The role of soil components in the sorption of tetracycline and heavy metals in soils

Abstract

A natural black soil (BS) was treated to obtain three individual soils referred to as removed organic matter (ROM), removed metal oxide (ROX) and humic acid (HA), and the sorption behaviors of tetracycline (TC) and heavy metals (Cu²⁺ and Cd²⁺) on BS and three treated soils were investigated to evaluate the role and contribution of different soil components (organic matter, clay and metal oxide). The three treated soils all showed stronger sorption capacities toward TC than BS, and the sorption amount of ROM, ROX, and HA for TC was greater than that of BS by 1.2 times, 2.3 times, and 3.3 times at an initial TC concentration of 25 mg L⁻¹. Differently, the sorption capacity of BS for Cu²⁺ and Cd²⁺ was stronger than that of ROM. The multiple linear regression analysis suggested that soil organic matter made the greatest contribution toward the sorption of TC, whereas, metal oxide was the key component influencing the sorption of Cu²⁺ and Cd²⁺. The presence of Cu²⁺ enhanced the TC sorption of BS, ROM and ROX, but had a suppression effect on HA because of the competition of Cu²⁺. The presence of Cd²⁺ did not exert obvious effects on TC sorption of BS, but exhibited a suppression effect on TC sorption of ROM, ROX and HA, which was likely to relate to the surface potentials of the soils. The results in this study are expected to give an insight into the role of different soil components in the sorption and co-sorption of TC and heavy metal through a mathematical model and to reveal the sorption mechanism.