Great idea! Sounds like it is going to be a very interesting project.
First of all, you need to figure out exactly which toxins you want to test for. This depends on the exact purpose of your project. If you are just trying to determine overall air quality, I would reccomend using the EPA's six "criteria pollutatns," which are generally accepted indicators of air quality. These pollutants are ozone, carbon monoxide, nitrogen dioxide, sulfer dioxide, particulate matter, and lead. This site: http://www.epa.gov/air/oaqps/greenbk/o3co.html#Ozone
provides a lot of good information on what each of these pollutants indicates, and how it can be tested. In general, the easiest way to test air quality would be to, if it is within your budget, get an atmospheric test kit that includes everything you need to do these basic tests. These are generally avaiable at science supply stores, but check with environmental science teachers at you school first, as they may already have some for use in labs.
If there is something more specific than general air quality that you are worried about, this site: http://www.kn.sbc.com/wired/fil/pages/l ... ollja.html
[url] provides links to a lot of really helpful sites about all sorts of pollutants and atmospheric testing background information, which may be helpful in narrowing down what you want to test for.
Once you have figured out what you are going to test and how, you will need to set up your experiment. You'll probably want to test the air where you will be performing your experiment before adding plants, to get a baseline reading. After that, you have a few options. Which one you choose really depends on what level of project you are aiming for and your grade level. The most detailed experimental design would probably require enclosing each plant in a fairly large (to avoid suffocation) container, and having another identical container with no plant. At given time intervals (you will have to figure out how fast the plants can change the atmosphere, which will dictate how often you should perform tests), you could repeat the atmospheric tests on each container. You can then analyze this data to see if, over time, the pollutants decreased in the environments including the plants. The empty containers would serve as controls, to make sure that this decrease wasn't occuring naturally, without plant involvement.
Depending on the requirements for your project, you may be able to simplify that a lot. For instance, if you have access to a sealed room, you could take a baseline measurement in that room and then put a plant in it. Then you could take the same sort of measurements that you would have in the above set-up. In this case, it would be assumed that all change in atmospheric pollutants was due to the plant, because no pollutants would be able to enter the sealed room.
I hope that made sense, and helped. If you have further questions, please ask! You project sounds like it should be fascinating and fun! Good luck.
- Emily Dolson[/url]