海产养殖常用药物三氯异氰尿酸的光化学降解行为

The Photochemical Degradation of a Typical Aquaculture Drug Trichloroisocyanuric Acid

[目的]含氯杀菌剂是渔业生产中广为应用的水体消毒药剂,光化学降解是其在水中分解的主要途径和速率限制步骤之一。研究典型海产养殖药物的光化学降解行为,有助于保证其施用效果及降低海产品农残。选择海产养殖常用药物三氯异氰尿酸(TCCA),在不同的光照强度下测定其反应速率。选择较优的光照条件,在不同的pH值、不同的温度条件下,通过离子色谱法对水中各时间段的氯离子浓度进行测定,研究其水中光化学降解行为。[结果]不同的光照强度和条件下,TCCA中氯离子解离速度变化较为明显,且解离速度随波长的增加而减小。紫外光照射条件下,酸性溶液抑制解离,碱性溶液促进解离;温度升高有利于药物的降解。TCCA的降解基本符合一级动力学,且时段不同反应速率常数不同。[结论]水产养殖的用药杀菌过程中,应该尽量使水质保持中性。对于海产养殖而言,由于通常情况下海水的pH值显弱碱性,所以在使用药物时应尽量在晴天使用,此时的光照效果及紫外强度均较大,这样既能使药物完全发挥效果也会使药物尽快解离。

[Aims] As one of the main decomposing pathway of chlorine-containing fungicides, photochemical degradation does great effect on its duration and residue, which makes it important to study the degradation behavior and dynamics. A typical fungicide was widely used in fishing, i.e., Trichloroisocyanuric Acid （TCCA） was chosen in this experiment to study the photochemical degradation. This work measured chloride ion concentration by ion chromatography in different light intensity conditions. Furthermore, based on the best lighting condition, TCCA＇s degradation in different pH values and temperature conditions were discussed. [Results] The results showed that the dissociation rate of chloride ion dropped with the increase of the wavelength of the light. Under the best lighting condition （UV）, TCCA degraded in different pH conditions and temperature conditions. Dissociation inhibition was appeared under acid circumstance showed, while alkaline solution promoted dissociation, and the increase of temperature was beneficial to the degradation of TCCA. Degradation of TCCA was basically in accordance with first-order kinetics, and in different period reaction rate constant was different. [Conclusions] Chlorine-containing fungicide should be added under neutral circumstance in aquaculture. As to usually alkaline mariculture circumstance, the use of chlorine-containing fungicide should be used during better lighting and bigger UV intensity conditions, to get better efficacy and less residues.