Science Buddies: "Ask an Expert"

I want to see if algae can phytoremediate pesticide. I am thinking of atrazine because it can be measured using test strips. I cannot do the more complex ELISA test because the equipment is beyond my reach and I think you need special training. Is there any advice on making this work?

Also, I need to make a 4 or 5 ppb solution of atrazine from a 4% solution that is available in the store. Can you help with the math?

I am excited about this idea but nervous that I won't be able to measure any different. If you think another pesticide is better and can be measured, please tell me!

Help!

Hi,

The use of bioremediation to clean up pesticides or herbicides is a great topic and one that I am very much interested in also. The use of pesticides is necessary to keep insects and other critters from destroying crops but if we can come up with effective ways to mop up the residues before they get into our drinking water that will be a great accomplishment.

I think atrazine is an excellent choice for bioremediation as it is one of the most commonly used herbicides in the world. Which algal species are you going to test for removing atrazine? I found one paper that used Selenastrum for bioremediation, an alga that I had never heard of: http://www.researchgate.net/publication ... de_removal

If you have a 4% solution of ATZ that means it contains 4 parts ATZ per 100, so you are going to have to dilute it by 10 million to get 4 parts per billion. One billion divided by 100 = 10 million. Do you have access to basic lab equipment like pipets and graduated cylinders that measure volumes according to the metric system? If not, let me know and I can work out the dilution in ounces.
The metric method is the most accurate so do try to use it if you can.
If you don’t have a lab pipettor that measures 0.1 mL, you can use a 1 mL insulin syringe. Just be sure to dispose of it safely. You will also need two 1 liter (L) bottles with caps containing exactly 1 L (1000 mL) of water. Soda bottles are fine. Be sure to wear safety glasses and disposable exam gloves. A plastic apron would also be a good idea to prevent splashing any of the atrazine on your clothing. According to the EPA it has low toxicity, but it is better to be careful: http://www.epa.gov/pesticides/factsheet ... ground.htm

Take up the 4% ATZ in the syringe and carefully transfer 0.1 mL into 1 L (liter) of water. This gives you a 4 parts per million solution (4 pts/100 x 1 pt/10,000). Put the cap on the bottle and gently invert it several times until the atrazine is completely diluted. Now rinse the syringe several times with clean water and pull up 1 mL of the diluted solution and transfer it to the second 1 L bottle of water (1 to 1000 dilution). Put the cap on and invert to mix. This is your 4 ppb ATZ solution. If you need more than 1 L you could use 2 L bottles and double everything.

Other experts, PLEASE check my calculations! Math is not my best subject, but I am pretty sure my dilution formula is correct. Check it to be sure.

Good luck!

Sybee

Obtaining a 4 ppb solution from 4% atrazine

1. Convert 4% atrazine to ppb concentration
4% x (10^9 ppb)/100% = 4 x 10^7 ppb

2. Determine the volume of 4% atrazine you need to use to prepare you 4 ppb solution using the M1V1 = M2V2 formula

(4 x 10^7 ppb) (V1) = (4 ppb) V2

3. Assuming that you know the volume of the 4 ppb atrazine solution that you want to use, you can solve for V1

V1 = [(4ppb)V2]/ (4 x 10^7)

Hope this helps. You can check the site below for further information.

http://water.me.vccs.edu/courses/env211/lesson8_4.htm

By the way I checked Sybee's calculations are correct.

4ppb means 4 parts per one billion (10^9). 4% means 4 parts per 100. To create a 4ppb solution from a 4 % solution, one must ciliute the 4% solution by 10 million

10^9 / 100 = 10^7 = 10 million

If you dilute 0.1 mL of 4% solution to a volume of one one liter, you would get 4 ppm atrazine solution.

(4/100)(1/10000) = 4 x 10-6

You use 10,000 because there are 1000 ml in 1 L and 0.1 mL is 1/10 of 1 mL (10x 1000 = 10,000 parts).

If you dilute the 4 ppm atrazine solution by 1 liter, you get a 4 ppb atrazine concentration.

(4 x 10-6) / 1000 = 4 x 10-9