New possibility for characterization of dissociation behaviour of supramolecular electrolytes: results obtained for the International Humic Substances Society standard and reference samples by coulometry

Abstract Background Humic substances can be considered as polyelectrolytes with supramolecular character and complicated behaviour in water environment. The fractions of humic substances dissolved in water are the most active ones and determinative for their functioning in nature, where the proton-binding and dissociation ability play a crucial role. The dissociation behaviour of humic and fulvic acids can be affected by different circumstances including their concentration which is directly connected with the molecular organization of humic particles in solution and the accessibility of their ionizable functional groups. This study is focused just on these active fractions and their dissociation behaviour in the dependence on their content in studied system. Results Standards and reference samples of International Humic Substances Society were used. Flow-through coulometry was used to determine the total content of acidic functional groups in fulvic solutions and humic leachates. The amount of dissociated acidic groups was determined on the basis of potentiometry. Several differences between the behaviour of humic and fulvic acids were found. While whole samples of fulvic acids including the weakest functional groups were analysed, only the active dissolved humic fractions containing stronger acidic functional groups were characterized. The fractions containing higher amounts of the weakest functional groups remained insoluble. The dissociation degree of fulvic acids decreased with their increasing content, but a maximum on its concentration dependence obtained for humic acids was observed. Conclusions Two different values of dissociation constants were determined for each sample. The first was determined on the basis of the extrapolation of infinite dilution, second was determined as their average value in the region of high concentrations in which it was constant. Obtained values characterize the functioning of dissolved humic substances from point of view of their dissociation ability. The results obtained by this approach can help to predict the acid–base behaviour of dissolved organic carbon in soil and generally in nature. The acid–base behaviour of dissolved organic carbon depends on its ratio to water. It behaves differently in soil which is dry and in soil which is wet or saturated by water.

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Sources and fate of terrestrial dissolved organic carbon in lakes of a Boreal Plains region recently affected by wildfire

Biogeosciences Discussions ◽

10.5194/bgd-10-6093-2013 ◽

2013 ◽

Vol 10 (4) ◽

pp. 6093-6141 ◽

Cited By ~ 4

Author(s):

D. Olefeldt ◽

K. J. Devito ◽

M. R. Turetsky

Keyword(s):

Organic Carbon ◽

Dissolved Organic Carbon ◽

Primary Productivity ◽

Fulvic Acids ◽

Lake Morphometry ◽

Humic And Fulvic Acids ◽

Study Region ◽

Boreal Plains ◽

Peat Pore Water ◽

Surface Geology

Abstract. Downstream mineralization and sedimentation of terrestrial dissolved organic carbon (DOC) render lakes important for landscape carbon cycling in the boreal region, with regulating processes potentially sensitive to perturbations associated with climate change including increased occurrence of wildfire. In this study we assessed chemical composition and reactivity (during both dark and UV incubations) of DOC from lakes and terrestrial sources within a peatland-rich western boreal plains region partially affected by a recent wildfire. While wildfire was found to increase aromaticity of DOC in peat pore-water above the water table, it had no effect on concentrations or composition of DOC from peatland wells and neither affected mineral well or lake DOC characteristics. Lake DOC composition reflected a mixing of peatland and mineral groundwater, with a greater influence of mineral sources to lakes in coarse- than fine-textured settings. Peatland DOC was less biodegradable than mineral DOC, but both mineralization and sedimentation of peatland DOC increased substantially during UV incubations through selective removal of aromatic humic and fulvic acids. DOC composition in lakes with longer residence times had characteristics consistent with increased UV-mediated processing. We estimate that about half of terrestrial DOC inputs had been lost within lakes, mostly due to UV-mediated processes. The importance of within-lake losses of aromatic DOC from peatland sources through UV-mediated processes indicate that terrestrial-aquatic C linkages in the study region are largely disconnected from recent terrestrial primary productivity. Together, our results suggest that characteristics of the study region (climate, surface geology and lake morphometry) render linkages between terrestrial and aquatic C cycling insensitive to the effects of wildfire by determining dominant terrestrial sources and within-lake processes of DOC removal.

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Potentiometric analysis of humic substances and other colloids

Canadian Journal of Chemistry ◽

10.1139/v83-286 ◽

1983 ◽

Vol 61 (7) ◽

pp. 1671-1682 ◽

Cited By ~ 8

Author(s):

Paul A. Arp

Keyword(s):

Humic Substances ◽

Functional Groups ◽

Surface Potential ◽

Goodness Of Fit ◽

Dissociation Constants ◽

High Surface ◽

Colloidal Suspensions ◽

Acid Base ◽

Titration Curves ◽

Consistent Information

The acid–base behaviour of colloidal suspensions of γ-Al2O3, TiO2 (rutile), high surface-charge latex, and humic substances in water is reexamined by using a Nernst-like model and two electrostatic models to simulate the proton-affecting surface potential. The Nernst-like model is based on the assumption that the proton-affecting surface potential is proportional to the Nernst potential. The other models are based on conventional double-layer assumptions. All models yield numerically consistent information about (i) number of chemically discernible functional groups (or collections of functional groups), (ii) their dissociation constants and concentrations, (iii) the free H+- (or OH−-) concentrations in the suspending medium, (iv) surface area of colloidal substance, and (v) surface potential (and charge) as function of ph. Potentiometric analyses are performed on documented titration curves by employing a modified version of the ACBA (acid–base) program developed by Arena etal. The goodness-of-fit information provided by this program suggests that the Nernst-like model is particularly useful for generating and verifying estimates for surface capacities as function of ph.

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Quantitative elemental and structural analysis of dissolved organic carbon fractions from lakes near Sudbury, Ontario

Canadian Journal of Chemistry ◽

10.1139/v96-275 ◽

1996 ◽

Vol 74 (12) ◽

pp. 2460-2470 ◽

Cited By ~ 10

Author(s):

Roy Carl Boerschke ◽

Elizabeth Ann Gallie ◽

Nelson Belzile ◽

Richard Neville Gedye ◽

James Robert Morris

Keyword(s):

Organic Carbon ◽

Dissolved Organic Carbon ◽

Organic Acids ◽

Humic Substances ◽

Humic Acids ◽

Nmr Spectra ◽

Fulvic Acids ◽

Published Data ◽

Organic Carbon Fractions ◽

C Nmr

Dissolved organic carbon (DOC) was quantitatively isolated as five separate fractions from two Sudbury area lakes (Ontario, Canada) using the tandem XAD-8/XAD-4 resin technique. Fulvic acids made up ≈ 48% of the total, humic acids ≈ 8%, hydrophobic neutrals ≈ 8%, XAD-4 acids ≈ 11%, and XAD-4 acetonitrile extracts ≈ 13%. Hydrophobic:hydrophilic ratios were about 65:35. Solid-state CPMAS 13C NMR indicated a primarily aliphatic nature in all fractions. Percent aromaticity was in the order humic acids > fulvic acids > XAD-4 acetonitrile extracts ≈ XAD-4 acids ≈ hydrophobic neutrals. Titration analysis showed that the 13C NMR peaks of fulvic acids, humic acids, and XAD-4 acids from 160–190 ppm were primarily carboxyl in nature. The XAD-4 acids were the most acidic, suggesting that they may be important geochemical agents. 13C NMR indicated that polysaccharides formed < 20% of any fraction. The two neutral fractions (hydrophobic neutrals and XAD-4 acetonitrile extracts) had relatively high N contents, possibly due to the acetonitrile used to extract them. However, the 13C NMR spectra did not show significant quantities of acetonitrile. The elemental and structural composition covaries in the three acid fractions, such that if one acid is enriched or depleted, so are the others. This suggests that the humic and non-humic acids form a continuum in which all fractions are affected by the same formative processes. Compared to published data for other freshwater samples, the three acid fractions from the Sudbury area lakes have low or very low aromaticity. This may indicate that the acid and metal loadings in the Sudbury area have affected the structure of the organic acids, despite the circumneutral character of the study lakes. These are the first quantitative 13C NMR results published for the hydrophobic neutrals and XAD-4 acetonitrile extracts, so comparisons are not possible. Key words: aquatic DOC, organic acids, 13C NMR, humic substances, non-humic substances.

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EFFECT OF HUMIC AND FULVIC ACIDS ON MICROBIAL GROWTH

10.46793/iccbi21.137r ◽

2021 ◽

Author(s):

Milanka Radulovic ◽

◽

Svetlana Mitrovski

Keyword(s):

Humic Acid ◽

Humic Substances ◽

Minimal Medium ◽

Microbial Growth ◽

Growth Curves ◽

Fulvic Acids ◽

Humic And Fulvic Acids ◽

Staphyloccocus Aureus ◽

Low Ionic Strength ◽

Strength Medium

Peat is a natural substrate for growth of microorganisms because it is rich in compounds that microorganisms can use as sources of carbon, nitrogen and growth factors. Peat originating from Vlasina lake in Eastern Serbia is especially rich in organic matter. The content of humic substances (humic acid, fulvic acid and humine) is almost twice that found in other peat-rich regions of similar origin and geochemical age. Humic and fluvic acids are known to promote microbial growth. In this work, humic and fulvic acids were first extracted from Vlasina lake peat and then added to minimal medium (synthetic, low ionic strength medium). The humic substances were added separately and combined in a 1:1 ratio by mass to study their individual and combined effect on microbial growth of Escherichia coli ATCC 25922 (Gr–), Staphyloccocus aureus (Gr+) i Aureobasidium pullulans, strain CH-1. The microbial growth was measured microspectrophotometrically over a 24-hour period and growth curves were obtained for a range of acid concentrations between 25 µg cm-3 and 100 µg cm-3. It was found that both humic and fulvic acids promote the growth of all three microorganisms by up to a maximum of 40%-80% the extent of which varied with the concentration of the acid and the identity of the microorganism. In general, humic acid was found to result in higher microbial growth (at highest concentrations, up to ~80% for all three microbial species).

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Development of an ICP−IDMS Method for Dissolved Organic Carbon Determinations and Its Application to Chromatographic Fractions of Heavy Metal Complexes with Humic Substances

Analytical Chemistry ◽

10.1021/ac971283p ◽

1998 ◽

Vol 70 (10) ◽

pp. 2038-2043 ◽

Cited By ~ 35

Author(s):

Jochen Vogl ◽

Klaus G. Heumann

Keyword(s):

Heavy Metal ◽

Organic Carbon ◽

Dissolved Organic Carbon ◽

Metal Complexes ◽

Humic Substances

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Transformation of humic substances and functional groups of soil organic carbon after wildfire

Archives of Agronomy and Soil Science ◽

10.1080/03650340.2019.1702165 ◽

2019 ◽

Vol 67 (1) ◽

pp. 29-37 ◽

Cited By ~ 1

Author(s):

Xin Yue ◽

Shimei Li ◽

Qaiser Hussain ◽

Shengai Jin ◽

Qinghua Liu ◽

...

Keyword(s):

Organic Carbon ◽

Soil Organic Carbon ◽

Humic Substances ◽

Functional Groups

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Nanoemulsions Based on Biopolymers Loaded with Humic and Fulvic Acids Derived from Hydrothermally Treated Biomass

Proceedings ◽

10.3390/proceedings2019029082 ◽

2019 ◽

Vol 29 (1) ◽

pp. 82

Author(s):

Malina Desliu-Avram ◽

Stefan-Ovidiu Dima ◽

Anca-Andreea Turcanu ◽

Elena Radu ◽

Ana-Maria Stanciuc ◽

...

Keyword(s):

Complex Systems ◽

Humic Substances ◽

Fulvic Acids ◽

Humic And Fulvic Acids

Humic substances (HS) are complex systems widely spread in nature as a result of the humification process of biomass, although hardly quantifiable and understood. Various polyphenols are considered to be the main precursors of HS. [...]

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Chemical nature of soil humified fractions and their bioactivity

Pesquisa Agropecuária Brasileira ◽

10.1590/s0100-204x2004000300005 ◽

2004 ◽

Vol 39 (3) ◽

pp. 233-240 ◽

Cited By ~ 24

Author(s):

Luciano Pasqualoto Canellas ◽

Arnoldo Rocha Façanha

Keyword(s):

Humic Substances ◽

Chemical Nature ◽

Biochemical Marker ◽

Soil Depth ◽

Fulvic Acids ◽

Soil Samples ◽

Humic And Fulvic Acids ◽

Fourier Transformed Infrared Spectroscopy ◽

Maize Roots ◽

Humus Composition

The aim of this work was to evaluate the humus composition from an Ultisol from Campos dos Goytacazes, RJ, Brazil. Soil samples of four depths (0-0.05, 0.05-0.10, 0.10-0.20 and 0.20-0.40 m) and its chemical nature were analysed by elemental composition, E4/E6 ratios and Fourier transformed infrared spectroscopy. The bioactivity of these humified substances was evaluated through their action on maize root growth and H+-ATPase activity of roots microsomes. In topsoil, the content of high condensed alkaline soluble humic substances is greater than that found in the subsuperficial layers. The chemical nature of humic and fulvic acids also varied with the soil depth. The humic acids isolated from the soil samples exhibited higher bioactivity compared with the fulvic acids. Moreover, the results suggest that more condensed humic substances can promote highest stimulation of the microsomal H+-ATPases from maize roots. These data reinforce the concept that the activity of the H+ pumps can be used as a biochemical marker for evaluation of humic substances bioactivity.

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