Characterization of Metal Ion Complexation and Aggregation of Humic Substances

化学部门的这一奖项支持了堪萨斯大学化学系的Cynthia K. Larive的研究，该研究开发了一种新方法，用于表征金属离子络合以及从地表水和地表水中分离出的腐植酸和黄腐酸的聚集。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. Robert Carper。脉冲场梯度核磁共振（NMR）光谱将用于测定腐植酸和黄腐酸的聚集状态和金属离子诱导的聚集程度。电位滴定法将用于测量金属离子络合，核磁共振弛豫率将表明金属离子交换率和形成常数。这种基础广泛的方法将使研究人员能够构建富里酸和腐植酸中竞争性金属离子结合和交换率的模型。来自Suwannee河和Wakarusa河的样本将用于新方法一般性的初步测试。腐植酸和黄腐酸从土壤和植物有机质中渗透到地下水和地表水中，本质上是异质的。它们是溶解有机碳的主要成分，作为一个群体，它们与有机污染物（如杀虫剂和除草剂）相互作用，增加它们的溶解度。因此，它们在人为有机污染物的运输和生物利用度中起着重要作用。本研究的重点是腐植酸和黄腐酸在金属离子络合中的作用，以及开发新的分析方法，这些方法将同时测定自然系统样品中的金属离子浓度、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.