Effects of Soil Sodicity and Gypsum Application on Dynamic Behavior of Heavy Metal Elements in Soils Under Wastewater Irrigation

Response of soil environment to wastewater irrigation affects sustainability of irrigation agriculture. Effects of soil sodicity and gypsum application on dynamical behavior of heavy metal elements under effluent irrigation were studied by means of soil column leaching method in laboratory. Three treatments were designed: nonsodic soil saturated with sodium adsorption ratio (SAR) 0, sodic soil saturated with SAR 30 and sodic soil saturated with SAR 30 + gypsum application. Fe accumulated in all experimental soils, but its increased percentage in sodic soil was greater than that in nonsodic soil or gypsum-applied sodic soil. After leaching of 19~23 pore volumes, Fe contents increased to 0.93 and 0.563 mg·kg-1 from initial content 0.43 mg·kg-1, respectively, in sodic soils with and without application of gypsum. Application of gypsum obviously decreased accumulation of Fe in sodic soil. Manganese and Zn accumulated in sodic soil but eluviated in nonsodic soil and gypsum-applied sodic soil. After leaching of 19~23 pore volumes, Zn content in sodic soil increased to 0.160 mg·kg-1 from initial content of 0.085 mg·kg-1, which was much lower than 100 mg·kg-1 of the First Class Criteria for National Soil Environmental Quality. Gypsum application in sodic soil changed dynamical behavior of Mn and Zn. Copper accumulated in nonsodic soil but eluviated in sodic soils no matter whether gypsum was applied or not, its content in nonsodic increased to 0.322 mg·kg-1 at the end of experiment from initial content of 0.208 mg·kg-1, which also was much lower than 35 mg·kg-1 of the First Class Criteria. Nickel eluviated in all tested soil conditions, but gypsum application in sodic soil increased eluviation of Ni from the soil. Accumulations of some heavy metal elements in soils didn't affect irrigation application of studied wastewater for a long period.