New Insights into the Brown Carbon Chromophores and Formation Pathways for Aqueous Reactions of a-Dicarbonyls with Amines and Ammonium

Lu Yang; Jincan Shen; Ting Wang

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New Insights into the Brown Carbon Chromophores and Formation Pathways for Aqueous Reactions of a-Dicarbonyls with Amines and Ammonium

机译：New Insights into the Brown Carbon Chromophores and Formation Pathways for Aqueous Reactions of a-Dicarbonyls with Amines and Ammonium

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Aqueous-phase reactions of a-dicarbonyls with ammonium or amines have been identified as important sources of secondary brown carbon (BrC). However, the identities of most chromophores in these reactions and the effects of pH remain largely unknown. In this study, the chemical structures, formation pathways, and optical properties of individual BrC chromophores formed through aqueous reactions of a-dicarbonyls (glyoxal and methylglyoxal) with ammonium, amino acids, or methylamine at different pH's were characterized in detail by liquid chromatog-raphy-photodiode array-high resolution tandem mass spectrometry. In total, 180 chromophores are identified, accounting for 29— 79% of the light absorption of bulk BrC for different reactions. Thereinto, ISS newly identified chromophores, including 76 imidazoles, 57 pyrroles, 10 pyrazines, 9 pyridines, and 3 imidazole-pyrroles, explain additionally 9—69% of the light absorption, and these chromophores mainly involve four formation pathways, including previously unrecognized reactions of ammonia or methylamine with the methylglyoxal dimer for the formation of pyrroles. The pH in these reactions also shows remarkable effects on the formation and transformation of BrC chromophores; e.g., with the increase of pH from 5.0 to 7.0, the light absorption contributions of imidazoles in identified chromophores decrease from 72% to 65%, while the light absorption contributions of pyrazines increase from 5% to 13% for the methylglyoxal + ammonium reaction; meanwhile, more small nitrogen heterocycles transformed into oligomers (e.g., C9 and C12 pyrroles) via reaction with methylglyoxal. These newly identified chromophores and proposed formation pathways are instructive for future field studies of the formation and transformation of aqueous-phase BrC.

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来源
《Environmental Science & Technology: ES&T》 |2023年第33期|12351-12361|共11页
作者
Lu Yang; Jincan Shen; Ting Wang;
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作者单位

State Key Laboratory of Loess Science, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China;

State Key Laboratory of Loess Science, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, Chinaj University of Chinese Academy of Sciences, Beijing 100049, China;

Key Laboratory of Detection Technology R&D on Food Safety, Food Inspection and Quarantine Technology Center of Shenzhen Customs District, Shenzhen 518045, China;

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收录信息美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
原文格式 PDF
正文语种英语
中图分类环境科学、安全科学;
关键词
brown carbon; chromophore; aqueous-phase reaction; glyoxal and methylglyoxal; amines;

New Insights into the Brown Carbon Chromophores and Formation Pathways for Aqueous Reactions of a-Dicarbonyls with Amines and Ammonium

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