Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is carbon with variable amounts of other elements. Coal is formed if dead plant matter decays into peat and over millions of years the heat and pressure of deep burial converts the peat into coal. Vast deposits of coal originates in former wetlands—called coal forests—that covered much of the Earth's tropical land areas during the late Carboniferous and Permian times; as a fossil fuel burned for heat, coal supplies about a quarter of the world's primary energy and two-fifths of its electricity. Some iron and steel making and other industrial processes burn coal; the extraction and use of coal causes much illness. Coal damages the environment, including by climate change as it is the largest anthropogenic source of carbon dioxide, 14 Gt in 2016, 40% of the total fossil fuel emissions; as part of the worldwide energy transition many countries use less coal. The largest consumer and importer of coal is China.
China mines account for half the world's coal, followed by India with about a tenth. Australia accounts for about a third of world coal exports followed by Russia; the word took the form col in Old English, from Proto-Germanic *kula, which in turn is hypothesized to come from the Proto-Indo-European root *gu-lo- "live coal". Germanic cognates include the Old Frisian kole, Middle Dutch cole, Dutch kool, Old High German chol, German Kohle and Old Norse kol, the Irish word gual is a cognate via the Indo-European root. Coal is composed of macerals and water. Fossils and amber may be found in coal. At various times in the geologic past, the Earth had dense forests in low-lying wetland areas. Due to natural processes such as flooding, these forests were buried underneath soil; as more and more soil deposited over them, they were compressed. The temperature rose as they sank deeper and deeper; as the process continued the plant matter was protected from biodegradation and oxidation by mud or acidic water.
This trapped the carbon in immense peat bogs that were covered and buried by sediments. Under high pressure and high temperature, dead vegetation was converted to coal; the conversion of dead vegetation into coal is called coalification. Coalification starts with dead plant matter decaying into peat. Over millions of years the heat and pressure of deep burial causes the loss of water and carbon dioxide and an increase in the proportion of carbon, thus first lignite sub-bituminous coal, bituminous coal, lastly anthracite may be formed. The wide, shallow seas of the Carboniferous Period provided ideal conditions for coal formation, although coal is known from most geological periods; the exception is the coal gap in the Permian -- Triassic extinction event. Coal is known from Precambrian strata, which predate land plants—this coal is presumed to have originated from residues of algae. Sometimes coal seams are interbedded with other sediments in a cyclothem; as geological processes apply pressure to dead biotic material over time, under suitable conditions, its metamorphic grade or rank increases successively into: Peat, a precursor of coal Lignite, or brown coal, the lowest rank of coal, most harmful to health, used exclusively as fuel for electric power generation Jet, a compact form of lignite, sometimes polished.
Bituminous coal, a dense sedimentary rock black, but sometimes dark brown with well-defined bands of bright and dull material It is used as fuel in steam-electric power generation and to make coke. Anthracite, the highest rank of coal is a harder, glossy black coal used for residential and commercial space heating. Graphite is difficult to ignite and not used as fuel. Cannel coal is a variety of fine-grained, high-rank coal with significant hydrogen content, which consists of liptinite. There are several international standards for coal; the classification of coal is based on the content of volatiles. However the most important distinction is between thermal coal, burnt to generate electricity via steam. Hilt's law is a geological observation, the higher its rank, it applies if the thermal gradient is vertical. The earliest recognized use is from the Shenyang area of China where by 4000 BC Neolithic inhabitants had begun carving ornaments from black lignite. Coal from the Fushun mine in northeastern China was used to smelt copper as early as 1000 BC.
Marco Polo, the Italian who traveled to China in the 13th century, described coal as "black stones... which burn like logs", said coal was so plentiful, people could take three hot baths a week. In Europe, the earliest reference to the use of coal as fuel is from the geological treatise On stones by the Greek scientist Theophrastus: Among the materials that are dug because they are useful, those known as anthrakes are made of earth, once set on fire, they burn like charcoa
Lignite referred to as brown coal, is a soft, combustible, sedimentary rock formed from compressed peat. It is considered the lowest rank of coal due to its low heat content, it has a carbon content around 60–70 percent. It is mined all around the world, is used exclusively as a fuel for steam-electric power generation, is the coal, most harmful to health. Lignite is brownish-black in color and has a carbon content around 60–70 percent, a high inherent moisture content sometimes as high as 75 percent, an ash content ranging from 6–19 percent compared with 6–12 percent for bituminous coal; the energy content of lignite ranges from 10 to 20 MJ/kg on a mineral-matter-free basis. The energy content of lignite consumed in the United States averages 15 MJ/kg, on the as-received basis; the energy content of lignite consumed in Victoria, averages 8.4 MJ/kg. Lignite has a high content of volatile matter which makes it easier to convert into gas and liquid petroleum products than higher-ranking coals, its high moisture content and susceptibility to spontaneous combustion can cause problems in transportation and storage.
It is now known that efficient processes which remove latent moisture locked within the structure of brown coal will relegate the risk of spontaneous combustion to the same level as black coal, transform the calorific value of brown coal to a black coal equivalent fuel, reduce the emissions profile of'densified' brown coal to a level similar to or better than most black coals. However, removing the moisture increases the cost of the final lignite fuel; because of its low energy density and high moisture content, brown coal is inefficient to transport and is not traded extensively on the world market compared with higher coal grades. It is burned in power stations near the mines, such as in Australia's Latrobe Valley and Luminant's Monticello plant in Texas; because of latent high moisture content and low energy density of brown coal, carbon dioxide emissions from traditional brown-coal-fired plants are much higher per megawatt generated than for comparable black-coal plants, with the world's highest-emitting plant being Hazelwood Power Station until its closure in March 2017.
The operation of traditional brown-coal plants in combination with strip mining, can be politically contentious due to environmental concerns. In 2014, about 12 percent of Germany's energy and 27 percent of Germany's electricity came from lignite power plants, while in 2014 in Greece, lignite provided about 50 percent of its power needs. An environmentally beneficial use of lignite can be found in its use in cultivation and distribution of biological control microbes that suppress plant disease causing microbes; the carbon enriches the organic matter in the soil while the biological control microbes provide an alternative to chemical pesticides. Reaction with quaternary amine forms a product called amine-treated lignite, used in drilling mud to reduce fluid loss during drilling. Lignite begins as an accumulation of decayed plant material, or peat. Burial by other sediments results in increasing temperature, depending on the local geothermal gradient and tectonic setting, increasing pressure.
This causes compaction of the loss of some of the water and volatile matter. This process, called coalification, concentrates the carbon content, thus the heat content, of the material. Deeper burial and the passage of time result in further expulsion of moisture and volatile matter transforming the material into higher-rank coals such as bituminous and anthracite coal. Lignite deposits are younger than higher-ranked coals, with the majority of them having formed during the Tertiary period; the Latrobe Valley in Victoria, contains estimated reserves of some 65 billion tonnes of brown coal. The deposit is equivalent to 25 percent of known world reserves; the coal seams are up to 100 metres thick, with multiple coal seams giving continuous brown coal thickness of up to 230 metres. Seams are covered by little overburden. Lignite can be separated into two types; the first is xyloid lignite or fossil wood and the second form is the compact lignite or perfect lignite. Although xyloid lignite may sometimes have the tenacity and the appearance of ordinary wood, it can be seen that the combustible woody tissue has experienced a great modification.
It is reducible to a fine powder by trituration, if submitted to the action of a weak solution of potash, it yields a considerable quantity of humic acid. Leonardite is an oxidized form of lignite, which contains high levels of humic acid. Jet is a gem-like form of lignite used in various types of jewelry. "Coal and lignite domestic consumption". Global Energy Statistical Yearbook. 2016. Geography in action – an Irish case study Photograph of lignite Coldry:Lignite Dewatering Process Why Brown Coal Should Stay in the Ground Victoria Australia Brown Coal Factsheet Australian mines atlas
In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae and protozoa. Bacterial spores are not part of a sexual cycle but are resistant structures used for survival under unfavourable conditions. Myxozoan spores release amoebulae into their hosts for parasitic infection, but reproduce within the hosts through the pairing of two nuclei within the plasmodium, which develops from the amoebula. Spores are haploid and unicellular and are produced by meiosis in the sporangium of a diploid sporophyte. Under favourable conditions the spore can develop into a new organism using mitotic division, producing a multicellular gametophyte, which goes on to produce gametes. Two gametes fuse to form a zygote; this cycle is known as alternation of generations. The spores of seed plants, are produced internally and the megaspores, formed within the ovules and the microspores are involved in the formation of more complex structures that form the dispersal units, the seeds and pollen grains.
The term spore derives from the ancient Greek word σπορά spora, meaning "seed, sowing", related to σπόρος sporos, "sowing," and σπείρειν speirein, "to sow." In common parlance, the difference between a "spore" and a "gamete" is that a spore will germinate and develop into a sporeling, while a gamete needs to combine with another gamete to form a zygote before developing further. The main difference between spores and seeds as dispersal units is that spores are unicellular, while seeds contain within them a multicellular gametophyte that produces a developing embryo, the multicellular sporophyte of the next generation. Spores germinate to give rise to haploid gametophytes, while seeds germinate to give rise to diploid sporophytes. Vascular plant spores are always haploid. Vascular plants heterosporous. Plants that are homosporous produce spores of the same type. Heterosporous plants, such as seed plants, spikemosses and ferns of the order Salviniales produce spores of two different sizes: the larger spore in effect functioning as a "female" spore and the smaller functioning as a "male".
Such plants give rise to the two kind of spores from within separate sporangia, either a megasporangium that produces megaspores or a microsporangium that produces microspores. In flowering plants, these sporangia occur within anthers, respectively. Fungi produce spores, as a result of sexual, or asexual, reproduction. Spores are haploid and grow into mature haploid individuals through mitotic division of cells. Dikaryotic cells result from the fusion of two haploid gamete cells. Among sporogenic dikaryotic cells, karyogamy occurs to produce a diploid cell. Diploid cells undergo meiosis to produce haploid spores. Spores can be classified in several ways: In fungi and fungus-like organisms, spores are classified by the structure in which meiosis and spore production occurs. Since fungi are classified according to their spore-producing structures, these spores are characteristic of a particular taxon of the fungi. Sporangiospores: spores produced by a sporangium in many fungi such as zygomycetes.
Zygospores: spores produced by a zygosporangium, characteristic of zygomycetes. Ascospores: spores produced by an ascus, characteristic of ascomycetes. Basidiospores: spores produced by a basidium, characteristic of basidiomycetes. Aeciospores: spores produced by an aecium in some fungi such as rusts or smuts. Urediniospores: spores produced by a uredinium in some fungi such as rusts or smuts. Teliospores: spores produced by a telium in some fungi such as rusts or smuts. Oospores: spores produced by an oogonium, characteristic of oomycetes. Carpospores: spores produced by a carposporophyte, characteristic of red algae. Tetraspores: spores produced by a tetrasporophyte, characteristic of red algae. Chlamydospores: thick-walled resting spores of fungi produced to survive unfavorable conditions. Parasitic fungal spores may be classified into internal spores, which germinate within the host, external spores called environmental spores, released by the host to infest other hosts. Meiospores: spores produced by meiosis.
Examples are the precursor cells of gametophytes of seed plants found in flowers or cones, the zoospores produced from meiosis in the sporophytes of algae such as Ulva. Microspores: meiospores that give rise to a male gametophyte. Megaspores: meiospores that give rise to a female gametophyte. Mitospores: spores produced by mitosis. Fungi in which only mitospores are found are called "mitosporic fungi" or "anamorphic fungi", are classified under the taxon Deuteromycota. Spores can be differentiated by. Zoospores: mobile spores that move by means of one or more flagella, can be found in some algae and fungi. Aplanospores: immobile spores that may potentially grow flagella. Autospores: immobile spores that cannot develop flagella. Ballistospores: spores that are forcibly discharged or ejected from the fungal fruiting body as the result of an internal force, such as buildup of pressure. Most basidiospores are ballistospores, another notable e
Alginite is a component of some types of kerogen alongside amorphous organic matter. Alginite consists of organic-walled marine microfossils, distinct from inorganic -walled microfossils that comprise diatomaceous earth. Alginite is a complex soil aggregate of algae based biomass fossil, clay turned volcanic ash and calcium carbonate; this material contains a complete spectrum of minerals, macro- and micro-organisms helping to turn lands fertile again in regions where soil has been degraded in the past. At least two forms of alginite are distinguishable, "alginite A" and "alginite B"; the "A" form contains morphologically distinguishable microfossils while the "B" form is more amorphous and film-like. Akiko Omura and Koichi Hoyanagi. "Relationships Between Composition Of Organic Matter, Depositional Environments, And Sea-Level Changes In Backarc Basins, Central Japan". Journal of Sedimentary Research. 74. Archived from the original on 2007-03-25. Simon Coxhell and Barry Fehlberg. "Julia Creek Vanadium and Oil Shale Deposit".
AIG Journal. Archived from the original on 2005-12-28
Pollen is a fine to coarse powdery substance comprising pollen grains which are male microgametophytes of seed plants, which produce male gametes. Pollen grains have a hard coat made of sporopollenin that protects the gametophytes during the process of their movement from the stamens to the pistil of flowering plants, or from the male cone to the female cone of coniferous plants. If pollen lands on a compatible pistil or female cone, it germinates, producing a pollen tube that transfers the sperm to the ovule containing the female gametophyte. Individual pollen grains are small enough to require magnification to see detail; the study of pollen is called palynology and is useful in paleoecology, paleontology and forensics. Pollen in plants is used for transferring haploid male genetic material from the anther of a single flower to the stigma of another in cross-pollination. In a case of self-pollination, this process takes place from the anther of a flower to the stigma of the same flower. Pollen is used as food and food supplement.
However, because of agricultural practices, it is contaminated by agricultural pesticides. Pollen itself is not the male gamete; each pollen grain contains a generative cell. In flowering plants the vegetative tube cell produces the pollen tube, the generative cell divides to form the two sperm cells. Pollen is produced in the microsporangia in the male cone of a conifer or other gymnosperm or in the anthers of an angiosperm flower. Pollen grains come in a wide variety of shapes and surface markings characteristic of the species. Pollen grains of pines and spruces are winged; the smallest pollen grain, that of the forget-me-not, is around 6 µm in diameter. Wind-borne pollen grains can be as large as about 90–100 µm. In angiosperms, during flower development the anther is composed of a mass of cells that appear undifferentiated, except for a differentiated dermis; as the flower develops, four groups of sporogenous cells form within the anther. The fertile sporogenous cells are surrounded by layers of sterile cells that grow into the wall of the pollen sac.
Some of the cells grow into nutritive cells that supply nutrition for the microspores that form by meiotic division from the sporogenous cells. In a process called microsporogenesis, four haploid microspores are produced from each diploid sporogenous cell, after meiotic division. After the formation of the four microspores, which are contained by callose walls, the development of the pollen grain walls begins; the callose wall is broken down by an enzyme called callase and the freed pollen grains grow in size and develop their characteristic shape and form a resistant outer wall called the exine and an inner wall called the intine. The exine is. Two basic types of microsporogenesis are recognised and successive. In simultaneous microsporogenesis meiotic steps I and II are completed prior to cytokinesis, whereas in successive microsporogenesis cytokinesis follows. While there may be a continuum with intermediate forms, the type of microsporogenesis has systematic significance; the predominant form amongst the monocots is successive.
During microgametogenesis, the unicellular microspores undergo mitosis and develop into mature microgametophytes containing the gametes. In some flowering plants, germination of the pollen grain may begin before it leaves the microsporangium, with the generative cell forming the two sperm cells. Except in the case of some submerged aquatic plants, the mature pollen grain has a double wall; the vegetative and generative cells are surrounded by a thin delicate wall of unaltered cellulose called the endospore or intine, a tough resistant outer cuticularized wall composed of sporopollenin called the exospore or exine. The exine bears spines or warts, or is variously sculptured, the character of the markings is of value for identifying genus, species, or cultivar or individual; the spines may be less than a micron in length referred to as spinulose, or longer than a micron referred to as echinate. Various terms describe the sculpturing such as reticulate, a net like appearance consisting of elements separated from each other by a lumen.
The pollen wall protects the sperm. The pollen grain surface is covered with waxes and proteins, which are held in place by structures called sculpture elements on the surface of the grain; the outer pollen wall, which prevents the pollen grain from shrinking and crushing the genetic material during desiccation, is composed of two layers. These two layers are the tectum and the foot layer, just above the intine; the tectum and foot layer are separated by a region called the columella, composed of strengthening rods. The outer wall is constructed with a resistant biopolymer called sporopollenin. Pollen apertures are regions of the pollen wall that may involve exine thinning or a significant reduction in exine thickness, they allow shrinking and swelling of the grain caused by changes in moisture content. Elongated apertures or furrows in the pollen grain are called sulci. Apertures that are more circular are called pores. Colpi and pores are major features in the identification of classes of pollen.
Pollen may be referre
A mineral is, broadly speaking, a solid chemical compound that occurs in pure form. A rock may consist of a single mineral, or may be an aggregate of two or more different minerals, spacially segregated into distinct phases. Compounds that occur only in living beings are excluded, but some minerals are biogenic and/or are organic compounds in the sense of chemistry. Moreover, living beings synthesize inorganic minerals that occur in rocks. In geology and mineralogy, the term "mineral" is reserved for mineral species: crystalline compounds with a well-defined chemical composition and a specific crystal structure. Minerals without a definite crystalline structure, such as opal or obsidian, are more properly called mineraloids. If a chemical compound may occur with different crystal structures, each structure is considered different mineral species. Thus, for example and stishovite are two different minerals consisting of the same compound, silicon dioxide; the International Mineralogical Association is the world's premier standard body for the definition and nomenclature of mineral species.
As of November 2018, the IMA recognizes 5,413 official mineral species. Out of more than 5,500 proposed or traditional ones; the chemical composition of a named mineral species may vary somewhat by the inclusion of small amounts of impurities. Specific varieties of a species sometimes have official names of their own. For example, amethyst is a purple variety of the mineral species quartz; some mineral species can have variable proportions of two or more chemical elements that occupy equivalent positions in the mineral's structure. Sometimes a mineral with variable composition is split into separate species, more or less arbitrarily, forming a mineral group. Besides the essential chemical composition and crystal structure, the description of a mineral species includes its common physical properties such as habit, lustre, colour, tenacity, fracture, specific gravity, fluorescence, radioactivity, as well as its taste or smell and its reaction to acid. Minerals are classified by key chemical constituents.
Silicate minerals comprise 90% of the Earth's crust. Other important mineral groups include the native elements, oxides, carbonates and phosphates. One definition of a mineral encompasses the following criteria: Formed by a natural process. Stable or metastable at room temperature. In the simplest sense, this means. Classical examples of exceptions to this rule include native mercury, which crystallizes at −39 °C, water ice, solid only below 0 °C. Modern advances have included extensive study of liquid crystals, which extensively involve mineralogy. Represented by a chemical formula. Minerals are chemical compounds, as such they can be described by fixed or a variable formula. Many mineral groups and species are composed of a solid solution. For example, the olivine group is described by the variable formula 2SiO4, a solid solution of two end-member species, magnesium-rich forsterite and iron-rich fayalite, which are described by a fixed chemical formula. Mineral species themselves could have a variable composition, such as the sulfide mackinawite, 9S8, a ferrous sulfide, but has a significant nickel impurity, reflected in its formula.
Ordered atomic arrangement. This means crystalline. An ordered atomic arrangement gives rise to a variety of macroscopic physical properties, such as crystal form and cleavage. There have been several recent proposals to classify amorphous substances as minerals; the formal definition of a mineral approved by the IMA in 1995: "A mineral is an element or chemical compound, crystalline and, formed as a result of geological processes." Abiogenic. Biogenic substances are explicitly excluded by the IMA: "Biogenic substances are chemical compounds produced by biological processes without a geological component and are not regarded as minerals. However, if geological processes were involved in the genesis of the compound the product can be accepted as a mineral."The first three general characteristics are less debated than the last two. Mineral classification schemes and their definitions are evolving to match recent advances in mineral science. Recent changes have included the addition of an organic class, in both the new Dana and the Strunz classification schemes.
The organic class includes a rare group of minerals with hydrocarbons. The IMA Commission on New Minerals and Mineral Names adopted in 2009 a hierarchical scheme for the naming and classification of mineral groups and group names and established seven commissions and four working groups to review and classify minerals into an official listing of their published names. According to these new r