pH依赖的水相棕色碳形成:速度常数和太阳吸收和大气光化学的影响
Lu Yang1,2, Ru-Jin Huang1,3,2, Wei Yuan1
1State Key Laboratory of Loess Science, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China.
Environmental science & technology
|January 3, 2024
概括
二次棕色碳 (BrC) 是由α-二碳基与氨基的反应形成的. 这项研究量化了BrC形成动力学和pH效应,揭示了对于大气化学至关重要的pH依赖光吸收.
科学领域:
- 大气化学 大气化学
- 有机气溶形成有机气溶形成
- 频谱学是一种光谱学.
背景情况:
- α-二碳酸与氨基/氨的水相反应是二次棕色碳 (BrC) 的关键来源.
- BrC形成的动力学和pH依赖性仍然不明,影响大气模型.
- 棕色碳显著影响地球的辐射平衡和大气光化学.
研究的目的:
- 为了研究BrC形成的动力学从水性反应的glyoxal和甲基glyoxal与各种化合物 (氨,氨基酸,胺).
- 为了确定pH对BrC形成速率和光学特性的影响.
- 量化pH取决于BrC对太阳辐射吸收和大气光解速率的影响.
主要方法:
- 进行了大量的水相反应动力学实验,涉及多种pH值的α-二碳和化合物.
- 在300-500nm范围内测量产生的BrC的光吸收,以确定吸收性.
- 对于BrC生产的pH参数化速率常数 (kBrCII) 的推导.
主要成果:
- 对于BrC形成的确定的pH参数化速率常数:log10 (((kBrCII) = (1.0 ± 0.1) ×pH - (7.4 ± 1.0) 对于glyoxal和log10 (((kBrCII) = (1.0 ± 0.1) ×pH - (6.3 ± 0.9) 对于methylglyoxal.
- 观察到BrC的吸收性随着pH值呈指数增大,pH值≥6.5的甲基酸衍生BrC具有与燃烧产生的BrC相似的特性.
- 证明了在pH 7.0下形成的BrC吸收的太阳辐射比pH 5.0高14-16倍,可能将O3和NO2光解速率降低一个数量级.
结论:
- BrC形成动力学强烈依赖pH值,主要由核友性添加途径驱动.
- BrC太阳吸收的显著pH驱动变化影响大气辐射转移和光化学过程.
- 对于气候和空气质量建模而言,对pH依赖的BrC形成的准确表示至关重要.
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