诺氟沙星在4种土壤中的吸附-解吸特征

采用批平衡吸附试验,研究了诺氟沙星在河南封丘潮土、江西鹰潭红壤、苏南常熟水稻土和南京黄棕壤等4种土壤中的吸附行为.结果表明,诺氟沙星的土壤吸附-解吸不同程度地偏离线性模型,但均可用Freundlich模型和Langmuir模型进行良好的线性拟合.其K_f值变化较大,分别为潮土82.0 L/kg、黄棕壤432 L/kg、水稻土5 677 L/kg和红壤8 790 L/kg,显示诺氟沙星在4种土壤中的吸附行为存在较大的差异.此外,诺氟沙星在4种土壤上的解吸过程存在滞后现象.其中,诺氟沙星在红壤中的滞后现象明显与其他3种土壤不同,其滞后系数至少大5倍以上.研究表明4种土壤中诺氟沙星的吸附参数K_f值与土壤pH呈极显著负相关,与土壤溶液中诺氟沙星阳离子形态比例则呈极显著正相关.在不同pH（5～9）下,红壤和水稻土的诺氟沙星吸附参数lgK_d随pH的升高先增加而后降低,黄棕壤和潮土中则不同程度地线性下降.可见,阳离子吸附可能是诺氟沙星土壤吸附的重要机理,而低pH下红壤和水稻土中诺氟沙星的吸附是阳离子吸附和土壤溶液共存阳离子竞争性吸附共同作用的结果.

Adsorption and Desorption of Norfloxacin on Four Typical Soils in China

Batch equilibrium experiments were used to reveal norfloxacin (NOR) adsorption/desorption on four kinds of soils, namely Ustic Cambosols collected form Fengqiu of Henan, Ali-Perudic Ferrosols collected from Yingtan of Jiangxi, Gleyic-Stagnic Anthrosols collected from Changshu and Udic Argosols collected from Nanjing of Jiangsu. Results show that the experimental data are best described by the Freundlich and Langmuir model, but not fitted successfully by the linear model. Different sorption behaviors of NOR are observed in the four tested soils, with the Kf values varying greatly from 82.0 L/kg (Cambosols) and 432 L/kg (Argosols) to 5677 L/kg (Anthrosols) and 8790 L/kg (Ferrosols). The apparent sorption-desorption hysteresis is found, and the hysteresis index in Ali-Perudic Ferrosols is at least as five times as those in the other tested soils. Moreover, the Kf values are in a significantly negative correlation to soil pH but significantly positive correlated to the percentage of cationic NOR in solution. Given at different pH (5~9), NOR lgKd is increased slightly and then decreased with the rise of pH in Ali-Perudic Ferrosols and Gleyic-Stagnic Anthrosols, while decreased linearly in Udic Argosols and Ustic Cambosols. It could be deduced that cation adsorptions is the predominant sorption mechanism of NOR on the four soils, and at low pH, NOR cation adsorption in Ali-Perudic Ferrosols and Gleyic-Stagnic Anthrosols is affected by the competitive adsorption of co-existing cations in soil solution.