Diurnal variation of dissolved oxygen in coastal zone ecosystems : a case study : Vietnam and Denmark | |
| Author | Kim Thi Thuy Ngoc |
| Call Number | AIT Thesis no.EV-99-29 |
| Subject(s) | Coastal ecology--Vietnam Coastal ecology--Denmark |
| Note | A thesis submitted in partial fulfilment of the requirement for the degree of Master of Science, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Abstract | A mathematical model: VisSim system was used to calculate the variation of Dissolved Oxygen in one year in Denmark and three days in Vietnam. The available data such as light, temperature, salinity, wind speed were used as input data to calculate variables and processes which cause the variation of DO such as oxygen saturation (Cs), maximum production at noon (P max), re-aeration rate, Respiration, Photosynthesis, Re-aeration, Water exchange. The simulated curves were compared with the observed values. The rate of Photosynthesis as well as light intensity in Denmark and Vietnam was then compared together. The study shows that the simulated and measured curves have a good agreement. However, this agreement sometime very modest. The variances for the observed values and for the difference between observed and simulated values in Denmark are 2.94, 0.66 respectively whereas in Vietnam the variances are 0.52 and 0.15. This show that model is able to describe a major part of the observed oxygen variations. The primary production in Denmark is lower than in Vietnam at the same time of year, because of lower light intensity. A two dimensional mathematical model: the MIKE21 system was used for describing hydrodynamics and BOD-DO processes at the Doson beach. The model describes the currents in the two horizontal dimensions as a function of bathymetry, tidal forces and wind forces. The resulting currents are used for proceeding Water Quality (WQ) Module to calculate the biological and chemical processes, which cause the variation of Dissolved Oxygen. The results from the MIKE21 model demonstrate very complicated oxygen variations induced by the combination of two periodically varying forces: the light intensity and the tidal forcing varying with a different frequency. |
| Year | 1999 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Energy and Climate Change (Former title: Department of Energy, Environment, and Climate Change (DEECC)) |
| Academic Program/FoS | Environmental Engineering (EV) |
| Chairperson(s) | Dahl-Madsen, Karl Iver; |
| Examination Committee(s) | Suphat Vongvisessomjai ;Webb, Edward; |
| Scholarship Donor(s) | DANIDA (Danish International Development Agency) ; |
| Degree | Thesis (M.Sc.) - Asian Institute of Technology, 1999 |