Collaborative Research: Atmospheric Processing of Iron--Does Particle Size Influence Iron Solubility?

该项目将研究颗粒大小对铁的大气反应的影响，进而研究颗粒大小对铁溶解度的影响。特别是，如何颗粒大小影响铁溶解度在大气处理过程中通过两种不同的机制将进行研究。首先，粒子大小对云水中铁光还原过程中铁溶解度的影响将被确定。在真实云水和模拟云水中对含水铁的光化学还原进行了很好的研究，然而，颗粒大小从未被认为是一个变量，但可能很重要，因为只有有限的气溶胶大小部分才能形成云凝结核（CCN）。以前的实验室研究集中在太大或太小而不能作为CCN的颗粒上，可能低估或高估了实际大气系统中光化学产生的可溶性铁。其次，研究了在与气态二氧化硫反应过程中，颗粒大小对铁溶解度的影响。铁相与氯化钠混合的暴露将分别在两种相对湿度（20%和80%）下进行研究，这两种相对湿度分别代表干燥的大陆环境和潮湿的海洋环境。这将有助于确定在铁-硫相互作用过程中，是气粒反应更重要还是液粒反应更重要。暴露于二氧化硫后，溶解铁部分的铁同位素组成将被确定并用于阐明机制。这项研究将对了解铁在大陆和海洋气溶胶中的溶解度做出有价值的贡献。研究结果将与更广泛的问题有关，即大气中的铁如何影响海洋生产力，从而影响其与全球碳循环的关系。铁在开放海洋的许多地方是一种限制性营养物质，人们已经付出了大量努力来确定大气颗粒物中铁对海洋生物的可用性。这项研究还将促进下一代大气科学家的培训。该项目将资助亚利桑那州立大学（ASU）的一名博士生，该研究是他/她论文工作的核心。此外，每年有一名来自北亚利桑那大学（NAU）的本科生将与亚利桑那州立大学的主要研究人员和博士生一起工作。化学系是一个非博士学位。发放部门。因此，与亚利桑那州立大学的研究人员合作，将为NAU的本科生提供在NAU通常不可能实现的研究方法和技术的培训。此外，NAU在授予美洲原住民学生学位方面是全国领先的。这些独特的人口统计数据将通过NAU的部落环境专业人员研究所来招募关注环境的美国原住民本科生。

This project will examine the influence of particle size on atmospheric reactions of iron and, in turn, the influence of particle size on iron solubility. In particular, how particle size affects iron solubility during atmospheric processing by two different mechanisms will be investigated. First, the effect of particle size on iron solubility during photoreduction of iron in cloud waters will be determined. Photochemical reduction of aqueous iron has been well studied in authentic and simulated cloud waters, however, particle size has never been considered as a variable but may be important because only a restricted aerosol size fraction can form cloud condensation nuclei (CCN). Previous laboratory studies focusing on particles too big or too small to act as CCN may under- or overestimate the soluble iron resulting from photochemistry in real atmospheric systems. Second, the influence of particle size on iron solubility during reaction with gaseous sulfur dioxide will be investigated. Exposure of iron phases mixed with sodium chloride will be studied at two relative humidities (20% and 80%) representative of dry continental and wet marine environments, respectively. This will allow determination of whether gas-particle or liquid-particle reactions are more important during iron-sulfur interactions. Following exposure to sulfur dioxide, the iron isotope composition of the dissolved iron fraction will be determined and used to elucidate mechanisms.This research will be a valuable contribution to understanding iron solubility in continental and marine aerosols. The results will be relevant to the broader question of how atmospheric iron affects ocean productivity and, hence, its relation to the global carbon cycle. Iron is a limiting nutrient in many parts of the open ocean and substantial effort has been put forth to determine the availability of iron in atmospheric particulate matter to marine life. This study will also advance the training of the next generation of atmospheric scientists. The project will fund one Ph.D. student at Arizona State University (ASU), with this research being the core of his/her thesis work. In addition, one undergraduate student each year from Northern Arizona University (NAU) will work with the principal investigators and the Ph.D. student at ASU. The Department of Chemistry at NAU is a non-Ph.D. granting department. Therefore, collaboration with ASU researchers will provide undergraduate students at NAU training in research approaches and techniques that are not normally possible at NAU. Furthermore, NAU is among the national leaders in granting degrees to Native American students. These unique demographics will be drawn upon to recruit environmentally-focused Native American undergraduates through the Institute for Tribal Environmental Professionals at NAU.