Biomass feedstocks.

Historically, humans have harnessed biomass-derived energy since the time when people began burning wood fuel. Even in 2019, biomass is the only source of fuel for domestic use in many developing countries. All biomass is biologically-produced matter based in carbon, hydrogen and oxygen. The estimated biomass production in the world is approximately 100 billion metric tons of carbon per year, about half in the ocean and half on land.  Wood and residues from wood, for instance spruce, birch, eucalyptus, willow, oil palm, remains the largest biomass energy source today. It is used directly as a fuel or processed into pellet fuel or other forms of fuels. Biomass also includes plant or animal matter that can be converted into fuel, fibers or industrial chemicals. There are numerous types of plants, including corn, switchgrass, miscanthus, hemp, sorghum, sugarcane, and bamboo. The main waste energy feedstocks are wood waste, agricultural waste, municipal solid waste, manufacturing waste, and landfill gas. Sewage sludge is another source of biomass. There is ongoing research involving algae or algae-derived biomass. Other biomass feedstocks are enzymes or bacteria from various sources, grown in cell cultures or hydroponics.  Based on the source of biomass, biofuels are classified broadly into two major categories:  First-generation biofuels are derived from food sources, such as sugarcane and corn starch. Sugars present in this biomass are fermented to produce bioethanol, an alcohol fuel which serve as an additive to gasoline, or in a fuel cell to produce electricity.  Second-generation biofuels utilize non-food-based biomass sources such as perennial energy crops (low input crops), and agricultural/municipal waste. There is huge potential for second generation biofuels but the resources are currently under-utilized.

Thermal conversions.

Thermal conversion processes use heat as the dominant mechanism to upgrade biomass into a better and more practical fuel. The basic alternatives are torrefaction, pyrolysis, and gasification, these are separated principally by the extent to which the chemical reactions involved are allowed to proceed (mainly controlled by the availability of oxygen and conversion temperature).  There are other less common, more experimental or proprietary thermal processes that may offer benefits, such as hydrothermal upgrading. Some have been developed for use on high moisture content biomass, including aqueous slurries, and allow them to be converted into more convenient forms.

Chemical conversion.

A range of chemical processes may be used to convert biomass into other forms, such as to produce a fuel that is more practical to store, transport and use, or to exploit some property of the process itself. Many of these processes are based in large part on similar coal-based processes, such as the Fischer-Tropsch synthesis. Biomass can be converted into multiple commodity chemicals.

Biochemical conversion.

As biomass is a natural material, many highly efficient biochemical processes have developed in nature to break down the molecules of which biomass is composed, and many of these biochemical conversion processes can be harnessed. In most cases, microorganisms are used to perform the conversion process: anaerobic digestion, fermentation, and composting.  Glycoside hydrolases are the enzymes involved in the degradation of the major fraction of biomass, such as polysaccharides present in starch and lignocellulose. Thermostable variants are gaining increasing roles as catalysts in biorefining applications, since recalcitrant biomass often needs thermal treatment for more efficient degradation.

Electrochemical conversion.

Biomass can be directly converted to electrical energy via electrochemical (electrocatalytic) oxidation of the material. This can be performed directly in a direct carbon fuel cell, direct liquid fuel cells such as direct ethanol fuel cell, a direct methanol fuel cell, a direct formic acid fuel cell, a L-ascorbic Acid Fuel Cell (vitamin C fuel cell), and a microbial fuel cell. The fuel can also be consumed indirectly via a fuel cell system containing a reformer which converts the biomass into a mixture of CO and H before it is consumed in the fuel cell.

Environmental impact.

On combustion, the carbon from biomass is released into the atmosphere as carbon dioxide (CO). After a period of time ranging from a few months to decades, the CO produced from combustion is absorbed from the atmosphere by plants or trees. However, the carbon storage capacity of forests may be reduced overall if destructive forestry techniques are employed.  All biomass crops sequester carbon. For example, soil organic carbon has been observed to be greater below switchgrass crops than under cultivated cropland, especially at depths below. For Miscanthus x giganteus, McCalmont et al. found accumulation rates ranging from 0.42 to 3.8 tonnes per hectare per year, with a mean accumulation rate of 1.84 tonne (0.74 tonnes per acre per year), or 20% of total harvested carbon per year. The grass sequesters carbon in its continually increasing root biomass, together with carbon input from fallen leaves. Typically, perennial crops sequester more carbon than annual crops because the root buildup is allowed to continue undisturbed over many years. Also, perennial crops avoid the yearly tillage procedures (plowing, digging) associated with growing annual crops. Tilling induces soil aeration, which accelerates the soil carbon decomposition rate, by stimulating soil microbe populations. Also, tilling makes it easier for the oxygen (O) atoms in the atmosphere to attach to carbon (C) atoms in the soil, producing CO2.  The simple proposal that biomass is carbon-neutral put forward in the early 1990s has been superseded by the more nuanced proposal that for a particular bioenergy project to be carbon neutral, the total carbon sequestered by a bioenergy crop's root system must compensate for all the emissions from the related, aboveground bioenergy project. This includes any emissions caused by direct or indirect land use change. Many first generation bioenergy projects are not carbon neutral given these demands. Some have even higher total GHG emissions than some fossil based alternatives. Transport fuels might be worse than solid fuels in this regard.  Some are carbon neutral or even negative, especially perennial crops. The amount of carbon sequestrated and the amount of GHG (greenhouse gases) emitted affect how the total GHG life cycle cost of a bioenergy project develops. Specifically, a GHG/carbon-negative life cycle is possible if the total below-ground carbon accumulation more than compensates for the above-ground total life-cycle GHG emissions. Biomass releases carbon dioxide gas that was absorbed during its growth cycle, indicating that released gas can be processed by photosynthetic methods. Plants that are the source of the biomass may be a carbon-neutral energy source.  Successful sequestration is dependent on planting sites, as the best soils for sequestration are those that are currently low in carbon. The assumption that annual cropland provides greater potential for soil carbon sequestration than grassland appears to be over‐simplistic, but there is an opportunity to improve predictions of soil carbon sequestration potential using the information on the initial soil carbon stock as a stronger predictor of ∆C [change in carbon amount] than prior land use.  Forest-based biomass projects has received criticism for ineffective GHG mitigation from a number of environmental organizations, including Greenpeace and the Natural Resources Defense Council. Environmental groups also argue that it might take decades for the carbon released by burning biomass to be recaptured by new trees. Biomass burning produces air pollution in the form of carbon monoxide, volatile organic compounds, particulates and other pollutants. In 2009 a Swedish study of the giant brown haze that periodically covers large areas in South Asia determined that two thirds of it had been principally produced by residential cooking and agricultural burning, and one third by fossil-fuel burning. The use of wood biomass as an industrial fuel has been shown to produce fewer particulates and other pollutants than the burning seen in wildfires or open field fires.

Biomass is plant or animal material used for energy production (electricity or heat), or in various industrial processes as raw substance for a range of products. It can be purposely grown energy crops (e.g. miscanthus, switchgrass), wood or forest residues, waste from food crops (wheat straw, bagasse), horticulture (yard waste), food processing (corn cobs), animal farming (manure, rich in nitrogen and phosphorus), or human waste from sewage plants.

Biomasa je souhrn látek tvořících těla všech organismů, jak rostlin, bakterií, sinic a hub, tak i živočichů. Odhaduje se, že veškerá biomasa na Zemi obsahuje 550 gigatun uhlíku, přičemž na rostliny z toho připadá 450 gigatun uhlíku. Tímto pojmem tak často označujeme rostlinnou biomasu využitelnou i pro energetické účely. Energie biomasy má tedy převážně svůj prapůvod ve slunečním záření a fotosyntéze, a proto se jedná o obnovitelný zdroj energie.


History.

Cellulose was discovered in 1838 by the French chemist Anselme Payen, who isolated it from plant matter and determined its chemical formula. Cellulose was used to produce the first successful thermoplastic polymer, celluloid, by Hyatt Manufacturing Company in 1870. Production of rayon ("artificial silk") from cellulose began in the 1890s and cellophane was invented in 1912. Hermann Staudinger determined the polymer structure of cellulose in 1920. The compound was first chemically synthesized (without the use of any biologically derived enzymes) in 1992, by Kobayashi and Shoda.

Structure and properties.

Cellulose has no taste, is odorless, is hydrophilic with the contact angle of 20–30 degrees, is insoluble in water and most organic solvents, is chiral and is biodegradable. It was shown to melt at 467 °C in pulse tests made by Dauenhauer "et al." (2016). It can be broken down chemically into its glucose units by treating it with concentrated mineral acids at high temperature.  Cellulose is derived from -glucose units, which condense through β(1→4)-glycosidic bonds. This linkage motif contrasts with that for α(1→4)-glycosidic bonds present in starch and glycogen. Cellulose is a straight chain polymer. Unlike starch, no coiling or branching occurs and the molecule adopts an extended and rather stiff rod-like conformation, aided by the equatorial conformation of the glucose residues. The multiple hydroxyl groups on the glucose from one chain form hydrogen bonds with oxygen atoms on the same or on a neighbor chain, holding the chains firmly together side-by-side and forming "microfibrils" with high tensile strength. This confers tensile strength in cell walls where cellulose microfibrils are meshed into a polysaccharide "matrix". The high tensile strength of plant stems and of the tree wood also arises from the arrangement of cellulose fibers intimately distributed into the lignin matrix. The mechanical role of cellulose fibers in the wood matrix responsible for its strong structural resistance, can somewhat be compared to that of the reinforcement bars in concrete, lignin playing here the role of the hardened cement paste acting as the "glue" in between the cellulose fibers. Mechanical properties of cellulose in primary plant cell wall are correlated with growth and expansion of plant cells. Live fluorescence microscopy techniques are promising in investigation of the role of cellulose in growing plant cells.  Compared to starch, cellulose is also much more crystalline. Whereas starch undergoes a crystalline to amorphous transition when heated beyond 60–70 °C in water (as in cooking), cellulose requires a temperature of 320 °C and pressure of 25 MPa to become amorphous in water.  Several different crystalline structures of cellulose are known, corresponding to the location of hydrogen bonds between and within strands. Natural cellulose is cellulose I, with structures I and I. Cellulose produced by bacteria and algae is enriched in I while cellulose of higher plants consists mainly of I. Cellulose in regenerated cellulose fibers is cellulose II. The conversion of cellulose I to cellulose II is irreversible, suggesting that cellulose I is metastable and cellulose II is stable. With various chemical treatments it is possible to produce the structures cellulose III and cellulose IV.  Many properties of cellulose depend on its chain length or degree of polymerization, the number of glucose units that make up one polymer molecule. Cellulose from wood pulp has typical chain lengths between 300 and 1700 units; cotton and other plant fibers as well as bacterial cellulose have chain lengths ranging from 800 to 10,000 units. Molecules with very small chain length resulting from the breakdown of cellulose are known as cellodextrins; in contrast to long-chain cellulose, cellodextrins are typically soluble in water and organic solvents.  Cellulose contains 44.44% carbon, 6.17% hydrogen, and 49.39% oxygen. The chemical formula of cellulose is (CHO)n where n is the degree of polymerization and represents the number of glucose groups.  Plant-derived cellulose is usually found in a mixture with hemicellulose, lignin, pectin and other substances, while bacterial cellulose is quite pure, has a much higher water content and higher tensile strength due to higher chain lengths.  Cellulose is soluble in Schweizer's reagent, cupriethylenediamine, cadmiumethylenediamine (Cadoxen), "N"-methylmorpholine "N"-oxide, and lithium chloride / dimethylacetamide. This is used in the production of regenerated celluloses (such as viscose and cellophane) from dissolving pulp. Cellulose is also soluble in many kinds of ionic liquids.  Cellulose consists of fibrils with crystalline and amorphous regions. These cellulose fibrils may be individualized by mechanical treatment of cellulose pulp, often assisted by chemical oxidation or enzymatic treatment, yielding semi-flexible cellulose nanofibrils generally 200 nm to 1 μm in length depending on the treatment intensity. Cellulose pulp may also be treated with strong acid to hydrolyze the amorphous fibril regions, thereby producing short rigid cellulose nanocrystals a few 100 nm in length. These nanocelluloses are of high technological interest due to their self-assembly into cholesteric liquid crystals, production of hydrogels or aerogels, use in nanocomposites with superior thermal and mechanical properties, and use as Pickering stabilizers for emulsions.

Processing.

Assay.

Given a cellulose-containing material, the carbohydrate portion that does not dissolve in a 17.5% solution of sodium hydroxide at 20 °C is "α cellulose", which is true cellulose. Acidification of the extract precipitates "β cellulose". The portion that dissolves in base but does not precipitate with acid is "γ cellulose".  Cellulose can be assayed using a method described by Updegraff (1969), where the fiber is dissolved in acetic and nitric acid to remove lignin, hemicellulose, and xylosans. The resulting cellulose is allowed to react with anthrone in sulfuric acid. The resulting coloured compound is assayed spectrophotometrically at a wavelength of approximately 635 nm.  In addition, cellulose can be represented by the difference between acid detergent fiber (ADF) and acid detergent lignin (ADL).  Luminescent conjugated oligothiophenes can also be used to detect cellulose using fluorescence microscopy or spectrofluorometric methods.

Biosynthesis.

In plants cellulose is synthesized at the plasma membrane by rosette terminal complexes (RTCs). The RTCs are hexameric protein structures, approximately 25 nm in diameter, that contain the cellulose synthase enzymes that synthesise the individual cellulose chains. Each RTC floats in the cell's plasma membrane and "spins" a microfibril into the cell wall.  RTCs contain at least three different cellulose synthases, encoded by "CesA" ("Ces" is short for "cellulose synthase") genes, in an unknown stoichiometry. Separate sets of "CesA" genes are involved in primary and secondary cell wall biosynthesis. There are known to be about seven subfamilies in the plant "CesA" superfamily, some of which include the more cryptic, tentatively-named "Csl" (cellulose synthase-like) enzymes. These cellulose syntheses use UDP-glucose to form the β(1→4)-linked cellulose.  Bacterial cellulose is produced using the same family of proteins, although the gene is called "BcsA" for "bacterial cellulose synthase" or "CelA" for "cellulose" in many instances. In fact, plants acquired "CesA" from the endosymbiosis event that produced the chloroplast. All cellulose synthases known belongs to glucosyltransferase family 2 (GT2).  Cellulose synthesis requires chain initiation and elongation, and the two processes are separate. Cellulose synthase ("CesA") initiates cellulose polymerization using a steroid primer, sitosterol-beta-glucoside, and UDP-glucose. It then utilizes UDP-D-glucose precursors to elongate the growing cellulose chain. A cellulase may function to cleave the primer from the mature chain.  Cellulose is also synthesised by tunicate animals, particularly in the tests of ascidians (where the cellulose was historically termed "tunicine" (tunicin)).

Breakdown (cellulolysis).

Cellulolysis is the process of breaking down cellulose into smaller polysaccharides called cellodextrins or completely into glucose units; this is a hydrolysis reaction. Because cellulose molecules bind strongly to each other, cellulolysis is relatively difficult compared to the breakdown of other polysaccharides. However, this process can be significantly intensified in a proper solvent, e.g. in an ionic liquid.  Most mammals have limited ability to digest dietary fiber such as cellulose. Some ruminants like cows and sheep contain certain symbiotic anaerobic bacteria (such as "Cellulomonas" and "Ruminococcus" spp.) in the flora of the rumen, and these bacteria produce enzymes called cellulases that help the microorganism to digest cellulose; the breakdown products are then used by the bacteria for proliferation. The bacterial mass is later digested by the ruminant in its digestive system (stomach and small intestine). Horses use cellulose in their diet by fermentation in their hindgut via symbiotic bacteria which produce cellulase to digest cellulose. Similarly, some termites contain in their hindguts certain flagellate protozoa producing such enzymes, whereas others contain bacteria or may produce cellulase.  The enzymes used to cleave the glycosidic linkage in cellulose are glycoside hydrolases including endo-acting cellulases and exo-acting glucosidases. Such enzymes are usually secreted as part of multienzyme complexes that may include dockerins and carbohydrate-binding modules.

Breakdown (thermolysis).

At temperatures above 350 °C, cellulose undergoes thermolysis (also called ‘pyrolysis’), decomposing into solid char, vapors, aerosols, and gases such as carbon dioxide. Maximum yield of vapors which condense to a liquid called "bio-oil" is obtained at 500 °C.  Semi-crystalline cellulose polymers react at pyrolysis temperatures (350–600 °C) in a few seconds; this transformation has been shown to occur via a solid-to-liquid-to-vapor transition, with the liquid (called "intermediate liquid cellulose" or "molten cellulose") existing for only a fraction of a second. Glycosidic bond cleavage produces short cellulose chains of two-to-seven monomers comprising the melt. Vapor bubbling of intermediate liquid cellulose produces aerosols, which consist of short chain anhydro-oligomers derived from the melt.  Continuing decomposition of molten cellulose produces volatile compounds including levoglucosan, furans, pyrans, light oxygenates and gases via primary reactions. Within thick cellulose samples, volatile compounds such as levoglucosan undergo ‘secondary reactions’ to volatile products including pyrans and light oxygenates such as glycolaldehyde.

Hemicellulose.

Hemicelluloses are polysaccharides related to cellulose that comprise about 20% of the biomass of land plants. In contrast to cellulose, hemicelluloses are derived from several sugars in addition to glucose, especially xylose but also including mannose, galactose, rhamnose, and arabinose. Hemicelluloses consist of shorter chains – between 500 and 3000 sugar units. Furthermore, hemicelluloses are branched, whereas cellulose is unbranched.

Derivatives.

The hydroxyl groups (-OH) of cellulose can be partially or fully reacted with various reagents to afford derivatives with useful properties like mainly cellulose esters and cellulose ethers (-OR). In principle, though not always in current industrial practice, cellulosic polymers are renewable resources.  Ester derivatives include:  The cellulose acetate and cellulose triacetate are film- and fiber-forming materials that find a variety of uses. The nitrocellulose was initially used as an explosive and was an early film forming material. With camphor, nitrocellulose gives celluloid.  Ether derivatives include:  The sodium carboxymethyl cellulose can be cross-linked to give the croscarmellose sodium (E468) for use as a disintegrant in pharmaceutical formulations.

Applications.

Cellulose for industrial use is mainly obtained from wood pulp and cotton. The kraft process is used to separate cellulose from lignin, another major component of plant matter.

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 -glucose units. Cellulose is an important structural component of the primary cell wall of green plants, many forms of algae and the oomycetes. Some species of bacteria secrete it to form biofilms. Cellulose is the most abundant organic polymer on Earth. The cellulose content of cotton fiber is 90%, that of wood is 40–50%, and that of dried hemp is approximately 57%.

Celulóza (dříve běžně "celulosa") je polysacharid sestávající z beta-D-glukózy. Jednotlivé glukózové jednotky jsou spojené glykosidovou vazbou β-1,4 a tvoří dlouhé, nerozvětvené řetězce, které jsou zcela nerozpustné ve vodě. Celulóza je hlavní stavební látkou rostlinných primárních buněčných stěn a spolu s ligninem a hemicelulózami se podílí na stavbě sekundárních buněčných stěn; celulóza je nejrozšířenějším biopolymerem na zemském povrchu, ročně jí vzniká až 1,5×10 tun. Mimo to se však vyskytuje i u některých živočichů, konkrétně u pláštěnců ("Tunicata").


Etymology and names.

This river was known to the ancient Indians in Sanskrit as "Sindhu" and the Persians as "Hindu" which was regarded by both of them as "the border river". The variation between the two names is explained by the Old Iranian sound change "*s" > "h", which occurred between 850–600 BCE according to Asko Parpola. From the Persian Achaemenid Empire, the name passed to the Greeks as "Indós" (Ἰνδός). It was adopted by the Romans as "Indus".  Southworth suggests that the name "Sindhu" is derived from "Cintu", the Proto-Dravidian word for date, a fruit commonly found in Sindh.  The meaning of "Sindhu" as a "large body of water, sea, or ocean" is a later meaning in Classical Sanskrit. A later Persian name for the river was "Darya", which similarly has the connotations of large body of water and sea. Other variants of the name "Sindhu" include Assyrian "Sinda" (as early as the 7th century BC), Persian "Ab-e-sind", Pashto "Abasind", Arab "Al-Sind", Chinese "Sintow", and Javanese "Santri".  In other languages of the region, the river is known as (Darya-ī Sindh) in Urdu सिन्धु ("Sindhu") in Hindi, سنڌو ("Sindhu") in Sindhi, ("Sindh") in Shahmukhi Punjabi, ਸਿੰਧ ਨਦੀ ("Sindh Nadī") in Gurmukhī Punjabi, اباسين ("Abāsin" lit. "Father of Rivers") in Pashto, نهر السند ("Nahar al-Sind") in Arabic, སེང་གེ་གཙང་པོ། ("singi khamban" lit. "Lion River" or "Lion Spring") in Tibetan, ("Yìndù") in Chinese, "Nilab" in Turki and සින්දු නදී ("Sindhu Nadi") in Sinhalese.

Description.

The Indus River provides key water resources for Pakistan's economy – especially the "breadbasket" of Punjab province, which accounts for most of the nation's agricultural production, and Sindh. The word Punjab means "land of five rivers" and the five rivers are Jhelum, Chenab, Ravi, Beas and Sutlej, all of which finally flow into the Indus. The Indus also supports many heavy industries and provides the main supply of potable water in Pakistan.  The ultimate source of the Indus is in Tibet; the river begins at the confluence of the Sengge Zangbo and Gar Tsangpo rivers that drain the Nganglong Kangri and Gangdise Shan (Gang Rinpoche, Mt. Kailash) mountain ranges. The Indus then flows northwest through Ladakh, India, and Baltistan into Gilgit, just south of the Karakoram range. The Shyok, Shigar and Gilgit rivers carry glacial waters into the main river. It gradually bends to the south and descends into the Punjab plains at Kalabagh, Pakistan. The Indus passes gigantic gorges deep near the Nanga Parbat massif. It flows swiftly across Hazara and is dammed at the Tarbela Reservoir. The Kabul River joins it near Attock. The remainder of its route to the sea is in the plains of the Punjab and Sindh, where the flow of the river becomes slow and highly braided. It is joined by the Panjnad at Mithankot. Beyond this confluence, the river, at one time, was named the "Satnad River" ("sat" = "seven", "nadī" = "river"), as the river now carried the waters of the Kabul River, the Indus River and the five Punjab rivers. Passing by Jamshoro, it ends in a large delta to the South of Thatta in the Sindh province of Pakistan  The Indus is one of the few rivers in the world to exhibit a tidal bore. The Indus system is largely fed by the snows and glaciers of the Himalayas, Karakoram and the Hindu Kush ranges of Tibet, the Indian states and union territories of Ladakh and Himachal Pradesh and the Gilgit-Baltistan region of Pakistan. The flow of the river is also determined by the seasons – it diminishes greatly in the winter, while flooding its banks in the monsoon months from July to September. There is also evidence of a steady shift in the course of the river since prehistoric times – it deviated westwards from flowing into the Rann of Kutch and adjoining Banni grasslands after the 1816 earthquake. Presently, Indus water flows in to the Rann of Kutch during its floods breaching flood banks.  The traditional source of the river is the "Sênggê Kanbab" (a.k.a. Sênggê Zangbo, Senge Khabab) or "Lion's Mouth", a perennial spring, not far from the sacred Mount Kailash marked by a long low line of Tibetan chortens. There are several other tributaries nearby, which may possibly form a longer stream than Sênggê Kanbab, but unlike the Sênggê Kanbab, are all dependent on snowmelt. The Zanskar River, which flows into the Indus in Ladakh, has a greater volume of water than the Indus itself before that point.

History.

The major cities of the Indus Valley Civilisation, such as Harappa and Mohenjo-daro, date back to around 3300 BC, and represent some of the largest human habitations of the ancient world. The Indus Valley Civilisation extended from across northeast Afghanistan to Pakistan and northwest India, with an upward reach from east of Jhelum River to Ropar on the upper Sutlej. The coastal settlements extended from Sutkagan Dor at the Pakistan, Iran border to Kutch in modern Gujarat, India. There is an Indus site on the Amu Darya at Shortughai in northern Afghanistan, and the Indus site Alamgirpur at the Hindon River is located only from Delhi. To date, over 1,052 cities and settlements have been found, mainly in the general region of the Ghaggar-Hakra River and its tributaries. Among the settlements were the major urban centres of Harappa and Mohenjo-daro, as well as Lothal, Dholavira, Ganeriwala, and Rakhigarhi. Only 90–96 of more than 800 known Indus Valley sites have been discovered on the Indus and its tributaries. The Sutlej, now a tributary of the Indus, in Harappan times flowed into the Ghaggar-Hakra River, in the watershed of which were more Harappan sites than along the Indus.  Most scholars believe that settlements of Gandhara grave culture of the early Indo-Aryans flourished in Gandhara from 1700 BC to 600 BC, when Mohenjo-daro and Harappa had already been abandoned.  The Rigveda describes several rivers, including one named "Sindhu". The Rigvedic "Sindhu" is thought to be the present-day Indus river. It is attested 176 times in its text, 94 times in the plural, and most often used in the generic sense of "river". In the Rigveda, notably in the later hymns, the meaning of the word is narrowed to refer to the Indus river in particular, e.g. in the list of rivers mentioned in the hymn of "Nadistuti sukta". The Rigvedic hymns apply a feminine gender to all the rivers mentioned therein, except for the Brahmaputra.  The word "India" is derived from the Indus River. In ancient times, "India" initially referred to those regions immediately along the east bank of the Indus, but by 300 BC, Greek writers including Herodotus and Megasthenes were applying the term to the entire subcontinent that extends much farther eastward.  The lower basin of the Indus forms a natural boundary between the Iranian Plateau and the Indian subcontinent; this region embraces all or parts of the Pakistani provinces Balochistan, Khyber Pakhtunkhwa, Punjab and Sindh and the countries Afghanistan and India. The first West Eurasian empire to annex the Indus Valley was the Persian Empire, during the reign of Darius the Great. During his reign, the Greek explorer Scylax of Caryanda was commissioned to explore the course of the Indus. It was crossed by the invading armies of Alexander, but after his Macedonians conquered the west bank—joining it to the Hellenic world, they elected to retreat along the southern course of the river, ending Alexander's Asian campaign. Alexander's admiral Nearchus set out from the Indus Delta to explore the Persian Gulf, until reaching the Tigris River. The Indus Valley were later dominated by the Mauryan and Kushan Empires, Indo-Greek Kingdoms, Indo-Scythians and Hepthalites. Over several centuries Muslim armies of Muhammad bin Qasim, Mahmud of Ghazni, Mohammed Ghori, Tamerlane and Babur crossed the river to invade Sindh and Punjab, providing a gateway to the Indian subcontinent.

Geology.

The Indus river feeds the Indus submarine fan, which is the second largest sediment body on the Earth. It consists of around 5 million cubic kilometres of material eroded from the mountains. Studies of the sediment in the modern river indicate that the Karakoram Mountains in northern Pakistan and India are the single most important source of material, with the Himalayas providing the next largest contribution, mostly via the large rivers of the Punjab (Jhelum, Ravi, Chenab, Beas and Sutlej). Analysis of sediments from the Arabian Sea has demonstrated that prior to five million years ago the Indus was not connected to these Punjab rivers which instead flowed east into the Ganga and were captured after that time. Earlier work showed that sand and silt from western Tibet was reaching the Arabian Sea by 45 million years ago, implying the existence of an ancient Indus River by that time. The delta of this proto-Indus river has subsequently been found in the Katawaz Basin, on the Afghan-Pakistan border.  In the Nanga Parbat region, the massive amounts of erosion due to the Indus river following the capture and rerouting through that area is thought to bring middle and lower crustal rocks to the surface.  In November 2011, satellite images showed that the Indus river had re-entered India, feeding Great Rann of Kutch, Little Rann of Kutch and a lake near Ahmedabad known as Nal Sarovar. Heavy rains had left the river basin along with the Lake Manchar, Lake Hemal and Kalri Lake (all in modern-day Pakistan) inundated. This happened two centuries after the Indus river shifted its course westwards following the 1819 Rann of Kutch earthquake.  The Induan Age at start of the Triassic Period of geological time is named for the Indus region.

Wildlife.

Accounts of the Indus valley from the times of Alexander's campaign indicate a healthy forest cover in the region, which has now considerably receded. The Mughal Emperor Babur writes of encountering rhinoceroses along its bank in his memoirs (the Baburnama). Extensive deforestation and human interference in the ecology of the Shivalik Hills has led to a marked deterioration in vegetation and growing conditions. The Indus valley regions are arid with poor vegetation. Agriculture is sustained largely due to irrigation works. The Indus river and its watershed has a rich biodiversity. It is home to around 25 amphibian species.

Mammals.

The Indus river dolphin ("Platanista indicus minor") is found only in the Indus River. It is subspecies of the South Asian river dolphin. The Indus river dolphin formerly also occurred in the tributaries of the Indus river. According to the World Wildlife Fund it is one of the most threatened cetaceans with only about 1,000 still existing.  There are two otter species in the Indus River basin: the Eurasian otter in the northeastern highland sections and the smooth-coated otter elsewhere in the river basin. The smooth-coated otters in the Indus River represent a subspecies found nowhere else, the Sindh otter ("Lutrogale perspicillata sindica").

Fish.

The Indus River basin has a high diversity, being the home of more than 180 freshwater fish species, including 22 which are found nowhere else. Fish also played a major role in earlier cultures of the region, including the ancient Indus Valley Civilisation where depictions of fish were frequent. The Indus script has a commonly used fish sign, which in its various forms may simply have meant "fish", or referred to stars or gods.  In the uppermost, highest part of the Indus River basin there are relatively few genera and species: "Diptychus", "Ptychobarbus", "Schizopyge", "Schizopygopsis" and "Schizothorax" snowtrout, "Triplophysa" loaches, and the catfish "Glyptosternon reticulatum". Going downstream these are soon joined by the golden mahseer "Tor putitora" (alternatively "T. macrolepis", although it often is regarded as a synonym of "T. putitora") and "Schistura" loaches. Downriver from around Thakot, Tarbela, the Kabul–Indus river confluence, Attock Khurd and Peshawar the diversity rises strongly, including many cyprinids ("Amblypharyngodon", "Aspidoparia", "Barilius", "Chela", "Cirrhinus", "Crossocheilus", "Cyprinion", "Danio", "Devario", "Esomus", "Garra", "Labeo", "Naziritor", "Osteobrama", "Pethia", "Puntius", "Rasbora", "Salmophasia", "Securicula" and "Systomus"), true loaches ("Botia" and "Lepidocephalus"), stone loaches ("Acanthocobitis" and "Nemacheilus"), ailiid catfish ("Clupisoma"), bagridae catfish ("Batasio", "Mystus", "Rita" and "Sperata"), airsac catfish ("Heteropneustes"), schilbid catfish ("Eutropiichthys"), silurid catfish ("Ompok" and "Wallago"), sisorid catfish ("Bagarius", "Gagata", "Glyptothorax" and "Sisor"), gouramis ("Trichogaster"), nandid leaffish ("Nandus"), snakeheads ("Channa"), spiny eel ("Macrognathus" and "Mastacembelus"), knifefish ("Notopterus"), glassfish ("Chanda" and "Parambassis"), clupeids ("Gudusia"), needlefish ("Xenentodon") and gobies ("Glossogobius"), as well as a few introduced species. As the altitude further declines the Indus basin becomes overall quite slow-flowing as it passes through the Punjab Plain. Major carp become common, and chameleonfish ("Badis"), mullet ("Sicamugil") and swamp eel ("Monopterus") appear. In some upland lakes and tributaries of the Punjab region snowtrout and mahseer are still common, but once the Indus basin reaches its lower plain the former group is entirely absent and the latter are rare. Many of the species of the middle sections of the Indus basin are also present in the lower. Notable examples of genera that are present in the lower plain but generally not elsewhere in the Indus River basin are the "Aphanius" pupfish, "Aplocheilus" killifish, palla fish ("Tenualosa ilisha"), catla ("Labeo catla"), rohu ("Labeo rohita") and "Cirrhinus mrigala". The lowermost part of the river and its delta are home to freshwater fish, but also a number of brackish and marine species. This includes including pomfret and prawns. The large delta has been recognized by conservationists as an important ecological region. Here, the river turns into many marshes, streams and creeks and meets the sea at shallow levels.  Palla fish ("Tenualosa ilisha") of the river is a delicacy for people living along the river. The population of fish in the river is moderately high, with Sukkur, Thatta, and Kotri being the major fishing centres – all in the lower Sindh course. As a result, damming and irrigation has made fish farming an important economic activity.

Economy.

The Indus is the most important supplier of water resources to the Punjab and Sindh plains – it forms the backbone of agriculture and food production in Pakistan. The river is especially critical since rainfall is meagre in the lower Indus valley. Irrigation canals were first built by the people of the Indus Valley Civilisation, and later by the engineers of the Kushan Empire and the Mughal Empire. Modern irrigation was introduced by the British East India Company in 1850 – the construction of modern canals accompanied with the restoration of old canals. The British supervised the construction of one of the most complex irrigation networks in the world. The Guddu Barrage is long – irrigating Sukkur, Jacobabad, Larkana and Kalat. The Sukkur Barrage serves over.  After Pakistan came into existence, a water control treaty signed between India and Pakistan in 1960 guaranteed that Pakistan would receive water from the Indus River and its two tributaries the Jhelum River & the Chenab River independently of upstream control by India.  The Indus Basin Project consisted primarily of the construction of two main dams, the Mangla Dam built on the Jhelum River and the Tarbela Dam constructed on the Indus River, together with their subsidiary dams. The Pakistan Water and Power Development Authority undertook the construction of the Chashma-Jhelum link canal – linking the waters of the Indus and Jhelum rivers – extending water supplies to the regions of Bahawalpur and Multan. Pakistan constructed the Tarbela Dam near Rawalpindi – standing long and high, with an long reservoir. It supports the Chashma Barrage near Dera Ismail Khan for irrigation use and flood control and the Taunsa Barrage near Dera Ghazi Khan which also produces 100,000 kilowatts of electricity. The Kotri Barrage near Hyderabad is long and provides additional water supplies for Karachi. The extensive linking of tributaries with the Indus has helped spread water resources to the valley of Peshawar, in the Khyber Pakhtunkhwa. The extensive irrigation and dam projects provide the basis for Pakistan's large production of crops such as cotton, sugarcane and wheat. The dams also generate electricity for heavy industries and urban centers.

People.

The inhabitants of the regions are mainly Muslim as Pakistan is an Islamic country through which the Indus river passes and forms a major natural feature and resource are diverse in ethnicity, religion, national and linguistic backgrounds. On the northern course of the river in the union territory of Ladakh in India, live the Buddhist people of Ladakh, of Tibetan stock, and the Dards of Indo-Aryan or Dardic stock and practising Islam. Then it descends into Baltistan, northern Pakistan passing the main Balti city of Skardu. A river from Dubair Bala also drains into it at Dubair Bazar. People living in this area are mainly Kohistani and speak the Kohistani language. Major areas through which the Indus river passes in Kohistan are Dasu, Pattan and Dubair. As it continues through Pakistan, the Indus river forms a distinctive boundary of ethnicity and cultures – upon the western banks the population is largely Pashtun, Baloch, and of other Iranian stock. The eastern banks are largely populated by people of Indo-Aryan stock, such as the Punjabis and the Sindhis. In northern Punjab and the Khyber Pakhtunkhwa, ethnic Pashtun tribes live alongside Dardic people in the hills (Khowar, Kalash, Shina, etc.), Burushos (in Hunza), and Punjabi people.  The people living along the Indus river speak Punjabi and Sindhi on the eastern side (in Punjab and Sindh provinces respectively), Pushto plus Balochi as well as Barohi (in Khyber Pakhtoonkha and Baluchistan provinces). In the province of Sindh, the upper third of the river is inhabited by people speaking Saraiki; which is a somewhat transitional dialect of the Punjabi and Sindhi languages.  The ethnicities of the Indus Valley (Pakistan and Northwest India) have a greater amount of ANI (or West Eurasian) admixture than other South Asians, including inputs from Western Steppe Herders, with evidence of more sustained and multi-layered migrations from the west.

Modern issues.

The Indus is a strategically vital resource for Pakistan's economy and society. After Pakistan and India declared Independence from the British Raj, the use of the waters of the Indus and its five eastern tributaries became a major dispute between India and Pakistan. The irrigation canals of the Sutlej valley and the Bari Doab were split – with the canals lying primarily in Pakistan and the headwork dams in India disrupting supply in some parts of Pakistan. The concern over India building large dams over various Punjab rivers that could undercut the supply flowing to Pakistan, as well as the possibility that India could divert rivers in the time of war, caused political consternation in Pakistan. Holding diplomatic talks brokered by the World Bank, India and Pakistan signed the Indus Waters Treaty in 1960. The treaty gave India control of the three easternmost rivers of the Punjab, the Sutlej, the Beas and the Ravi, while Pakistan gained control of the three western rivers, the Jhelum, the Chenab and the Indus. India retained the right to use of the western rivers for non-irrigation projects.  Large-scale diversion of the river's water for irrigation has raised far-reaching issues. Sediment clogging from poor maintenance of canals has affected agricultural production and vegetation on numerous occasions. Irrigation itself is increasing soil salinization, reducing crop yields and in some cases rendering farmland useless for cultivation. And ecologically, the reduced flow of fresh water and silt into the Indus delta is threatening the area's mangrove forests.  There are also concerns that the Indus River may be shifting its course westwards, although the progression spans centuries.

Indus delta.

Originally, the delta used to receive almost all of the water from the Indus river, which has an annual flow of approximately, and is accompanied by of silt. Since the 1940s, dams, barrages and irrigation works have been constructed on the river Indus. The Indus Basin Irrigation System is the "largest contiguous irrigation system developed over the past 140 years" anywhere in the world. This has reduced the flow of water and by 2018, the average annual flow of water below the Kotri barrage was, and annual amount of silt discharged was estimated at. As a result, the 2010 Pakistan floods were considered "good news" for the ecosystem and population of the river delta as they brought much needed fresh water. Any further utilization of the river basin water is not economically feasible.  Vegetation and wildlife of the Indus delta are threatened by the reduced inflow of fresh water, along with extensive deforestation, industrial pollution and global warming. Damming has also isolated the delta population of Indus river dolphins from those further upstream.

Effects of climate change on the river.

The Tibetan Plateau contains the world's third-largest store of ice. Qin Dahe, the former head of the China Meteorological Administration, said the recent fast pace of melting and warmer temperatures will be good for agriculture and tourism in the short term, but issued a strong warning:  "There is insufficient data to say what will happen to the Indus," says David Grey, the World Bank's senior water advisor in South Asia. "But we all have very nasty fears that the flows of the Indus could be severely, severely affected by glacier melt as a consequence of climate change," and reduced by perhaps as much as 50 percent. "Now what does that mean to a population that lives in a desert [where], without the river, there would be no life? I don't know the answer to that question," he says. "But we need to be concerned about that. Deeply, deeply concerned."  U.S. diplomat Richard Holbrooke said, shortly before his death in 2010, that he believed that falling water levels in the Indus River "could very well precipitate World War III."

Pollution.

Over the years factories on the banks of the Indus River have increased levels of water pollution in the river and the atmosphere around it. High levels of pollutants in the river have led to the deaths of endangered Indus river dolphin. The Sindh Environmental Protection Agency has ordered polluting factories around the river to shut down under the Pakistan Environmental Protection Act, 1997. Death of the Indus river dolphin has also been attributed to fishermen using poison to kill fish and scooping them up. As a result, the government banned fishing from Guddu Barrage to Sukkur.  The Indus is second among a group of ten rivers responsible for about 90% of all the plastic that reaches the oceans. The Yangtze is the only river contributing more plastic.

2010 floods.

Frequently, Indus river is prone to moderate to severe flooding. In July 2010, following abnormally heavy monsoon rains, the Indus River rose above its banks and started flooding. The rain continued for the next two months, devastating large areas of Pakistan. In Sindh, the Indus burst its banks near Sukkur on 8 August, submerging the village of Mor Khan Jatoi. In early August, the heaviest flooding moved southward along the Indus River from severely affected northern regions toward western Punjab, where at least of cropland was destroyed, and the southern province of Sindh., over two thousand people had died and over a million homes had been destroyed since the flooding began.

2011 floods.

The 2011 Sindh floods began during the Pakistani monsoon season in mid-August 2011, resulting from heavy monsoon rains in Sindh, eastern Balochistan, and southern Punjab. The floods caused considerable damage; an estimated 434 civilians were killed, with 5.3 million people and 1,524,773 homes affected. Sindh is a fertile region and often called the "breadbasket" of the country; the damage and toll of the floods on the local agrarian economy was said to be extensive. At least of arable land were inundated. The flooding followed the previous year's floods, which devastated a large part of the country. Unprecedented torrential monsoon rains caused severe flooding in 16 districts of Sindh.

Barrages, bridges, levees and dams.

In Pakistan currently there are six barrages on the Indus: Guddu barrage, Sukkur Barrage, Kotri barrage (also called Ghulam Muhammad barrage), Taunsa Barrage, Chashma Barrage and Jinnah Barrage. Another new barrage called "Sindh barrage" is planned as terminal barrage on Indus River. There are some bridges on river Indus, such as, Dadu Moro Bridge, Larkana Khairpur Indus River Bridge, Thatta-Sujawal bridge, Jhirk-Mula Katiar bridge and recently planned Kandhkot-Ghotki bridge.  The entire left bank of Indus river in Sind province is protected from river flooding by constructing around 600 km long levees. The right bank side is also leveed from Guddu barrage to Lake Manchar. In response to the levees construction, the river has been aggrading rapidly over the last 20 years leading to breaches upstream of barrages and inundation of large areas.  Tarbela Dam in Pakistan is constructed on the Indus River, while the controversial Kalabagh dam is also being constructed on Indus river. Pakistan is also building Munda Dam.

The Indus River (also called the Sindhū) is one of the longest rivers in Asia. It flows through China (western Tibet), India (Ladakh) and Pakistan. Originating in the Tibetan Plateau in the vicinity of Lake Manasarovar, the river runs a course through the Ladakh region of India, towards Gilgit-Baltistan and then flows in a southerly direction along the entire length of Pakistan to merge into the Arabian Sea near the port city of Karachi in Sindh. It is the longest river of Pakistan.

Indus (tibetsky སེང་གེ་ཁ་འབབ, wylie "Seng-ge kha-'abb," "Sênggê Zangbo (Lví řeka),", [Daryā-e Sindhu], [Siñdhū] nebo [Sindhu], [Ābāsinn], [Sindhū], [Sindhūnadī], [Sindhu nadī], [Sind], [Indos]) je nejvýznamnější řeka v Pákistánu. Protéká Tibetskou autonomní oblastí v ČLR, Ladakem v indickém státě Džammú a Kašmír přes pákistánskou část Kašmíru Gilgit-Baltistán a provincie Chajbar Paštúnchwá, Paňdžáb a Sindh. Řeka dala jméno dnešní "Indii" (přes řecké "Sinthos" a latinské "Sindus)". Před rozdělením Britské Indie na Pákistán a Indii v roce 1947 byla po Ganze druhou nejvýznamnější řekou této britské kolonie – z hlediska geografického, kulturního i obchodního. Je 3 180 km dlouhá. Povodí má rozlohu 980 000 km2.


Application.

Phytoremediation may be applied to polluted soil or static water environment. Examples where phytoremediation has been used successfully include the restoration of abandoned metal mine workings, and sites where polychlorinated biphenyls have been dumped during manufacture and mitigation of ongoing coal mine discharges reducing the impact of contaminants in soils, water, or air. Contaminants such as metals, pesticides, solvents, explosives, and crude oil and its derivatives, have been mitigated in phytoremediation projects worldwide. Many plants such as mustard plants, alpine pennycress, hemp, and pigweed have proven to be successful at hyperaccumulating contaminants at toxic waste sites.  Not all plants are able to accumulate heavy metals or organics pollutants due to differences in the physiology of the plant. Even cultivars within the same species have varying abilities to accumulate pollutants.  This technology has been increasingly investigated and has been employed at sites with soils contaminated with lead, uranium, and arsenic. While it has the advantage that environmental concerns may be treated in situ, one major disadvantage of phytoremediation is that it requires a long-term commitment, as the process is dependent on a plant's ability to grow and thrive in an environment that is not ideal for normal plant growth.

Case studies.

Kaltag School oil seep (Alaska).

The Alaska Department of Environmental Conservation (ADEC) has been monitoring fuel oil spills at the Kaltag School in Kaltag, Alaska, since 1991. The community has been working with ADEC to use a phytoremediation plan drafted by scientists at the University of Alaska Fairbanks. The ADEC continues to keep the public informed of the progress on their website.

Processes.

A range of processes mediated by plants or algae are tested in treating environmental problems:

Phytoextraction.

Phytoextraction (or "phytoaccumulation" or "phytosequestration") exploits the ability of plants or algae to remove contaminants from soil or water into harvestable plant biomass. The roots take up substances from the soil or water and concentrate it above ground in the plant biomass Organisms that can uptake high amounts of contaminants are called hyperaccumulators. Phytoextraction can also be performed by plants (e.g. Populus and Salix) that take up lower levels of pollutants, but due to their high growth rate and biomass production, may remove a considerable amount of contaminants from the soil. Phytoextraction has been growing rapidly in popularity worldwide for the last twenty years or so. Typically, phytoextraction is used for heavy metals or other inorganics. At the time of disposal, contaminants are typically concentrated in the much smaller volume of the plant matter than in the initially contaminated soil or sediment. After harvest, a lower level of the contaminant will remain in the soil, so the growth/harvest cycle must usually be repeated through several crops to achieve a significant cleanup. After the process, the soil is remediated. Mining of these extracted metals through phytomining, is also being experimented with as a way of recovering the material. Hyperaccumulating plants are often metallophyte. Induced or assisted phytoextraction is a process where a conditioning fluid containing a chelator or another agent is added to soil to increase metal solubility or mobilization so that the plants can absorb them more easily. While such additives can increase metal uptake by plants, they can also lead to large amounts of available metals in the soil beyond what the plants are able to translocate, causing potential leaching into the subsoil or groundwater.  Examples of plants that are known to accumulate the following contaminants:

Phytostabilization.

Phytostabilization reduces the mobility of substances in the environment, for example, by limiting the leaching of substances from the soil. It focuses on the long term stabilization and containment of the pollutant. The plant immobilizes the pollutants by binding them to soil particles making them less available for plant or human uptake. Unlike phytoextraction, phytostabilization focuses mainly on sequestering pollutants in soil near the roots but not in plant tissues. Pollutants become less bioavailable, resulting in reduced exposure. The plants can also excrete a substance that produces a chemical reaction, converting the heavy metal pollutant into a less toxic form. Stabilization results in reduced erosion, runoff, leaching, in addition to reducing the bioavailability of the contaminant. An example application of phytostabilization is using a vegetative cap to stabilize and contain mine tailings.

Phytodegradation.

Phytodegradation (also called phytotransformation) uses plants or microorganisms to degrade organic pollutants in the soil or within the body of the plant. The organic compounds are broken down by enzymes that the plant roots secrete and these molecules are then taken up by the plant and released through transpiration. This process works best with organic contaminants like herbicides, trichloroethylene, and methyl "tert"-butyl ether.  Phytotransformation results in the chemical modification of environmental substances as a direct result of plant metabolism, often resulting in their inactivation, degradation (phytodegradation), or immobilization (phytostabilization). In the case of organic pollutants, such as pesticides, explosives, solvents, industrial chemicals, and other xenobiotic substances, certain plants, such as Cannas, render these substances non-toxic by their metabolism. In other cases, microorganisms living in association with plant roots may metabolize these substances in soil or water. These complex and recalcitrant compounds cannot be broken down to basic molecules (water, carbon-dioxide, etc.) by plant molecules, and, hence, the term "phytotransformation" represents a change in chemical structure without complete breakdown of the compound. The term "Green Liver" is used to describe phytotransformation, as plants behave analogously to the human liver when dealing with these xenobiotic compounds (foreign compound/pollutant). After uptake of the xenobiotics, plant enzymes increase the polarity of the xenobiotics by adding functional groups such as hydroxyl groups (-OH).  This is known as Phase I metabolism, similar to the way that the human liver increases the polarity of drugs and foreign compounds (drug metabolism). Whereas in the human liver enzymes such as cytochrome P450s are responsible for the initial reactions, in plants enzymes such as peroxidases, phenoloxidases, esterases and nitroreductases carry out the same role.  In the second stage of phytotransformation, known as Phase II metabolism, plant biomolecules such as glucose and amino acids are added to the polarized xenobiotic to further increase the polarity (known as conjugation). This is again similar to the processes occurring in the human liver where glucuronidation (addition of glucose molecules by the UGT class of enzymes, e.g. UGT1A1) and glutathione addition reactions occur on reactive centres of the xenobiotic.  Phase I and II reactions serve to increase the polarity and reduce the toxicity of the compounds, although many exceptions to the rule are seen. The increased polarity also allows for easy transport of the xenobiotic along aqueous channels.  In the final stage of phytotransformation (Phase III metabolism), a sequestration of the xenobiotic occurs within the plant. The xenobiotics polymerize in a lignin-like manner and develop a complex structure that is sequestered in the plant. This ensures that the xenobiotic is safely stored, and does not affect the functioning of the plant. However, preliminary studies have shown that these plants can be toxic to small animals (such as snails), and, hence, plants involved in phytotransformation may need to be maintained in a closed enclosure.  Hence, the plants reduce toxicity (with exceptions) and sequester the xenobiotics in phytotransformation. Trinitrotoluene phytotransformation has been extensively researched and a transformation pathway has been proposed.

Phytostimulation.

Phytostimulation (or rhizodegradation) is the enhancement of soil microbial activity for the degradation of organic contaminants, typically by organisms that associate with roots. This process occurs within the rhizosphere, which is the layer of soil that surrounds the roots. Plants release carbohydrates and acids that stimulate microorganism activity which results in the biodegradation of the organic contaminants. This means that the microorganisms are able to digest and break down the toxic substances into harmless form. Phytostimulation has been shown to be effective in degrading petroleum hydrocarbons, PCBs, and PAHs. Phytostimulation can also involve aquatic plants supporting active populations of microbial degraders, as in the stimulation of atrazine degradation by hornwort.

Phytovolatilization.

Phytovolatilization is the removal of substances from soil or water with release into the air, sometimes as a result of phytotransformation to more volatile and/or less polluting substances. In this process, contaminants are taken up by the plant and through transpiration, evaporate into the atmosphere. This is the most studied form of phytovolatilization, where volatilization occurs at the stem and leaves of the plant, however indirect phytovolatilization occurs when contaminants are volatilized from the root zone. Selenium (Se) and Mercury (Hg) are often removed from soil through phytovolatilization. Poplar trees are one of the most successful plants for removing VOCs through this process due to its high transpiration rate.

Rhizofiltration.

Rhizofiltration is a process that filters water through a mass of roots to remove toxic substances or excess nutrients. The pollutants remain absorbed in or adsorbed to the roots. This process is often used to clean up contaminated groundwater through planting directly in the contaminated site or through removing the contaminated water and providing it to these plants in an off-site location. In either case though, typically plants are first grown in a greenhouse under precise conditions.

Biological hydraulic containment.

Biological hydraulic containment occurs when some plants, like poplars, draw water upwards through the soil into the roots and out through the plant, which decreases the movement of soluble contaminants downwards, deeper into the site and into the groundwater.

Phytodesalination.

Phytodesalination uses halophytes (plants adapted to saline soil) to extract salt from the soil to improve its fertility

Role of genetics.

Breeding programs and genetic engineering are powerful methods for enhancing natural phytoremediation capabilities, or for introducing new capabilities into plants. Genes for phytoremediation may originate from a micro-organism or may be transferred from one plant to another variety better adapted to the environmental conditions at the cleanup site. For example, genes encoding a nitroreductase from a bacterium were inserted into tobacco and showed faster removal of TNT and enhanced resistance to the toxic effects of TNT. Researchers have also discovered a mechanism in plants that allows them to grow even when the pollution concentration in the soil is lethal for non-treated plants. Some natural, biodegradable compounds, such as exogenous polyamines, allow the plants to tolerate concentrations of pollutants 500 times higher than untreated plants, and to absorb more pollutants.

Hyperaccumulators and biotic interactions.

A plant is said to be a hyperaccumulator if it can concentrate the pollutants in a minimum percentage which varies according to the pollutant involved (for example: more than 1000 mg/kg of dry weight for nickel, copper, cobalt, chromium or lead; or more than 10,000 mg/kg for zinc or manganese). This capacity for accumulation is due to hypertolerance, or "phytotolerance": the result of adaptative evolution from the plants to hostile environments through many generations. A number of interactions may be affected by metal hyperaccumulation, including protection, interferences with neighbour plants of different species, mutualism (including mycorrhizae, pollen and seed dispersal), commensalism, and biofilm.

Phytoscreening.

As plants are able to translocate and accumulate particular types of contaminants, plants can be used as biosensors of subsurface contamination, thereby allowing investigators to quickly delineate contaminant plumes. Chlorinated solvents, such as trichloroethylene, have been observed in tree trunks at concentrations related to groundwater concentrations. To ease field implementation of phytoscreening, standard methods have been developed to extract a section of the tree trunk for later laboratory analysis, often by using an increment borer. Phytoscreening may lead to more optimized site investigations and reduce contaminated site cleanup costs.

Phytoremediation /ˌfaɪtəʊrɪˌmiːdɪˈeɪʃən/ () refers to the technologies that 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".

Fytoremediace je termín shrnující metody využívající zelené rostliny k odstranění znečišťujících látek z prostředí. Jsou metodou využití živých rostlin přímo na místě znečištění. Název fytoremediace pochází z řeckého slova phyto = rostlina a latinského remedium = čistit. Vybrané druhy rostlin se využívají k extrakci toxických kovů, včetně radioaktivních izotopů, i k odstranění některých organických látek. Prostředím, z něhož jsou znečišťující látky odstraňovány jsou půda, sedimenty, kaly a voda. Mezi znečišťující látky, které jsou takto odstraňovány patří například těžké kovy, radionuklidy, explosiva, barviva, pesticidy nebo i léčiva. Úspěšnost ovlivňuje zejména rozpustnost znečišťující látky, typ média a doba uplynulá od kontaminace. Je předpoklad, že úspěšnost remediace by bylo možné značně zvýšit pomocí genetických manipulací u vhodných rostlin.


Genetic basis.

Several gene families are involved in the processes of hyperaccumulation including upregulation of absorption and sequestration of heavy metal metals. These hyperaccumulation genes (HA genes) are found in over 450 plant species, including the model organisms "Arabidopsis" and Brassicaceae. The expression of such genes is used to determine whether a species is capable of hyperaccumulation. Expression of HA genes provides the plant with capacity to uptake and sequester metals such as As, Co, Fe, Cu, Cd, Pb, Hg, Se, Mn, Zn, Mo and Ni in 100–1000x the concentration found in sister species or populations.  The capacity for hyperaccumulation is dependent on two major factors: environmental exposure and expression of members of the ZIP gene family. Although experiments have shown that the hyperaccumulation is partially dependent on environmental exposure (i.e. only plants exposed to metal are observed with high concentrations of that metal), hyperaccumulation is ultimately dependent on the presence and upregulation of genes involved with that process. It has been shown that hyperaccumulation capacities can be inherited in "Thlaspi caerulescens" (Brassicaceae) and others. As there is a wide variety among hyperaccumulating species that span across different plant families, it is likely that HA genes were ecotypically selected for. In most hyperaccumulating plants, the main mechanism for metal transport are the proteins coded by genes in the ZIP family, however other families such as the HMA, MATE, YSL and MTP families have also been observed to be involved. The ZIP gene family is a novel, plant-specific gene family that encodes Cd, Mn, Fe and Zn transporters. The ZIP family plays a role in supplying Zn to metalloproteins.  In one study on "Arabidopsis", it was found that the metallophyte "Arabidopsis halleri" expressed a member of the ZIP family that was not expressed in a non-metallophytic sister species. This gene was an iron regulated transporter (IRT-protein) that encoded several primary transporters involved with cellular uptake of cations above the concentration gradient. When this gene was transformed into yeast, hyperaccumulation was observed. This suggests that overexpression of ZIP family genes that encode cation transporters is a characteristic genetic feature of hyperaccumulation. Another gene family that has been observed ubiquitously in hyperaccumulators are the ZTP and ZNT families. A study on T. caerulescens identified the ZTP family as a plant specific family with high sequence similarity to other zinc transporter4. Both the ZTP and ZNT families, like the ZIP family, are zinc transporters. It has been observed in hyperaccumulating species, that these genes, specifically ZNT1 and ZNT2 alleles are chronically overexpressed.  While the exact mechanism by which these genes facilitate hyperaccumulation is not yet characterized, expression patterns correlate heavily with individual hyperaccumulation capacity and metal exposure, suggesting these gene families play a regulatory role. As the presence and expression zinc transporter gene families are highly prevalent in hyperaccumulators, the capacity to accumulate a wide range of heavy metals is likely due to an inability of the zinc transporters to discriminate against certain metal ions. The response of the plants to hyperaccumulation of any metal also supports this theory as it has been observed that AhHMHA3 is expressed in hyperaccumulating individuals. AhHMHA3 has been identified to be expressed in response to and aid of Zn detoxification. In another study, using metallophytic and non-metallophytic "Arabidopsis" populations, back crosses indicated pleiotropy between Cd and Zn tolerances. This response suggests that plants are unable to detect specific metals, and that hyperaccumulation is likely a result of an overexpressed Zn transportation system.  The overall effect of these expression patterns has been hypothesized to assist in plant defense systems. In one hypothesis, "the elemental defense hypothesis", provided by Poschenrieder, it is suggested that the expression of these genes assist in antiherbivory or pathogen defenses by making tissues toxic to organisms attempting to feed on that plant. Another hypothesis, "the joint hypothesis", provided by Boyd, suggests that expression of these genes assists in systemic defense.

A hyperaccumulator is a plant capable of growing in soil or water with very high concentrations of metals, absorbing these metals through their roots, and concentrating extremely high levels of metals in their tissues. The metals are concentrated at levels that are toxic to closely related species not adapted to growing on the metalliferous soils. Compared to non-hyperaccumulating species, hyperaccumulator roots extract the metal from the soil at a higher rate, transfer it more quickly to their shoots, and store large amounts in leaves and roots. The ability to hyperaccumulate toxic metals compared to related species has been shown to be due to differential gene expression and regulation of the same genes in both plants.

Hyperakumulátory jsou rostliny, které jsou schopny koncentrovat v nadzemních částech množství kovů vysoce převyšující obsah kovů v půdě nebo v neakumulujícich rostlinách. Tatoi schopnost je využívána při odstranění znečištění prostředí při fytoextrakci.


Overview.

In the establishment of socialism in the former Russian Empire, Bolshevism was the ideological basis for the Soviet Union. As the vanguard party who guide the establishment and development of socialism, the communist party represented their policies as correct. Because Leninism was the revolutionary means to achieving socialism in the praxis of government, the relationship between ideology and decision-making inclined to pragmatism and most policy decisions were taken in light of the continual and permanent development of Marxist–Leninist ideology, i.e. ideological adaptation to actual conditions.  Within five years of the death of Vladimir Lenin (1924), Joseph Stalin completed his rise to power and was the leader of the Soviet Union who theorised and applied the socialist theories of Lenin and Karl Marx as political expediencies used to realise his plans for the Soviet Union and for world socialism. The book "Concerning Questions of Leninism" (1926) represented Marxism–Leninism as a separate communist ideology and featured a global hierarchy of communist parties and revolutionary vanguard parties in each country of the world. With that, Stalin's application of Marxism–Leninism to the situation of the Soviet Union became Stalinism, the official state ideology until his death in 1953. In Marxist political discourse, Stalinism, denoting and connoting the theory and praxis of Stalin, has two usages, namely praise of Stalin by Marxist–Leninists who believe Stalin successfully developed Lenin's legacy and criticism of Stalin by Marxist–Leninists and other Marxists who repudiate Stalin's political purges, social-class repressions and bureaucratic terrorism. As the Left Opposition to Stalin within the Soviet party and government, Leon Trotsky and Trotskyists argued that Marxist–Leninist ideology contradicted Marxism and Leninism in theory, therefore Stalin's ideology was not useful for the implementation of socialism in Russia. Moreover, Trotskyists within the party identified their anti-Stalinist communist ideology as Bolshevik–Leninism and supported the permanent revolution to differentiate themselves from Stalin's justification and implementation of socialism in one country. After the Sino-Soviet split of the 1960s, the Communist Party of China

History.

Bolsheviks, February Revolution and Great War (1903–1917).

Although Marxism–Leninism was created after Vladimir Lenin's death during the regime of Josef Stalin in the Soviet Union, continuing to be the official state ideology after de-Stalinisation and of other Marxist–Leninist states, the basis for elements of Marxism–Leninism predate this. The philosophy of Marxism–Leninism originated as the pro-active, political praxis of the Bolshevik faction of the Russian Social Democratic Labour Party in realising political change in Tsarist Russia. Lenin's leadership transformed the Bolsheviks into the party's political vanguard which was composed of professional revolutionaries who practised democratic centralism to elect leaders and officers as well as to determine policy through free discussion, then decisively realised through united action. The vanguardism of proactive, pragmatic commitment to achieving revolution was the

October Revolution and Russian Civil War (1917–1922).

In March 1917, the abdication of Tsar Nicholas II led to the Russian Provisional Government (March–July 1917), who then proclaimed the Russian Republic (September–November 1917). Later in the October Revolution, the Bolshevik's seizure of power against the Provisional Government resulted in their establishment of the Russian Soviet Federative Socialist Republic (1917–1991), yet parts of Russia remained occupied by the counter-revolutionary White Movement of anti-communists who had united to form the White Army to fight the Russian Civil War (1917–1922) against the Bolshevik government. Moreover, despite the White–Red civil war, Russia remained a combatant in the Great War that the Bolshevik's had quit with the Treaty of Brest-Litovsk which then provoked the Allied Intervention to the Russian Civil War by the armies of seventeen countries, featuring Great Britain, France, Italy, the United States and Imperial Japan. Elsewhere, the successful October Revolution in Russia had facilitated the German Revolution of 1918–1919 and revolutions and

Stalin's rise to power (1922–1928).

As he neared death after suffering strokes, Lenin's Testament (December 1922) named Trotsky and Stalin as the most able men in the Central Committee, but he harshly criticised them. Lenin said that Stalin should be removed from being the General Secretary of the party and that he be replaced with "some other person who is superior to Stalin only in one respect, namely, in being more tolerant, more loyal, more polite, and more attentive to comrades". Upon his death (21 January 1924), Lenin's political testament was read aloud to the Central Committee, who choose to ignore Lenin's ordered removal of Stalin as General Secretary because enough members believed Stalin had been politically rehabilitated in 1923. Consequent to personally spiteful disputes about the praxis of Leninism, the October Revolution veterans Lev Kamenev and Grigory Zinoviev said that the true threat to the ideological integrity of the party was Trotsky, who was a personally charismatic political leader as well as the commanding officer of the Red Army in the Russian Civil War and revolutionary partner of the dead Lenin. To thwart Trotsky's likely election to head the

Socialism in one country (1928–1945).

Beginning in 1928, Stalin's five-year plans for the national economy of the Soviet Union achieved the rapid industrialisation (coal, iron and steel, electricity and petroleum, among others) and the collectivisation of agriculture. It achieved 23.6% of collectivisation within two years (1930) and 98.0% of collectivisation within thirteen years (1941). As the revolutionary vanguard, the communist party organised Russian society to realise rapid industrialisation programs as defence against Western interference with socialism in Bolshevik Russia. The five-year plans were prepared in the 1920s whilst the Bolshevik government fought the internal Russian Civil War (1917–1922) and repelled the external Allied intervention to the Russian Civil War (1918–1925). Vast industrialisation was initiated mostly based with a focus on heavy industry. During the 1930s, the rapid industrialisation of the country accelerated the Soviet people's sociological transition from poverty to relative plenty when politically illiterate peasants passed from Tsarist serfdom to self-determination and became politically aware urban citizens. The Marxist–Leninist economic régime modernised Russia from the illiterate, peasant society characteristic of monarchy to the

Cold War, de-Stalinisation and Maoism (1945–1980).

Upon Allied victory concluding the Second World War (1939–1945), the members of the Grand Alliance resumed their expediently suppressed, pre-war geopolitical rivalries and ideological tensions which disunity broke their anti-fascist wartime alliance into the anti-communist Western Bloc and the communist Eastern Bloc. The renewed competition for geopolitical hegemony resulted in the bi-polar Cold War (1945–1991), a protracted state of tension (military and diplomatic) between the United States and the Soviet Union which often threatened a Soviet–American nuclear war, but it usually featured proxy wars in the Third World.  The events that precipitated the Cold War in Europe were the Soviet and Yugoslav, Bulgarian and Albanian military interventions to the Greek Civil War (1944–1949) on behalf of the Communist Party of Greece; and the Berlin Blockade (1948–1949) by the Soviet Union. The event that precipitated the Cold War in continental Asia was the resumption of the Chinese Civil War (1927–1949) fought between the anti-communist Kuomintang and the Communist Party of China. After military defeat exiled Generalissimo Chiang Kai-shek and his Kuomintang nationalist government to Formosa island (Taiwan), Mao Zedong established the People's Republic of China on 1 October 1949. In the late 1940s, the geopolitics of the Eastern Bloc countries under the hegemony of Stalinist Russia featured an official-and-personal style of socialist diplomacy that failed Stalin and Tito when Tito refused to subordinating Yugoslavia to the Soviet Union. In 1948, circumstance and cultural personality aggravated the matter into the Yugoslav–Soviet split (1948–1955) that resulted from Tito's rejection of Stalin's demand to subordinate the Socialist Federal Republic of Yugoslavia to the geopolitical agenda (economic and military) of the Soviet Union, i.e. Tito at Stalin's disposal. Stalin punished Tito's refusal by denouncing him as an ideological revisionist of Marxism–Leninism; by denouncing Yugoslavia's practice of Titoism as socialism deviated from the cause of world communism; and by expelling the Communist Party of Yugoslavia from the Communist Information Bureau (Cominform). The break from the Eastern Bloc allowed the development of a socialism with Yugoslav characteristics which allowed doing business with the capitalist West to develop the socialist economy and the establishment of Yugoslavia's diplomatic and commercial relations with countries of the Eastern Bloc and the Western Bloc. Yugoslavia's international relations matured into the Non-Aligned Movement (1961) of countries without political allegiance to any power bloc.  At the death of Stalin in 1953, Nikita Khrushchev

Reform and collapse (1980–1992).

Social resistance to the policies of Marxist–Leninist regimes in Eastern Europe accelerated in strength with the rise of the Solidarity, the first non-Marxist–Leninist controlled trade union in the Warsaw Pact that was formed in the People's Republic of Poland in 1980.  In 1985, Mikhail Gorbachev rose to power in the Soviet Union and began policies of radical political reform involving political liberalisation, called perestroika and glasnost. Gorbachev's policies were designed at dismantling authoritarian elements of the state that were developed by Stalin, aiming for a return to a supposed ideal Leninist state that retained one-party structure while allowing the democratic election of

Post-Cold War era (1992–present).

Since the fall of the Eastern European Marxist–Leninist regimes, the Soviet Union and a variety of African Marxist–Leninist regimes, only a few Marxist–Leninist parties remained in power. This include China, Cuba, Laos and Vietnam. Most Marxist–Leninist communist parties outside of these nations have fared relatively poorly in elections, although other parties have remained or became a relative strong force. This include Russia, where the Communist Party of the Russian Federation has remained a significant political force, winning the 1995 legislative election, almost winning the 1996 presidential election and generally remaining the second most popular party. In Ukraine, the Communist Party of Ukraine has also exerted influence and governed the country after the 1994 parliamentary election and again after the 2006 parliamentary election. However, the 2014 parliamentary election following the Russian invasion of Ukraine and the annexation of Crimea resulted in the loss of its 32 members and no parliamentary representation.  In Europe, several Marxist–Leninist parties remain strong. In Cyprus, Dimitris Christofias of AKEL won the 2008 presidential

Ideology.

Economy.

The goal of Marxist–Leninist political economy is the emancipation of men and women from the dehumanisation caused by mechanistic work that is psychologically alienating (without work–life balance) which is performed in exchange for wages that give limited financial-access to the material necessities of life (i.e. food and shelter). That personal and societal emancipation from poverty (material necessity) would maximise individual liberty by enabling men and women to pursue their interests and innate talents (artistic, industrial and intellectual) whilst working by choice, without the economic coercion of poverty. In the communist society of upper-stage economic development, the elimination of alienating labour (mechanistic work) depends upon the

International relations.

Marxism–Leninism aims to create an international communist society. It opposes colonialism and imperialism and advocates decolonisation and anti-colonial forces. It supports anti-fascist international alliances and has advocated the creation of popular fronts between communist and non-communist anti-fascists against strong fascist movements. This Marxist–Leninist approach to international relations derives from the analyses (political, economic, sociological and geopolitical) that Lenin presented in the essay "Imperialism, the Highest Stage of Capitalism" (1917). Extrapolating from five philosophical bases of Marxism, namely that human history is the history of class struggle between a ruling class and an exploited class; that capitalism creates antagonistic social classes, i.e. the bourgeois exploiters and the exploited proletariat; that capitalism employs nationalist war to further private economic expansion; that socialism is an economic system that voids social classes through public ownership of the means of production and so will eliminate the economic causes of war; and that once the state (socialist or communist) withers away, so shall international relations wither away because they are projections of national economic forces, Lenin said that the capitalists' exhaustion of domestic sources of investment profit by way of price-fixing trusts and cartels, then prompts the same capitalists to export investment capital to undeveloped countries

Political system.

Marxism–Leninism supports the creation of a one-party state led by a communist party as a means to develop socialism and then communism. The political structure of the Marxist–Leninist state involves the rule of a communist vanguard party over a revolutionary socialist state that represents the will and rule of the proletariat. Through the policy of democratic centralism, the communist party is the supreme political institution of

Society.

Marxism–Leninism supports universal social welfare. The Marxist–Leninist state provides for the national welfare with universal healthcare, free public education (academic, technical and professional) and the social benefits (childcare and continuing education) necessary to increase the productivity of the workers and the socialist economy to develop a communist society. As part of the planned economy, the Marxist–Leninist state is meant to develop the proletariat's universal education (academic and technical) and their class consciousness (political education) to facilitate their contextual understanding of the historical development of communism as presented in Marx's theory of history.  Marxism–Leninism supports the emancipation of women and ending the exploitation of women. Marxist–Leninist policy on family law has typically involved the elimination of the political power of the bourgeoisie, the abolition of private property and an education that teaches citizens to abide by a disciplined and self-fulfilling lifestyle dictated by the social norms of communism as a means to establish a new social order. The judicial reformation of family law eliminates patriarchy from the legal system. This facilitates the political emancipation of women

Teleology.

The Marxist–Leninist worldview is atheist, wherein all human activity results from human volition and not the will of supernatural beings (gods, goddesses and demons) who have direct agency in the public and private affairs of human society. The tenets of the Soviet Union's national policy of Marxist–Leninist atheism originated from the philosophies of Georg Wilhelm Friedrich Hegel (1770–1831) and Ludwig Feuerbach (1804–1872) as well

Criticism.

Marxism–Leninism has been widely criticised due to its relations with Stalinism, the Soviet Union and state repression in Marxist–Leninist states. Classical and orthodox Marxists were critical of Stalin's political economy and single-party government in the Soviet Union.  Italian left communist Amadeo Bordiga dismissed Marxism–Leninism as political opportunism that preserved capitalism because of the claim that the exchange of commodities would occur under socialism and that the use of popular front organisations by the Communist International and a political vanguard organised by organic centralism were politically more effective than a vanguard organised by democratic centralism. American Marxist Raya Dunayevskaya dismissed Marxism–Leninism as a type of state capitalism because state ownership of the means of production is a form of state capitalism and single-party rule is undemocratic whereas the dictatorship of the proletariat is democratic, further arguing that the doctrine is neither Marxism nor Leninism, but rather a composite ideology that Stalin used to expediently determine what is communism and what is not communism for the countries of the Eastern Bloc.  Trotskyists claim that Marxism–Leninism led to the establishment of a degenerated workers' state. Others such as philosopher Eric Voegelin claim that Marxism–Leninism is in its core inherently oppressive, arguing that the "Marxian vision dictated the Stalinist outcome not because the communist utopia was inevitable but because it was impossible". Criticism like this has itself been criticised for philosophical determinism, i.e. that the negative events in the movement's history were predetermined by their convictions. Historian Robert Vincent Daniels argues that Marxism was used to "justify Stalinism, but it was no longer allowed to serve either as a policy directive or an explanation of reality" during Stalin's rule. In complete contrast, E. Van Ree argues that Stalin continued to be in "general agreement" with the classical works of Marxism until his death.

Marxism–Leninism is a political philosophy that seeks to establish a socialist state to develop further into socialism and eventually communism, a classless social system with common ownership of the means of production and with full social and economic equality of all members of society. Marxist–Leninists espouse a wide array of views depending on their understanding of orthodox Marxism and Leninism, but they generally support the idea of a vanguard party, a communist party-led state, state-dominance over the economy, internationalism and opposition to capitalism, fascism, imperialism and liberal democracy. As an ideology, it was developed by Joseph Stalin in the late 1920s based on his understanding and synthesis of both orthodox Marxism and Leninism. It was the official state ideology of the Soviet Union and the other ruling parties making up the Eastern Bloc as well as the political parties of the Communist International after Bolshevisation. Today, Marxism–Leninism is the ideology of Stalinist and Maoist political parties around the world and remains the official ideology of the ruling parties of China, Cuba, Laos and Vietnam.

Marxismus-leninismus je komunistická ideologie oficiálně založená na teoriích marxismu a leninismu. Jako samostatnou ideologii ji sestavil Josif Vissarionovič Stalin v knize "Otázky leninismu". Marxismus-leninismus byla oficiální státní a stranickou ideologií SSSR a KSSS a ostatních spřátelených komunistických režimů a stran a to i po odhalení kultu osobnosti XX. sjezdem KSSS.