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Title: Agricultural Pesticides and Selected Degradation Products in Five Tidal Regions and the Mainstem of Chesapeake Bay

Author
item McConnell, Laura
item Rice, Clifford
item Hapeman, Cathleen
item Drakeford, Leticia
item HARMAN-FETCHO, JENNIFER - FORMERLY ARS
item Bialek Kalinski, Krystyna
item FULTON, MICHAEL - NOAA
item ALLEN, GREGORY - USEPA

Submitted to: Environmental Toxicology and Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/12/2007
Publication Date: 12/1/2007
Citation: Mcconnell, L.L., Rice, C., Hapeman, C.J., Drakeford, L., Harman-Fetcho, J.A., Bialek Kalinski, K.M., Fulton, M.H., Allen, G. 2007. Agricultural Pesticides and Selected Degradation Products in Five Tidal Regions and the Mainstem of Chesapeake Bay. Environmental Toxicology and Chemistry. 26(12):2567-2578. http://hdl.handle.net/10113/12848.

Interpretive Summary: The Chesapeake Bay (CB) Watershed is home to 15 million people. The watershed contains ~150 major rivers and streams. Nutrients, sediment, air pollution, and toxics from the water sources and the surrounding airshed are major problems contributing to poor water quality in many regions of this struggling ecosystem. In the late summer and early fall of 2004, sixty-one stations within five tidal regions were characterized with respect to toxics: on the Delmarva Peninsula – the Chester, Nanticoke, and Pocomoke Rivers and on the Western Shore – the Rhode and South Rivers and the Lower Mobjack Bay including the Back and Poquoson Rivers. In a separate effort during the early spring of 2000, surface and deeper water samples were collected for pesticide analysis from 21 stations spanning the CB main stem. Herbicides were the most frequently detected chemicals at all stations in both studies. Rivers on the Delmarva Peninsula acted as sources of herbicides to the CB main stem with the highest concentrations found in the upstream portions of the estuaries. Herbicide concentrations in the Western Shore rivers showed no spatial trends and were the same as in the CB main stem. Of the 5 watershed regions in the 2004 study, the highest concentrations were found in the Chester River. The Chester River watershed contains the highest agricultural land use and lowest amount of forest land compared with the other regions.

Technical Abstract: Nutrients, sediment, air pollution, and toxics from the water sources and the surrounding airshed are major problems contributing to poor water quality in many regions of the Chesapeake Bay (CB). Toxics are defined as chemicals that may affect the reproduction, development, and ultimately, the survival of living resources. In the late summer and early fall of 2004, sixty-one stations within five tidal regions were characterized with respect to toxics: on the Delmarva Peninsula – the Chester, Nanticoke, and Pocomoke Rivers and on the Western Shore – the Rhode and South Rivers and the Lower Mobjack Bay including the Back and Poquoson Rivers. In a separate effort during the early spring of 2000, surface and deeper water samples were collected for pesticide analysis from 21 stations spanning the CB main stem. The highest herbicide concentrations were observed in the Chester River; atrazine, simazine and metolachlor and their degradation products were the most frequently detected chemicals. The Choptank, Nanticoke and Pocomoke Rivers acted as sources of herbicides to the CB main stem, while herbicide levels in the Rhode and South Rivers and in the Lower Mobjack Bay were the same as the CB main stem. A metolachlor degradation product, metolachlor ethane sulfonic acid (MESA) was found in greater concentrations than the parent in almost all of the tidal regions, indicating environmental persistence. The highest herbicide concentrations were found in the Chester River. The Chester River watershed contains the highest agricultural land use and lowest amount of forest land compared with the other regions.