2) 10 µg/L Atrazine: The general trend in the data indicates that the main detections of atrazine are in the tributaries while significantly lower concentrations have been found in the Bay itself. During June of 2011, atrazine concentrations from the upper Chop Tank River were logged. The average of all recorded concentrations was 0.29 µg/L. The highest recorded concentration was 10 µg/L (Chesapeake Bay Program; USDA: Hively et al. 2011).