2,4-Dichloro-6-nitrophenol (DCNP) is a toxic nitrated byproduct of 2,4-dichlorophenol (2,4-DCP) commonly found in agriculturally impacted waters (e.g., paddy waters). DCNP has both genotoxicity and developmental toxicity and can cause endocrine disrupting effects on aquatic species. Herein, we investigated the photolysis of DCNP under UV₂₅₄ irradiation in aqueous solutions. Results show that the anionic form of DCNP (DCNP⁻) is more photoreactive than the neutral form (DCNP⁰) due to its higher molar absorption coefficient and quantum yield. The presence of Suwannee River natural organic matter (SRNOM) inhibits the direct photolysis of DCNP through light screening. A series of photoproducts were identified by solid phase extraction (SPE) and high resolution-mass spectrometry (HR-MS) analysis. The photolysis of DCNP generates several photoproducts, including photoreduction, photonucleophilic substitution, photoionization, and dimerization intermediates. The primary photochemical mechanisms include photoionization from the singlet state and heterolytic C–Cl bond splitting in the triplet state. This contribution may shed some light on the photochemical transformation and fate of DCNP in UV-based engineering systems or natural sunlit surface waters.

2,4-二氯-6-硝基苯酚 (DCNP) 是 2,4-二氯苯酚 (2,4-DCP) 的有毒硝化副产物，常见于受农业影响的水域（例如稻田水）。DCNP 具有遗传毒性和发育毒性，可对水生物种造成内分泌干扰作用。在此，我们研究了 DCNP 在 UV ₂₅₄照射下在水溶液中的光解作用。结果表明，阴离子形式的 DCNP (DCNP ^- ) 比中性形式 (DCNP ⁰) 由于其较高的摩尔吸收系数和量子产率。Suwannee River 天然有机物 (SRNOM) 的存在通过光屏蔽抑制 DCNP 的直接光解。通过固相萃取 (SPE) 和高分辨率质谱 (HR-MS) 分析鉴定了一系列光产物。DCNP 的光解产生多种光产物，包括光还原、光亲核取代、光离子化和二聚化中间体。主要的光化学机制包括单线态的光离子化和三线态的异裂 C-Cl 键分裂。这一贡献可能会揭示 DCNP 在基于紫外线的工程系统或自然阳光照射的地表水中的光化学转化和命运。