ZHUANG 9403739 This project is preliminary work in support of proposed research on the redox chemistry and availability of iron to phytoplankton which will be submitted to NSF. The ability to reliably quantify Fe(II) in aerosols, rainwater, and seawater is one of the most important elements in further understanding the biogeochemical cycling of iron in both atmospheric and aqueous environments. We have developed a high performance liquid chromatographic method that has enabled us to determine ultratrace amounts of iron(II) in aerosols, rainwater, seawater {Yi et al., 1992}. The Fe(II) concentration in remote marine aerosols and rainwater has been determined for the first time {Zhuang et al.,1992a}. This novel method is the first to use HPLC to separate and determine the iron redox species. While many experts in this field have noted that these previous studies have contributed new knowledge on iron chemistry in the atmosphere and in seawater, others have argued that because Fe(II) in seawater is known to be thermodynamically unstable and difficult to measure, our new method may be inaccurate. Despite publication in the peer-reviewed journals, the methodology continues to be the subject of some controversy. Development of this new method for the measurement of Fe(II) is still exploratory, and it will potentially have great impact on environmental chemistry, specifically, on chemical oceanography. We propose to verify and refine this highly sensitive and specific method. We will focus on addressing the questions raised by reviewers in our previous proposal and further clarify our new findings. The objectives of this study are: 1) to rigorously verify and refine as needed our newly developed method using HPLC with a UV/visible detector to determine Fe(II) in aerosols, rainwater, and seawater, 2) to demonstrate the capability of the method to measure Fe(II) in surface seawater collected from a variety of coastal environments, 3) to determine directly the residence time of Fe(II) in artificial and natural surface seawater collected in coastal waters.
