National Water-Quality Assessment (NAWQA) Project
Model predictions show that the highest frequencies of atrazine detection in shallow ground water beneath agricultural areas are expected in parts of the western Corn Belt, eastern Great Plains, Pacific Northwest (eastern Washington), and Mid-Atlantic regions (especially southeastern Pennsylvania). These areas represent relatively high atrazine use in hydrologic settings that favor the transport of pesticides to ground water.
Full study can be found at the Pesticides National Synthesis Project Website by accessing the USGS Circular 1291 (see Chapter 7).