Problems of superabsorbent polymers application in desert regions

According to the super absorbent polymer manufacturers, super absorbent polymer can improve the physical properties of light soils to absorb and store more water. This study was aimed to investigate the effect of environmental factors such as salinity and duration on super absorbent polymer to store water in sandy soils. Two separate experiments were conducted using A-200 polymer in the field and laboratory conditions. In the field experiment, a site of sand dune from Kashan desert, Iran, was selected and the soil was mixed with a polymer in a ratio of 0.6% w/w. Then, the soil moisture curves were measured three times at three-month intervals. The water uptake of the mixture was decreased from 13.2% to 4.4% and 3.7% at the first to the third times, respectively. In the laboratory experiment, the effect of soil salinity was investigated on the water uptake of pure polymer. Results showed that the net water uptake of the polymer was strongly dependent on concentration of dissolved salts as well as the valence of ions in the solution. The result also showed that the lowest decrease in the water uptake of polymers was obtained from the mixed sodium chloride and sodium sulfate solution in compare to control, and the highest decrease in water uptake was obtained from the mixed calcium chloride and calcium sulfate solution. It seems that applying superabsorbent polymers is non-economic due to the loss of water retention during the time, affected by environmental factors or the presence of salts (minerals) in the soil. Therefore, it is suggested to use natural absorbent material such as compost and clay soil in natural resources area to supply the water requirements of plants.