Investigating the effects of designed ponds in the quantitative and qualitative assessment of evaporation reduction through octadecanol fatty alcohol in the semi-arid region of Khorramabad, Lorestan

In the methods of utilizing nanometer coatings, it is usually possible to reduce the amount of evaporation by using long chain molecules and spreading them on water and forming molecular monolayers. In this research, quantitative (evaporation reduction rate) and qualitative (chemical parameters) effects of octadecanol monolayer dissolved in ethanol as a chemical evaporation control method were investigated. Every three days, it was sprayed (4% concentration) on the water surface of natural ponds with dimensions of 2×2×2 cubic meters located in Faculty of Natural Resources meteorological research station. Accumulated evaporation for the two measured months in the control pond was 559 mm and in the pond with the octadecanol monolayer was 455 mm. Quantitative and qualitative analysis results in the two-month period between the two control ponds and the pond with octadecanol monolayer from 2021/8/23 to 2021/10/22 were performed based on ANOVA test, by comparing means with Tukey's and Duncan's methods. The octadecanol monolayer sample had a significant difference at 0.05 level in terms of changes in the rate of evaporation compared with the control, and the octadecanol monolayer with 20% efficiency was significantly effective in terms of reducing evaporation. Selected qualitative parameters including electrical conductivity, dissolved oxygen were investigated. The results of obtained data using SPSS software and ANOVA test, showed a non-significant difference due to sig greater than 0.05% of dissolved oxygen and electrical conductivity between the average of the control pond and the ponds with octadecanol monolayer. In the control pond, due to the possibility of contact with the air and more incoming radiation, the concentration of dissolved oxygen increased compared to the pond with octadecanol monolayer. The achieved results showed 5% decrease in electrical conductivity and in dissolved oxygen in the pond with the monolayer of the mentioned composition compared to the control pond. In terms of changes in water surface temperature (physical parameter), which was measured with a thermometer, its average was 24.4 ⁰C in the pond with octadecanol monolayer, while it was 23.11 ⁰C in the control pond with monolayer. Empirically, the effect of a dense layer in reducing evaporation losses is proportional to the increase in water surface temperature.