环境因子对腐殖酸诱导双氯芬酸光降解的影响

Influence of Environmental Factors on the Humic Acid-induced Photodegradation of Diclofenac

采用腐殖酸(HA)作为溶解有机质的代表物,考察了HA浓度、pH、离子强度和溶解氧等环境因子对HA诱导双氯芬酸(DCF)光降解的影响。结果表明:DCF在纯水和HA溶液中的光化学降解过程均服从一级动力学规律。与DCF纯水溶液相比,当HA浓度由0增至5.0 mgC/L时,DCF光降解速率增大,但当HA浓度高于5.0 mgC/L时,DCF的光降解过程受到抑制。在环境浓度水平(5.0 mgC/L)下,HA对DCF光降解的诱导作用随DCF初始浓度增大而逐渐减弱。同时,HA对DCF光降解的诱导作用还受到多种水环境因子的影响,其随pH增大先减弱后增强,随离子强度增大而增强,随溶解氧浓度增大而减弱。研究结果可为环境水体中药物的归趋预测及生态风险评价提供依据。

Humic acid (HA) was selected as a representative compound for dissolved organic matter and influences of HA concentration, pH, ionic strength and dissolved oxygen on the HA-induced photodegradation of diclofenac (DCF) were studied. The results showed that the degradation of DCF obeyed the first-order kinetics model in either pure water or HA solutions. Compared to DCF in pure water, the photodegradation rate of DCF in HA solutions increased as increasing of the HA concentration in the range of from 0 to 5.0 mgC/L, while decreased as increasing of the HA concentration when higher than 5.0 mgC/L. At the environmentally relevant concentration level (5.0 mgC/L), the promotion effect of HA was weakened by higher initial concentrations of DCF. The promotion effect of HA was also closely related to water matrix properties, for example, it was initially weakened and then strengthened as the pH increased, it was strengthened as the ionic strength increased but was weakened as the dissolved oxygen concentration increased. The results of this study provided supports on the fate prediction and ecological risk assessment of pharmaceuticals in the aquatic environment.