THE EFFECTS OF THE APPLICATIONS OF ZEOLITE AND BIOCHAR TO THE SOILS IRRIGATED WITH TREATED WASTEWATER ON THE HEAVY METAL CONCENTRATIONS OF THE SOILS AND LEACHING WATERS FROM THE SOILS

Abstract

The reuse of wastewaters for agricultural irrigation is a method used in arid and semi-arid regions. The heavy metal accumulation in soils caused by wastewaters and the heavy metals transported by the waters leaching into the underground from these soils are important environmental issues. The study investigates the effects of Biochar (Bc) and Zeolite (Zt) applications on the heavy metal accumulation in soils (entisol and vertisol) that were irrigated with treated urban wastewater (TWW). The effects of Bc and Zt on the heavy metal concentrations of the leaching water (LW) from the soils were investigated as well. In the study, increasing doses of Bc (1%, 2%, and 4%) and Zt (5%, 10%, and 20%) were mixed into two soil classes of heavy- and fine-textured soils. The mixtures were irrigated with TWW at certain intervals. At the end of the trial, the chromium (Cr), iron (Fe), nickel (Ni), cobalt (Co), copper (Cu), lead (Pb), and cadmium (Cd) contents of the samples collected from the soils and leaching irrigation waters were determined. The results revealed that Bc and Zt caused heavy metal accumulation in both soil classes, while they decreased the heavy metal concentrations of the LW. The adsorbents are commonly used as soil amendments and have been determined to cause heavy metal accumulation in soils but reduced the heavy metal concentrations in waters by serving as filters.