Composition and properties of atmospheric particles in the eastern Atlantic and impacts on gas phase uptake rates
Composition and properties of atmospheric particles in the eastern Atlantic and impacts on gas phase uptake rates
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DOI：
10.5194/acp-9-9299-2009
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发表时间：
2009-12
影响因子：
6.3
通讯作者：
James Allan;D. Topping;Nicholas Good;M. Irwin;Michael Flynn;P. I. Williams;H. Coe;A. Baker-A.-Bake
中科院分区：
文献类型：
--
作者：
James Allan;D. Topping;Nicholas Good;M. Irwin;Michael Flynn;P. I. Williams;H. Coe;A. Baker-A.-Bake
海洋气溶胶成分仍然是气候和大气化学研究中的一大不确定因素。除了它们的物理尺寸和化学成分外，吸湿性也起着重要作用，增加了颗粒的表面积和散射潜力。在海洋环境中的气溶胶组成和模拟以及海洋边界层中的活性卤素实验期间，在RRS发现号上和佛得角大气观测站同时进行了气溶胶测量。这些措施包括在线测量数量和干尺寸，以及用于离线分析水离子的批量收集。此外，发现号上的测量包括使用Aerodyne气溶胶质谱仪在线测量成分，使用多角度吸收光度计测量光吸收，使用加湿差分迁移率粒子分析仪(DMPS)和光学粒子计数器(OPC)测量环境湿度粒度分布，以及使用吸湿性串联差分迁移率分析仪(HTDMA)测量吸湿性。在发现号靠近佛得角期间，发现平台之间在海盐(Ss)和非海盐(NSS)模式方面有很好的一致性，并显示出与遥远的海洋空气一致的成分。当发现号接近非洲海岸时，气溶胶显示出大陆影响的迹象，例如粒子数量增加、光学吸收、NSS模式增强和尘埃粒子。在此期间，佛得角的网站没有受到这种影响。氯和溴的浓度相对于钠与海水的浓度有很大的偏差，这表明大气中的卤素处理(和/或氯化物的酸置换)已经发生。利用增湿的DMPS和OPC数据合成了随时间变化的环境尺寸分布，并使用HTDMA数据将其修正为环境湿度。还预测了次碘酸(HoI)的异质吸收速率，发现NSS积累模式是该物种最重要的粒度分布部分，可以作为该物种的惰性汇。在非洲影响期间，由于添加了粗颗粒和细颗粒，预测的摄取率提高了约2倍。采用气溶胶直径相关平衡模型(ADDEM)对NSS组分的吸湿性进行了模拟，并与HTDMA数据进行了比较。这是第一次利用海洋数据对这一模式进行这种协调研究，并在文书的决议范围内达成了良好的一致意见。还模拟了吸湿生长对HOI吸收的影响，发现与同等的干颗粒相比，环境吸收速率大约增加了一倍。
Marine aerosol composition continues to represent a large source of uncertainty in the study of climate and atmospheric chemistry. In addition to their physical size and chemical composition, hygroscopicity plays a significant role, increasing the particles' surface areas and scattering potential. Simultaneous aerosol measurements were performed on board the RRS Discovery and at the Cape Verde atmospheric observatory during the Aerosol Composition and Modelling in the Marine Environment (ACMME) and Reactive Halogens in the Marine Boundary Layer (RHAMBLE) experiments. These included online measurements of number and dry size and bulk collection for offline analysis of aqueous ions. In addition, the measurements on board the Discovery included online measurements of composition using an Aerodyne Aerosol Mass Spectrometer, optical absorption using a Multi Angle Absorption Photometer, ambient humidity size distribution measurements using a humidified differential mobility particle sizer (DMPS) and optical particle counter (OPC) and hygroscopicity measurements with a hygroscopicity tandem differential mobility analyser (HTDMA). Good agreement between platforms in terms of the sea salt (ss) and non sea salt (nss) modes was found during the period when the Discovery was in close proximity to Cape Verde and showed a composition consistent with remote marine air. As the Discovery approached the African coast, the aerosol showed signs of continental influence such as an increase in particle number, optical absorption, enhancement of the nss mode and dust particles. The Cape Verde site was free of this influence during this period. Chloride and bromide showed concentrations with significant deviations from seawater relative to sodium, indicating that atmospheric halogen processing (and/or acid displacement for chloride) had taken place. The time dependent ambient size distribution was synthesised using humidified DMPS and OPC data, corrected to ambient humidity using HTDMA data. Heterogeneous uptake rates of hypoiodous acid (HOI) were also predicted and the nss accumulation mode was found to be the most significant part of the size distribution, which could act as an inert sink for this species. The predicted uptake rates were enhanced by around a factor of 2 during the African influence period due to the addition of both coarse and fine particles. The hygroscopicity of the nss fraction was modelled using the Aerosol Diameter Dependent Equilibrium Model (ADDEM) using the measured composition and results compared with the HTDMA data. This was the first time such a reconciliation study with this model has been performed with marine data and good agreement was reached within the resolution of the instruments. The effect of hygroscopic growth on HOI uptake was also modelled and ambient uptake rates were found to be approximately doubled compared to equivalent dry particles.