磺胺嘧啶在覆铁石英砂中迁移特征及数值模拟

为了探讨磺胺类抗生素在土壤中的迁移特征，以磺胺嘧啶（SDZ）为研究对象，以石英砂（QS）为介质，采用高温加热法制备覆铁石英砂（IOCS），通过土柱出流实验，研究不同铁含量和离子强度对SDZ在IOCS中迁移的影响，并利用Hydrus-1D软件对结果进行模拟.土柱出流实验结果表明，随着IOCS表面铁含量增加，其表面粗糙度越大，且表面携带的正电荷越多，SDZ越容易吸附在IOCS表面，其相对浓度峰值越低，不利于SDZ的迁移；离子强度的增加，促进了SDZ在QS和IOCS中的迁移，这主要是受静电作用、表面络合作用和竞争吸附作用的控制.模拟结果显示，非平衡单点吸附模型（OSM）可以较好地模拟不同铁含量和离子强度下SDZ的迁移过程，拟合曲线与实测曲线几乎重合，R²>0.97，RMSE<0.032，拟合效果较好；反演所得吸附分配系数k_F随着铁含量的增加而增加，随离子强度的增加而减小；阻滞因子R_d与其呈现相同的变化趋势；吸附特征参数β>1，而一阶动力学速率常数α均较小.

Characteristics of sulfadiazine migration in iron oxide coated sand and a comparison with simulation results

In order to investigate the migration characteristics of sulfonamide antibiotics in soil, sulfadiazine (SDZ) was used as a model component, and quartz sand (QS) was used as a medium to obtain iron oxide coated sand (IOCS). The effects of iron content and ionic strength on the migration of SDZ in IOCS were studied through column experiments, and the obtained results were simulated by Hydrus-1D software. The results of column experiments showed that the migration of SDZ was inhabited with an increase in the iron content on the surface of IOCS. The more the iron content, the higher the roughness, and the more the positive charge is carried through, which is beneficial to the adsorption of SDZ. An increase in the ionic strength promoted the migration of SDZ in QS and IOCS, which is mainly controlled by electrostatic interaction, surface complexation, and competitive adsorption. The migration process of SDZ under different iron contents and ionic strength can be better simulated by non-equilibrium one-site sorption model (OSM) in Hydrus-1D. The fitted curve is in agreement with the measured curve, where R²>0.97 and RMSE<0.032. The adsorption distribution coefficient, k_F increased with an increase in iron content and decreased with an increase in ionic strength. The retardation factor, R_d showed the same trend as k_F. The adsorption characteristic parameter β>1, and the first-order kinetic rate constant α were observed to be small.