Study of Na & Ca Exchange Relations and Selectivity Coefficient of Drained Marsh Soils in Southern Iraq

Abstract

This study was carried out in some soils of dried marshes in the governorates of Basra, Dhi Qar, and Maysan in southern Iraq. The sites for six snodep were selected ifahS-lA, Al-Mashab, Al-Chibayish, Al-Hammar, Al-Azim, and Al-Musharrah. Their coordinates were determined using a GPS device. Through the quantitative calculation of the selectivity coefficient in the ion exchange system according to Gapon (KG)and Vanselow (KV) at the ratios (2:8) and (8:2) sodium-calcium and for concentrations of 100, 200, 400, and 800mmolcliter−1, their coordinates were determined in order to determine the reciprocal relationship between calcium and sodium as well as the extent of selectivity of the study soils for any of the two ions. The results showed that all the soils under study tended towards a preference for calcium by binding at the exchange sites compared to the sodium ion, and it showed a high preference for the study soils for calcium compared to sodium in low salt concentrations preference decreased with increasing salinity. The results of the study for the linear relationship between each of the values of the coefficient of preference (KG and KV) and the clay separation at the different soils of the study showed that there is a highly significant negative correlation (r) (-0.878 and - 0.9516) at the ratio 8:2 sodium: calcium, respectively. While no correlation appeared when studying the relationship between the selectivity coefficient constants (KG and KV) and each of the organic matter and the degree of soil reaction (pH) and lime (CaCO3).