Palmer-Felgate,E.J., Mortimer,R.J.G., Krom,M.D. and Jarvie,H.P.(2010): Impact of point-source pollution on phosphorus and nitrogen cycling in stream-bed sediments. Environ. Sci. Technol., 44, 908-914.

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w(Abstract)
@Diffusive equilibrium in thin films was used to study the cycling of phosphorus and nitrogen at the sediment-water interface in situ and with minimal disturbance to redox conditions. Soluble reactive phosphate (SRP), nitrate, nitrite, ammonium, sulfate, iron, and manganese profiles were measured in a rural stream, 12 m upstream, adjacent to, and 8 m downstream of a septic tank discharge. Sewage fungus adjacent to the discharge resulted in anoxic conditions directly above the sediment. SRP and ammonium increased with depth through the fungus layer to environmentally significant concentrations (440 and 1800ƒÊM, respectively) due to release at the sediment surface. This compared to only 0.8ƒÊM of SRP and 2.0ƒÊM of ammonium in the water column upstream of the discharge. Concomitant removal of ammonium, nitrite and nitrate within 0.5 cm below the fungus-water interface provided evidence for anaerobic ammonium oxidation (anammox). gHotspotsh of porewater SRP (up to 350ƒÊM) at the downstream site demonstrated potential in-stream storage of the elevated P concentrations from the effluent. These results provide direct in situ evidence of phosphorus and nitrogen release from river-bed sediments under anoxic conditions created by sewage-fungus, and highlight the wider importance of redox conditions and rural point sources on in-stream nutrient cycling.x

Introduction
Experimental section
@Study site
@Reach characterization
@DET probes
Results and discussion
@Reach characterization
@DET gel profiles
@Wider implications
Acknowledgments
Supporting information available
Literature cited


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