| Popis: |
The equivalent retention of Ca 2+ and SO 4 2- from gypsum solutions in acid subsoils has recently been reported. The term salt sorption has been coined to describe this process, yet little is known about the nature of the reactions involved. This study was conducted to determine if other cation-anion combinations would exhibit similar behavior and to examine the extractability of the sorbed ions. An unfertilized acid Cecil (clayey, kaolinitic, thermic Typic Kanhapludult) subsoil was equilibrated using a saturated paste technique, with solutions of six different salts at a loading rate of =14.0 mmol c kg -1 . The salt solutions used were CaSO 4 , MgSO 4 , Na 2 SO 4 , CaCl 2 , MgCl 2 , and a deionized water control. This soil exhibited salt sorption with all six electrolyte solutions. The SO 4 salts were almost completely sorbed with both cation and anion uptake on the order 13.8 mmol c kg -1 . Calcium and magnesium chloride were sorbed at =11.7 mmol c kg -1 , and NaCI was sorbed at 8.2 mmol c kg -1 . The treated soils were air dried and extracted with successive portions of deionized water or 0.5 M NH 4 NO 3 . A relatively large proportion of both cations and anions were removed by repeated extraction with water, suggesting that ionic strength played an important role in the salt sorption process. Nearly all of the sorbed cations and Cl - were recovered by neutral salt extraction, but |
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