فهرست مطالب شیرین فرخانی

In this study, the relationship between dissolved oxygen reduction in the Gulf of Oman and changes in effective factors such as temperature and thermal stratification, exchanges with nearby water bodies, biological activities, chlorophyll-a concentration, and primary production was studied. The data used in this research were extracted from the measurement data available on global sites such as the World Ocean Atlas and SeaWiFS and MODIS satellite images. Comparing the average annual DO profiles in the Gulf of Oman showed a decrease in the upper 1000 m layer in 2010 compared to 1960. The DO reduction in the surface mixed layer was 0.4 mg/l and reached 3.7 mg/l at 100 m depth. At depths more than 100 m, the amount of change decreased and reached 0.1 mg/l at 1000 m. Due to the deoxygenation, the thickness of the surface layer with DO˃2 mg/l decreased from 150 m to 80 m. The results demonstrated that the drop in DO in the surface mixed layer was consistent with the decrease in gas solubility caused by the temperature increment in this layer. Regarding the severe reduction of DO in the layer below the surface mixed layer, it was shown that the strengthening of thermal vertical stratification and intensification of thermocline (0.01°C/m increase in thermal gradient) were the most important factors.

Rivers are amongst the most important sources of water supply all over the world. Increasing urban development, industrial activities and a significant increase in the volume of urban effluents have polluted rivers and in many places water quality of these vital resources have been seriously endangered. In this study, using the QUAL2K numerical model, the quality status of Haraz River has been investigated and the impact of effluents entering the river has been identified. According to the results of qualitative modeling of the river in 2016, at kilometer 48, where the Amol diversion dam is located, the BOD rate suddenly increases which is due to the reduction of flow velocity and discharge and the increase in the discharge of pollutants to the river related to workshops and factories. In spring and summer the concentration of dissolved oxygen is critical in the reaches from Amol diversion dam to the estuary of the river by the Caspian Sea. In terms of acidity, the water of Haraz River is alkaline. The EC parameter also decreases along the river due to the gradual deposition of soluble and suspended solids into the water. The concentration of nitrate in water also increases after the diversion dam, although it is not significant in total.