根系带电特征对根系吸附和吸收抗生素的影响

Antibiotics use is and has been, a common practice worldwide. With large consumption and low metabolism rate, antibiotics may directly reach into the soil environment through the manure spreading in agriculture, and thus have potentially bad effects on human health and natural ecosystem. Currently, the antibiotics adsorption on different soil components has been concerned primarily, and we have a good knowledge of the adsorption mechanisms. However, there is few reports about the effect of root electrochemical characteristics on adsorption and absorption of antibiotics by roots, and the mechanism study needs more concern. We have confirmed that root electrochemical characteristics played an important role on adsorption and absorption of ions by roots, hence we guess root electrochemical characteristics may also affect the adsorption and absorption of antibiotics by roots. Consequently, doxycycline (tetracyclines) and norfloxacin (fluoroquinolones) will be selected as the research objects, and the soybean and maize roots with different electrochemical characteristics as the adsorbing medium. With hydroponic experiments, batch experiments and pot experiments, we propose to reveal the mechanisms of antibiotics adsorption on roots and the key influencing factors, and to investigate the possible influencing mechanisms of antibiotics adsorption by roots negatively charged on antibiotics absorption by roots using streaming potential, fourier transform infrared spectrum and other characterization methods. This study can enrich the interaction theory of charged materials in the soil, and provide scientific basis for the risk assessment and pollution control of antibiotics.

抗生素用量大且代谢率低，可通过畜禽粪便农用等途径进入土壤而影响人类健康和生态环境。虽然土壤不同组分对抗生素吸附的研究已有很多，对其吸附机制的了解较为深入，但根系的带电特征对根系吸附和吸收抗生素影响的研究还不多见，其机制研究亟待深入。我们已研究证实根系的带电特征会影响根系对离子的吸附和吸收，因此我们推测根系的带电特征也会影响根系对抗生素的吸附和吸收。本项目拟选用四环素类抗生素强力霉素和喹诺酮类抗生素诺氟沙星为研究对象，以带电特征差异较大的大豆和玉米根系为吸附介质，采用水培、批平衡和盆栽试验的研究方法，结合流动电位、傅里叶红外光谱等电化学特征表征手段，探明带电根系吸附抗生素的机制及其关键影响因素，揭示带电根系吸附抗生素对其吸收抗生素的可能影响机制。该研究可丰富土壤中带电物质间相互作用的理论，为抗生素的风险评价和污染治理提供科学依据。

抗生素用量大且代谢率低，可通过畜禽粪便农用等途径进入土壤，然后通过根系进入植物体，进而通过食物链影响人类健康和生态环境。根系是抗生素进入植物体的第一道屏障，但目前根系的带电特征对根系吸附和吸收抗生素影响的研究还不多见。因此，本研究选取了四环素、强力霉素、磺胺嘧啶和诺氟沙星为研究对象，以大豆、玉米和小麦根系为吸附材料，采用水培实验、吸附解吸实验和土培试验的研究方法，重点研究了带电根系吸附抗生素的机理、环境条件对根系吸附和吸收抗生素的影响。结果表明，大豆根系所带的负电荷高于玉米和小麦，且根表含羟基、羧基、酰胺基等官能团，可通过静电吸附和络合作用等吸附抗生素；静电作用和络合作用对抗生素在根表的吸附贡献相当。抗生素在根表的吸附随抗生素初始浓度、抗生素亲水性和根系的阳离子交换量的增加而增加，随pH的改变和根系粒径的增加而降低，共存阴离子和小分子有机酸可以减少抗生素的吸附，共存阳离子对抗生素的吸附基本无明显影响。诺氟沙星在根表的吸附量最大，四环素和强力霉素其次，磺胺嘧啶最弱。对比不同植物种类时，抗生素的吸附量与抗生素对根伸长的抑制程度正相关。在研究同一植物品种时，抗生素浓度增加并未加剧对植株生长的抑制，单一抗生素与二元、三元复合抗生素对植株生物量的影响无显著差异。根表的氯化钙提取态抗生素与根系吸收及地上部累积的抗生素正相关。抗生素毒害导致根系的SOD活性明显升高，叶片叶绿素含量降低，地上部累积的抗生素增加，土壤细菌的多样性下降，但并未明显影响土壤和植物体内细菌的抗生素抗性基因基因丰度。时间较短的水培试验与时间较长的土培试验结果并不完全吻合，说明水培试验的简单体系在模拟真实土壤环境中抗生素的迁移规律有一定局限性。研究结果可丰富土壤中带电物质间相互作用的理论，为抗生素的风险评价和污染治理提供科学依据。