Wednesday, October 19, 2011

Pesticide Detection Results

Last week the students turned in revised versions of their abstracts and figures from the ELISA and GC-MS analyses that we performed on a water sample from the Haw River in Alamance County. The laboratory protocol was based on an article from the Journal of Chemical Education and is available on request.

Jacqueline Meadows has agreed to let me share her abstract and figures on the blog so you can see our results. Luckily, both ELISA and GC-MS analysis indicated acceptably low levels of pesticides in the original water sample.

Pesticides are chemicals used to increase the amount of yield from crops. Though these compounds are useful in the productivity of farming, they may also have harmful implications when they run off into waterways, like lakes and rivers. The purpose of this experiment was to analyze the concentration of two pesticides, atrazine and simazine, in a water sample taken from the Haw River. The sample was tested as obtained from the river and also spiked with relatively high concentrations of atrazine and simazine. The concentrations were evaluated using ELISA and gas chromatography mass spectrometry (GC-MS). The ELISA method revealed an original sample concentration of 0.890±0.123 ppb of atrazine and a spiked sample concentration of 112±0.1 ppb of atrazine. The GC-MS, however, reported an atrazine concentration of 0.00±0.26 ppb and a simazine concentration of 1.74±0.05 ppb in the original sample, and concentrations of 73.4±0.2 ppb and 129±0.04 ppb in atrazine and simazine, respectively, for the spiked sample. The average retention time of atrazine was 12.65 minutes and that of simazine was 12.55 minutes for the GC experiment. The ELISA data was more sensitive than the GC because it was able to detect smaller amounts of the pesticide, whereas the GC method was able to quickly and efficiently separate the different pesticides for analysis.


Figure 1: ELISA data for atrazine standards.
Figure 2: Gas chromatography peak areas for given concentrations of atrazine and simazine standards.

(Abstract and Figures courtesy of Jacqueline Meadows)

Friday, October 7, 2011

First Classroom Visit!

Today the undergraduates had their first classroom visit to Rankin Elementary School here in Greensboro, NC. The visit was a huge success!

In Ms. Kanipes' classroom, Charnell and Julalak led the students in a Play-Doh ecosystem activity. Each table group of 5th graders made an ecosystem, complete with volcanos, flowers, and frogs, among other things. Then they sprinkled Kool-Aid drink mix powder on a field in the ecosystem to represent pesticide treatment. Each group "made it rain" on their ecosystem using a spray bottle of water, so that the students could see how rain water carries pesticides in run-off into rivers and streams. Fantastic demo! They also had the students do a card matching vocabulary activity.

In Ms. Crutchfield's classroom, Talibah and Jordan led the students in a role playing game about the effects of pesticides. The students were assigned roles to play: farmer, crop, pesticide, pest, weed, or "good bugs" (like ladybugs and bees). After the farmers watered the crops, the crops grew, but were attacked by pests and weeds. The pesticides were allowed to tap players on the shoulder and make them sit down, but they could also tap the ladybugs and bees! This game led to a very fruitful discussion with the students about the unintended ecological consequences of many pesticides.

In Ms. Lewis' classroom, Bridget, Ronald, and William started by showing a clip from a Captain Planet video about pesticides. Then the A&T group had each 5th grade student start with a cup of water, some of which were contaminated with "pesticide" (acid). The students used droppers to mix the water from their cups, and at the end, they used pH paper to show how contaminated water can spread through the water system without obvious changes to how the water looks. The class also played Pesticide Bingo from the EPA website.

In Ms. Weyant's classroom, Jacquie and Shaylon had the students identify objects and substances that do and do not below in the ecosystem around a river. Candy prizes resulted in lots of lively participation as the students learned about the positive and negative effects of pesticides by answering questions and doing a crossword puzzle. After the presentation, one table group of 5th graders assured me that my students had done a very good job teaching them and proved their point by highlighting all the important things they'd learned about pesticides this afternoon.

Each classroom visit closed with the announcement that the 5th graders would see the NC A&T students again in November when the Rankin elementary students visit our campus. We can't wait for the next event!