جستجوی مقالات مرتبط با کلیدواژه "نیترات" در نشریات گروه "مهندسی دریا"

Caspian Sea and its coastal areas are one of the most important ecosystems. There is great diversity associated with non-biological parameters of water, in this largest lake in the world. In this study the physical and chemical parameters, including nitrates, phosphate, temperature, salinity, dissolved oxygen, transparency, EC and pH were investigated. Sampling was performed in 2008 in thirteen regions from Astara to Khajenafas in the south coastal waters of Caspian Sea. There were three stations in each area and sampling was done from surface waters (5 and 10 m) from each station. In this study, the mean temperature, salinity, pH, EC, water transparency, dissolved oxygen, nitrate and phosphate were 19.6 ° C, 11.8 ppt, 8.7, 17.28 (mm/cm), 82.23 cm, 6.22, 0.061 and 0.014 mg/l, respectively. Maximum and minimum of nitrate levels were 0.154 and 0.007mg/l in Kyashahr and Astara, respectively. The peak level of phosphate concentration (0.062mg/l) was found in Bandar Torkaman and the minimum level (0.001 mg/l) was obtained in the Anzali and Nashtaroud. The results show that concentrations of nitrate and phosphate were higher in south-east compared with south-west coast of the Caspian Sea. There was a significant difference in nitrate concentration in different regions (P< 0.05), but there was no significant difference in the concentration of nutrients in the water column (p>0.05). Results indicate that an increase in level of nitrate was found in compared to previous years. There were positive correlations in dissolved oxygen with nitrate levels and negative correlations with temperature and water transparency. Temperature, salinity and EC had positive correlation and the correlation of temperature with dissolved oxygen was negative.

Changes in abundance and biomass of cyanobacteria have been studied in the southern part of the Caspian Sea (the stretch between Tonekabon and Amirabad) in four seasons (spring, summer, autumn, winter) in which samples were taken from five depths of 5, 10, 20, 50 and 100 meters in the stations of Tonekabon, Noshahr, Babolsar and Amirabad. Samples were fixed with formalin (2%) before transferring to the lab for both qualitative and quantitative analyses. The results of this study showed higher abundance and biomass of cyanobacteria in euphotic layer compared to aphotic layer. Temperature, ammonium, nitrate and nitrite levels have shown significant differences.

This study performed in  Caspian Sea in order to estimate nutrients includeing nitrate, phosphate and physicochemical factors (pH, temperature and salinity) from April to October in 2008 . Sampling have done in eastern south of Caspian Sea in seven transects in 56 station on surface water, 5 and 10 meter. The mean temperature, salinity and pH were 26.9°± 4.72° C,  12.13± 2.33 ppt and 8.69± 0.79 respectively. The mean nitrate was 0.061± 0.0161mg/l and phosphate was  0.017±  0.011mg/l. Min and Max of nitrate and phosphate were 0.021, 0.131 and 0.001, 0.096 mg/l respectively .The concentration of salinity, nitrate and phosphate were higher in compared to western south Caspian Sea. There was significant differences in nitrate concentration in transects (P<0.05), but the other parameters were not significantly different (P>0.05). There were not meaningful difference in all parameters upon surface waters, 5 and 10 m.   Results showed that the concentration of nitrate and phosphate have increased compared to past years.