Molecular weight, polydispersity, and spectroscopic properties of aquatic humic substances

Environmental Science & Technology
By: , and 

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Abstract

The number- and weight-averaged molecular weights of a number of aquatic fulvic acids, a commercial humic acid, and unfractionated organic matter from four natural water samples were measured by high-pressure size exclusion chromatography (HPSEC). Molecular weights determined in this manner compared favorably with those values reported in the literature. Both recent literature values and our data indicate that these substances are smaller and less polydisperse than previously believed. Moreover, the molecular weights of the organic matter from three of the four natural water samples compared favorably to the fulvic acid samples extracted from similar environments. Bulk spectroscopic properties of the fulvic substances such as molar absorptivity at 280 nm and the E4/E6 ratio were also measured. A strong correlation was observed between molar absorptivity, total aromaticity, and the weight average molecular weights of all the humic substances. This observation suggests that bulk spectroscopic properties can be used to quickly estimate the size of humic substances and their aromatic contents. Both parameters are important with respect to understanding humic substance mobility and their propensity to react with both organic and inorganic pollutants. 

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Molecular weight, polydispersity, and spectroscopic properties of aquatic humic substances
Series title Environmental Science & Technology
DOI 10.1021/es00060a015
Volume 28
Issue 11
Year Published 1994
Language English
Publisher ACS
Contributing office(s) Toxic Substances Hydrology Program
Description 6 p.
First page 1853
Last page 1858