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Characterizing Triazines and Triazine Transformation Products in the Cedar Run

Spencer Clark, Alex Streicher, June Liu, and Thomas B. Huff

Abstract

            Atrazine is one of the most commonly used herbicides in the United States. It is applied to farms that grow corn, wheat, and alfalfa. During periods of rainfall, atrazine runs off into the local watershed and begins to degrade into a number of transformation products. This study focused on determining the concentrations of atrazine and its degredates: hydroxyatrazine, desethylatrazine, desisopropylatrazine, desethyldesisopropylatrazine, desethylhydroxyatrazine, and desisopropylhydroxyatrazine. Other herbicides studied included simazine and propazine. Water samples were taken from three main samples sites and one additional sample site within the Cedar Run Basin in both Prince William County and Fauquier County, VA and were analyzed using a high pressure liquid chromatography mass spectrometry system (HPLC/MS). In addition, to further analyze the transformation of atrazine in the Cedar Run Basin, bacteria samples were taken and cultured in two types of media: sterile river water with dextrose added, and nutrient broth. The concentration of atrazine and its transformation products were analyzed over time using the HPLC/MS.

 

Background
            The Prince William County area, although it has become somewhat more urbanized in recent years, mainly consists of farmland. Herbicides are used to prevent the growth of weeds on farms, and are applied in large quantities on the surface of the fields. When a storm hits, a sizable portion of herbicides run off into the local watershed. Recent scientific research points towards the overall danger of these chemicals. Some are suspected to be carcinogens, others mimic the function of hormones, disrupting the normal function of the endocrine systems in both humans and other organisms, namely fish. On the flip-side, bacteria have adapted to using some herbicides as a source of nutrients, so one could argue that it is good for the bacteria. The main point is that the streams that were sampled in this study runoff into the Occoquan River, the main source of Fairfax County’s drinking water. Any herbicides detected in these streams will eventually find their way into water consumed by humans. It is important to study the impact that both the native stream microorganisms have on the degradation and mineralization of herbicides, and to determine the overall levels of these herbicides in the Cedar Run Basin, the local watershed in Prince William County.

Description
            We measured levels of atrazine, the most-used herbicide in the United States, in water taken from sites which lead into Occoquan River. By using the high performance liquid chromatography in tandem with mass spectroscopy machine, we were able to determine the concentration of atrazine, as well as many other pesticides. We discovered that levels increased after rainfall, due to the fact that the water runs off of the surface of the farm ground, rinsing all applied chemicals into the waterways. We also noticed that levels were much higher than expected in certain areas, indicating the possible overuse of these common pesticides.
            We also wished to determine the effect that the environment has on these chemicals. Certain bacteria have been known to degrade atrazine as a source of nitrogen, using a particular enzyme unique to only specific bacteria. By measuring levels in tubes of bacteria from the sampling sites and atrazine of the major by-product of atrazine degradation over time, we were able to determine that bacteria found in Northern Virginian waterways degrade atrazine into simpler forms.

 

 

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