Pyrimidine and purine bases (adenine, cytosine, guanine and thymine) are important precursors of organic chloramines (OC) and disinfection by-products (DBPs) during chlor(am)ination. In this study, OC and DBP formation derived from pyrimidine and purine bases during chlor(am)ination, post-chlor(am)ination after pretreated by UV alone and UV/chlorination were systematically investigated with ultraviolet light-emitting diodes (UV-LEDs, 265 and 275 nm) and low pressure mercury lamp (LPUV, 254 nm). The results revealed that higher OC formation was observed during chlorination than that during chloramination of pyrimidine and purine bases. The degradation of pyrimidine and purine bases followed the pseudo-first-order kinetics. Both solution pH and UV wavelength played vital influence on the degradation of pyrimidine and purine bases. In terms of fluence-based rate constants (k_obs), the degradation rates of pyrimidine and purine bases decreased in the order of 275 nm > 265 nm > 254 nm in alkaline conditions. The synergistic effects of k_{obs, chlorine,} k_{obs, •OH} and k_{obs, RCS} contributed to the differences of pyrimidine and purine bases degradation at different pH values and UV wavelengths. A vital suppression of OC formation was observed during post-chlorination after pretreated by 275 nm UV-LED/chlorination. In addition, compared with LPUV (254 nm), less DBP formation was observed at UV-LED (275 nm), especially during the UV/chlorine process. The phenomena obtained in this study indicated that 275 nm UV-LED combined with chlorine could be a preferred method to promote pyrimidine and purine bases degradation and control OC and DBP formation in practical water treatment.

嘧啶和嘌呤碱基（腺嘌呤、胞嘧啶、鸟嘌呤和胸腺嘧啶）是氯（胺）化过程中有机氯胺 (OC) 和消毒副产物 (DBP) 的重要前体。在这项研究中，使用紫外发光二极管（UV-LEDs）系统地研究了在氯（氨）化过程中、单独用紫外线预处理后的氯（氨）化后和紫外线/氯化过程中嘧啶和嘌呤碱衍生的 OC 和 DBP 的形成。 , 265 和 275 nm) 和低压汞灯 (LPUV, 254 nm)。结果表明，在氯化过程中观察到的 OC 形成比在嘧啶和嘌呤碱的氯胺化过程中形成的 OC 更高。嘧啶和嘌呤碱基的降解遵循伪一级动力学。溶液 pH 值和 UV 波长对嘧啶和嘌呤碱的降解起着至关重要的影响。k _obs )，在碱性条件下，嘧啶和嘌呤碱基的降解率以 275 nm > 265 nm > 254 nm 的顺序降低。k _obs、氯、 k _obs、•OH和k _obs、RCS的协同作用导致嘧啶和嘌呤碱在不同 pH 值和 UV 波长下降解的差异。在经过 275 nm UV-LED/氯化预处理后，在后氯化过程中观察到 OC 形成的重要抑制。此外，与 LPUV (254 nm) 相比，在 UV-LED (275 nm) 处观察到的 DBP 形成较少，尤其是在 UV/氯工艺过程中。本研究中获得的现象表明，275 nm UV-LED 与氯结合可能是在实际水处理中促进嘧啶和嘌呤碱降解和控制 OC 和 DBP 形成的首选方法。