The Characteristics of Sediments and Their Potential of Nutrient Release at a Marsh Associated with a Reclaimed Rice Paddy

摘要

The characteristics of sediments at a marsh associated with a reclaimed rice paddy field were investigated. The marsh mainly received effluent and nonpoint source (NPS) pollution from the paddy field. The contributed watershed area of the paddy field is around 3,000 ha, and the marsh area is 154 ha. Then the potential of nutrient release from the sediments was evaluated through the incubation experiments both in the aerobic and anaerobic conditions, respectively. The sediments texture is loamy sand and it present a lightly polluted status. Total nitrogen (TN) content of the sediments ranges 180 to 507 mg N/kg (dry weight). For total phosphorus (TP), the range is around 203 to 251 mg P/kg (dry weight). The ratio of nitrogen to phosphorus (N/P) in the sediments is 0.8 to 2.0, rather lower than the values of 5.0 to 7.0 in the receiving effluent from the paddy field. The potential of ammonium release is around 70 mg N/m2/d in the aerobic conditions, and 36 mg N/m2/d in the anaerobic conditions, respectively. Phosphorus shows release risk in the anaerobic conditions other than that in the aerobic conditions.