State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, 210093, People's Republic of China.
Ecotoxicology. 2011 Jul;20(5):1141-7. doi: 10.1007/s10646-011-0665-6. Epub 2011 Apr 3.
Contamination of environmental matrixes by human and animal wastes containing antibiotics is a growing health concern. Because tetracycline is one of the most widely-used antibiotics in the world, it is important to understand the factors that influence its mobility in soils. This study investigated the effects of pH, background electrolyte cations (Li(+), Na(+), K(+), Ca(2+) and Mg(2+)), heavy metal Cu(2+) and humic acid (HA) on tetracycline adsorption onto kaolinite. Results showed that tetracycline was greatly adsorbed by kaolinite over pH 3-6, then decreased with the increase of pH, indicating that tetracycline adsorption mainly through ion exchange of cations species and complexation of zwitterions species. In the presence of five types of cations (Li(+), Na(+), K(+), Ca(2+) and Mg(2+)), tetracycline adsorption decreased in accordance with the increasing of atomic radius and valence of metal cations, which suggested that outer-sphere complexes formed between tetracycline and kaolinite, and the existence of competitor ions lead to the decreasing adsorption. The presence of Cu(2+) greatly enhanced the adsorption probably by acting as a bridge ion between tetracycline species and the edge sites of kaolinite. HA also showed a major effect on the adsorption: at pH < 6, the presence of HA increased the adsorption, while the addition of HA showed little effect on tetracycline adsorption at higher pH. The soil environmental conditions, like pH, metal cations and soil organic matter, strongly influence the adsorption behavior of tetracycline onto kaolinite and need to be considered when assessing the environmental toxicity of tetracycline.
环境基质受到含有抗生素的人类和动物废物的污染是一个日益严重的健康问题。由于四环素是世界上使用最广泛的抗生素之一，因此了解影响其在土壤中迁移的因素非常重要。本研究调查了 pH 值、背景电解质阳离子（Li(+)、Na(+)、K(+)、Ca(2+) 和 Mg(2+)）、重金属 Cu(2+) 和腐殖酸（HA）对四环素在高岭土上吸附的影响。结果表明，四环素在 pH 3-6 范围内被高岭土强烈吸附，然后随着 pH 值的增加而降低，这表明四环素吸附主要通过阳离子种类的离子交换和两性离子种类的络合作用。在五种类型的阳离子（Li(+)、Na(+)、K(+)、Ca(2+) 和 Mg(2+)）存在的情况下，随着金属阳离子原子半径和价态的增加，四环素的吸附量降低，这表明四环素与高岭土之间形成了外球络合物，而竞争离子的存在导致吸附量减少。Cu(2+) 的存在大大增强了吸附作用，可能是因为 Cu(2+) 充当了四环素物种和高岭土边缘位点之间的桥接离子。HA 也对吸附有重大影响：在 pH < 6 时，HA 的存在增加了吸附，而在较高 pH 值下，HA 的添加对四环素的吸附几乎没有影响。土壤环境条件，如 pH 值、金属阳离子和土壤有机质，强烈影响四环素在高岭土上的吸附行为，在评估四环素的环境毒性时需要考虑这些因素。
