Pesticides in the atmosphere of the Mississippi River Valley, part II - air

Weekly composite air samples were collected from early April through to mid -September 1995 at three paired urban and agricultural sites along the Miss issippi River region of the Midwestern United States. The paired sampling s ites were located in Mississippi, Iowa, and Minnesota. A background site, r emoved from dense urban and agricultural areas, was located on the shore of Lake Superior in Michigan. Each sample was analyzed for 49 compounds; of t hese, 21 of 26 herbicides, 13 of 19 insecticides, and 4 of 4 related transf ormation products were detected during the study, with most pesticides dete cted in more than one sample. The maximum number of pesticides detected in an air sample was 18. Herbicides were the predominant type of pesticide det ected at every site. Detection frequencies of most herbicides were similar at the urban and agricultural sites in Iowa and Minnesota. In Mississippi, herbicides generally were detected more frequently at the agricultural site . The insecticides chlorpyrifos, diazinon, and carbaryl, which are used in agricultural and non-agricultural settings, were detected more frequently i n urban sites than agricultural sites in Mississippi and Iowa. Methyl parat hion was detected in 70% of the samples from the Mississippi agricultural s ite and at the highest concentration (62 ng/m(3) air) of any insecticide me asured in the study. At the background site, dacthal (100%), atrazine (35%) , cyanazine (22%), and the (primarily atrazine) triazine transformation pro ducts CIAT (35%) and CEAT (17%) were detected most frequently, suggesting t heir potential for Long-range atmospheric transport. (C) 2000 Elsevier Scie nce B.V. All rights reserved.