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Evaluation of the Water Quality of Gorgan Bay and Miankaleh Wetland using Field Studies and Ecological Modeling

Yousefi, Mohammad Mahdi | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 57392 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Raie, Mohammad
  7. Abstract:
  8. Most marine areas such as bays and lagoons are usually exposed to the high pollution load of their catchment area. Gorgan Bay and Miankaleh Wetland is a connected water body that is subject to the entry of various pollutants through the surrounding agricultural and urban areas, due to the ecological importance of this area and its registration as a biosphere reserve in the United Nations. It is important to control and evaluate its water quality. TSI and NSF-WQI environmental indicators have been used to evaluate the level of water pollution and water quality respectively. TSI and NSF-WQI indices have been evaluated in 8 stations in January and September 2023. The parameters of total nitrogen, total phosphorus, chlorophyll-a and secchi depth for TSI index, 2 parameters of ammonia and phosphate to determine the limiting parameter of eutrophication. parameters of phosphate, nitrate, pH, BOD, turbidity, dissolved oxygen, total dissolved solids and coliform were measured for NSF-WQI index. According to the results obtained in the two months of January and September 2023, the water body was in a hypereutrophic state on average, and its trophic index value was 74.9 and 75.9, respectively, as an average of 8 stations, and the limiting factor of eutrophication in Both months are phosphorus. According to the NSF-WQI index, the average quality of water in these two months is medium, and the average values of its 8 stations in January and September 2023 are 69.5 and 61.5, respectively. According to the obtained results, the southeastern part of the bay has more polluted conditions in terms of nutrition and water quality than other parts of the bay. According to the measured data as well as the existing data of the Environmental Protection Organization for this area and on the other hand, using the recent measured data of the main waterways leading to this water area, to create a simultaneous numerical model of hydrodynamics and quality. Water based on irregular network and limited volume for Gorgan Bay and Miankaleh Wetland has been studied in order to simulate flow circulation, fate and transport of pollutants. The water quality model includes the cycles of biochemical oxygen requirements, dissolved oxygen, phosphate, nitrate, ammonia, nitrite and finally the cycle of the chlorophyll-a parameter, which is finally based on the surface concentration of the chlorophyll-a parameter to check the level of trophicity of the area based on criteria OECD has been paid. The result of the water quality model, according to the OECD nutritional criteria, the average concentration of chlorophyll-a in this water body is around 30 micrograms/liter, and the probability of hypereutrophic conditions in the body is around 60%, the probability of eutrophic conditions is 39% and mesotrophic is 1%
  9. Keywords:
  10. Miankaleh Peninsula ; Water Quality Modeling ; Gorgan Bay ; OECD Standard ; National Sanitation Foundation (NSF)Water Quality Index ; Carlson Trophy Index (TSI)Nutrient

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