溶解性有机质对罗红霉素光降解的影响研究

近年来,罗红霉素(ROX)因其用量大、检出频率高和生态风险大引起了广泛关注.本文主要研究了环境pH条件下不同的溶解性有机质(DOM),包括富里酸(PLFA)、腐殖酸(SRHA)和天然有机质(SRNOM)对罗红霉素光降解的影响及主要活性物种对其光降解的贡献.结果表明:纯水中罗红霉素可发生自敏化光降解,在pH 6～8条件下,罗红霉素光降解的一级反应速率常数为0.0033～0.0049 h~(-1).DOM促进了罗红霉素光降解,其促进效果从大到小为PLFASRNOMSRHA.DOM共存时罗红霉素光降解的反应速率常数随pH增加而增加,在pH 6时为0.0145～0.0266 h~(-1),在pH 8时为0.0273～0.0577 h~(-1).通过异丙醇淬灭实验发现,羟基自由基(·OH)对罗红霉素光降解起主要贡献,其贡献率在pH 6时为83.45%～98.70%,在pH 8时降低至76.76%～78.02%;3种DOM体系中产生的单态氧(~1O_2)的稳态浓度在(5.15～7.86)×10~(-14) mol·L~(-1)范围内;在pH 6、7和8的条件下,~1O_2与罗红霉素的二级反应速率常数分别为2.27×10~5、1.96×10~6和1.51×10~7 L·mol~(-1)·s~(-1).~1O_2对罗红霉素的光降解的贡献随pH升高而升高,在pH 6时为0.21%～0.43%,在pH 8时为4.85%～11.33%.

Effect of dissolved organic matter on the photodegradation of roxithromycin

In recent years, roxithromycin (ROX) has attracted wide attention mainly due to its large usage, high detection rate in aquatic environment and the potential ecological risk. This study investigated the effects of different dissolved organic matter (DOM), including Pony Lake fulvic acid (PLFA), Suwannee River humic acid (SRHA) and natural organic matter (SRNOM), on the degradation of ROX under ambient pH conditions, and corresponding contribution of primary reactive species. The results showed that ROX degraded by self-sensitization in pure water, and the apparent reaction rate constant was determined as 0.0033~0.0049 h^-1 under pH 6~8. DOM was found to promote the degradation of ROX with the promoting rate in the order of PLFA > SRNOM > SRHA. The ROX degradation rate constants in the presence of DOM increased with solution pH, with the values of 0.0145~0.0266 h^-1 at pH 6 and 0.0273~0.0577 h^-1 at pH 8. Based on the isopropanol quenching experiment,·OH was found to play the most important role in the degradation of ROX, with the contribution of 83.45%~98.70% at pH 6 and 76.76%~78.02% at pH 8. In addition, the singlet oxygen (¹O₂) also formed in DOM system with the steady state concentration of (5.15~7.86)×10^-14 mol·L^-1. The second order rate constants between ¹O₂ and ROX were determined to be 2.27×10⁵, 1.96×10⁶ and 1.51×10⁷ L·mol^-1·s^-1 at pH 6, 7 and 8, respectively. The contribution of ¹O₂ on the degradation of ROX increased with solution pH, which accounted for 0.21%~0.43% at pH 6 and 4.85%~11.33% at pH 8.