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Title:   Author  item
                                            NINO DE GUZMAN, G - University Of Marylanditem
                                            Hapeman, Cathleenitem
                                            PRABHAKARA, K - University Of Marylanditem
                                            Codling, Etonitem
                                            Shelton, Danielitem
                                            Rice, Clifforditem
                                            Hively, Wells

                                                         - *Dean*item
                                            McCarty, Gregoryitem
                                            TORRENTS, A - University Of Maryland
  Submitted to: Science of the Total Environment
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 3/21/2012
                                    Publication  Date: 5/26/2012
                                    Citation: Nino De Guzman, G.T., Hapeman, C.J., Prabhakara, K., Codling, E.E., Shelton, D.R., Rice, C., Hively, W.D., Mccarty, G.W., Torrents, A. 2012. Potential pollutant sources in a Choptank River subwatershed: Influence of agricultural and residential land use and aqueous and atmospheric sources. Science of the Total Environment. 430:270-279.Interpretive Summary: Agriculture and animal feeding operations have been implicated as sources of water pollution along the Choptank River, an estuary and tributary of the Chesapeake Bay.  This study examined a subwatershed within the Choptank River watershed for effects of land use on water quality.  Water and sediment samples were collected from 2009-2010 under mostly baseflow conditions and analyzed for nutrients (nitrogen and phosphorus), arsenic, and select bacteria.  While all these materials were observed in areas of residential, industrial, and agricultural land use, some differences were found.  Some forms of phosphorus were more associated where poultry production occurred.  Nitrogen levels appeared to be affected more by changes in climate than land use and may be influenced by atmospheric transport and deposition of ammonia during drier weather.  Arsenic proved a satisfactory marker for poultry runoff, as concentrations reflected known or suspected hot spots for infiltration.  Bacterial levels in water and sediment samples showed little change during the sampling regime, both spatially and temporally.  However, slight fluctuations were observed during wetter and drier periods.  Presence of impervious surfaces were noted to have shifted flow paths of some runoff, possibly undermining the mitigation efforts put in place to protect surface waterways.  These data will be useful for regulators, extension specialists, and decision-makers in modifying agricultural management practices to protect sensitive ecosystems.
                                Technical Abstract: Agriculture and animal feeding operations have been implicated as sources of water pollution along the Choptank River, an estuary and tributary of the Chesapeake Bay.  This study examined a subwatershed within the Choptank River watershed for effects of land use on water quality.  Water and sediment samples were collected May–October 2009 and April–June 2010 under mostly baseflow conditions and analyzed for nutrients (N, P), arsenic, and select bacteria.  Measured ortho-phosphate concentration was more associated with residential, industrial, and agicultural land use, while the remaining phosphorus fraction (organic-P) near poultry production was significantly higher (p less than 0.05).  No significant differences between land uses were observed for nitrate-N.  However, significant temporal differences were observed in ammonium-N concentrations and appeared to be affected more by changes in climate than land use.  Atmospheric deposition was postulated as a possible ammonia source during drier weather.  Significant differences (p less than 0.05) in arsenic concentrations were observed from areas of higher poultry production versus residential and non-poultry production areas, although even at the highest levels (4 ppb) were below the maximum contaminant level for drinking water (10 ppb).  Enterococcus and E. coli levels in water and sediment samples showed little change during the sampling regime, both spatially and temporally.  However, slight fluctuations were observed during wetter and drier periods.  The presence of impervious surfaces was noted to have shifted flow paths of some runoff, possibly undermining the mitigation efforts put in place to protect surface waterways.  A better understanding of these features and local natural attenuation predispositions will support mitigation practices already in place for surface water protection.


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