大气中的棕色碳在中国雾中以二次形成为主
Xiaodi Liu1, Can Wu1, Zheng Li1
1Key Laboratory of Geographic Information Science of the Ministry of Education, School of Geographic Sciences, East China Normal University, Shanghai 200241, China.
The Science of the total environment
|June 16, 2024
概括
棕色碳 (BrC) 显著影响气候. 这项研究表明,二次反应,特别是涉及有氧化有机气溶 (OOA),是中国雾事件中BrC光吸收的主要驱动因素.
科学领域:
- 大气化学 大气化学
- 气溶科学 气溶科学
- 环境科学 环境科学
背景情况:
- 棕色碳 (BrC) 是一种吸光有机气溶 (OA),在大气辐射强迫中起着至关重要的作用.
- 对BrC的物理化学性质的有限理解阻碍了对其环境影响的准确评估.
研究的目的:
- 在中国长江三角洲 (YRD) 地区冬季调查BrC的光学特征和化学成分.
- 为了确定不同OA因子在不同湿度条件下对BrC光吸收的贡献.
主要方法:
- 使用高分辨率气溶质谱法 (HR-AMS) 来分析PM$_{2.5}$的化学成分.
- 紫外线光谱法用于测量BrC的光学特性.
- 在相对湿度低 (<80%RH) 和高 (>80%RH) 的条件下分析BrC贡献.
主要成果:
- 在PM$_{2.5}$中的BrC主要是由水溶性有机物,包括较少氧化氧化OA (LO-OOA),较多氧化氧化OA (MO-OOA),化石燃料OA (FFOA) 和生物质燃烧OA (BBOA).
- 在365nm时,MO-OOA和BBOA的光吸收率最高,质量吸收系数 (MAC) 分别为0.74±0.04和0.73±0.03m$^2$g$^{-1}$.
- 在高RH雾时期,MO-OOA占总光吸收的62%,而在低RH时期,LO-OOA贡献了44%.
结论:
- 二次反应,特别是涉及LO-OOA和MO-OOA,是YRD地区雾事件期间BrC光吸收的主要来源,平均占75%以上.
- 氨显著增强了BrC的形成和光吸收,特别是在高RH雾条件下.
- 这些发现强调了二次气溶形成过程在确定中国BrC气候影响方面的重要性.
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