RUI: Temporal Variability of Iron Speciation in Rain

RUI：雨中铁形态的时间变化

• 批准号: 9729425
• 负责人: Robert Kieber
• 金额: $ 29.78万
• 依托单位: University of North Carolina at Wilmington
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-09-15 至 2002-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9729425&HistoricalAwards=false
• 关键词: RUI; Temporal; Variability; Iron; Speciation

The specific objective of this research is to determine the speciation of iron in various types of rain events. Speciation is the precise chemical form of the iron in rain, including free and complexed ferrous and ferric iron. This information is crucial to the understanding of several important chemical processes in the atmosphere which depend on the concentration and speciation of iron, as well as the impacts of rainwater iron on aquatic ecosystems. Any change in iron speciation in rain may alter the rate of marine primary productivity, because speciation affects the bioavailability of iron as a nutrient, as well as the residence time for iron in seawater. Marine primary productivity plays a significant role in carbon removal from the atmosphere, and hence impacts global warming.Preliminary data indicate that approximately half of the iron in rain passes through a fine filter (nominally dissolved), with the remaining fraction in the larger particulate phase. Data from a June thunderstorm in Wilmington, NC, suggest that part of the dissolved iron occurred as an organic complex. Data from an early summer rain suggest that photochemical reduction of iron proceeds as the day progresses, and changes are large enough and rapid enough to be observed in rainwater.The presence of organically bound iron in rain, and of large variations in Fe(II) concentration, indicate that iron speciation is highly variable in rain. This research will assess how the relative abundance of iron species vary both temporally with time of day, season and storm history, and as a function of concentrations of ligands capable of complexation. Ligands to be investigated include oxalate, formate, sulfate, amino acids, and soil humics. This will be accomplished by careful sampling, analysis and laboratory experiments. The variability of Fe(II) in rain suggests that controlled photochemical experiments will give a useful indication of the potential for generation of Fe(II) in rain, which concentration analyses alone cannot provide.The sampling site in Wilmington, NC, a coastal location, is ideal for this study because continental and maritime storms bring rain with a wide range in rainwater composition. A twelve year record of rainwater composition exists for this site; and supporting rain data essential for a study of iron speciation (pH, hydrogen peroxide, organic acids, amino acids, aldehydes, nitrite and inorganic anions) are currently being collected by the same laboratory.This project is supported under the Research in Undergraduate Institutions (RUI) program and will involve, among other participants, undergraduate and Master's students.

这项研究的具体目的是确定各种降雨事件中铁的物种形成。物种是雨中铁的精确化学形式，包括游离和络合亚铁和铁铁。该信息对于理解大气中的几个重要化学过程至关重要，这些化学过程取决于铁的浓度和形态以及雨水铁对水生生态系统的影响。雨中铁物种形成的任何变化都可能改变海洋初级生产率的速度，因为物种影响铁作为营养素的生物利用度以及海水中铁的停留时间。海洋初级生产力在从大气中去除碳中起着重要作用，因此会影响全球变暖。预先数据表明，雨中铁的大约一半通过细过滤器（名义上溶解），其余部分在较大的颗粒相。来自北卡罗来纳州威尔明顿的6月雷暴的数据表明，溶解的铁的一部分是作为有机络合物发生的。初夏雨水的数据表明，随着一天的进行，铁的流动减少，变化足够大，足够快地在雨水中观察到。在雨中存在有机铁的存在，而Fe（II）浓度的变化很大，表明铁物种在雨中的变化很大。这项研究将评估铁物种的相对丰度如何随着一天的时间，季节和风暴史而变化，以及能够络合的配体浓度的函数。要研究的配体包括草酸盐，甲酸，硫酸盐，氨基酸和土壤蜂巢。这将通过仔细的采样，分析和实验室实验来实现。雨中的Fe（II）的变异性表明，受控的光化学实验将为雨水分析而产生Fe（ii）的潜力，这是北卡罗来纳州威尔明顿的采样地点，这是这项研究的理想选择，因为这项研究是大陆和海上风暴带来雨水范围广泛的雨水。该网站存在十二年的雨水组成记录；目前正在同一实验室收集并支持对铁物种形成研究（pH，PH，氢过氧化氢，有机酸，氨基酸，醛，亚硝酸盐和无机阴离子）必不可少的降雨数据。同一实验室正在收集该项目。在本科研究所（RUI）计划（RUI）计划（RUI）的研究下，这项项目受到了其他参与者的毕业生和硕士学位的研究。