14746 IUPAC Gold Book - humic substances 10.1351/goldbook.14746 14746 current 1 Nonvolatile organic anionic polyelectrolytes, of biological origin, in the molecular mass range \(\pu{500\!{-}\! 5000}\), which have complex structures and are variable in composition. Humic substances occur naturally as deposits on sediment and soil particles and constitute \(\pu{30\!{-}\! 50 \%}\) of the dissolved organic carbon (DOC) in natural waters. Humic substances are classified according to solubility and may contain humic acid, fulvic acid, and humin. dissolved organic carbon https://goldbook.iupac.org//terms/view/14595 fulvic acid https://goldbook.iupac.org//terms/view/14703 soil https://goldbook.iupac.org//terms/view/15036 PAC, 2009, 81, 829. 'Glossary of terms used in ecotoxicology (IUPAC Recommendations 2009)' on page 897 (https://doi.org/10.1351/PAC-REC-08-07-09) https://goldbook.iupac.org/terms/view/14746/html https://goldbook.iupac.org/terms/view/14746/json https://goldbook.iupac.org/terms/view/14746/plain Citation: 'humic substances' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.14746 The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms. If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org . The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using. 2026-04-18T02:00:48+00:00