| dc.description.abstract | The Danshuei River system is the largest estuarine system in Taiwan. It consists of three major tributaries: Tahan Stream, Hsintien Stream and Keelung River. The estuary is the primary conduit for the transport of water and material from its drainage basin to the coastal ocean. The ultimate fates of land-derived materials, such as pollutants, depend on the water movement in the estuaries. To predict the fate and transport of materials from land to the ocean requires the knowledge of water movement through this stretch of water body. The heavy metal in the rivers and estuaries mainly includes dissolved and particulated phases .The latter is the heavy metal absorbed on the suspended sediment. In general, the distribution coefficient determines the amount of dissolved and sorbed fractions.
In order to understand the physical transport characteristics of heavy metal transports in rivers and estuaries, a vertical (laterally averaged) two-dimensional heavy metal transport model was developed and based on hydrodynamics, salt, and sediment transport models. The model was applied to the Danshuei River estuarine system which is the largest tidal river in Taiwan and to simulate the copper transport including total, dissolved, and sorbed copper concentrations. The upstream boundaries of the computational domain are: Cheng-Ling Bridge (Tahan Stream), Hsiu-Lang Bridge (Hsintien Stream), Wu-Du (Keelung River). The downstream is at the Danshuei River mouth. The comparisons of field measurement and computed tidal elevation, velocity, salinity, suspend sediment concentration show that they are in good agreement. In order to validate the accuracy of the Heavy metal transport model, two field measurements conducted by the National Center for Ocean Research (NCOR) during 2001 to 2002, were adopted for comparison with simulation results. According to pictures from pollutant area and measured data conducted by the Environmental Protection Administration and National Center for Ocean Research, the high copper concentration exhibits near the Hsin-Hai Bridge. The simulated results reveal that point source loading (250 kg/day) should be added near the Hsin-Hai Bridge to match the field data.
After the model calibration and verification, the heavy metal transport model was applied to investigate the impacts on copper distribution in the water column under different conditions of sediment bed fluxes. The model was also used to comprehend the tidally averaged salinity distributions, residual current, suspended sediment concentration, copper concentration and fluxes. | en_US |