Guangxi Key Laboratory of Agric-Environment and Agric-products Safety, National Demonstration Center for Experimental Plant Science Education, College of Agriculture, Guangxi University, Nanning, Guangxi, 530004, China.
Chemosphere. 2021 Jul;274:129655. doi: 10.1016/j.chemosphere.2021.129655. Epub 2021 Jan 25.
To reveal the adsorption mechanisms of imazamox, imazapic, and imazethapyr on sediment and batch experiments were carried out in this study. The adsorption kinetics of three imidazolinone herbicides on sediment were accurately described by the pseudo-second-order kinetic model(R > 0.9004). The values of adsorption capacity (Q) were ranged from 0.0183 to 0.0859 mg kg for three herbicides. Adsorption equilibrium was reached within 24 h for three herbicides on sediment, and well fitted by the Freundlich model(R > 0.9561). The K of values for adsorption obtained sediment samples were ranged from 0.2501 to 1.322 L mg kgfor three herbicides. These results indicated that intraparticle diffusion and external mass transport were the main rate controlling steps of the adsorption of herbicides on sediment and that the chemical adsorption was dominant during the adsorption processes. The calculated hysteresis coefficient H were 0.9422,0.7877 and 0.744 for imazmox, imazapic and imazethapyr in raw sediment, respectively, indicating that there is a hysteresis in desorption. The influences of solution pH and sediment organic carbon content on the imidazolinone herbicide adsorption behaviors were also examined. Which shown that the adsorption process for herbicides was highly pH-dependent and adsorption efficiency was closely related to the organic matter content of the sediment, suggesting that electrostatic interactions played crucial roles in the adsorption behavior between sediment and imidazolinone herbicides, and the herbicides were mostly absorbed by the amorphous materials of sediment. These research findings are important for assessing the fate and transport of imidazolinone herbicides in water-sediment systems.
为揭示咪草烟、咪唑乙烟酸和咪草烟在沉积物中的吸附机制，本研究进行了吸附动力学和等温吸附实验。三种咪唑啉酮类除草剂在沉积物上的吸附动力学过程可以很好地用准二级动力学模型来描述（R＞0.9004）。三种除草剂在沉积物上的吸附量（Q）范围为 0.0183-0.0859mgkg。三种除草剂在 24h 内达到吸附平衡，且很好地符合 Freundlich 模型（R＞0.9561）。吸附平衡常数（K）范围为 0.2501-1.322Lmgkg。这些结果表明，内扩散和外部传质是除草剂在沉积物上吸附的主要速率控制步骤，且化学吸附是吸附过程中的主要作用机制。在原状沉积物中，咪草烟、咪唑乙烟酸和咪草烟的解吸滞后系数（H）分别为 0.9422、0.7877 和 0.744，表明解吸存在滞后现象。此外，还考察了溶液 pH 和沉积物有机碳含量对三种咪唑啉酮类除草剂吸附行为的影响。结果表明，除草剂的吸附过程对 pH 高度依赖，且吸附效率与沉积物中有机质含量密切相关，这表明静电相互作用在除草剂与沉积物之间的吸附行为中起关键作用，且除草剂主要被沉积物中的无定形物质所吸附。这些研究结果对于评估水-沉积物系统中咪唑啉酮类除草剂的归趋和传输具有重要意义。
