Humic substances are important in environmental chemistry of soil and waters. They are naturally occurring organic substances ubiquitously present in aquatic and soil environments.  They consist of large organic molecules with many aromatic rings, carbon double bonds, and various functional groups, acting as binding agents (ligands) to bind metal ions and thus control their speciation and fate in the environment.  UV-Vis spectroscopy can provide information to understand the structures and behaviors of humic substances.  A spectroscopic index was created to reflect the UV-Vis spectrum of a humic substance sample and thus link the index value to the properties and structures of humic substances. Experimentally, the index IS obtained by using the UV-Vis spectra of a humic substance sample in a series of dilutions.  The index is given by the slope of the plot of the slopes of the calibrations (abs. vs. concentration) from the UV-Vis scans of the series dilutions of the humic substance sample vs. wavelength of the UV-VIS scan. A group of soil humic substance samples were extracted using NaOH solution. The index values of these samples ranged from 3.9 to 25.9, exhibiting a wide variation of the index values.  These preliminary results show some potential for the use of this index.  Further research will be carried out to test more humic substance samples from a variety of sources. A large pool of the index values will make it ready to further link the index to the properties and structures of the humic substance samples. ​

Study on UV-Vis spectroscopic characteristics of soil humic substances

249th National Meeting (2015)

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