(188f) Field Sampling of Water/Sediments for Atrazine and Amoxicillin Contaminations In the Rio Grande Basin

Atrazine (C₈H₁₄ClN₅) is the most extensively used Herbicide (Weed Killer for corn, sugarcane and other crops) with an annual usage > 60 million pounds and much makes its way into streams, rivers, lakes and drinking water supplies. Atrazine adsorbed in sediments is determined by hot solvent extraction followed by HPLC (Agilent 1100 HPLC with a Zerobax Eclipse C-8 Column and a variable wavelength detector at 222 nm). Field Sampling efforts included 11 expeditions and 114 sites visited in CO, NM, and TX. The project provides a valuable profile on the extent of atrazine and amoxicillin pollutions in term of time and location and identifies the environmental risks of polluted water and sediments along the Rio Grande Basin due to herbicide/antibiotic uses. We are currently analyzing both atrazine and its main degradation byproduct: hydroxyatrazine to determine whether many of the sites are in compliance with the EPA intermediate-term level of concern: 37.5 ppb over a 90-day period. Soxhlet Hot Solvent extraction was done to 6 sediment samples from the Summer 2010 expedition and the results are compared with the prediction from the Soil/Sediment Sorption Coefficient of atrazine and the soil organic carbon content. Atrazine entrained in sediment sometimes exceeds this level.  Further sampling and analysis are thus warranted to ensure the water quality in the Rio-Grande Basin. We are currently analyzing amoxicillin (C₁₆H₁₉N₃O₅S) contaminants in the water samples collected from the field with new HPLC columns (Zorbax SB-C18 3.5 µm, 4.6 X 75 mm) and a Variable Wavelength UV detector. The Amoxicillin concentrations range from 1021- 53871ppb from 19 field water samples.