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 In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atoms, which are made up of interacting subatomic part ...

composed of

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. Th ...

s that have come from the feces and remains of

organism In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells ( cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and fu ...

s such as

plant Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae excl ...

s and

animal Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and go through an ontogenetic stage ...

s. Organic molecules can also be made by chemical reactions that do not involve life. Basic structures are created from

cellulose Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell wa ...

tannin Tannins (or tannoids) are a class of astringent, polyphenolic biomolecules that bind to and precipitate proteins and various other organic compounds including amino acids and alkaloids. The term ''tannin'' (from Anglo-Norman ''tanner'' ...

cutin Cutin is one of two waxy polymers that are the main components of the plant cuticle, which covers all aerial surfaces of plants. It is an insoluble substance with waterproof quality. Cutin also harbors cuticular waxes, which assist in cuticle st ...

, and

lignin Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity a ...

, along with other various

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...

lipid Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids in ...

s, and

carbohydrate In organic chemistry, a carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula (where ''m'' may o ...

s. 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.

Formation

Living organisms In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and fun ...

are composed of organic compounds. In life, they secrete or excrete organic material into their environment, shed body parts such as leaves and roots and after organisms die, their bodies are broken down by bacterial and fungal action. Larger molecules of organic matter can be formed from the polymerization of different parts of already broken down matter. The composition of natural organic matter depends on its origin, transformation mode, age, and existing environment, thus its bio-physicochemical functions vary with different environments.Nicola Senesi, Baoshan Xing, and P.M. Huang, Biophysico-Chemical Processes Involving Natural Nonlifiidulfitving Organic Matter in Environmental Systems, New York: IUPAC, 2006.

Natural ecosystem functions

Organic matter is common throughout the

ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syst ...

and is cycled through decomposition processes by soil microbial communities that are crucial for nutrient availability. After degrading and reacting, it can move into

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

and mainstream

water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as ...

via waterflow. Organic matter provides nutrition to living organisms. Organic matter acts as a

buffer Buffer may refer to: Science * Buffer gas, an inert or nonflammable gas * Buffer solution, a solution used to prevent changes in pH * Buffering agent, the weak acid or base in a buffer solution * Lysis buffer, in cell biology * Metal ion buffer * ...

in aqueous solution to maintain a neutral pH in the environment. The buffer acting component has been proposed to be relevant for neutralizing

acid rain Acid rain is rain or any other form of precipitation that is unusually acidic, meaning that it has elevated levels of hydrogen ions (low pH). Most water, including drinking water, has a neutral pH that exists between 6.5 and 8.5, but ac ...

.Steve Cabaniss, Greg Madey, Patricia Maurice, Yingping Zhou, Laura Leff, Olacheesy head Bob Wetzel, Jerry Leenheer, and Bob Wershaw, comps, Stochastic Synthesis of Natural Organic Matter, UNM, ND, KSU, UNC, USGS, 22 Apr 2007.

Source cycle

Some organic matter not already in the soil comes from

groundwater Groundwater is the water present beneath Earth's surface in rock and Pore space in soil, soil pore spaces and in the fractures of stratum, rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit ...

. When the groundwater saturates the soil or sediment around it, organic matter can freely move between the phases. Groundwater has its own sources of natural organic matter including: * organic matter deposits, such as

kerogen Kerogen is solid, insoluble organic matter in sedimentary rocks. Comprising an estimated 1016 tons of carbon, it is the most abundant source of organic compounds on earth, exceeding the total organic content of living matter 10,000-fold. It ...

and

coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is formed when ...

. * soil and sediment organic matter. * organic matter infiltrating into the subsurface from rivers, lakes, and marine systems." Organisms decompose into organic matter, which is then transported and recycled. Not all biomass migrates, some is rather stationary, turning only over the course of millions of years.

Soil organic matter

The organic matter in

derives from plants, animals and microorganisms. In a forest, for example, leaf litter and woody material falls to the forest floor. This is sometimes referred to as organic material. When it decays to the point in which it is no longer recognizable, it is called soil organic matter. When the organic matter has broken down into a stable substance that resist further decomposition it is called

humus 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 Lati ...

. Thus soil organic matter comprises all of the organic matter in the soil exclusive of the material that has not decayed. An important property of

soil organic matter 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 b ...

is that it improves the capacity of a soil to hold water and nutrients, and allows their slow release, thereby improving the conditions for plant growth. Another advantage of humus is that it helps the soil to stick together which allows

nematode The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant- parasitic nematodes also known as eelworms. They are a diverse animal phylum inhabiting a bro ...

s, or microscopic bacteria, to easily decay the nutrients in the soil.Crow, W. T
“Organic Matter, Green Manures and Cover Crops For Nematode Management.”
University of Florida. The Institute of Food and Agricultural Sciences Feb. 2009 Web 10 October 2009 There are several ways to quickly increase the amount of humus. Combining compost, plant or animal materials/waste, or green manure with soil will increase the amount of humus in the soil. # Compost: decomposed organic material. # Plant and animal material and waste: dead plants or plant waste such as leaves or bush and tree trimmings, or animal manure. # Green manure: plants or plant material that is grown for the sole purpose of being incorporated with soil. These three materials supply nematodes and bacteria with nutrients for them to thrive and produce more humus, which will give plants enough nutrients to survive and grow.

Priming effect

The '' priming effect'' is characterized by intense changes in the natural process of soil organic matter (SOM) turnover, resulting from relatively moderate intervention with the soil. The phenomenon is generally caused by either pulsed or continuous changes to inputs of fresh organic matter (FOM). Priming effects usually result in an acceleration of mineralization due to a ''trigger'' such as the FOM inputs. The cause of this increase in decomposition has often been attributed to an increase in microbial activity resulting from higher energy and nutrient availability released from the FOM. After the input of FOM, specialized microorganisms are believed to grow quickly and only decompose this newly added organic matter. The turnover rate of SOM in these areas is at least one order of magnitude higher than the bulk soil. Other soil treatments, besides organic matter inputs, which lead to this short-term change in turnover rates, include "input of mineral fertilizer, exudation of organic substances by roots, mere mechanical treatment of soil or its drying and rewetting." Priming effects can be either ''positive'' or ''negative'' depending on the reaction of the soil with the added substance. A positive priming effect results in the acceleration of mineralization while a negative priming effect results in immobilization, leading to N unavailability. Although most changes have been documented in C and N pools, the priming effect can also be found in phosphorus and sulfur, as well as other nutrients. Löhnis was the first to discover the priming effect phenomenon in 1926 through his studies of

green manure In agriculture, a green manure is a crop specifically produced to be incorporated into the soil while still green. Typically, the green manure's biomass is incorporated with a plow or disk, as is often done with (brown) manure. The primary goal ...

decomposition and its effects on

legume A legume () is a plant in the family Fabaceae (or Leguminosae), or the fruit or seed of such a plant. When used as a dry grain, the seed is also called a pulse. Legumes are grown agriculturally, primarily for human consumption, for livestock for ...

plants in soil. He noticed that when adding fresh organic residues to the soil, it resulted in intensified mineralization by the humus N. It was not until 1953, though, that the term ''priming effect'' was given by Bingeman in his paper titled, ''The effect of the addition of organic material on the decomposition of an organic soil''. Several other terms had been used before ''priming effect'' was coined, including priming action, added nitrogen interaction (ANI), extra N and additional N. Despite these early contributions, the concept of the priming effect was widely disregarded until about the 1980s-1990s. The priming effect has been found in many different studies and is regarded as a common occurrence, appearing in most plant soil systems. However, the mechanisms which lead to the priming effect are more complex then originally thought, and still remain generally misunderstood. Although there is a lot of uncertainty surrounding the reason for the priming effect, a few ''undisputed facts'' have emerged from the collection of recent research: # The priming effect can arise either instantaneously or very shortly (potentially days or weeks) after the addition of a substance is made to the soil. # The priming effect is larger in soils that are rich in C and N as compared to those poor in these nutrients. # Real priming effects have not been observed in sterile environments. # The size of the priming effect increases as the amount of added treatment to the soil increases. Recent findings suggest that the same priming effect mechanisms acting in soil systems may also be present in aquatic environments, which suggests a need for broader considerations of this phenomenon in the future.

Decomposition

One suitable definition of organic matter is biological material in the process of decaying or

decomposing Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is e ...

, such as

. A closer look at the biological material in the process of decaying reveals so-called

organic compounds In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The s ...

( biological molecules) in the process of breaking up (disintegrating). The main processes by which soil molecules disintegrates are by

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...

l or fungal enzymatic catalysis. If bacteria or fungi were not present on Earth, the process of decomposition would have proceeded much slower.

Organic chemistry

Measurements of organic matter generally measure only

s or

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon ma ...

, and so are only an approximation of the level of once-living or decomposed matter. Some definitions of organic matter likewise only consider "organic matter" to refer to only the carbon content, or organic compounds, and do not consider the origins or decomposition of the matter. In this sense, not all organic compounds are created by living organisms, and living organisms do not only leave behind organic material. A clam's shell, for example, while biotic, does not contain much organic carbon, so may not be considered organic matter in this sense. Conversely,

urea Urea, also known as carbamide, is an organic compound with chemical formula . This amide has two amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest amide of carbamic acid. Urea serves an important ...

is one of many organic compounds that can be synthesized without any biological activity. Organic matter is heterogeneous and very complex. Generally, organic matter, in terms of weight, is: * 45–55%

* 35–45%

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...

* 3–5%

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-to ...

* 1–4%

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

The molecular weights of these compounds can vary drastically, depending on if they repolymerize or not, from 200 to 20,000 amu. Up to one third of the

present is in

aromatic compounds Aromatic compounds, also known as "mono- and polycyclic aromatic hydrocarbons", are organic compounds containing one or more aromatic rings. The parent member of aromatic compounds is benzene. The word "aromatic" originates from the past groupin ...

in which the carbon atoms form usually six-membered rings. These rings are very stable due to

resonance stabilization In chemistry, resonance, also called mesomerism, is a way of describing bonding in certain molecules or polyatomic ions by the combination of several contributing structures (or ''forms'', also variously known as ''resonance structures'' or '' ...

, so they are difficult to break down. The aromatic rings are also susceptible to

electrophilic In chemistry, an electrophile is a chemical species that forms bonds with nucleophiles by accepting an electron pair. Because electrophiles accept electrons, they are Lewis acids. Most electrophiles are positively charged, have an atom that carr ...

and

nucleophilic In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they are ...

attack from other electron-donating or electron-accepting material, which explains the possible polymerization to create larger molecules of organic matter. There are also reactions that occur with organic matter and other material in the soil to create compounds never seen before. Unfortunately, it is very difficult to characterize these because so little is known about natural organic matter in the first place. Research is currently being done to figure out more about these new compounds and how many of them are being formed."Topic Snapshot: Natural Organic Material", American Water Works Association Research Foundation, 2007, 22 April 2007

Aquatic

Aquatic organic matter can be further divided into two components: (1) dissolved organic matter (DOM), measured as

colored dissolved organic matter Colored dissolved organic matter (CDOM) is the optically measurable component of dissolved organic matter in water. Also known as ''chromophoric'' dissolved organic matter, ''yellow substance'', and ''gelbstoff'', CDOM occurs naturally in aquati ...

(CDOM) or

dissolved organic carbon Dissolved organic carbon (DOC) is the fraction of organic carbon operationally defined as that which can pass through a filter with a pore size typically between 0.22 and 0.7 micrometers. The fraction remaining on the filter is called partic ...

(DOC), and (2) particulate organic matter (POM). They are typically differentiated by that which can pass through a 0.45 micrometre filter (DOM), and that which cannot (POM).

Detection

Organic matter plays an important role in drinking water and wastewater treatment and recycling, natural aquatic ecosystems, aquaculture, and environmental rehabilitation. It is therefore important to have reliable methods of detection and characterisation, for both short- and long-term monitoring. A variety of analytical detection methods for organic matter have existed for up to decades, to describe and characterise organic matter. These include, but are not limited to: total and dissolved organic carbon,

mass spectrometry Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a '' mass spectrum'', a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is u ...

nuclear magnetic resonance (NMR) spectroscopy Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy or magnetic resonance spectroscopy (MRS), is a spectroscopic technique to observe local magnetic fields around atomic nuclei. The sample is placed in a magnetic fie ...

, infrared (IR) spectroscopy, UV-Visible spectroscopy, and

fluorescence spectroscopy Fluorescence spectroscopy (also known as fluorimetry or spectrofluorometry) is a type of electromagnetic spectroscopy that analyzes fluorescence from a sample. It involves using a beam of light, usually ultraviolet light, that excites the electro ...

. Each of these methods has its own advantages and limitations.

Water purification

The same capability of natural organic matter that helps with water retention in soil creates problems for current water purification methods. In water, organic matter can still bind to metal ions and minerals. These bound molecules are not necessarily stopped by the purification process, but do not cause harm to any humans, animals, or plants. However, because of the high level of reactivity of organic matter, by-products that do not contain nutrients can be made. These by-products can induce

biofouling Biofouling or biological fouling is the accumulation of microorganisms, plants, algae, or small animals where it is not wanted on surfaces such as ship and submarine hulls, devices such as water inlets, pipework, grates, ponds, and rivers tha ...

, which essentially clogs water filtration systems in water purification facilities, as the by-products are larger than membrane pore sizes. This clogging problem can be treated by chlorine disinfection (

chlorination Chlorination may refer to: * Chlorination reaction In chemistry, halogenation is a chemical reaction that entails the introduction of one or more halogens into a compound. Halide-containing compounds are pervasive, making this type of transform ...

), which can break down residual material that clogs systems. However, chlorination can form

disinfection by-products Disinfection by-products (DBPs) result from chemical reactions between organic and inorganic matter in water with chemical treatment agents during the water disinfection process. Chlorination disinfection byproducts Chlorinated disinfection agen ...

. Water with organic matter can be disinfected with

ozone Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the l ...

-initiated radical reactions. The ozone (three oxygens) has very strong

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or ...

characteristics. It can form

hydroxyl In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydrox ...

radicals (OH) when it decomposes, which will react with the organic matter to shut down the problem of biofouling.Cho, Min, Hyenmi Chung, and Jeyong Yoon, "Disinfection of Water Containing Natural Organic Matter by Using Ozone-Initiated Radical Reactions," Abstract, Applied and Environmental Microbiology Vol. 69 No.4 (2003): 2284-2291.

Vitalism

The equation of "organic" with living organisms comes from the now-abandoned idea of

vitalism Vitalism is a belief that starts from the premise that "living organisms are fundamentally different from non-living entities because they contain some non-physical element or are governed by different principles than are inanimate things." Wher ...

that attributed a special force to life that alone could create organic substances. This idea was first questioned after the artificial synthesis of urea by

Friedrich Wöhler Friedrich Wöhler () FRS(For) Hon FRSE (31 July 180023 September 1882) was a German chemist known for his work in inorganic chemistry, being the first to isolate the chemical elements beryllium and yttrium in pure metallic form. He was the fi ...

in 1828.

References

Bibliography

* * Cabaniss, Steve, Greg Madey, Patricia Maurice, Yingping Zhou, Laura Leff, Ola Olapade, Bob Wetzel, Jerry Leenheer, and Bob Wershaw, comps. Stochastic Synthesis of Natural Organic Matter. UNM, ND, KSU, UNC, USGS. 22 Apr. 2007. * Cho, Min, Hyenmi Chung, and Jeyong Yoon. "Disinfection of Water Containing Natural Organic Matter by Using Ozone-Initiated Radical Reactions." Abstract. Applied and Environmental Microbiology Vol. 69 No.4 (2003): 2284–2291. * Fortner, John D., Joseph B. Hughes, Jae-Hong Kim, and Hoon Hyung. "Natural Organic Matter Stabilizes Carbon Nanotubes in the Aqueous Phase." Abstract. Environmental Science & Technology Vol. 41 No. 1 (2007): 179–184. * "Researchers Study Role of Natural Organic Matter in Environment." Science Daily 20 Dec. 2006. 22 Apr. 2007 . * Senesi, Nicola, Baoshan Xing, and P.m. Huang. Biophysico-Chemical Processes Involving Natural Nonliving Organic Matter in Environmental Systems. New York: IUPAC, 2006. * "Table 1: Surface Area, Volume, and Average Depth of Oceans and Seas." Encyclopædia Britannica. * "Topic Snapshot: Natural Organic Material." American Water Works Association Research Foundation. 2007. 22 Apr. 2007 . * United States of America. United States Geological Survey. Earth's Water Distribution. 10 May 2007. * Water Sheds: Organic Matter. North Carolina State University. 1 May 2007 . {{DEFAULTSORT:Organic Matter Organic compounds Organic chemistry