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

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 (Cu(2+) and Cd(2+)) 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 Cu(2+) and Cd(2+) 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 Cu(2+) and Cd(2+). The presence of Cu(2+) enhanced the TC sorption of BS, ROM and ROX, but had a suppression effect on HA because of the competition of Cu(2+). The presence of Cd(2+) 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.