Column experiment for the evaluation of sodium and ammonium removal from an agricultural sandy soil amended with natural zeolitite

A series of column experiments on a sandy agricultural soil of the Po Delta area, treated with natural zeolitite, were performed in order to evaluate the efficiency of the zeolitite in reducing the Na excess derived from local brackish waters and the high NH4 contents due to fertilization practices. The soil, amended with 10 Kg/m2 of natural chabasite zeolitite, was introduced into a column (V=185,89 cm3, porevolume (p.v.) = 20ml). Two replicates were saturated with brackish water of marine origin (EC=18 mS/cm) and other two with a solution containing 10,157 ppm of NH4 (reflecting an “after fertilization” condition, following MAS limit of 170 Kg-N/ha); after saturation, the columns were left resting for 24 hours, in order to reach the equilibrium of the cations exchange reaction. Each column was then fluxed for 6 p.v. with Milly-Q Water, and the first drops of each p.v. were collected and analyzed via ICP-MS for major and trace element determination, and via UV-VIS spectrophotometer for Ammonium concentration. Results show that the amended soils saturated with brackish-marine water have a removal efficiency for Na of about 52% for the first p.v., that decreases at an average of about 21% after six p.v.; the amount of Na retained by the soil vary from 0.44 mg/g at the first p.v. to 0.18 mg/g after six p.v. The released cations were mainly Ca, K and Mg following the order Ca>K>Mg. Regarding the Ammonium saturated columns, the removal efficiency vary from an average of 58% at first p.v. to 50% after six p.v. and the amount of NH4 ions retained by the soil vary from an average of 1.72 mg/g at the first p.v. to an average of 1.5 mg/g after six p.v. These results indicate that, by the addiction of natural zeolitite in a sandy agricultural soil, the reduction of Na and NH4 loads from soils water is possible, opening prospective for an open field experimentation.