Abstract: The photochemical degradation of p-nitrophenol and 2,4-dinitrophenol in both natural seawater and artificial seawater was studied under the irradiation of mixed light sources(ultraviolet lamp/high pressure mercury lamp). The photolysis of the two nitrophenols was influenced by various factors including medium, heavy metal ions and photosensitizer. The photolysis of the two nitrophenols in natural seawater was faster than in artificial seawater, presumably due to the effect of inherent photosensitizers in natural seawater. The addition of Cu²⁺, Pb²⁺ or Cd²⁺ into the seawater solutions obviously increased the photolysis rate of the nitrophenols. Interestingly, we found that the presence of anthroquinone could accelerate the photolysis of p-nitrophenol in natural seawater but had almost no impact on the photolysis of 2,4-dinitrophenol. The half-lives of the photoreactions in natural seawater under our conditions were 40-54 min for p-nitrophenol and 37-69 min for 2,4-dinitrophenol, respectively. Our study suggests that photochemical degradation is an important removal pathway for the nitrophenols in seawater.

Key words: p-Nitrophenol, 2,4-Dinitrophenol, Photochemical oxidation, Seawater