不同类型土壤及黑炭对诺氟沙星的吸附

Norfloxacin Sorption to Environmental Black Carbon in Different Types of Soils

通过375℃热氧化方法,对中国不同区域6种土壤中的黑炭进行了分离定量,并研究了土壤及黑炭对诺氟沙星的吸附行为。结果表明,土壤中黑炭占有机碳含量的10.5%～33.6%,平均值为20.0%。所有土壤和黑炭样品对诺氟沙星的吸附均表现为非线性吸附,Freundlich模型对吸附数据的拟合效果很好。与原始土壤相比,黑炭对诺氟沙星的吸附非线性更强,吸附参数n值为0.343～0.663,说明黑炭比土壤具有更多的非均质性的吸附位。在给定液相平衡质量浓度ce下,黑炭的吸附能力参数Koc值较土壤样品高,表明黑炭对诺氟沙星的吸附能力更强。诺氟沙星的Kf值与土壤有机碳含量存在很好的正相关关系(R=0.980,p<0.01),揭示了土壤有机碳含量在诺氟沙星吸附能力中的重要性。相反,Kf值与土壤pH值表现出一定的负相关关系(R=0.744,p<0.05)。诺氟沙星的n值与土壤的黑炭相对含量(BC/TOC)显著负相关(R=0.980,p<0.01),揭示了土壤有机质中的黑炭在诺氟沙星吸附非线性中的支配作用。本研究为预测抗生素在土壤环境中的分布特征和最终归趋提供了理论依据。

Black carbon（BC） in six soils from different areas in China,were isolated upon treatments using a combustion method at 375 ℃ and their sorption isotherms for norfloxacin（NOF） were determined.BC accounted for 10.5%—33.6 % of the total organic carbon（TOC） in soils with an average of 20.0 %.All sorption isotherms of NOF were nonlinear and fitted well by the Freundlich model.Compared to soils,BC exhibited more nonlinear sorption with n values of 0.343～0.663,indicating that BC possessed more heterogeneous sorption sites for NOF.At a given ce,the BC had higher Koc value than the original soils,revealing a higher NOF sorption capacity for BC.There was a positive relation between Kf values and TOC（R=0.980,p0.01）,revealing the importance of TOC in NOF sorption capacity.However,a negative correlation between Kf values and pH value was observed（R=0.744,p0.05）.Moreover,a negative relation was found between n values and BC/TOC content of the original soils（R=0.980,p0.01）,indicating the dominance of BC in NOF sorption nonlinearity.Our finding can provide more information for predicting the distribution and fate of NOF in natural environment.