U.S. Geological Survey Toxic Substances Hydrology Program--Proceedings of the Technical Meeting Charleston South Carolina March 8-12,1999--Volume 2 of 3--Contamination of Hydrologic Systems and Related Ecosystems, Water-Resources Investigation Report 99-4018B

Pesticides in the Atmosphere of the Mississippi River Valley, Part II - Air

By William T. Foreman, Michael S. Majewski, Donald A. Goolsby, Frank W. Wiebe, and Richard H. Coupe

This report is available in pdf format: Foreman.pdf

ABSTRACT

Weekly composite air samples were collected from early April through mid-September 1995 at three paired urban and agricultural sites along the Mississippi River region of the Midwestern United States. The paired sampling sites were located in Mississippi, Iowa, and Minnesota. A background site, removed from dense urban and agricultural areas, was on the shore of Lake Superior in Michigan. Each sample was analyzed for 49 compounds; of these, 21 of 26 herbicides, 13 of 19 insecticides, and 4 of 4 related transformation products were detected during the study, with most pesticides detected in more than one sample. The maximum number of pesticides detected in an air sample was 18; this sample was from the Iowa City urban site in mid-June. Herbicides were the predominant type of pesticide detected at every site. The detection frequencies of most herbicides generally were comparable at the paired Iowa and Minnesota sites. In Mississippi, herbicides generally were detected more frequently at the agricultural site. The insecticides chlorpyrifos, diazinon, and carbaryl, which are used in agricultural and nonagricultural setttings, were detected more frequently in urban sites than agricultural sites in Mississippi and Iowa. Methyl parathion was detected in 70 percent of the samples from Rolling Fork, Miss., and at the highest concentration (62 nanograms per cubic meter of air) of any insecticide measured in the study. At the background site, dacthal (100 percent), atrazine (35 percent), cyanazine (22 percent), and the (primarily atrazine) triazine transformation products CIAT (35 percent) and CEAT (17 percent) were detected most frequently, suggesting their potential for long-range atmospheric transport. Estimates of the pesticides' particle and gas distribution provided insight into the primary mechanisms of pesticide transport and deposition.