Effect of Salinity on Evaporation and the Water Cycle

Abstract

This study is on the effect of salinity on evaporation from water bodies and probable influence on the water cycle. Five different salts were used in this study, different concentrations of Magnesium Sulphate, Sodium Hydroxide, Sodium Chloride, Ammonium Chloride and Potassium Nitrate solutions in the neighbourhood of 0.04, 0.08, 0.12, 0.16, 0.20 and 0.24 g/cm3 were prepared by dissolving 20, 40, 60, 80, 100 and 120 g weights of these salts in 500 cm3 of distilled water. The first evaporation can contained only 500 cm3 of distilled water and served as the control experiment. The solutions were introduced in evaporation cans each of capacity 700 cm3, stored under room temperature and evaporation allowed to take place. Evaporation from the cans were measured at 24 hours intervals for a period of 14 days. Results showed that in all salts, as salinity increases, evaporation is reduced. On the 10th day, evaporation retardation factors for Magnesium Sulphate, Sodium Hydroxide, Sodium Chloride, Ammonium Chloride and Potassium Nitrate were found to be 0.800, 0.490, 0.712, 0.820 and 0.822 respectively. Ratios of evaporation retardation factors were 1:1.6327 for Sodium hydroxide : Magnesium Sulphate; 1:1.4531 for  Sodium Hydroxide : Sodium Chloride; 1:1.6735 for  Sodium Hydroxide : Magnesium Sulphate; 1:1.4531 for Sodium Hydroxide: Sodium Chloride; 1:1.6327 for Sodium Hydroxide : Ammonium Chloride and 1:1.6776 for Sodium Hydroxide : Potassium Nitrate solutions. Highest evaporation took place in Potassium Nitrate solution at the ultimate concentration of 0.24 g/cm3, this was followed by Ammonium Chloride, Magnesium Sulphate, Sodium Chloride and Sodium Hydroxide. These salinity effects will impact on the outflow parameter in the water cycle with consequent reduction in evaporation which reduces precipitation, hence the formation of rain in the cloud would be inhibited and ultimately lead to climate change.