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Impact of Hydrofluoric Acid Treatment on Humic Acid Properties Extracted from Organic Soils and an Organic Amendment: A Technical Evaluation
Author(s) -
Audette Yuki,
Smith D. Scott,
Parsons Christopher T.,
Longstaffe James,
Chen Weibin,
Rezanezhad Fereidoun,
Evans Les J.,
Van Cappellen Philippe
Publication year - 2019
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2018.11.0419
Subject(s) - chemistry , organic matter , hydrofluoric acid , soil water , humic acid , aluminosilicate , extraction (chemistry) , soil organic matter , environmental chemistry , amendment , compost , soil ph , inorganic chemistry , organic chemistry , soil science , geology , fertilizer , agronomy , catalysis , biology , political science , law
The chemical and physical characteristics of humic acids (HA) may differ depending on their source, and the ideal extraction method should not modify the characteristics of HA. Hydrofluoric acid (HF) is often used in HA extraction methods to remove inorganic substances that are often present in the sample in addition to the organic molecules of interest. Organic soils contain up to 90% of organic matter and some may think that the necessity of the HF treatment is not crucial when extracting HA from organic soils. In this study, HA were extracted from turkey litter compost (TLC), an agricultural organic soil (AOS) and a riparian soil (RS), and the impact of HF on the properties of the extracted HA was assessed. HF decreased the ash content and the concentration of inorganic components in extracted materials, especially in the HA from RS, which had higher concentrations of aluminosilicates and amorphous Si. For TLC, no significant difference in either the total charge or charge distribution was observed with HF treated samples compared to untreated samples, while the HF treatment decreased the proton binding capacity at alkaline pH (≥7) in the HA from the two soils. We assume that aluminosilicates, amorphous Si and iron oxides left in the samples interacted with protons at alkaline pH, thus increasing the proton binding capacity. Therefore, HF treatment should be included when samples containing these mineral constituents even for materials rich in organic matter. Core Ideas Hydrofluoric acid did not affect functional group distribution or C concentration in humic acids. Proton binding capacity at alkaline pH of soil humic acids decreased after hydrofluoric acid treatment. Hydrofluoric acid did not affect characteristics of humic acids extracted from turkey litter compost. Humic acids from turkey litter compost had lower proton binding capacity than those from soils.