rate of accumulation?
To get some sort of measure of this you need to have some metal contaminated soils (all at the same concentration) and grow the different plants in them. It would pay to check which sorts of metals the plants can accumulate well, some work best with things like zinc, whereas others work better with other metals like magnesium. It would also pay to check the easiest way to contaminate soils with the metals- they will have to be in soluble form and biochemically available (pH, salt form etc.), you can't just disperse some ground up copper. From a quick google search it seems that the three you have chosen all accumulate metals fairly well, but it might be better to take a known accumulator and one you don't know about as a test (?).
There are some figures for normal concentrations here (pdf file): http://www.uvm.edu/vtvegandberry/factsheets/interpreting_heavy_metals_soil_tests.pdf. I would suggest making sure that the soil you use has a low clay content as clays tend to bind cations very strongly, which would likely be a problem for the plant uptake. Analysis of the plant accumulation would require a mass spectrometer of some sort - these probably won't be available in your undergrad labs, but your local chemistry department might be able to help and should be able to give good advice on how to do the analysis (especially if you get the lab head to contact them).
For the analysis you will need to work from dry weight of the tissue you are looking at, so you will need to collect enough so that you have about a gram (possibly more, depending on metal content and how you detect) of dry weight. You can assume that about 70-80% of the wet weight will be water, as a rough guideline for amount needed when picking. IIRC, the amounts accumulated are typically tiny (ppm or less) so you need to keep that in mind.