Mechanistic Aspects Regarding The Ultraviolet Degradation Of Polychlorinated Biphenyls In Different Media: Insights From Carbon And Chlorine Isotope Fractionation
ENVIRONMENTAL SCIENCE & TECHNOLOGY(2021)
摘要
In this study, the carbon and chlorine isotope fractionation during ultraviolet-photolysis of polychlorinated biphenyls (PCBs, including PCB18, PCB77, PCB110, and PCB138) in n-hexane (Hex), methanol/water (MeOH/H2O), and silica gel was first investigated to explore their mechanistic processes. We observed a significant variation in Lambda(Cl-C) (epsilon(Cl/)epsilon(C)) for the same PCBs in different photochemical systems, implying that PCB degradation processes in various photoreaction systems could differ. Although all substrates showed normal apparent carbon/chlorine kinetic isotope effects (C-/Cl-AKIE >1), the putative inverse C-AKIE of nondechlorinated pathways was suggested by C-13 depletion of the average carbon isotope composition of PCB138 and corresponding dechlorinated products in MeOH/H2O, which might originate from the magnetic isotope effect. Significant negative correlations were found between C-AKIE and relative disappearance quantum yields ("Phi") of ortho-dechlorinated substrates (PCB18, PCB110, and PCB138) in Hex and MeOH/H2O. However, the C-AKIE and "Phi" of PCB77 (meta/para-dechlorinated congener) obviously deviated from the above correlations. Furthermore, significantly different product-related carbon isotope enrichment factors of PCB77 in Hex were found. These results demonstrated the existence of dechlorination position-specific and masking effects in carbon isotope fractionations.
更多查看译文
关键词
uv-photodegradation, polychlorinated biphenyls, compound-specific isotope analysis, carbon isotope fractionation, chlorine isotope fractionation, disappearance quantum yields, mechanistic process
AI 理解论文
溯源树
样例
![](https://originalfileserver.aminer.cn/sys/aminer/pubs/mrt_preview.jpeg)
生成溯源树,研究论文发展脉络
Chat Paper
正在生成论文摘要