The Effect of the Different Ionic Composition of Saline Water on Cadmium Transport in Two Soils with Different Calcium Carbonate content

Recent researches have proven the effect of salinity of water and soil resources on the bioavailability of cadmium.In this study, the effect of different sources of salinity including sodium chloride, sodium sulfate and calcium chloride on cadmium transport in two different soils was investigated.Soil columns with a height and inner diameter of 50 and 10 cm, respectively, were subjected to leaching of cadmium solution at a concentration of 100 mg/L along with various salts of sodium chloride, sodium sulfate and calcium chloride at a concentration of 100 me/L for 10 days. The drained solutions were analyzed at three depths of 3, 7 and 50 cm. The simulation of cadmium chemical species in the soil solution was performed using Visual MINTEQ 3.The presence of salinity along with cadmium solution caused more transport and drain of cadmium than the control soil. The highest cadmium concentration drained from the columns was belonged to the soils which received calcium chloride with the mean of 19.6 mg/L whereas the lowest was determined in soil received sodium sulfate with the mean of 6.1 mg/L. Due to the formation of chloro-cadmium complexes, treatments containing chloride had a more obvious effect on the transport of cadmium in the soil columns. The simulation of cadmium speciation in solution containing chloride showed that CdCl+ and CdCl2(aq) account for more than 80% of the cadmium species, while in those containing sodium sulfate, this dominant mainly included two species of Cd(SO4)2- 2 and Cd(SO4)(aq). Generally, salinity conditions affected by chloride ions in cadmium polluted lands can increase the potential of this toxic metal entering water sources and food chain.