中文摘要：

在模拟日光照射下,考察了氧氟沙星和诺氟沙星在纯水和天然水中的光降解行为,结果表明,氧氟沙星和诺氟沙星的光降解随p H增加（p H=4—10）先增快后减慢,两种抗生素以两性离子形态存在时光解最快.氧氟沙星和诺氟沙星在天然水中的光降解显著慢于其在相似p H条件下（p H=8）纯水中的光降解,天然水中的溶解性物质对两种抗生素的光降解总体表现为抑制作用.以Suwannee河富里酸为例,研究了溶解性有机质（DOM）的影响机制,发现淡水中高浓度的DOM主要通过竞争光吸收抑制氧氟沙星和诺氟沙星的光解,而海水中低浓度的DOM可以通过淬灭活性物种抑制两种抗生素的光解.天然水中的金属阳离子（Ca2＋和Fe3＋）和NO-3分别通过配位作用和光致生成·OH影响氧氟沙星和诺氟沙星的降解.由此可见,氧氟沙星和诺氟沙星在天然水中的光化学行为依赖于水体p H值和溶解性物质的综合影响.

英文摘要：

The photochemical transformation of ofloxacin and norfloxacin in pure and natural water was investigated under the simulated sunlight irradiation. The results show that the photolytic rate constants of ofloxacin and norfloxacin increased to a peak and then decreased with pH increasing from 4 to 10. Ofloxacin and norfloxacin in zwitter ionic forms photodegraded the fastest. The photodegradation rates of ofloxacin and norfloxacin in natural water were slower than that in pure water with similar pH condition （pH = 8 ）. The water constituents in natural water played an inhibiting role. The Suwannee River fulvic acid was adopted as a model to investigate the effect mechanisms of dissolved organic matter （DOM）. The results show that high concentration DOM in freshwater slowed the photodegradation of ofloxacin and norfloxacin mainly by competitive light absorption, and the inhibition of low concentration DOM in seawater is due to the quenching of reactive species photogenerated by antibiotics. Metal cations （e.g., Ca2＋ and Fe3） and NO3 in natural water affected the photodegradation of ofloxacin and norfloxacin by complexation and photogeneration of ＂OH, respectively. Thus, the photodegradation of ofloxacin and norfloxacin in natural water depends on the integrative influence of pH and the water constituents.