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.

本研究的具体目标是确定各种类型的降雨事件中铁的形态。形态是雨水中铁的精确化学形式，包括游离态和络合态亚铁和三价铁。这些信息对于理解大气中几个重要的化学过程至关重要，这些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。雨水中铁形态的任何变化都可能改变海洋初级生产力的速率，因为形态影响铁作为营养素的生物利用度，以及铁在海水中的停留时间。海洋初级生产力在从大气中去除碳的过程中发挥着重要作用，从而影响全球变暖，初步数据表明，雨水中约有一半的铁通过精细过滤器（名义上溶解），其余部分以较大的颗粒相存在。来自北卡罗来纳州威尔明顿6月雷暴的数据表明，部分溶解的铁以有机复合物的形式存在。从初夏雨的数据表明，光化学还原铁的收益，随着一天的进展，变化是足够大，足够快，在雨水中观察到的存在下，有机结合的铁在雨中，和大的变化，在Fe（II）浓度，表明铁的形态是高度可变的雨。这项研究将评估铁物种的相对丰度如何随时间变化，一天中的时间，季节和风暴的历史，并作为能够络合的配体的浓度的函数。研究的配体包括草酸盐、甲酸盐、硫酸盐、氨基酸和土壤腐殖酸。这将通过仔细取样、分析和实验室实验来完成。Fe（II）在雨中的变化表明，控制光化学实验将给出一个有用的指示生成的Fe（II）在雨中的潜力，浓度分析本身不能provid.The采样点在威尔明顿，NC，沿海位置，是理想的这项研究，因为大陆和海上风暴带来的雨水组成范围很广的雨。该场址有12年的雨水组成记录;和支持降雨数据的铁形态的研究至关重要（pH、过氧化氢、有机酸、氨基酸、醛类、亚硝酸盐和无机阴离子）目前由同一个实验室收集。该项目得到了本科院校研究（RUI）计划的支持，参与者包括本科生和硕士生。