EVAPORATION LOSS FROM SANDY SOILS MIXED WITH A POLYACRYLAMIDE HYDROGEL UNDER DIFFERENT SALINE CONDITIONS

The application of a polyacrylamide hydrogel increased both the water retained by a sand soil and a sand mixed with the polymer and the evap oration time. The water inside the hydrogel showed three states of eva poration when the polymer was swollen in distilled water. These states were evidenced by three straight lines and were attributed to: i) unb ound water, ii) water weakly bound to hydrophilic sites, and iii) stro ngly bound water. The increase of total soluble salts reduced the thre e states of the evaporation rate of water to two states. A further inc rease of total soluble salts above a concentration of 10 meq.L(-1) for NaCl, and 5 meq.L(-1) for CaCl2, reduced the two states of water in t he hydrogel to one state.