Sieving of Ground Water Silica by Soils

Adsorption of silica and other chemical constituents from siliceous saline irrigation water was studied on saline and non-saline soils (Calciorthids). The depletion of silica increased with the rise in pH of the soil leachate. There was consistent trend of silica retention by non-saline soil behaving like a sieve. The composition of soil extract indicated similar content of silica irrespective of its original concentration in the extracting water. The amount of silica adsorbed per unit mass of soil decreased with the narrowing of soil to solution ratio. Saline soil exhibited higher affinity to silica adsorption, however, unirrigated non-saline soil generally indicated a steady state retention behaviour. The interaction of other chemical constituents of siliceous saline water with soil indicated sodification due to decrease and increase in the concentration of sodium and calcium ions, respectively in the leachates whereas magnesium behaved indifferently. Silica again was sieved off from original content of 53.5 μg/ml to a steady state concentration level of about 11.5 μg/ml in the leachates.