Magnitude of Nitrogen Pollution in Stream Water due to Intensive Livestock Farming Practices

概要

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This study was conducted to evaluate the magnitude of nitrogen (N) pollution in stream water associated with intensive livestock farming practices. An extensive water sampling was carried out from stream tributaries, open channels, drainages, and seepages during the snow-melting season in 2001. Total nitrogen (TN) concentration was determined and water flow was measured. The lowest concentration of TN in the headwater of tributary 'A' was as low as 0.39 mg N L^-1 (0.03 g s^-1 of N load), and the concentration reached a value of 5 mg N L^-1 in the outlet of the stream, which resulted in a N load of 1.37 g s^-1. The increase in the N load (1.34 g s^-1) was mainly due to drainage from a constructed wetland for Livestock wastes, other drainages, and seepages from around the livestock sheds. The maximum concentration of TN in the drainage and seepage water from the constructed wetland was very high, 63 mg N L^-1, which resulted in a N load of 0.53 g s^-1 into the open channel that reached tributary 'A.' About 40% of the increased N load in the main tributary in the intensive livestock farming area was occupied by a single constructed wetland confirming that the drainage from this facility acted as the point source of pollution in the area.
社団法人日本土壌肥料学会の論文