Hydrodynamic features, appearance of scum, and spatial distribution of odor in urban estuaries

Abstract

 The water level, salinity, turbidity, and dissolved oxygen (DO) were monitored from April to October 2018 when scum was most apparent in the Shakujii River estuary. The strength of odor representation or component; odor index or the total strength; and odor similarity of scum, air, water and sediment were analyzed using the odor machine. Results of the monitoring showed that scum appears two to five days after rainfall, when DO is less than 6 mg/L, at suspended sediment concentration of approximately 15 mg/L and less than 1 salinity level. The spatial distribution of odor showed that the relatively downstream areas of the rivers have higher odor index and similarity with scum. The strongest odor component of scum and sediment was organic acid followed by hydrogen sulfide and sulfur. Hydrogen sulfide was the strongest odor component of water and air. The analysis of similarity with scum and loss on ignition showed that the Shakujii River has a high probability to generate scum. The percent odor similarity to scum may be attributed to the organic matter content of sediments.