A landfill site is a site for the disposal of waste materials by burial. It is the oldest form of waste treatment. Landfills have been the most common method of organized waste disposal and remain so in many places around the world; some landfills are used for waste management purposes, such as the temporary storage and transfer, or processing of waste material. Unless they are stabilized, these areas may experience severe shaking or soil liquefaction of the ground during a large earthquake. Operators of well-run landfills for non-hazardous waste meet predefined specifications by applying techniques to: confine waste to as small an area as possible compact waste to reduce volumeThey can cover waste with layers of soil or other types of material such as woodchips and fine particles. During landfill operations, a scale or weighbridge may weigh waste collection vehicles on arrival and personnel may inspect loads for wastes that do not accord with the landfill's waste-acceptance criteria. Afterward, the waste collection vehicles use the existing road network on their way to the tipping face or working front, where they unload their contents.
After loads are deposited, compactors or bulldozers can spread and compact the waste on the working face. Before leaving the landfill boundaries, the waste collection vehicles may pass through a wheel-cleaning facility. If necessary, they return to the weighbridge for re-weighing without their load; the weighing process can assemble statistics on the daily incoming waste tonnage, which databases can retain for record keeping. In addition to trucks, some landfills may have equipment to handle railroad containers; the use of "rail-haul" permits landfills to be located at more remote sites, without the problems associated with many truck trips. In the working face, the compacted waste is covered with soil or alternative materials daily. Alternative waste-cover materials include chipped wood or other "green waste", several sprayed-on foam products, chemically "fixed" bio-solids, temporary blankets. Blankets can be lifted into place at night and removed the following day prior to waste placement; the space, occupied daily by the compacted waste and the cover material is called a daily cell.
Waste compaction is critical to extending the life of the landfill. Factors such as waste compressibility, waste-layer thickness and the number of passes of the compactor over the waste affect the waste densities; the term landfill is shorthand for a municipal landfill or sanitary landfill. These facilities were first introduced early in the 20th century, but gained wide use in the 1960s and'70s, in an effort to eliminate open dumps and other "unsanitary" waste disposal practices; the sanitary landfill is an engineered facility that confines waste. But, not all it does, it is a biological reactor in which microbes break down complex organic waste into simpler, less toxic compounds over time. These reactors must be operated according to regulatory standards and guidelines. Aerobic decomposition is the first stage by which wastes are broken down in a landfill; these are followed by four stages of anaerobic degradation. Solid organic material in solid phase decays as larger organic molecules degrade into smaller molecules.
These smaller organic molecules begin to dissolve and move to the liquid phase, followed by hydrolysis of these organic molecules, the hydrolyzed compounds undergo transformation and volatilization as carbon dioxide and methane, with rest of the waste remaining in solid and liquid phases. During the early phases, little material volume reaches the leachate, as the biodegradable organic matter of the waste undergoes a rapid decrease in volume. Meanwhile, the leachate's chemical oxygen demand increases with increasing concentrations of the more recalcitrant compounds compared to the more reactive compounds in the leachate. Successful conversion and stabilization of the waste depends on how well microbial populations function in syntrophy, i.e. an interaction of different populations to provide each other's nutritional needs.: The life cycle of a municipal landfill undergoes five distinct phases: Phase I - Initial adjustment: As the waste is placed in the landfill, the void spaces contain high volumes of molecular oxygen.
With added and compacted wastes, the O2 content of the landfill bioreactor strata decreases. Microbial populations grow, density increases. Aerobic biodegradation dominates, i.e. the primary electron acceptor is O2. Phase II - Transition: The O2 is degraded by the existing microbial populations; the decreasing O2 leads to more anaerobic conditions in the layers. The primary electron acceptors during transition are nitrates and sulphates, since O2 is displaced by CO2 in the effluent gas. Phase III - Acid formation: Hydrolysis of the biodegradable fraction of the solid waste begins in the acid formation phase, which leads to rapid accumulation of volatile fatty acids in the leachate; the increased organic acid content decreases the leachate pH from 7.5 to 5.6. During this phase, the decomposition intermediate compounds like the VFAs contribute much COD. Long-chain volatile organic acids are converted to acetic acid, CO2, hydrogen gas. High concentrations of VFAs increase both the biochemical oxygen demand and VOA concentrations, which initiates H2 production by fermentative ba
In organic chemistry, sometimes called phenolics, are a class of chemical compounds consisting of a hydroxyl group bonded directly to an aromatic hydrocarbon group. The simplest of the class is phenol, C6H5OH. Phenolic compounds are classified as simple phenols or polyphenols based on the number of phenol units in the molecule. Phenols are synthesized industrially as well as naturally. Phenols have distinct properties and are distinguished from other alcohols, they have higher acidities. The acidity of the hydroxyl group in phenols is intermediate between that of aliphatic alcohols and carboxylic acids. Loss of a hydrogen cation from the hydroxyl group of a phenol forms a corresponding negative phenolate ion or phenoxide ion, the corresponding salts are called phenolates or phenoxides, although the term aryloxides is preferred according to the IUPAC Gold Book. Phenols can have two or more hydroxy groups bonded to the aromatic ring in the same molecule; the simplest examples are each having two hydroxy groups on a benzene ring.
Phenols are reactive species toward oxidation. Oxidative cleavage, for instance cleavage of 1,2-dihydroxybenzene to the monomethylester of 2,4 hexadienedioic acid with oxygen, copper chloride in pyridine Oxidative de-aromatization to quinones known as the Teuber reaction. Oxidizing reagents are Fremy's oxone. In reaction depicted below 3,4,5-trimethylphenol reacts with singlet oxygen generated from oxone/sodium carbonate in an acetonitrile/water mixture to a para-peroxyquinole; this hydroperoxide is reduced to the quinole with sodium thiosulfate. Phenols are oxidized to hydroquinones in the Elbs persulfate oxidation Phenols are susceptible to Electrophilic aromatic substitutions. Illustrative of a large-scale electrophilic aromatic substitution is the production of bisphenol A, produced on a scale 1 million tons; this compound is synthesized by the condensation of acetone. Phenols undergo esterfication. Phenol esters are active esters. Reaction of naphtols and hydrazines and sodium bisulfite in the Bucherer carbazole synthesis Several laboratory methods for the synthesis of phenols: by an ester rearrangement in the Fries rearrangement by a rearrangement of N-phenylhydroxylamines in the Bamberger rearrangement by dealkylation of phenolic ethers by reduction of quinones by replacement of an aromatic amine by an hydroxyl group with water and sodium bisulfide in the Bucherer reaction by hydrolysis of diazonium salts, See: Conversion of Diazonium Salt to Phenol by oligomerisation with formaldehyde + base catalysed reaction with epichlorohydrin to epoxi resin components by reaction with acetone/ketones to e.g. Bisphenol A, an important monomer for resins, e.g. polycarbonate, epoxi resins by the oxidation of aryl silanes—an aromatic variation of the Fleming-Tamao oxidation by the addition of benzene and propene in H3PO4 to form cumene O2 is added with H2SO4 to form phenol There are various classification schemes.
A used scheme is based on the number of carbons and was devised by Jeffrey Harborne and Simmonds in 1964 and published in 1980: The majority of these compounds are soluble molecules but the smaller molecules can be volatile. Phenols chemically interact with many other substances. Stacking, a chemical property of molecules with aromaticity, is seen occurring between phenolic molecules; when studied in mass spectrometry, phenols form adduct ions with halogens. They can interact with the food matrices or with different forms of silica
Carbon capture and storage
Carbon capture and storage is the process of capturing waste carbon dioxide from large point sources, such as biomass or fossil fuel power plants, transporting it to a storage site, depositing it where it will not enter the atmosphere an underground geological formation. The aim is to prevent the release of large quantities of CO2 into the atmosphere, it is a potential means of mitigating the contribution of fossil fuel emissions to global warming and ocean acidification. Although CO2 has been injected into geological formations for several decades for various purposes, including enhanced oil recovery, the long term storage of CO2 is a new concept; the first commercial example was the Weyburn-Midale Carbon Dioxide Project in 2000. Another example is SaskPower's Boundary Dam.'CCS' can be used to describe the scrubbing of CO2 from ambient air as a climate engineering technique. CCS applied to a modern conventional power plant could reduce CO2 emissions to the atmosphere by 80–90% compared to a plant without CCS.
The IPCC estimates that the economic potential of CCS could be between 10% and 55% of the total carbon mitigation effort until year 2100. Carbon dioxide can be captured out of air or fossil fuel power plant flue gas using adsorption, membrane gas separation, or adsorption technologies. Amines are the leading carbon scrubbing technology; however capturing and compressing CO2 and other system costs are estimated to increase the cost per watt-hour energy produced by 21–91% for fossil fuel power plants. A trial of bio-energy with carbon capture and storage at a wood-fired unit in Drax power station in the UK started in 2019: if successful this could remove a tiny amount of CO2 from the atmosphere. Storage of the CO2 is envisaged either in deep geological formations, or in the form of mineral carbonates. Deep ocean storage is not considered feasible due to the associated effect of ocean acidification. Geological formations are considered the most promising sequestration sites; the National Energy Technology Laboratory reported that North America has enough storage capacity for more than 900 years worth of carbon dioxide at current production rates.
A general problem is that long term predictions about submarine or underground storage security are difficult and uncertain, there is still the risk that CO2 might leak into the atmosphere. CCS is related to pyrogenic carbon capture and storage. Capturing CO2 is most effective at point sources, such as large fossil fuel or biomass energy facilities, industries with major CO2 emissions, natural gas processing, synthetic fuel plants and fossil fuel-based hydrogen production plants. Extracting CO2 from air is possible, although the far lower concentration of CO2 in air compared to combustion sources presents significant engineering challenges. Organisms that produce ethanol by fermentation generate cool pure CO2 that can be pumped underground. Fermentation produces less CO2 than ethanol by weight. Flue gas from the combustion of coal in oxygen has a large concentration of CO2, about 10-15% CO2 whereas natural gas power plant flue gas is about 5–10% CO2. Therefore, it is more cost efficient to capture CO2 from coal-fired power plants.
Impurities in CO2 streams, like sulfurs and water, could have a significant effect on their phase behaviour and could pose a significant threat of increased corrosion of pipeline and well materials. In instances where CO2 impurities exist with air capture, a scrubbing separation process would be needed to clean the flue gas. According to the Wallula Energy Resource Center in Washington state, by gasifying coal, it is possible to capture 65% of carbon dioxide embedded in it and sequester it in a solid form. Broadly, three different configurations of technologies for capture exist: post-combustion, pre-combustion, oxyfuel combustion: In post combustion capture, the CO2 is removed after combustion of the fossil fuel—this is the scheme that would be applied to fossil-fuel burning power plants. Here, carbon dioxide is captured from flue gases at other large point sources; the technology is well understood and is used in other industrial applications, although not at the same scale as might be required in a commercial scale power station.
Post combustion capture is most popular in research because existing fossil fuel power plants can be retrofitted to include CCS technology in this configuration. The technology for pre-combustion is applied in fertilizer, gaseous fuel, power production. In these cases, the fossil fuel is oxidized, for instance in a gasifier; the CO from the resulting syngas reacts with added steam and is shifted into CO2 and H2. The resulting CO2 can be captured from a pure exhaust stream; the H2 can now be used as fuel. There are several advantages and disadvantages when compared to conventional post combustion carbon dioxide capture; the CO2 is removed after combustion of fossil fuels, but before the flue gas is expanded to atmospheric pressure. This scheme is applied to new fossil fuel burning power plants, or to existing plants where re-powering is an option; the capture before expansion, i.e. from pressurized gas, is standard in all industrial CO2 capture processes, at the same scale as will be required for utility power plants.
In oxy-fuel combustion the fuel is burne
The Negev is a desert and semidesert region of southern Israel. The region's largest city and administrative capital is Beersheba, in the north. At its southern end is the Gulf of Aqaba and the resort city of Eilat, it contains several development towns, including Dimona and Mitzpe Ramon, as well as a number of small Bedouin cities, including Rahat and Tel as-Sabi and Lakyah. There are several kibbutzim, including Revivim and Sde Boker; the desert is home to the Ben-Gurion University of the Negev, whose faculties include the Jacob Blaustein Institutes for Desert Research and the Albert Katz International School for Desert Studies, both located on the Midreshet Ben-Gurion campus adjacent to Sde Boker. Although a separate region, the Negev was added to the proposed area of Mandatory Palestine to become Israel, on 10 July 1922, having been conceded by British representative St John Philby ”in Trans-Jordan’s name”. In October 2012, global travel guide publisher Lonely Planet rated the Negev second on a list of the world's top ten regional travel destinations for 2013, noting its current transformation through development.
The origin of the word'negev' is from the Hebrew root denoting'dry'. In the Bible, the word Negev is used for the direction'south'. In Arabic, the Negev is known as al-Naqab or an-Naqb, though it was not thought of as a distinct region until the demarcation of the Egypt-Ottoman frontier in the 1890s and has no traditional Arabic name. During the British Mandate, it was called Beersheba sub-district; the Negev covers more than half of Israel, over some 13,000 km² or at least 55% of the country's land area. It forms an inverted triangle shape whose western side is contiguous with the desert of the Sinai Peninsula, whose eastern border is the Arabah valley; the Negev has a number of interesting geological features. Among the latter are three enormous, craterlike makhteshim, which are unique to the region: Makhtesh Ramon, HaMakhtesh HaGadol, HaMakhtesh HaKatan; the Negev is a rocky desert. It is a melange of brown, dusty mountains interrupted by wadis and deep craters, it can be split into five different ecological regions: northern and central Negev, the high plateau and the Arabah Valley.
The northern Negev, or Mediterranean zone, receives 300 mm of rain annually and has fertile soils. The western Negev receives 250 mm of rain per year, with light and sandy soils. Sand dunes can reach heights of up to 30 metres here. Home to the city of Beersheba, the central Negev has an annual precipitation of 200 mm and is characterized by impervious soil, known as loess, allowing minimum penetration of water with greater soil erosion and water runoff; the high plateau area of Negev Mountains/Ramat HaNegev stands between 370 metres and 520 metres above sea level with extreme temperatures in summer and winter. The area gets 100 mm of rain per year, with inferior and salty soils; the Arabah Valley along the Jordanian border stretches 180 km from Eilat in the south to the tip of the Dead Sea in the north. The Arabah Valley is arid with 50 mm of rain annually, it has inferior soils. Vegetation in the Negev is sparse, but certain trees and plants thrive there, among them Acacia, Retama, Urginea maritima and Thymelaea.
A small population of Arabian leopards, an endangered animal in the Arabian peninsula, survives in the southern Negev. The Negev Tortoise is a critically endangered species that lives only in the sands of the western and central Negev Desert; the Negev shrew is a species of mammal of the family Soricidae found only in Israel. Hyphaene thebaica or doum palm can be found in the Southern Negev. Evrona is the most northerly point in the world; the Negev region is arid, receiving little rain due to its location to the east of the Sahara, extreme temperatures due to its location 31 degrees north. However the northernmost areas of the Negev, including Beersheba, are semi-arid; the usual rainfall total from June through October is zero. Snow and frost are rare in the northern Negev, snow and frost are unknown in the vicinity of Eilat in the southernmost Negev. Nomadic life in the Negev dates back at least 4,000 years and as much as 7,000 years; the first urbanized settlements were established by a combination of Canaanite, Amorite and Edomite groups circa 2000 BC.
Pharaonic Egypt is credited with introducing copper mining and smelting in both the Negev and the Sinai between 1400 and 1300 BC. In the Bible, the term Negev only relates to the northern, semiarid part of what we call Negev today, located in the general area of the Arad-Beersheba Valley. According to the Book of Genesis chapter 13, Abraham lived for a while in the Negev after being banished from Egypt. During the Exodus journey to the promised land, Moses sent twelve scouts into the Negev to assess the land and population; the northern part of biblical Negev was inhabited by the Tribe of Judah and the southern part of biblical Negev by the Tribe of Simeon. The Negev was part of the Kingdom of Solomon, with varied extension to the s
Ida-Viru County, or Ida-Virumaa, is one of 15 counties of Estonia. It is the most north-eastern part of the country; the county contains large deposits of oil shale - the main mineral mined in Estonia. As oil shale is used in thermal power plants, the earth in Ida-Viru contains most of Estonia's energy resources; the capital of the county is the town of Jõhvi, administratively united with the Jõhvi Parish. In January 2016 Ida-Viru County had a population of 146,506 – constituting 12.6% of the total population in Estonia.. It borders Jõgeva County in the southwest and Russia in the east. During the latter part of the period of Soviet rule of Estonia, Ida-Virumaa was called Kohtla-Järve district, its administrative capital was Kohtla-Järve; the County Government is led by a governor, appointed by the country's government for a term of five years. The current governor of Ida-Viru county is Andres Noormägi. In January 2017, the population of Ida-Virumaa was 143,880, which makes it the third largest county in Estonia.
44.6 % of the population are 55.4 % women. In the aftermath of World War II, Estonia was occupied by the Soviet Union and large swaths of Ida-Viru County underwent ethnic cleansing by the Soviet authorities. Estonians, who were forced out of the major population centers, including Narva, were replaced by colonists from Russia; as a result of mass migration from the Soviet Union, Ida-Viru County is now the only county in Estonia where ethnic Russians have replaced the indigenous Estonian population. By ethnic origin, on 1 January 2017, 73.1% of the population were Russians, 18.9% were Estonians, 2.3% were Ukrainians, 2.1% were Belarusians and 0.9% were Finns. Ida-Virumaa County is subdivided into 8 municipalities. There are 217 villages in Ida-Virumaa. Official website Ida-Virumaa Tourism Portal
Fly ash or flue ash known as pulverised fuel ash in the United Kingdom, is a coal combustion product, composed of the particulates that are driven out of coal-fired boilers together with the flue gases. Ash that falls to the bottom of the boiler is called bottom ash. In modern coal-fired power plants, fly ash is captured by electrostatic precipitators or other particle filtration equipment before the flue gases reach the chimneys. Together with bottom ash removed from the bottom of the boiler, it is known as coal ash. Depending upon the source and composition of the coal being burned, the components of fly ash vary but all fly ash includes substantial amounts of silicon dioxide, aluminium oxide and calcium oxide, the main mineral compounds in coal-bearing rock strata; the minor constituents of fly ash depend upon the specific coal bed composition but may include one or more of the following elements or compounds found in trace concentrations: arsenic, boron, chromium, hexavalent chromium, lead, mercury, selenium, strontium and vanadium, along with small concentrations of dioxins and PAH compounds.
It has unburnt carbon. In the past, fly ash was released into the atmosphere, but air pollution control standards now require that it be captured prior to release by fitting pollution control equipment. In the United States, fly ash is stored at coal power plants or placed in landfills. About 43% is recycled used as a pozzolan to produce hydraulic cement or hydraulic plaster and a replacement or partial replacement for Portland cement in concrete production. Pozzolans ensure the setting of concrete and plaster and provide concrete with more protection from wet conditions and chemical attack. In the case that fly ash is not produced from coal, for example when solid waste is incinerated in a waste-to-energy facility to produce electricity, the ash may contain higher levels of contaminants than coal ash. In that case the ash produced is classified as hazardous waste. Fly ash material solidifies while suspended in the exhaust gases and is collected by electrostatic precipitators or filter bags. Since the particles solidify while suspended in the exhaust gases, fly ash particles are spherical in shape and range in size from 0.5 µm to 300 µm.
The major consequence of the rapid cooling is that few minerals have time to crystallize, that amorphous, quenched glass remains. Some refractory phases in the pulverized coal do not melt, remain crystalline. In consequence, fly ash is a heterogeneous material. SiO2, Al2O3, Fe2O3 and CaO are the main chemical components present in fly ashes; the mineralogy of fly ashes is diverse. The main phases encountered are a glass phase, together with quartz and the iron oxides hematite, magnetite and/or maghemite. Other phases identified are cristobalite, free lime, calcite, halite, portlandite and anatase; the Ca-bearing minerals anorthite, gehlenite and various calcium silicates and calcium aluminates identical to those found in Portland cement can be identified in Ca-rich fly ashes. The mercury content can reach 1 ppm, but is included in the range 0.01 - 1 ppm for bituminous coal. The concentrations of other trace elements vary as well according to the kind of coal combusted to form it. In fact, in the case of bituminous coal, with the notable exception of boron, trace element concentrations are similar to trace element concentrations in unpolluted soils.
Two classes of fly ash are defined by ASTM C618: Class F fly ash and Class C fly ash. The chief difference between these classes is the amount of calcium, silica and iron content in the ash; the chemical properties of the fly ash are influenced by the chemical content of the coal burned. Not all fly ashes meet ASTM C618 requirements, although depending on the application, this may not be necessary. Fly ash used as a cement replacement must meet strict construction standards, but no standard environmental regulations have been established in the United States. Seventy-five percent of the fly ash must have a fineness of 45 µm or less, have a carbon content, measured by the loss on ignition, of less than 4%. In the US, LOI must be under 6%; the particle size distribution of raw fly ash tends to fluctuate due to changing performance of the coal mills and the boiler performance. This makes it necessary that, if fly ash is used in an optimal way to replace cement in concrete production, it must be processed using beneficiation methods like mechanical air classification.
But if fly ash is used as a filler to replace sand in concrete production, unbeneficiated fly ash with higher LOI can be used. Important is the ongoing quality verification; this is expressed by quality control seals like the Bureau of Indian Standards mark or the DCL mark of the Dubai Municipality. The burning of harder, older anthracite and bituminous coal produces Class F fly ash; this fly ash is pozzolanic in nature, contains less than 7% lime. Possessing pozzolanic properties, the glassy silica and alumina of Class F fly ash requires a cementing agent, such as Portland cement, quicklime, or hydrated lime—mixed with water to react and produce cementitious compounds. Alternatively, adding a chemical activator such as sodium silicate to a Class F ash can form a geopolymer. Fly ash produced from the burning of younger lignite or sub-bituminous coal, in addition to having pozzolanic properties has s
In situ is a Latin phrase that translates to "on site" or "in position." It can mean "locally", "on site", "on the premises", or "in place" to describe where an event takes place and is used in many different contexts. For example, in fields such as physics, chemistry, or biology, in situ may describe the way a measurement is taken, that is, in the same place the phenomenon is occurring without isolating it from other systems or altering the original conditions of the test. In the aerospace industry, equipment on-board aircraft must be tested in situ, or in place, to confirm everything functions properly as a system. Individually, each piece may work but interference from nearby equipment may create unanticipated problems. Special test equipment is available for this in situ testing. In archaeology, in situ refers to an artifact that has not been moved from its original place of deposition. In other words, it is stationary, meaning "still." An artifact being in situ is critical to the interpretation of that artifact and of the culture which formed it.
Once an artifact's'find-site' has been recorded, the artifact can be moved for conservation, further interpretation and display. An artifact, not discovered in situ is considered out of context and as not providing an accurate picture of the associated culture. However, the out of context artifact can provide scientists with an example of types and locations of in situ artifacts yet to be discovered; when excavating a burial site or surface deposit "in situ" refers to cataloging, mapping, photographing human remains in the position they are discovered. The label in situ indicates. Thus, an archaeological in situ find may be an object, looted from another place, an item of "booty" of a past war, a traded item, or otherwise of foreign origin; the in situ find site may still not reveal its provenance, but with further detective work may help uncover links that otherwise would remain unknown. It is possible for archaeological layers to be reworked on purpose or by accident. For example, in a Tell mound, where layers are not uniform or horizontal, or in land cleared or tilled for farming.
The term in situ is used to describe ancient sculpture, carved in place such as the Sphinx or Petra. This distinguishes it from statues that were carved and moved like the Colossi of Memnon, moved in ancient times. In art, in situ refers to a work of art made for a host site, or that a work of art takes into account the site in which it is installed or exhibited. For a more detailed account see: Site-specific art; the term can refer to a work of art created at the site where it is to be displayed, rather than one created in the artist's studio and installed elsewhere. In architectural sculpture the term is employed to describe sculpture, carved on a building from scaffolds, after the building has been erected. Used to describe the site specific dance festival “Insitu”. Held in Queens, New York. A fraction of the globular star clusters in our galaxy, as well as those in other massive galaxies, might have formed in situ; the rest might have been accreted from now defunct dwarf galaxies. In astronomy, in situ refers to in situ planet formation, in which planets are hypothesized to have been formed in the orbit that they are observed to be in rather than migrating from a different orbit.
In biology and biomedical engineering, in situ means to examine the phenomenon in place where it occurs. In the case of observations or photographs of living animals, it means that the organism was observed in the wild as it was found and where it was found; this means. The organism had not been moved to another location such as an aquarium; this phrase in situ when used in laboratory science such as cell science can mean something intermediate between in vivo and in vitro. For example, examining a cell within a whole organ intact and under perfusion may be in situ investigation; this would not be in vivo as the donor is sacrificed by experimentation, but it would not be the same as working with the cell alone. In vitro was among the first attempts to qualitatively and quantitatively analyze natural occurrences in the lab; the limitation of in vitro experimentation was that they were not conducted in natural environments. To compensate for this problem, in vivo experimentation allowed testing to occur in the original organism or environment.
To bridge the dichotomy of benefits associated with both methodologies, in situ experimentation allowed the controlled aspects of in vitro to become coalesced with the natural environmental compositions of in vivo experimentation. In conservation of genetic resources, "in situ conservation" is the process of protecting an endangered plant or animal species in its natural habitat, as opposed to ex situ conservation. In chemistry, in situ means "in the reaction mixture." There are numerous situations in which chemical intermediates are synthesized in situ in various processes. This may be done because the species is unstable, cannot be isolated, or out of convenience. Examples of the former include the Corey-Chaykovsky adrenochrome. In biomedical engineering, protein nanogels made by the in situ polymerization method provide a versatile platform for storage and release of therapeutic