Abstract

Water samples were taken from 36 wells in agricultural lands in Erbil governorate, Iraqi Kurdistan region. Soil samples were taken from five calcareous and seven gypsiferous soils from different locations in Erbil and Ninava governorates. Some of the chemical properties of the studied waters and soils were analyzed. Then, the water types, soil types, the ion pair, ion pairs and activity, and ion strength were calculated. The main results were summarized as follow:
The water of (11, 10, 9, 2, 2, and 2) wells before correcting ion pairs plus activity had (Ca-SO4, Ca-HCO3, Mg-SO4, Mg-HCO3, Na-HCO3, Na-SO4) types, respectively. After correcting ion pairs and activity, the water of (1, 16, 3, 6,7, and 3) wells had the mentioned types, which means correcting ion pairs and activity had a great impact on changing the water types, respectively.
The soil samples represent seven gypsiferous and five calcareous soils, depending on their calcium carbonate and gypsum content. The amount of ion pairs in Gypsiferous soils is higher than their amount in calcareous soils. The ratio between ion pairs in Gypsiferous to calcareous soil ranged from 0.628 to 3.192. The highest value was recorded for (CaSO4) 0, while the lowest value was for (MgHCO3) 0. The series of ion pairs for both Gypsiferous and calcareous soils were arranged as ((CaSO4)0, (MgSO4)0, (CaHCO3)+, (MgHCO3)+, (NaSO4)-, (KSO4)-, and (NaHCO3)0). The dominant ions that contribute in ion pairs formation are Ca+2 and SO4-2; the highest values were recorded from Sinu1 location, while the lowest values were recorded at Akre location for both ions. The highest correlation coefficient value between ion strength and ion pairs was recorded in gypsiferous soil compared with calcareous soil with the mean of correlation coefficient of (r= 0.71** and 0.54*), respectively.