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Title: Pollutant fate and spatio-temporal variability in the choptank river estuary: factors influencing water quality

Author
item WHITALL, DAVID - National Oceanic & Atmospheric Administration (NOAA)
item Hively, Wells - Dean
item LEIGHT, ANDREW - National Oceanic & Atmospheric Administration (NOAA)
item Hapeman, Cathleen
item McConnell, Laura
item FISHER, THOMAS - University Of Maryland
item Codling, Eton
item Rice, Clifford
item McCarty, Gregory
item Sadeghi, Ali

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/6/2010
Publication Date: 2/20/2010
Citation: Whitall, D., Hively, W.D., Leight, A.K., Hapeman, C.J., Mcconnell, L.L., Fisher, T., Codling, E.E., Rice, C., Mccarty, G.W., Sadeghi, A.M. 2010. Pollutant fate and spatio-temporal variability in the choptank river estuary: factors influencing water quality. Science of the Total Environment. 408:2096-2108.

Interpretive Summary: Restoration of the Chesapeake Bay, a national treasure and the largest estuary in the United States, is a national priority. Federal agencies have also recently been tasked with an Executive Order to “use their expertise and resources to contribute significantly to improving the health of the Chesapeake Bay.” In order to document progress in this restoration effort, detailed water quality data and assessments of potential effects from a variety of pollutants on keystone species will be required. A study was conducted to examine water quality conditions in a tributary of the Chesapeake Bay, the Choptank River estuary, a system which has been classified as impaired waters under the Federal Clean Water Act since 1998 and is very much like the Chesapeake Bay ecosystem. Land use in the watershed is dominated by agriculture, which can contribute nutrients (nitrogen and phosphorus), metals (arsenic and copper), and herbicides (metolachlor, atrazine, simazine, and their degradation products). Nutrient concentrations were highest in the upstream waters, suggesting that agricultural sources were the primary source, although waste water treatment plants also contributed nutrients to the river. Arsenic concentrations, which can be associated with poultry feed additives, were generally low. However, copper concentrations were elevated above national water quality criteria, with the spatial patterns suggesting downstream point (i.e., non-agricultural) sources, such as recreational boating. Commonly used pesticides were also detected in the estuary but at concentrations unlikely to cause ecological problems. These results reaffirm the need to examine multiple stressors from multiple land uses to define the full effects of anthropogenic activity on the estuary and the Chesapeake Bay.

Technical Abstract: Restoration of the Chesapeake Bay, a national treasure and the largest estuary in the United States, is a national priority, and documentation of progress of this restoration effort is needed. A study was conducted to examine water quality conditions in a tributary of the Chesapeake, the Choptank River estuary, a system which has been classified as impaired waters under the Federal Clean Water Act since 1998. Water quality parameters (salinity, temperature, dissolved oxygen, chlorophyll a), nutrients, herbicide and herbicide degradation products, arsenic, and copper concentrations were measured at seven sampling stations along the navigable portion of the estuary during 13 sampling events over a period of three years. Results indicate that agriculture is a primary source of nitrate in the estuary and that both agriculture and waste water treatment plants are important sources of phosphorous. Recreational boating activities are an important source of copper to the lower estuary with concentrations exceeding both chronic and acute water quality criteria in all samples measured. Atrazine, simazine, metolachlor, and their degradation products (CIAT, CEAT, and MESA) are released into the headwaters; total herbicide levels do not approach established levels of concern for aquatic organisms. The metolachlor degradation product MESA, which is conservative with dilution in the estuary, was used to demonstrate that nitrate from agricultural sources in the head waters is efficiently delivered into the Chesapeake Bay main stem with little biological processing in the Choptank River estuary. This work provides a baseline from which to examine future changes in Choptank River water quality and results may be used to design future monitoring programs needed to assess the effectiveness of pollutant mitigation practices.