The acidity of atmospheric particles and clouds
The acidity of atmospheric particles and clouds
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DOI：
10.5194/acp-20-4809-2020
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发表时间：
2020-04-24
影响因子：
6.3
通讯作者：
Zuend, Andreas
中科院分区：
文献类型：
--
作者：
Pye, Havala O. T.;Nenes, Athanasios;Zuend, Andreas
酸度，定义为pH值，是水化学的中心成分。在大气中，凝聚相(气溶胶颗粒、云水和雾滴)的酸度控制着半挥发性气体(如HNO3、NH3、HCl、有机酸和碱)的相分配以及化学反应速度。它对大气中污染物的寿命、沉积和人类健康都有影响。尽管它在大气过程中起着基本作用，但直到最近，该领域关于颗粒酸度的研究才有所增加。即使有了这样的增长，许多细颗粒pH值的估计也必须基于热力学模型计算，因为没有可操作的技术来直接测量。目前的信息表明，酸性细颗粒无处不在，但受观测约束的pH估计在空间和时间覆盖范围上是有限的。云和雾通常也是酸性的，但程度低于颗粒物，其PH值范围对人为排放的硫磺和氮氧化物以及环境氨非常敏感。历史测量表明，近几十年来，由于对人为排放的控制，云雾液滴的pH值发生了变化，而气溶胶颗粒有限的趋势数据表明，由于关键酸和碱的半挥发性以及颗粒中的缓冲作用，酸度可能相对恒定。本文综述了关于大气凝聚相，特别是粒子和云滴的酸度的知识现状。它包括估算酸度和酸碱度的建议、标准命名法、基于观测的当前酸碱度估计值的综合以及局部和全球尺度上的新模型计算。
Acidity, defined as pH, is a central component of aqueous chemistry. In the atmosphere, the acidity of condensed phases (aerosol particles, cloud water, and fog droplets) governs the phase partitioning of semivolatile gases such as HNO3, NH3, HCl, and organic acids and bases as well as chemical reaction rates. It has implications for the atmospheric lifetime of pollutants, deposition, and human health. Despite its fundamental role in atmospheric processes, only recently has this field seen a growth in the number of studies on particle acidity. Even with this growth, many fine-particle pH estimates must be based on thermodynamic model calculations since no operational techniques exist for direct measurements. Current information indicates acidic fine particles are ubiquitous, but observationally constrained pH estimates are limited in spatial and temporal coverage. Clouds and fogs are also generally acidic, but to a lesser degree than particles, and have a range of pH that is quite sensitive to anthropogenic emissions of sulfur and nitrogen oxides, as well as ambient ammonia. Historical measurements indicate that cloud and fog droplet pH has changed in recent decades in response to controls on anthropogenic emissions, while the limited trend data for aerosol particles indicate acidity may be relatively constant due to the semivolatile nature of the key acids and bases and buffering in particles. This paper reviews and synthesizes the current state of knowledge on the acidity of atmospheric condensed phases, specifically particles and cloud droplets. It includes recommendations for estimating acidity and pH, standard nomenclature, a synthesis of current pH estimates based on observations, and new model calculations on the local and global scale.