Mechanistic Aspects Regarding the Ultraviolet Degradation of Polychlorinated Biphenyls in Different Media: Insights from Carbon and Chlorine Isotope Fractionation
| Autor: | Zihe Ren, Yankuan Tian, Yin-E Liu, Chuhong Zhu, Ya Cao, Shutao Gao, Bi-Xian Mai, Chenchen Huang, Yan-Hong Zeng, Xiao-Jun Luo |
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| Rok vydání: | 2021 |
| Předmět: |
Carbon Isotopes
Isotopes of chlorine chemistry.chemical_element General Chemistry Fractionation Chemical Fractionation 010501 environmental sciences Polychlorinated Biphenyls 01 natural sciences Carbon chemistry.chemical_compound chemistry Isotopes of carbon Environmental chemistry Kinetic isotope effect Chlorine Environmental Chemistry Methanol Magnetic isotope effect 0105 earth and related environmental sciences |
| Zdroj: | Environmental Science & Technology. 55:7731-7740 |
| ISSN: | 1520-5851 0013-936X |
| DOI: | 10.1021/acs.est.1c00726 |
| Popis: | 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 ΛCl-C (eCl/eC) 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 13C 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 ("Φ") of ortho-dechlorinated substrates (PCB18, PCB110, and PCB138) in Hex and MeOH/H2O. However, the C-AKIE and "Φ" 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. |
| Databáze: | OpenAIRE |
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