生物炭施用及老化对紫色土中抗生素吸附特征的影响

Effects of Biochar Application and Ageing on the Adsorption of Antibiotics in Purple Soil

以长江上游低山丘陵区典型坡耕地石灰性紫色土为研究对象,采用更接近实际田间土壤含水量条件的土水比(1 g∶1 mL,并对比1 g∶10 mL),通过批量平衡吸附实验,系统研究了施用新鲜生物炭(0%、1%和5%,质量分数)及田间老化作用(1 a)对3种抗生素(磺胺嘧啶、磺胺二甲基嘧啶和氟苯尼考)在低浓度条件下(0～5 mg·L^(-1))吸附特征的影响规律.结果表明,5种供试土壤中3种抗生素的吸附等温线均能被线性方程和Freundlich模型较好地拟合,且吸附过程中吸附自由能ΔG~θ在-0. 39～11. 53 kJ·mol^(-1)之间,表明对照土及施炭土对3种抗生素的吸附都以物理吸附为主;生物炭的施用能显著增加紫色土对3种抗生素的吸附,其中对K_(ow)值较小的磺胺二甲基嘧啶和氟苯尼考的增加幅度更大,生物炭施用比例越高则提高幅度越大;生物炭新鲜施用时效果更好,而老化后这种增强作用明显减弱.老化施炭土吸附平衡溶液的荧光峰响应强度均低于新鲜施炭土,故新鲜施炭土和老化施炭土的吸附性能差异可能是由于后者的生物炭所含不稳定、可溶解的有机质组分经老化后减少所致.

Effects of biochar application(at rates of 0%,1%,and 5%) and field ageing(for 1 a) on the sorption of three antibiotics(sulfadiazine,sulfamethazine,and florfenicol) were studied by batch equilibrium tests for a calcareous purple soil of sloping cropland,which is widely distributed in hilly areas of the upper Yangtze River. A soil-water ratio of 1 g ∶ 1 mL,which was close to the actual field soil water content condition,was adopted in the experiment,and comparisons were made to the commonly used ratio of 1 g ∶ 10 mL.The results showed that adsorption isotherm data of the studied antibiotics were fitted well by the linear and Freundlich model,and the free energy(ΔGθ) ranged from -0. 39 to 11. 53 kJ·mol-1,thus indicating that the adsorption of the three antibiotics on the control soils and biochar amended soils was mainly physical adsorption. Application of fresh biochar was found to markedly enhance the adsorption of antibiotics,especially for sulfamethazine and florfenicol of low Kow values,while such an effect was strongly weakened after ageing. The fluorescence peak response intensity of the adsorption equilibrium solution of the aged biochar amended soil was lower than that of the fresh biochar amended soil,so the difference in adsorption performance between fresh and aged biochar amended soils may have been due to the decrease of unstable and soluble organic matter in the latter’s biochar after aging.