Humic substance

Last updated
Humic acid isolated from peat Humic acid.jpg
Humic acid isolated from peat
Fulvic acid isolated from peat Fulvic acid.jpg
Fulvic acid isolated from peat

Humic substances (HS) are colored relatively recalcitrant organic compounds naturally formed during long-term decomposition and transformation of biomass residues. The color of humic substances varies from bright yellow to light or dark brown leading to black. The term comes from humus, which in turn comes from the Latin word humus , meaning "soil, earth". [1] Humic substances represent the major part of organic matter in soil, peat, coal, and sediments, and are important components of dissolved natural organic matter (NOM) in lakes (especially dystrophic lakes), rivers, and sea water. Humic substances account for 50 – 90% of cation exchange capacity in soils.

Contents

"Humic substances" is an umbrella term covering humic acid, fulvic acid and humin, which differ in solubility. By definition, humic acid (HA) is soluble in water at neutral and alkaline pH, but insoluble at acidic pH < 2. Fulvic acid (FA) is soluble in water at any pH. Humin is not soluble in water at any pH.

This definition of humic substances is largely operational. It is rooted in the history of soil science and, more precisely, in the tradition of alkaline extraction, which dates back to 1786, when Franz Karl Achard treated peat with a solution of potassium hydroxide and, after subsequent addition of an acid, obtained an amorphous dark precipitate (i.e., humic acid). Aquatic humic substances were isolated for the first time in 1806, from spring water by Jöns Jakob Berzelius.

In terms of chemistry, FA, HA, and humin share more similarities than differences and represent a continuum of humic molecules. All of them are constructed from similar aromatic, polyaromatic, aliphatic, and carbohydrate units and contain the same functional groups (mainly carboxylic, phenolic, and ester groups), albeit in varying proportions.

Water solubility of humic substances is primarily governed by interplay of two factors: the amount of ionizable functional groups and (mainly carboxylic) and molecular weight (MW). In general, fulvic acid has a higher amount of carboxylic groups and lower average molecular weight than does humic acid. Measured average molecular weights vary with source, however, molecular weight distributions of HA and FA significantly overlap.

Age and origin of the source material determine the chemical structure of humic substances. In general, humic substances derived from soil and peat (which takes hundreds to thousands of years to form) have higher molecular weight, higher amounts of O and N, more carbohydrate units, and fewer polyaromatic units than humic substances derived from coal and leonardite (which takes millions of years to form).

Isolation id HS is the result of a alkaline extraction from solid sources of NOM the adsorption of HS on a resin. [2] [3] [4] A newer view of humic substances is that they are not mostly high-molecular-weight macropolymers but rather represent a heterogeneous mixture of relatively small molecular components of the soil organic matter auto-assembled in supramolecular associations and are composed of a variety of compounds of biological origin and synthesized by abiotic and biotic reactions in soil. and surface waters [5] It is the large molecular complexity of the soil humeome [6] that confers to humic matter its bioactivity in, its stabilty in ecosystems ,soil and its role as plant growth promoter (in particular plant roots). [7]

The academic definition of humic substances is under debate and some researchers argue against the traditional concepts of humification and seek to forgo alkali extract method and directly analyze the soil, [8]

Concepts of humic substances

The formation of HS in nature is one of the least understood aspects of humus chemistry and one of the most intriguing. Historically, there have been three main theories to explain it: the lignin theory of Waksman (1932), the polyphenol theory, and the sugar-amine condensation theory of Maillard (1911). [9] [10] Humic substances are formed by the microbial degradation of dead biota matter, such as lignin, cellulose. ligno-cellulose and charcoal. [11] [12] Humic substances in the lab are resistant to further biodegradation. Their structure, elemental composition and content of functional groups of a given sample depend on the water or soil source and on the specific procedures and conditions of extraction. Nevertheless, the average properties of lab extractes HS from different sources are remarkably similar.

Fractionation

Historically, scientists have used variations of similar methods for extracting HS from NOM and separation the extracts into HA and FA. The International Humic Substances Society advocates the use of standard laboratory methods for preparation of humic and fulvic acids. Humic substances are extracted from soil and other solid sources using 0.1 M NaOH, under and a nitrogen atmosphere, to prevent abiotic oxidation of some of the components of HS. The HA is then precipitated at pH 1, and the soluble fraction is treated on a resin column to separate fulvic acid components from other acid soluble compounds. [13] The fraction of NOM not extracted by 0.1 NaOH is humin. Humic acid plus fulvic acid is extracted from natural waters using a resin column after microfiltration and acidification to pH 2. The humic materials are eluted from the column with NaOH, and humic acid is precipitated at pH 1. After adjusting the pH to 2 fulvic acid is separated from other acid soluble compounds, using a resin column as with solid phase sources. [14] An analytical method for quantifying humic acid and fulvic acid in commercial ores and humic products, has been developed based on the IHSS humic acid and fulvic acid preparation methods. [15]

Scientists associated with the IHSS have also isolated the entire NOM from black water streams using reverse osmosis  The retentate from this process contains both humic and fulvic acids, predominately humic acid. The NOM from hard water streams has been isolated using  reverse osmosis and electrodialysis in tandem. [16]

Extracted humic acid not a single acid; rather, it is a complex mixture of many different acids containing carboxyl and phenolate groups so that the mixture behaves functionally as a dibasic acid or, occasionally, as a tribasic acid. Commercial humic acid used to amend soil is manufactured using these same well established procedures. Humic acids can form complexes with ions that are commonly found in the environment creating humic colloids. [17]

A sequential chemical fractionation called Humeomics can be used to isolate more homogeneous humic fractions and determine their molecular structures by advanced spectroscopic and chromatographic methods. [18] Substances identified in humic extracts and directly in soil include mono-, di-, and tri-hydroxycarboxylic acids, fatty acids, dicarboxylic acids, linear alcohols, phenolic acids, terpenoids, carbohydrates, and amino acids. [19] This suggests humic molecules may form a supramolecular structures held together by non-covalent forces, such as van der Waals force, π-π, and CH-π bonds. [20]

Chemical characteristics

Since the dawn of modern chemistry, humic substances are among the most studied among natural materials. Despite long study, their molecular structure remains debatable The traditional view has been that humic substances are hetero- poly-condensates, in varying associations with clay. [21] A more recent view is that relatively small molecules also play major a role. [20]

A typical humic substance is a mixture of many molecules, some of which are based on a motif of aromatic nuclei with phenolic and carboxylic substituents, linked together;  The functional groups that contribute most to surface charge and reactivity of humic substances are phenolic and carboxylic groups. Humic substances commonly behave as mixtures of dibasic acids, with a pK 1 value around 4 for protonation of carboxyl groups and around 8 for protonation of phenolate groups in HA. Fulvic acids are more acidic than HA. There is considerable overall similarity among individual humic acids. For this reason, measured pK values for a given sample are average values relating to the constituent species. The other important characteristic is charge density. [22]

Model structure of a humic acid, having a variety of components including quinone, phenol, catechol, and sugar moieties Humic acid.svg
Model structure of a humic acid, having a variety of components including quinone, phenol, catechol, and sugar moieties
Model structure of a fulvic acid Fulvic acid.png
Model structure of a fulvic acid

The more recent determinations of molecular weights of HS show that the molecular weights are not as great as once thought.  Reported  number average molecular weights of soil HA are < 6000 but they are highly poly disperse with some components with much larger measure molecular weights and much lower. [23]  Measured number average molecular weights of aquatic HS with HA <= 1700 and FA< 900. [23]  The aquatic HA and FA are also highly poly disperse.  The number of individually distinct components in HS, as measured by mass spectroscopy is in the thousands  The average composition of HA and FA can be represented by model structures.

The presence of carboxylate and phenolate groups gives the humic acids the ability to form complexes with ions such as Mg2+, Ca2+, Fe2+, and Fe3+ creating humic colloids.. Many humic acids have two or more of these groups arranged so as to enable the formation of chelate complexes. [24] The formation of (chelate) complexes is an important aspect of the biological role of humic acids in regulating bioavailability of metal ions. [25]

Criticism

Decomposition products of dead plant materials form intimate associations with minerals, making it difficult to isolate and characterize soil organic constituents. 18th century soil chemists successfully used alkaline extraction to isolate a portion of the organic constituents in soil. This led to the theory that a 'humification' process created distinct 'humic substances' like 'humic acid', 'fulvic acid', and 'humin'. [8] However, modern chemical analysis methods applied to unprocessed mineral soil have not directly observed large humic molecules. This suggests that the extraction and fractionation techniques used to isolate humic substances alter the original chemical composition of the organic matter. Since the definition of humic substances like humic and fulvic acids relies on their separation through these methods, it raises the question of whether the distinction between these compounds accurately reflects the natural state of organic matter in soil. [26] Despite these concerns, the 'humification' theory persists in the field and in even textbooks, and attempts to redefine 'humic substances' in soil have resulted in a proliferation of conflicting definitions. This lack of consensus makes it difficult to communicate scientific understanding of soil processes and properties accurately." [8]

Determination of humic acids in water samples

The presence of humic acid in water intended for potable or industrial use can have a significant impact on the treatability of that water and the success of chemical disinfection processes. For instance, humic and fulvic acids can react with the chemicals used in the chlorination process to form disinfection byproducts such as dihaloacetonitriles, which are toxic to humans. [27] [28] Accurate methods of establishing humic acid concentrations are therefore essential in maintaining water supplies, especially from upland peaty catchments in temperate climates.

As a lot of different bio-organic molecules in very diverse physical associations are mixed together in natural environments, it is cumbersome to measure their exact concentrations in the humic superstructure. For this reason, concentrations of humic acid are traditionally estimated out of concentrations of organic matter, typically from concentrations of total organic carbon (TOC) or dissolved organic carbon (DOC).

Extraction procedures are bound to alter some of the chemical linkages present in the soil humic substances (mainly ester bonds in biopolyesters such as cutins and suberins). The humic extracts are composed of large numbers of different bio-organic molecules that have not yet been totally separated and identified. However, single classes of residual biomolecules have been identified by selective extractions and chemical fractionation, and are represented by alkanoic and hydroxy alkanoic acids, resins, waxes, lignin residues, sugars, and peptides.

Ecological effects

Organic matter soil amendments have been known by farmers to be beneficial to plant growth for longer than recorded history. [29] However, the chemistry and function of the organic matter have been a subject of controversy since humans began postulating about it in the 18th century. Until the time of Liebig, it was supposed that humus was used directly by plants, but, after Liebig showed that plant growth depends upon inorganic compounds, many soil scientists held the view that organic matter was useful for fertility only as it was broken down with the release of its constituent nutrient elements into inorganic forms. At the present time, soil scientists hold a more holistic view and at least recognize that humus influences soil fertility through its effect on the water-holding capacity of the soil. Also, since plants have been shown to absorb and translocate the complex organic molecules of systemic insecticides, they can no longer discredit the idea that plants may be able to absorb the soluble forms of humus; [30] this may in fact be an essential process for the uptake of otherwise insoluble iron oxides.

A study on the effects of humic acid on plant growth was conducted at Ohio State University which said in part "humic acids increased plant growth" and that there were "relatively large responses at low application rates". [31]

A 1998 study by scientists at the North Carolina State University College of Agriculture and Life Sciences showed that addition of humate to soil significantly increased root mass in creeping bentgrass turf. [32] [33]

A 2018 study by scientists at the University of Alberta showed that humic acids can reduce prion infectivity in laboratory experiments, but that this effect may be uncertain in the environment due to minerals in the soil that buffer the effect. [34]

Anthropogenic production

Humans can affect the production of humic substances via a variety of ways: by making use of natural processes by composting lignin or adding biochar (see soil rehabilitation), or by industrial synthesis of artificial humic substances from organic feedstocks directly. These artificial substances may be similarly divided into artificial humic acid (A-HA) and artificial fulvic acid (A-FA). [35]

Lignosulfonates, a by-product from the sulfite pulping of wood, are valorized in the industrial fabrication of concrete where they serve as water reducer, or concrete superplasticizer, to decrease the water-cement ratio (w/c) of fresh concrete while preserving its workability. The w/c ratio of concrete is one of the main parameter controlling the mechanical strength of hardened concrete and its durability. The same wood pulping process can also be applied to obtain humus-like substances by hydrolysis and oxidation. A kind of artificial "lignohumate" can be directly produced from wood in this way. [36]

Agricultural litter can be turned into an artificial humic substance by a hydrothermal reaction. The resulting mixture can increase the content of dissolved organic matter (DOM) and total organic carbon (TOC) in soil. [35]

Lignite (brown coal) may also be oxidized to produce humic substances, reversing the natural process of coal formation under anoxic and reducing conditions. This form of "mineral-derived fulvic acid" is widely used in China. [37] This process also occurs in nature, producing leonardite. [38]

Economic geology

In economic geology, the term humate refers to geological materials, such as weathered coal beds (leonardite), mudrock, or pore material in sandstones, that are rich in humic acids. Humate has been mined from the Fruitland Formation of New Mexico for use as a soil amendment since the 1970s, with nearly 60,000 metric tons produced by 2016. [39] Humate deposits may also play an important role in the genesis of uranium ore bodies. [40]

Technological applications

The heavy-metal binding abilities of humic acids have been exploited to develop remediation technologies for removing lead from waste water. To this end, Yurishcheva et al. coated magnetic nanoparticles with humic acids. After capturing lead ions, the nanoparticles can then be captured using a magnet. [41]

Ancient masonry

Archeology finds that ancient Egypt used mudbricks reinforced with straw and humic acids. [42]

See also

Related Research Articles

<span class="mw-page-title-main">Alkaloid</span> Class of naturally occurring chemical compounds

Alkaloids are a class of basic, naturally occurring organic compounds that contain at least one nitrogen atom. This group also includes some related compounds with neutral and even weakly acidic properties. Some synthetic compounds of similar structure may also be termed alkaloids. In addition to carbon, hydrogen and nitrogen, alkaloids may also contain oxygen or sulfur. Rarer still, they may contain elements such as phosphorus, chlorine, and bromine.

<span class="mw-page-title-main">Humus</span> Organic matter in soils resulting from decay of plant and animal materials

In classical soil science, humus is the dark organic matter in soil that is formed by the decomposition of plant and animal matter. It is a kind of soil organic matter. It is rich in nutrients and retains moisture in the soil. Humus is the Latin word for "earth" or "ground".

<span class="mw-page-title-main">Soil</span> Mixture of organic matter, minerals, gases, liquids, and organisms that together support life

Soil, also commonly referred to as earth, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support the life of plants and soil organisms. Some scientific definitions distinguish dirt from soil by restricting the former term specifically to displaced soil.

The first isolation of deoxyribonucleic acid (DNA) was done in 1869 by Friedrich Miescher. DNA extraction is the process of isolating DNA from the cells of an organism isolated from a sample, typically a biological sample such as blood, saliva, or tissue. It involves breaking open the cells, removing proteins and other contaminants, and purifying the DNA so that it is free of other cellular components. The purified DNA can then be used for downstream applications such as PCR, sequencing, or cloning. Currently, it is a routine procedure in molecular biology or forensic analyses.

<span class="mw-page-title-main">Phytoremediation</span> Decontamination technique using living plants

Phytoremediation technologies use living plants to clean up soil, air and water contaminated with hazardous contaminants. It is defined as "the use of green plants and the associated microorganisms, along with proper soil amendments and agronomic techniques to either contain, remove or render toxic environmental contaminants harmless". The term is an amalgam of the Greek phyto (plant) and Latin remedium. Although attractive for its cost, phytoremediation has not been demonstrated to redress any significant environmental challenge to the extent that contaminated space has been reclaimed.

The pedosphere is the outermost layer of the Earth that is composed of soil and subject to soil formation processes. It exists at the interface of the lithosphere, atmosphere, hydrosphere and biosphere. The pedosphere is the skin of the Earth and only develops when there is a dynamic interaction between the atmosphere, biosphere, lithosphere and the hydrosphere. The pedosphere is the foundation of terrestrial life on Earth.

Organic matter, organic material, or natural organic matter refers to the large source of carbon-based compounds found within natural and engineered, terrestrial, and aquatic environments. It is matter composed of organic compounds that have come from the feces and remains of organisms such as plants and animals. Organic molecules can also be made by chemical reactions that do not involve life. Basic structures are created from cellulose, tannin, cutin, and lignin, along with other various proteins, lipids, and carbohydrates. Organic matter is very important in the movement of nutrients in the environment and plays a role in water retention on the surface of the planet.

<span class="mw-page-title-main">Absorption (chemistry)</span> Chemical process

Absorption is a physical or chemical phenomenon or a process in which atoms, molecules or ions enter the liquid or solid bulk phase of a material. This is a different process from adsorption, since molecules undergoing absorption are taken up by the volume, not by the surface.

Humins are carbon-based macromolecular substances, that can be found in soil chemistry or as a by-product from saccharide-based biorefinery processes.

Glomalin is a hypothetical glycoprotein produced abundantly on hyphae and spores of arbuscular mycorrhizal (AM) fungi in soil and in roots. Glomalin was proposed in 1996 by Sara F. Wright, a scientist at the USDA Agricultural Research Service, but it was not isolated and described yet. The name comes from Glomerales, an order of fungi. Most AM fungi are of the division Glomeromycota. An elusive substance, it is mostly assumed to have a glue-like effect on soil, but it has not been isolated yet.

Potassium humate is the potassium salt of humic acid. It is manufactured commercially by alkaline extraction of brown coal (lignite) leonardite and is used mainly as a soil conditioner.

<span class="mw-page-title-main">Shilajit</span> Thick, sticky tar-like substance

Shilajit, salajeet, mumijo or mumlayi or mumie is an organic-mineral product of predominantly biological origin, formed in the mountains.

Soil chemistry is the study of the chemical characteristics of soil. Soil chemistry is affected by mineral composition, organic matter and environmental factors. In the early 1870s a consulting chemist to the Royal Agricultural Society in England, named J. Thomas Way, performed many experiments on how soils exchange ions, and is considered the father of soil chemistry. Other scientists who contributed to this branch of ecology include Edmund Ruffin, and Linus Pauling.

Acid–base extraction is a subclass of liquid–liquid extractions and involves the separation of chemical species from other acidic or basic compounds. It is typically performed during the work-up step following a chemical synthesis to purify crude compounds and results in the product being largely free of acidic or basic impurities. A separatory funnel is commonly used to perform an acid-base extraction.


Soil organic matter (SOM) is the organic matter component of soil, consisting of plant and animal detritus at various stages of decomposition, cells and tissues of soil microbes, and substances that soil microbes synthesize. SOM provides numerous benefits to soil's physical and chemical properties and its capacity to provide regulatory ecosystem services. SOM is especially critical for soil functions and quality.

<span class="mw-page-title-main">Superheated water</span> Pressurized liquid water at temperatures between the boiling and critical points

Superheated water is liquid water under pressure at temperatures between the usual boiling point, 100 °C (212 °F) and the critical temperature, 374 °C (705 °F). It is also known as "subcritical water" or "pressurized hot water". Superheated water is stable because of overpressure that raises the boiling point, or by heating it in a sealed vessel with a headspace, where the liquid water is in equilibrium with vapour at the saturated vapor pressure. This is distinct from the use of the term superheating to refer to water at atmospheric pressure above its normal boiling point, which has not boiled due to a lack of nucleation sites.

The International Humic Substances Society is a scientific society with a focus on research into natural organic matter (NOM) in soil and water.

<span class="mw-page-title-main">Phlobaphene</span>

Phlobaphenes are reddish, alcohol-soluble and water-insoluble phenolic substances. They can be extracted from plants, or be the result from treatment of tannin extracts with mineral acids. The name phlobaphen come from the Greek roots φλoιὀς (phloios) meaning bark and βαφή (baphe) meaning dye.

Cheluviation is the process in which the metal ions in the upper layer of the soil are combined with organic ligands to form coordination complexes or chelates, moving downwards through eluviation and then depositing.

<span class="mw-page-title-main">Irina Perminova</span> Russian chemist (born 1960)

Irina Vasilievna Perminova is a Russian scientist, Professor, Dr. Habil. in Analytical Chemistry, Chief Scientist, Head of the Laboratory of Natural Humic Systems at the Division of Medicinal Chemistry and Fine Organic Synthesis of the Department of Chemistry of the Moscow University, Moscow, Russia

References

  1. ↑ "Humus" . Retrieved 2024-07-20– via Dictionary.com Random House Dictionary Unabridged.
  2. ↑ Piccolo A. (2016). "In memoriam of Prof. F.J. Stevenson and the question of humic substances". Chemical and Biological Technologies in Agriculture. 3. doi: 10.1186/s40538-016-0076-2 .
  3. ↑ Drosos M.; et al. (May 15, 2017). "A molecular zoom into soil Humeome by a direct sequential chemical fractionation of soi". The Science of the Total Environment. 586: 807–816. Bibcode:2017ScTEn.586..807D. doi:10.1016/j.scitotenv.2017.02.059. PMID   28214121.
  4. ↑ "Source Materials for International Humic Substances Society Samples" . Retrieved 22 July 2020.
  5. ↑ Piccolo A.; et al. (2018). "The Molecular Composition of Humus Carbon: Recalcitrance and Reactivity in Soils". The Molecular Composition of Humus Carbon: Recalcitrance and Reactivity in Soils. In: The Future of Soil Carbon, Wiley and Sons. pp. 87–124. doi:10.1016/B978-0-12-811687-6.00004-3. ISBN   9780128116876.
  6. ↑ Nebbioso A. and Piccolo A. (2011). "Basis of a Humeomics Science: Chemical Fractionation and Molecular Characterization of Humic Biosuprastructures". Biomacromolecules. 12 (4): 1187–1199. doi:10.1021/bm101488e. PMID   21361272. S2CID   45333263.
  7. ↑ Canellas P.L and Olivares F.L. (2014). "TPhysiological responses to humic substances as plant growth promoter". Chemical and Biological Technologies in Agriculture. 1: 3. doi: 10.1186/2196-5641-1-3 .
  8. 1 2 3 Lehmann, J.; Kleber, M. (2015-12-03). "The contentious nature of soil organic matter". Nature. 528 (7580): 60–8. Bibcode:2015Natur.528...60L. doi: 10.1038/nature16069 . PMID   26595271. The development of this extraction method preceded theory, tempting scientists to develop explanations for the synthesis of materials resembling operationally extracted 'humic substances', rather than to develop an understanding of the nature of all organic matter in soil.[...] This lack of evidence means that 'humification' is increasingly questioned, yet the underlying theory persists in the contemporary literature, including current textbooks.[...] The issue has also been approached by redefining 'humic substances' as the portion of soil organic matter that cannot be molecularly characterized or by calling all soil organic matter 'humus'. We argue that this compromise – maintaining terminology but altering its meanings in varying ways – hampers scientific progress beyond the soil sciences. The [need for accurate models] of soil organic matter does not allow a confusing middle path; it requires leaving the traditional view behind to bring about lasting innovation and progress. This is critical as scientific fields outside the soil sciences base their research on the false premise of the existence of 'humic substances'. Thus an issue of terminology becomes a problem of false inference, with far-reaching implications beyond our ability to communicate scientifically accurate soil processes and properties.
  9. ↑ Stevenson, F.J. (1994). Humus Chemistry: Genesis, Composition, Reactions, Wiley & Sons, New York, 1994, pp. 188-210. ISBN   0471594741.
  10. ↑ Tan, K. H. (2014). Humic matter in soil and the environment: principles and controversies. 2nd ed. Boca Ranton: CRC Press. ISBN   1482234459.
  11. ↑ Ponomarenko, E.V.; Anderson, D.W. (2001), "Importance of charred organic matter in Black Chernozem soils of Saskatchewan", Canadian Journal of Soil Science, 81 (3): 285–297, doi:10.4141/s00-075, The present paradigm views humus as a system of heteropolycondensates, largely produced by the soil microflora, in varying associations with clay (Anderson 1979). Because this conceptual model, and simulation models rooted within the concept, do not accommodate a large char component, a considerable change in conceptual understanding (a paradigm shift) appears imminent.
  12. ↑ Mao, J.-D.; Johnson, R. L.; Lehmann, J.; Olk, D. C.; Neves, E. G.; Thompson, M. L.; Schmidt-Rohr, K. (2012). "Abundant and stable char residues in soils: implications for soil fertility and carbon sequestration". Environmental Science and Technology. 46 (17): 9571–9576. Bibcode:2012EnST...46.9571M. CiteSeerX   10.1.1.698.270 . doi:10.1021/es301107c. PMID   22834642.
  13. ↑ "Isolation of IHSS Soil Fulvic and Humic Acids | IHSS" . Retrieved 2024-10-24.
  14. ↑ "Isolation of IHSS Aquatic Humic and Fulvic Acids | IHSS" . Retrieved 2024-10-24.
  15. ↑ Lamar, Richard T; Olk, Daniel C; Mayhew, Lawrence; Bloom, Paul R (2014-05-01). "A New Standardized Method for Quantification of Humic and Fulvic Acids in Humic Ores and Commercial Products". Journal of AOAC International. 97 (3): 721–730. doi:10.5740/jaoacint.13-393. ISSN   1060-3271. PMID   25051616.
  16. ↑ "Isolation of NOM by Reverse Osmosis | IHSS" . Retrieved 2024-10-24.
  17. ↑ "Effects of Humic Acid on Animals and Humans: An Overview of Literature and a Review of Current Research" (PDF). vet servis.
  18. ↑ Nebbioso A. and Piccolo A. (2012). "Advances in humeomics: Enhanced structural identification of humic molecules after size fractionation of a soil humic acid". Analytica Chimica Acta. 720: 77–90. doi:10.1016/j.aca.2012.01.027. PMID   22365124.
  19. ↑ Drosos M. and Piccolo A. (2018). "The molecular dynamics of soil humus as a function of tillage". Land Degradation & Development. 29 (6): 1792–1805. doi:10.1002/ldr.2989. S2CID   135445097.
  20. 1 2 Piccolo, A. (2002). The Supramolecular structure of humic substances. A novel understanding of humus chemistry and implications in soil science. Advances in Agronomy. Vol. 75. pp. 57–134. doi:10.1016/S0065-2113(02)75003-7. ISBN   978-0-12-000793-6.
  21. ↑ Ponomarenko, E.V.; Anderson, D.W. (2001), "Importance of charred organic matter in Black Chernozem soils of Saskatchewan", Canadian Journal of Soil Science, 81 (3): 285–297, doi:10.4141/s00-075
  22. 1 2 Stevenson F.J. (1994). Humus Chemistry: Genesis, Composition, Reactions. New York: John Wiley & Sons.
  23. 1 2 Olk, D. C.; Bloom, P. R.; Perdue, E. M.; McKnight, D. M.; Chen, Y.; Farenhorst, A.; Senesi, N.; Chin, Y.-P.; Schmitt-Kopplin, P.; Hertkorn, N.; Harir, M. (2019). "Environmental and Agricultural Relevance of Humic Fractions Extracted by Alkali from Soils and Natural Waters". Journal of Environmental Quality. 48 (2): 217–232. doi: 10.2134/jeq2019.02.0041 . ISSN   0047-2425. PMID   30951132.
  24. ↑ Tipping, E (1994). "'WHAM – a chemical equilibrium model and computer code for waters, sediments, and soils incorporating a discrete site/electrostatic model of ion-binding by humic substances". Computers and Geosciences. 20 (6): 973–1023. Bibcode:1994CG.....20..973T. doi:10.1016/0098-3004(94)90038-8.
  25. ↑ Ghabbour, E.A.; Davies, G. (Editors) (2001). Humic Substances: Structures, Models and Functions. Cambridge, U.K.: RSC publishing. ISBN   978-0-85404-811-3.{{cite book}}: |author2= has generic name (help)
  26. ↑ Weil, Ray R.; Brady, Nyle C. (2017). The Nature and Properties of Soils (15th ed.). Columbus, Ohio: Pearson Education (published April 2017). p. 549. ISBN   978-0-13-325448-8. LCCN   2016008568. OCLC   936004363. [new analytical techniques have] found very little in the way of humic macromolecules in mineral soils. Instead, evidence suggests that the alkali extraction process itself actually creates giant polymers from smaller biomolecules.
  27. ↑ Oliver, Barry G. (1983). "Dihaloacetonitriles in drinking water: Algae and fulvic acid as precursors". Environmental Science & Technology. 17 (2): 80–83. Bibcode:1983EnST...17...80O. doi:10.1021/es00108a003. PMID   22295957.
  28. ↑ Peters, Ruud J.B.; De Leer, Ed W.B.; De Galan, Leo (1990). "Dihaloacetonitriles in Dutch drinking waters". Water Research. 24 (6): 797. doi:10.1016/0043-1354(90)90038-8.
  29. ↑ Lapedes, Daniel N., ed. (1966). McGraw-Hill encyclopedia of science and technology: an international reference work, Volume 12. McGraw-Hill. p. 428. ISBN   978-0070452657. The value of adding organic matter to the soil in the form of animal manures, green manures, and crop residues for producing favorable soil tilth has been known since ancient times
  30. ↑ Pan American Union. Dept. of Cultural Affairs. División de Fomento Científico, Pan American Union. Dept. of Scientific Affairs, Organization of American States. Dept. of Scientific Affairs (1984). Ciencia interamericana: Volumes 24–27. And since plants have shown their ability to absorb and translocate the complex molecules of systemic insecticides, they can no longer discredit the idea that plants are able to absorb the soluble humic nutrients, containing by far ...{{cite book}}: CS1 maint: multiple names: authors list (link)
  31. ↑ Arancon, Norman Q.; Edwards, Clive. A.; Lee, Stephen; Byrne, Robert (2006). "Effects of humic acids from vermicomposts on plant growth". European Journal of Soil Biology. 42: S65–S69. CiteSeerX   10.1.1.486.2522 . doi:10.1016/j.ejsobi.2006.06.004.
  32. ↑ Cooper, R. J.; Liu, Chunhua; Fisher, D. S. (1998). "Influence of Humic Substances on Rooting and Nutrient Content of Creeping Bentgrass". Crop Science. 38 (6): 1639. doi:10.2135/cropsci1998.0011183X003800060037x.
  33. ↑ Liu, Chunhua; Cooper, R. J. (August 1999). "Humic Substances Their Influence on Creeping Bentgrass Growth and Stress Tolerance" (PDF). TurfGrass Trends: 6.
  34. ↑ Kuznetsova, Alsu; Cullingham, Catherine; McKenzie, Debbie; Aiken, Judd M. (November 2018). "Soil humic acids degrade CWD prions and reduce infectivity". PLOS Pathogens. 14 (11): e1007414. doi: 10.1371/journal.ppat.1007414 . PMC   6264147 . PMID   30496301.
  35. 1 2 Tang, Chunyu; Li, Yuelei; Song, Jingpeng; Antonietti, Markus; Yang, Fan (2021-06-25). "Artificial humic substances improve microbial activity for binding CO2". iScience. 24 (6): 102647. Bibcode:2021iSci...24j2647T. doi:10.1016/j.isci.2021.102647. ISSN   2589-0042. PMC   8387571 . PMID   34466779.
  36. ↑ Yakimenko, Olga; Stepanov, Andrey; Patsaeva, Svetlana; Khundzhua, Daria; Osipova, Olesya; Gladkov, Oleg (3 July 2021). "Formation of Humic-Like Substances during the Technological Process of Lignohumate Synthesis as a Function of Time". Separations. 8 (7): 96. doi: 10.3390/separations8070096 .
  37. ↑ Gong, Guanqun; Xu, Liangwei; Zhang, Yingjie; Liu, Weixin; Wang, Ming; Zhao, Yufeng; Yuan, Xin; Li, Yajun (3 November 2020). "Extraction of Fulvic Acid from Lignite and Characterization of Its Functional Groups". ACS Omega. 5 (43): 27953–27961. doi:10.1021/acsomega.0c03388. PMC   7643152 . PMID   33163778.
  38. ↑ "Youngs, R.W. & Frost, C.M. 1963. Humic acids from leonardite – a soil conditioner and organic fertilizer. Ind. Eng. Chem., 55, 95–99" (PDF). Archived from the original (PDF) on 2010-06-01. Retrieved 2022-03-18.
  39. ↑ Newcomer, Robert W.; Nybo, John P.; Newcomer, Jacob K. (2020). "Humate in the upper Cretaceous Fruitland Formation in northwestern New Mexico" (PDF). New Mexico Geological Society Special Publication. 14: 41–46. Retrieved 26 October 2020.
  40. ↑ McLemore, Virginia T. (2020). "Uranium deposits in the Poison Canyon trend, Ambrosia Lake Subdistrict, Grants Uranium District, McKinley and Cibola Counties, New Mexico" (PDF). New Mexico Geological Society Special Publication. 14: 53–63. Retrieved 26 October 2020.
  41. ↑ Yurishcheva, A.A.; Kydralieva, K.A.; Zaripova, A.A.; Dzhardimalieva, G.I.; Pomogaylo, A.D.; Jorobekova, S.J. (2013). "Sorption of Pb2+ by magnetite coated with humic acids". J. Biol. Phys. Chem. 13 (2): 61–68. doi:10.4024/04YU13A.jbpc.13.02.
  42. ↑ Lucas, A.; Harris, J.R. (1998). Ancient Egyptian Materials and Industries. New York: Dover Publications. p. 62. ISBN   978-0-486-40446-2.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.