In order to develop effective strategies for toxics management, the Great Lakes National Program Office (GLNPO) of the United States Environmental Protection Agency (U.S. EPA), in 1994, launched an ambitious five year program to conduct a mass balance study of selected toxic pollutants in Lake Michigan for the target year of 1995 (U.S. EPA, 1998). Three persistent organic pollutants (POPs) and one heavy metal have been selected for the focus of the Lake Michigan Mass Balance (LMMB) study; polychlorinated biphenyls (PCBs), trans-nonachlor, atrazine and mercury. Atrazine is a broadleaf herbicide typically applied to corn, sorghum, sugarcane, pastures, sweet corn, seed crops and sod (Gianessi and Puffer, 1991). In 1991, applications to corn and sorghum accounted for approximately 95% of the total atrazine useage in the United State (Gianessi and Puffer, 1991). Atrazine is typically applied as a pre-emergent spray and/or a post-emergent spray although it can also be incorporated into the soil prior to planting (USDA, 1995a). Peer reviewed literature suggests that atmospheric sources of atrazine may be an important input of herbicide to the Lake Michigan system (Schottler and Eisenreich, 1997). The National Oceanic and Atmospheric Administration (NOAA) is collaborating with the LMMB study in its estimation of the atmospheric deposition of atrazine to Lake Michigan.