I have been interested of late in examining the potential for hydrophobic organic compounds to partition to DOC and thus would like to know some more about humic substances both quantitatively and qualitatively. I know that people look at aromaticity and other structural characteristics of humic substances and that it is also possible to separate DOC into humic acids, fulvic acids, and humins. Are any of these methods effective and not too difficult to get quality results? How useful does anyone find these results for general water quality or pollutant transport questions? Does anyone have any thoughts on standards that you like to use for humic substance analyses?
You can find the discussion of DOC and humic substances in this literature.
I am familiar with this Burkhard ES&T 2000 article. I have read it several times. What he is doing is assessing the Kdoc for particular compounds, and sometimes he is using Sigma Aldrich humic acid to look at the relationship between Kdoc and Kow.
But what I am really curious about is measuring the humic acid content directly of the particular DOC that I have. I was hoping someone might have some experience with particular methods to separate out humic fractions and to characterize those fractions. I have a few methods that I could try (e.g., van Zomeran and Coman 2007, http://pubs.acs.org/doi/abs/10.1021/es0709223), but I thought someone might have some good practical experience or advice for me. Perhaps someone has actually characterized or quantified surface water humics before?
I have no idea about new method about measuring DOC in water. As I know, first we filter the water using the membrance with 0.45 um pore size and then analyze them on TOC analyzer.
Dr. Wang suggests the 1st step. Also measure UV Absorbance at 254 nm is an indication of humic substance content . There are several suggestions in the humic literature on absorbance ratios the offer more qualitative information. A powerful technique is to examine fluorescence EEM (excitation emission matrices). See Diame McKinght's work. .
Spectroscopic methods for the measurement of organic content in natural water suffer the interference of nitrite and nitrate ions and other compounds which can absorb UV and/or can emit fluorescence.
It is necessary to point out that there is an evident difference between dissolved and dispersed organic matter, being the former part of the homogeneous solution, the second forming a number of micelles or vesicles as apparently separate phases.
After simple filtration to eliminate suspended solids, the extraction of micelles and vesicles can be easily obtained by dialysis or ultrafiltration.
For the characterization of dissolved organic matter you need chromatographic methods.
I do hesitate to use the term Fulvic Acid [FA] and Humic Acid. [HA]. These terms were introduced in 1919 (Odeen) and related to the extractable organic matter in soil according to pH.
In "modern times" the definaiton of FA and HA is indeed different.
Natural Organic Matter (NOM), is, according to my experience, very complex having a number of
please check the below links. I hope these suggestions are useful:
- https://www.osti.gov/servlets/purl/5569909
Chapter PREFACE, Introduction
- https://www.mdpi.com/1420-3049/25/4/918/pdf
- https://www.mdpi.com/1420-3049/25/4/918/pdf
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