两种微藻胞外分泌物与NO2-、NO3-对2，4-D光解的影响

在模拟太阳光照射下,利用旋转式光化学反应装置,研究了海水小球藻(Chlorella vulgaris)和新月菱形藻(Nitzschia closterium)的胞外分泌物(EOM),以及分别在NO-2或(和)NO-3共存条件下对2,4-二氯苯氧乙酸(2,4-D)光解的影响.实验结果表明,2,4-D在海水小球藻和新月菱形藻EOM及分别在NO-2、NO-3共存下的光解过程均符合准一级动力学反应.研究发现,2,4-D的光解速率随海水小球藻和新月菱形藻EOM浓度的增加而减小,表明这两种微藻EOM可抑制海水中2,4-D的光解.当在微藻EOM溶液中分别加入不同浓度的NO-2或NO-3后,微藻EOM对2,4-D光解的抑制作用减弱,且随着NO-2和NO-3浓度的增加,2,4-D光解速率明显增加.特别是当微藻EOM与NO-2或NO-3三者共存时,可进一步促进2,4-D的光解.

Influence of two microalgae extracellular organic matters, NO2- and NO3- on photodegradation of 2,4-Dichlorophenoxyacetic acid

The photolysis of 2,4-Dichlorophenoxyacetic acid (2,4-D) was investigated in Chlorella vulgaris or Nitzschia closterium extracellular organic matter (EOM) solutions, and the influence of coexistence with NO₂^- and NO₃^- was also studied in seawater using a rotary photochemical reaction device under the simulated solar light irradiation. The experimental results showed that the photolysis process of 2,4-D was accorded with the pseudo first order kinetics equation both in Chlorella vulgaris or Nitzschia closterium EOM and in the coexistence solutions with different concentrations of NO₂^- and NO₃^-. It has been found that the photolysis rate constant of 2,4-D decreased with the increasing concentration of Chlorella vulgaris or Nitzschia closterium EOM, which indicated that these two species of microalgae EOM could inhibit the 2,4-D photolysis. However, when NO₂^- or NO₃^- was added in the microalgae EOM solution, the photolysis rate constant of 2,4-D increased, which indicated that the inhibition of microalgae EOM decreased with the increasing concentration of NO₂^- or NO₃^-. Especially, the photolysis rate constant of 2,4-D could be further promoted under the coexistence of microalgae EOM with higher concentration of NO₂^- and NO₃^-.