Characterization of Metal Ion Complexation and Aggregation of Humic Substances

化学部的这一奖项支持堪萨斯大学化学系的辛西娅·K·拉里夫的研究，她开发了一种新的方法来表征从地下水和地表水中分离出来的腐植酸和富里酸的金属离子络合和聚集。该奖项是在1995年NSF/EPA环境研究伙伴关系的水和流域活动的环境地球化学和生物地球化学部分颁发的。参与该项目的是威奇托州立大学化学系的W·罗伯特·卡珀。脉冲梯度核磁共振波谱将用于确定胡敏酸和黄腐酸的聚集状态和金属离子诱导聚集的程度。将使用电位滴定方法来测量金属离子的络合作用，而核磁共振弛豫速率将指示金属离子交换速率和形成常数。这种基础广泛的方法将使研究人员能够构建一个富里酸和胡敏酸中竞争性金属离子结合和交换率的模型。来自苏万尼河和瓦卡鲁萨河的样本将用于新方法通用性的初步测试。腐殖酸和黄腐酸从土壤和植物有机质中浸出到地下水和地表水中，在鹦鹉螺中具有固有的异质性。它们是溶解有机碳的主要成分，作为一个整体，它们与杀虫剂和除草剂等有机污染物相互作用，增加了它们的溶解度。因此，它们在人为有机污染物的迁移和生物利用度方面发挥着重要作用。这项研究的重点是腐殖酸和黄腐酸参与金属离子的络合作用，并开发新的分析方法，同时测定自然体系样品中金属离子的浓度、络合和聚集。

This award in the Chemistry Division supports research by Cynthia K. Larive of the Chemistry Department, University of Kansas, for the development of a new method for characterizing metal ion complexation and the aggregation of humic and fulvic acids isolated from ground and surface waters. The award is made in the Environmental Geochemistry and Biogeochemistry section of the Water and Watersheds activity of the 1995 NSF/EPA Partnership for Environmental Research. Collaborating on the project is W. Robert Carper of the Chemistry Department, Wichita State University. Pulsed field gradient nuclear magnetic resonance (NMR) spectroscopy will be used to determine the aggregation state of humic and fulvic acids and the degree of metal-ion induced aggregation. Potentiometric titration methods will be used to measure metal ion complexation, and NMR relaxation rates will indicate metal ion exchange rates and formation constants. This broad-based approach will enable investigators to construct a model of competitive metal ion binding and exchange rates in fulvic and humic acids. Samples from the Suwannee and Wakarusa Rivers will be used in initial tests of the generality of the new method. Humic and fulvic acids leach into ground and surface waters from soil and plant organic matter and are inherently heterogeneous in nautre. They are the major constituents of dissolved organic carbon and, as a group, interact with organic pollutants such as pesticides and herbicides, increasing their solubility. For this reason, they play an important role in the transport and bioavailability of anthropogenic organic contaminants. This research is focused on the participation of humic and fulvic acids in the complexation of metal ions and the development of new methods for analysis which will simultaneously determine metal ion concentration, complexation, and aggregation in samples from natural systems.