浅层地下水中磺胺嘧啶与胡敏酸相互作用及相态间分布特征

研究抗生素在浅层地下水中不同相态间的分布特征,对于了解抗生素的行为特征及评估其危害具有重要的意义。本文利用三维荧光淬灭法研究了胡敏酸(humic acid, HA)对磺胺嘧啶(sulfadiazine, SD)在地下水中不同相态间分布规律的影响及相互作用,探讨了HA浓度、pH值、温度对SD在不同相态间分布的影响,对淬灭过程进行拟合并计算了分配系数、淬灭参数以及热力学参数。结果表明:地下水中SD浓度(0.5 mg/L)较低时或者HA浓度增加(0~20 mg/L)时,HA可显著促进悬浮相中SD比例的增加;SD对HA的淬灭机理为形成复合物的单一静态淬灭,结合位点数均约为1,荧光淬灭常数K_sv为5.271×10³ L/mol,淬灭速率常数K_q为5.271×10¹¹ L/(mol·s),属于自发的放热过程;体系处于低温(15 ℃)、弱碱性(8~10)pH值环境时,SD对HA的淬灭作用最强,HA对SD进入悬浮相的促进作用最明显。

Effect of humic acid on the phase distribution of sulfadiazine in shallow groundwater

It is important for exploring the behavioral characteristics of antibiotics and assessing their hazards by studying the distribution characteristics of antibiotics in shallow groundwater. In this paper, the interaction of sulfadiazine (SD) with humic acid (HA) and the effect of HA on the phase distribution of SD in shallow groundwater were studied by three-dimensional fluorescence quenching method. The effects of HA concentration, pH and temperature on SD in different phases were discussed, and the distribution coefficient as well as quenching and thermodynamic parameters for the quenching process were calculated. The results showed that both low SD (0.5 mg/L) and elevated HA (0-20 mg/L) can significantly increase SD partition in the suspension phase. The mechanism of HA fluorescence quenching by SD was to form HA·SD complex via a single static process. The number of binding site was 1; the quenching constant K_sv was 5.271×10³ L/mol; and the quenching rate constant K_q was 5.271×10 ¹¹ L/(mol·s). It showed the HA-SD interaction was a spontaneous exothermic process. In a low-temperature (15 ℃), neutral or weakly alkaline (pH 8-10) environment, antibiotics had the strongest quenching effect on HA, and, accordingly, HA had the most obvious promoting effect on SD entering the suspension phase.