Laboratory analyses of nutrient release processes from Haihe River sediment

Sediment samples were collected from the heavily contaminated Haihe River to conduct static nutrient release experiments with tap water, and to evaluate the effect of dredging depths, salinity and light on the corresponding release processes. The study is significant because it helps decision-makers to assess the likely impact of dredging (e.g. eutrophication) on contaminated freshwater and brackish rivers. The concentrations of total nitrogen and inorganic phosphorus were approximately 950 mg/kg and 760 mg/kg, respectively. The typical organic matter concentration was 8.6%. Data obtained from the nutrient leaching experiments indicated that 5cm-dredging of sediment reduced the water column total phosphorus, total dissolved phosphorus and ammonia-nitrogen concentrations insignificantly. In contrast, dredging 10cm surface sediment could improve the water quality. Higher salinity values benefited the release of nitrogen and phosphorus from sediment. In contrast to indoor experiments, concentrations of total phosphorus, total dissolved phosphorus and ammonia-nitrogen were higher for the outdoor experiments.