Direct aerosol chemical composition measurements to evaluate the physicochemical differences between controlled sea spray aerosol generation schemes
Direct aerosol chemical composition measurements to evaluate the physicochemical differences between controlled sea spray aerosol generation schemes
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DOI：
10.5194/amt-7-3667-2014
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发表时间：
2014-01-01
影响因子：
3.8
通讯作者：
Prather, K. A.
中科院分区：
文献类型：
--
作者：
Collins, D. B.;Zhao, D. F.;Prather, K. A.
控制实验室研究的物理和化学性质的海洋喷雾气溶胶（SSA）必须支持的物理和化学准确的代表性气泡介导的生产新生SSA颗粒。气泡破裂对海水的物理化学性质非常敏感。对于海水样本，SSA产生机制中的任何重要差异都被投射到所产生的气溶胶颗粒的组成中。使用直接的化学测量SSA在单颗粒水平，本研究提出了一个相互比较的三个实验室为基础的，气泡介导的SSA生产计划：气体被迫通过淹没烧结玻璃过滤器（“熔块”），一个脉冲的瀑布装置，并打破波浪在充满天然海水的波浪通道。破碎波产生的SSA颗粒的尺寸分辨的化学成分是更相似的暴跌瀑布比烧结玻璃过滤器产生的颗粒。由烧结玻璃过滤器产生的崩解泡沫产生的气溶胶含有较大比例的有机富集颗粒和不同的尺寸分辨元素组合物，特别是在0.8-2 μ m的干直径范围内。有趣的是，只有当颗粒在单颗粒水平上作为尺寸的函数进行化学分析时，方法之间的化学差异才会出现;所有尺寸的所有颗粒的元素组成的平均值掩盖了SSA样品之间的差异。当干燥时，由烧结玻璃过滤器产生的SSA具有最高分数的具有球形形态的颗粒，相比之下，当颗粒含有相对较少的有机碳时，对于纯NaCl颗粒所预期的更立方结构。除了相互比较的三个SSA生产方法，瀑布法的情节或“脉冲”的性质对SSA组成的作用进行了。在富含有机物的海水中，连续操作的暴跌瀑布导致表面泡沫的积累和SSA颗粒中有机物的过度表达相比，由脉冲暴跌瀑布产生的。在这一组实验中，SSA数尺寸分布的比较差异与气溶胶颗粒组成的差异一致，表明SSA的生产机制对所得气溶胶的物理和化学性质都具有重要的控制作用，这与颗粒的内部和外部混合状态有关。这项研究提供了深入了解每个气泡介导的SSA生成机制测试和它们产生的气溶胶颗粒之间的不可分割的物理化学差异，也作为未来SSA颗粒实验室研究的指导方针。
Controlled laboratory studies of the physical and chemical properties of sea spray aerosol (SSA) must be underpinned by a physically and chemically accurate representation of the bubble-mediated production of nascent SSA particles. Bubble bursting is sensitive to the physicochemical properties of seawater. For a sample of seawater, any important differences in the SSA production mechanism are projected into the composition of the aerosol particles produced. Using direct chemical measurements of SSA at the single-particle level, this study presents an intercomparison of three laboratory-based, bubble-mediated SSA production schemes: gas forced through submerged sintered glass filters ("frits"), a pulsed plunging-waterfall apparatus, and breaking waves in a wave channel filled with natural seawater. The size-resolved chemical composition of SSA particles produced by breaking waves is more similar to particles produced by the plunging waterfall than those produced by sintered glass filters. Aerosol generated by disintegrating foam produced by sintered glass filters contained a larger fraction of organic-enriched particles and a different size-resolved elemental composition, especially in the 0.8-2 mu m dry diameter range. Interestingly, chemical differences between the methods only emerged when the particles were chemically analyzed at the single-particle level as a function of size; averaging the elemental composition of all particles across all sizes masked the differences between the SSA samples. When dried, SSA generated by the sintered glass filters had the highest fraction of particles with spherical morphology compared to the more cubic structure expected for pure NaCl particles produced when the particle contains relatively little organic carbon. In addition to an intercomparison of three SSA production methods, the role of the episodic or "pulsed" nature of the waterfall method on SSA composition was undertaken. In organic-enriched seawater, the continuous operation of the plunging waterfall resulted in the accumulation of surface foam and an over-expression of organic matter in SSA particles compared to those produced by a pulsed plunging waterfall. Throughout this set of experiments, comparative differences in the SSA number size distribution were coincident with differences in aerosol particle composition, indicating that the production mechanism of SSA exerts important controls on both the physical and chemical properties of the resulting aerosol with respect to both the internal and external mixing state of particles. This study provides insight into the inextricable physicochemical differences between each of the bubble-mediated SSA generation mechanisms tested and the aerosol particles that they produce, and also serves as a guideline for future laboratory studies of SSA particles.