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Friday, October 7, 2022

Communist propaganda

From Wikipedia, the free encyclopedia
 
"Comrade Lenin Cleanses the Earth of Filth" by Viktor Deni
 
Clock hand labeled "communism" about to cut off a top-hatted and brandy-nosed caricature head labeled "Capital" as the caption reads "The final hour!"

Communist propaganda is the artistic and social promotion of the ideology of communism, communist worldview, communist society and interests of the communist movement. While it tends to carry a negative connotation in the Western world, the term propaganda broadly refers to any publication or campaign aimed at promoting a cause and is/was used for official purposes by most communist-oriented governments. The term may also refer to a political parties opponents campaign. Rooted in Marxist thought, the propaganda of communism is viewed by its proponents as the vehicle for spreading their idea of enlightenment of working class people and pulling them away from the propaganda of who they view to be their oppressors, that they claim reinforces exploitation, such as religion or consumerism. Communist propaganda therefore stands in opposition to bourgeois or capitalist propaganda.

In The ABC of Communism, Bolshevik theoretician Nikolai Bukharin wrote: "The State propaganda of communism becomes in the long run a means for the eradication of the last traces of bourgeois propaganda dating from the old régime; and it is a powerful instrument for the creation of a new ideology, of new modes of thought, of a new outlook on the world."

Theoretical origins

The Great Soviet Encyclopedia defines communist propaganda as being the expression of the essential worldview of the working class and its natural aims and interests defined by its historical position as the social force which will ultimately usher in the epoch of communism.

According to communist theory, the history of all society has been the history of class struggle and with each phase of this struggle comes a new set of social relationships that dictate the direction of society's development and, fundamentally, the system of producing and distributing goods and services. Arising from the creation of surplus during the neolithic revolution, the unequal distribution of this surplus has been reinforced by the state which represents the interests of the ruling class of the time. While all societies and civilizations have had their own unique history of development, they each pass through six distinctive stages of economic relationships sharing common characteristics, these being: primitive communism (hunter-gatherer societies), slavery, feudalism, capitalism, socialism, and finally a return to communism in a highly advanced form which is considered to be the epoch of humanity having become fully civilized.

Communist propaganda accordingly serves the same purpose as all its predecessor propaganda: to ideologically enforce the legitimacy of the working class (those who derive a living from selling their labor) as the ruling class of society. Within this context, the main counter-propaganda is bourgeois propaganda, or propaganda that promotes the rule of the capitalist class (those who derive a living from privately owning property and capital assets). Communist propaganda is defined as a scientifically based system of the dissemination of the communist ideology with the purpose of education, training and organizing of the masses.

Purposes

The Great Soviet Encyclopedia identifies the following functions of communist propaganda:

  • The link of the Communist Party with the working class and other working people
  • Incorporation of scientific socialism into the worker movements and revolutionary activities of the masses
  • Unification and organization of national divisions of the workers', communist, and democratic movements
  • Coordination of the activities of the above-mentioned movements, exchange of information and experience
  • Expression of the public opinion of the working class, working people, their needs and interests
  • Spread opposition to the bourgeois and revisionist propaganda
  • Dissemination of statistical data about socialist society (i.e., the one of a communist state).

Targets

As a common trait of any propaganda and its analogue, advertising, communist propaganda's goals and techniques are tuned according to the target audience. The most broad classification of targets is:

  • Domestic propaganda of the communist states
  • External propaganda of the communist states
  • Propaganda of the communist supporters outside the communist states

A more detailed classification of specific targets (workers, peasants, youth, women, etc.) may be found in the Communist Party documents, usually presented at the Congresses of the Communist Party.

Techniques

Use of Marxist ideology

Further information: Marxism

The creation of the Soviet Union was presented as the most important turning event in human history, based on the Marxist theory of historical materialism. This theory identified means of production as chief determinants of the historical process. They led to the creation of social classes, and class struggle was the 'motor' of history. The sociocultural evolution of societies had to progress inevitably from slavery, through feudalism and capitalism to communism. Furthermore, the Communist Party of the Soviet Union became the protagonist of history, as a "vanguard of the working class", according to development of this theory by Vladimir Lenin. Hence the unlimited powers of the Communist Party leaders were claimed to be as infallible and inevitable as the history itself. It also followed that a worldwide victory of communist countries is inevitable.

Class struggle played a central role in the social policies of the USSR and socialist countries, all of which constitutionally outlined the supremacy of the working class in dictating society's development towards communism. Other classes with interests hostile to those of the working class were subjected to repression. This primarily focused on capitalists, including anyone who derived their living from privately owning property or capital assets. In the USSR, which was founded on a class alliance between workers and peasants, a neo-capitalist class emerged by the 1930s as a result of the New Economic Policy introduced after the end of the civil war. Among the peasants, this new class (called Kulaks) accumulated disproportionately large amounts of wealth through merchant trading and small capital practices. Under Joseph Stalin, the government began to crack down on the Kulaks, to which their resistance was met with violent repression in what could arguably considered a second civil war. Kulaks who resisted the socialization of their assets, along with anyone who collaborated with or fought for them, were punished with imprisonment, deportation to Siberia, or even execution. Lev Kopelev, who was personally involved in actions against villagers deprived of food for collaborating with Kulaks explained his motivation:

It was excruciating to see and hear all this. And even worse to take part in it.... And I persuaded myself, explained to myself. I must not give in to debilitating pity. We were realizing historical necessity. We were performing our revolutionary duty. We were obtaining grain for our socialist Fatherland. For the Five Year Plan. Our goal was the universal triumph of the Communism, and for the sake of that goal everything was permissible - to lie, to steal, to destroy hundreds of thousands and even millions of people... everyone who stood in the way.

The violence that characterized the forced collectivization of agriculture in the Soviet Union eventually ended in the final years of the 1930s with the defeat of the Kulaks and their demise. By the 1950s, agriculture was entirely collectivized and the peasantry ceased to exist, as all agricultural workers held the same essential social relationship to their means of production as other industrial workers thus making them part of a working class.

Polarized values

While somewhat modified since the times of the détente, communist propaganda is centered around a number of polarized dichotomies: virtues of the communist world vs. vices of the capitalist world, such as:

  • communists are for peace; capitalists are for war
  • communists are for mutual cooperation; capitalists are for coercive exploitation
  • communists are for democracy; capitalists are for oligarchy

Still another polarization was focused on the real and alleged essence of various terms, such as "freedom", "democracy", often counterpointing, e.g., "bourgeois democracy" vs. "true democracy" or "people's democracy". The latter term is seen in the expression "countries of people's democracy" as applied to what are called "communist states" in the West.

Self-criticism

Main article: Self-criticism (Marxism–Leninism)

According to Jacques Ellul's book Propaganda: The Formation of Men's Attitudes complete propaganda can only be achieved when it is able to win over the adversary, or at least integrate it into the new frame of reference created by propaganda. This was achieved by Soviet propaganda in the self-criticism of its opponents so that the enemy of a regime can be made to declare, while still the enemy, that the regime was right and any opposition was criminal. The enemy accepts their condemnation as just and converts to a supporter of the regime as a result of totalitarian propaganda.

Means

Communist propaganda was delivered via:

  • Printed media
    • Manuals
    • Newspapers and magazines
    • Books
  • Radio and TV broadcasting
  • Congresses and conferences of various international organizations under various communist umbrellas, such as the World Peace Council
  • Local communist parties and "fellow-travellers"
  • Social media censorship

Communist manuals

During the years 1938–1953 the History of the CPSU(B). Short Course was an obligatory explanation of Soviet ideology. The book was translated into many languages.

Communist periodicals

A number of periodicals were printed by communist states, either exclusively for distribution abroad or with versions tailored for foreign audiences. While the Soviet Union and communist China were the major contributors, other communist states contributed their share as well. The lists below are for early 1960s compiled by J. Clews. The list contains mostly English language titles, but many of these journals were edited in many languages.

Soviet Union

Further information: Printed media in the Soviet Union and Censorship of images in the Soviet Union

People's Republic of China

Other

(Partial list)

Radio broadcasting

A 1952 article, "Communist broadcasts to Italy", reported that as of June 1952 the total communist radio broadcast to Italy amounted to 78 hours per week, as compared to 23 hours of the Voice of America and BBC, noting that Italy occupied a pivotal position in the East–West conflict of the time. These broadcasts originated not only from Moscow, but also from the countries of the Soviet Bloc, as well as from fake "underground resistance" radios probably located within the Soviet Bloc as well rather than in the West.

Film and stage

Soviet leaders believed that film was an important tool of propaganda (see Cinema of the Soviet Union). Soviet films helped to create the legends of the revolution: The Battleship Potemkin, October: Ten Days That Shook the World, and The End of St. Petersburg. Roman Karmen was a war cameraman and film director and one of the most influential figures in documentary film making. Obyknovennyy fashizm (Common Fascism aka A Night of Thoughts or Triumph Over Violence) (1965) by Mikhail Romm described totalitarian propaganda on the example of Nazism.

In 2007 a high ranking intelligence officer and defector from the Eastern Bloc, Ion Mihai Pacepa, stated that in February 1960, Nikita Khrushchev authorized a covert plan (known as Seat 12) to discredit the Vatican because of its strong anti-communist stance, with Pope Pius XII as the prime target. As part of that plan General Ivan Agayants, chief of the KGB's disinformation department, allegedly created the outline for what was to become the play, The Deputy, which, although fictional, purports to cast doubt on the Pontiff's moral credibility with regard to the Holocaust.

International organizations, congresses and festivals

During the Cold War the World Festivals of Youth and Students were held, with some exceptions, in capitals of communist states and were a powerful tool of communist propaganda.

Education

See also: Education in the Soviet Union, Education in People's Republic of Poland, Education in North Korea, and Education in East Germany

Education in the communist states included a considerable amount of indoctrination, both in special political and philosophical courses and in properly crafted courses of general education: history, geography, world literature, etc. Soviet ideology was taught in the Soviet Union divided into three disciplines: scientific communism, Marxism-Leninism (mostly in the form of Leninism) and communist political economy and was introduced as part of many courses, e.g., teaching Marx' or Lenin's views on topics of science or history. The Soviet format of education was imposed (with varying success) onto other satellite states.

Culture and arts

Main article: Socialist realism
 
Statue of Mao Zedong in Shenyang

From the early days of the first communist-ruled state, Soviet Russia, arts were recognized as a powerful means of propaganda and placed under strict control and censorship in all communist states. Lenin and Joseph Stalin were the preferred subjects, although almost all of Stalin's images and monuments were removed and/or destroyed after his death in 1956.

Kukryniksy were three propaganda caricaturists/cartoonists, who attacked all enemies of the Soviet Union.

Financial means

Further information: Active measures and Soviet influence on the peace movement

J. Clews cites German, French and British estimates of the early 1960s on the amount of money spent in the world for communist propaganda and political activities in the non-communist world, estimating to about $2 billion, i.e., about $2 per person outside the communists states, with major spenders being the Soviet Union and the People's Republic of China.

Perception in the West

The doorway of the newspaper La Clarte, a weekly communist newspaper, padlocked by the police in Montreal, Quebec, Canada in 1937

The basic aspects of the communist ideology, such as violent means for attaining its goals (revolution), abolition of private property and animosity towards religion were against the traditional values of the Western world and have met with strong opposition, including attempts to make the communist propaganda illegal in some states. For example:

  • In 1937, the Canadian province of Quebec enacted the "Padlock Law", which enabled police to prevent the use of any premises for the promotion of communism or Bolshevism. The Supreme Court of Canada struck down the Padlock Law as unconstitutional in 1957.
  • In 1962, the U.S. state of Louisiana passed a law identifying communist propaganda as a subversive activity and declared that "it shall be a felony for any person to knowingly, willfully and intentionally deliver, distribute, disseminate or store communist propaganda in the state of Louisiana except under the specific exemptions hereinafter provided."

Specific examples

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Phylogenetic comparative methods

From Wikipedia, the free encyclopedia

Phylogenetic comparative methods (PCMs) use information on the historical relationships of lineages (phylogenies) to test evolutionary hypotheses. The comparative method has a long history in evolutionary biology; indeed, Charles Darwin used differences and similarities between species as a major source of evidence in The Origin of Species. However, the fact that closely related lineages share many traits and trait combinations as a result of the process of descent with modification means that lineages are not independent. This realization inspired the development of explicitly phylogenetic comparative methods. Initially, these methods were primarily developed to control for phylogenetic history when testing for adaptation; however, in recent years the use of the term has broadened to include any use of phylogenies in statistical tests. Although most studies that employ PCMs focus on extant organisms, many methods can also be applied to extinct taxa and can incorporate information from the fossil record.

PCMs can generally be divided into two types of approaches: those that infer the evolutionary history of some character (phenotypic or genetic) across a phylogeny and those that infer the process of evolutionary branching itself (diversification rates), though there are some approaches that do both simultaneously. Typically the tree that is used in conjunction with PCMs has been estimated independently (see computational phylogenetics) such that both the relationships between lineages and the length of branches separating them is assumed to be known.

Applications

Phylogenetic comparative approaches can complement other ways of studying adaptation, such as studying natural populations, experimental studies, and mathematical models. Interspecific comparisons allow researchers to assess the generality of evolutionary phenomena by considering independent evolutionary events. Such an approach is particularly useful when there is little or no variation within species. And because they can be used to explicitly model evolutionary processes occurring over very long time periods, they can provide insight into macroevolutionary questions, once the exclusive domain of paleontology.

Home range areas of 49 species of mammals in relation to their body size. Larger-bodied species tend to have larger home ranges, but at any given body size members of the order Carnivora (carnivores and omnivores) tend to have larger home ranges than ungulates (all of which are herbivores). Whether this difference is considered statistically significant depends on what type of analysis is applied
 
Testes mass of various species of Primates in relation to their body size and mating system. Larger-bodied species tend to have larger testes, but at any given body size species in which females tend to mate with multiple males have males with larger testes.

Phylogenetic comparative methods are commonly applied to such questions as:

→ Example: how does brain mass vary in relation to body mass?

→ Example: do canids have larger hearts than felids?

→ Example: do carnivores have larger home ranges than herbivores?

→ Example: where did endothermy evolve in the lineage that led to mammals?

→ Example: where, when, and why did placentas and viviparity evolve?

  • Does a trait exhibit significant phylogenetic signal in a particular group of organisms? Do certain types of traits tend to "follow phylogeny" more than others?

→ Example: are behavioral traits more labile during evolution?

  • Do species differences in life history traits trade-off, as in the so-called fast-slow continuum?

→ Example: why do small-bodied species have shorter life spans than their larger relatives?

Phylogenetically independent contrasts

The standardized contrasts are used in conventional statistical procedures, with the constraint that all regressions, correlations, analysis of covariance, etc., must pass through the origin.

Felsenstein proposed the first general statistical method in 1985 for incorporating phylogenetic information, i.e., the first that could use any arbitrary topology (branching order) and a specified set of branch lengths. The method is now recognized as an algorithm that implements a special case of what are termed phylogenetic generalized least-squares models. The logic of the method is to use phylogenetic information (and an assumed Brownian motion like model of trait evolution) to transform the original tip data (mean values for a set of species) into values that are statistically independent and identically distributed.

The algorithm involves computing values at internal nodes as an intermediate step, but they are generally not used for inferences by themselves. An exception occurs for the basal (root) node, which can be interpreted as an estimate of the ancestral value for the entire tree (assuming that no directional evolutionary trends [e.g., Cope's rule] have occurred) or as a phylogenetically weighted estimate of the mean for the entire set of tip species (terminal taxa). The value at the root is equivalent to that obtained from the "squared-change parsimony" algorithm and is also the maximum likelihood estimate under Brownian motion. The independent contrasts algebra can also be used to compute a standard error or confidence interval.

Phylogenetic generalized least squares (PGLS)

Probably the most commonly used PCM is phylogenetic generalized least squares (PGLS). This approach is used to test whether there is a relationship between two (or more) variables while accounting for the fact that lineage are not independent. The method is a special case of generalized least squares (GLS) and as such the PGLS estimator is also unbiased, consistent, efficient, and asymptotically normal. In many statistical situations where GLS (or, ordinary least squares [OLS]) is used residual errors ε are assumed to be independent and identically distributed random variables that are assumed to be normal

whereas in PGLS the errors are assumed to be distributed as

where V is a matrix of expected variance and covariance of the residuals given an evolutionary model and a phylogenetic tree. Therefore, it is the structure of residuals and not the variables themselves that show phylogenetic signal. This has long been a source of confusion in the scientific literature. A number of models have been proposed for the structure of V such as Brownian motion Ornstein-Uhlenbeck, and Pagel's λ model. (When a Brownian motion model is used, PGLS is identical to the independent contrasts estimator.) In PGLS, the parameters of the evolutionary model are typically co-estimated with the regression parameters.

PGLS can only be applied to questions where the dependent variable is continuously distributed; however, the phylogenetic tree can also be incorporated into the residual distribution of generalized linear models, making it possible to generalize the approach to a broader set of distributions for the response.

Phylogenetically informed Monte Carlo computer simulations

Data for a continuous-valued trait can be simulated in such a way that taxa at the tips of a hypothetical phylogenetic tree will exhibit phylogenetic signal, i.e., closely related species will tend to resemble each other.

Martins and Garland proposed in 1991 that one way to account for phylogenetic relations when conducting statistical analyses was to use computer simulations to create many data sets that are consistent with the null hypothesis under test (e.g., no correlation between two traits, no difference between two ecologically defined groups of species) but that mimic evolution along the relevant phylogenetic tree. If such data sets (typically 1,000 or more) are analyzed with the same statistical procedure that is used to analyze a real data set, then results for the simulated data sets can be used to create phylogenetically correct (or "PC") null distributions of the test statistic (e.g., a correlation coefficient, t, F). Such simulation approaches can also be combined with such methods as phylogenetically independent contrasts or PGLS (see above).

Phylogenetic Pseudoreplication.jpg
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Sulfur cycle

From Wikipedia, the free encyclopedia
 
Sulfur cycle in general

The sulfur cycle is a biogeochemical cycle in which the sulfur moves between rocks, waterways and living systems. It is important in geology as it affects many minerals and in life because sulfur is an essential element (CHNOPS), being a constituent of many proteins and cofactors, and sulfur compounds can be used as oxidants or reductants in microbial respiration. The global sulfur cycle involves the transformations of sulfur species through different oxidation states, which play an important role in both geological and biological processes. Steps of the sulfur cycle are:

These are often termed as follows:

Assimilative sulfate reduction (see also sulfur assimilation) in which sulfate (SO2−
4) is reduced by plants, fungi and various prokaryotes. The oxidation states of sulfur are +6 in sulfate and –2 in R–SH.
Desulfurization in which organic molecules containing sulfur can be desulfurized, producing hydrogen sulfide gas (H2S, oxidation state = –2). An analogous process for organic nitrogen compounds is deamination.
Oxidation of hydrogen sulfide produces elemental sulfur (S8), oxidation state = 0. This reaction occurs in the photosynthetic green and purple sulfur bacteria and some chemolithotrophs. Often the elemental sulfur is stored as polysulfides.
Oxidation in elemental sulfur by sulfur oxidizers produces sulfate.
Dissimilative sulfur reduction in which elemental sulfur can be reduced to hydrogen sulfide.
Dissimilative sulfate reduction in which sulfate reducers generate hydrogen sulfide from sulfate.

Sulfur oxidation state

Sulfur has four main oxidation states in nature, which are −2, +2, +4, and +6. The common sulfur species of each oxidation state are listed as follows:

S2−: H2S, (CH3)2S, BaS

S0: native, or elemental, sulfur

S2+: SCl2

S4+: SO2, sulfite (SO2−
3)

S6+: SO2−
4 (H2SO4, CaSO4), SF6

Sulfur sources and sinks

Sulfur is found in oxidation states ranging from +6 in SO2−
4 to −2 in sulfides. Thus, elemental sulfur can either give or receive electrons depending on its environment. On the anoxic early Earth, most sulfur was present in minerals such as pyrite (FeS2). Over Earth history, the amount of mobile sulfur increased through volcanic activity as well as weathering of the crust in an oxygenated atmosphere. Earth's main sulfur sink is the oceans SO2−
4, where it is the major oxidizing agent.

Mean acidifying emissions of different foods per 100 grams of protein
Food Types Acidifying Emissions (g SO2eq per 100 g protein)
Beef
343.6
Cheese
165.5
Pork
142.7
Lamb and Mutton
139.0
Farmed Crustaceans
133.1
Poultry
102.4
Farmed Fish
65.9
Eggs
53.7
Groundnuts
22.6
Peas
8.5
Tofu
6.7

When SO2−
4 is assimilated by organisms, it is reduced and converted to organic sulfur, which is an essential component of proteins. However, the biosphere does not act as a major sink for sulfur, instead the majority of sulfur is found in seawater or sedimentary rocks including: pyrite rich shales, evaporite rocks (anhydrite and baryte), and calcium and magnesium carbonates (i.e. carbonate-associated sulfate). The amount of sulfate in the oceans is controlled by three major processes:

  1. input from rivers
  2. sulfate reduction and sulfide re-oxidation on continental shelves and slopes
  3. burial of anhydrite and pyrite in the oceanic crust.

The primary natural source of sulfur to the atmosphere is sea spray or windblown sulfur-rich dust, neither of which is long lived in the atmosphere. In recent times, the large annual input of sulfur from the burning of coal and other fossil fuels has added a substantial amount SO2 which acts as an air pollutant. In the geologic past, igneous intrusions into coal measures have caused large scale burning of these measures, and consequential release of sulfur to the atmosphere. This has led to substantial disruption to the climate system, and is one of the proposed causes of the Permian–Triassic extinction event.

Dimethylsulfide [(CH3)2S or DMS] is produced by the decomposition of dimethylsulfoniopropionate (DMSP) from dying phytoplankton cells in the ocean's photic zone, and is the major biogenic gas emitted from the sea, where it is responsible for the distinctive “smell of the sea” along coastlines. DMS is the largest natural source of sulfur gas, but still only has a residence time of about one day in the atmosphere and a majority of it is redeposited in the oceans rather than making it to land. However, it is a significant factor in the climate system, as it is involved in the formation of clouds.

Biologically and thermochemically driven sulfate reduction

Dissimilatory sulfate reduction pathway
 
3′-phosphoadenosine-5′-phosphosulfate
(key intermediate in the sulfur cycle)

Through the dissimilatory sulfate reduction pathway, sulfate can be reduced either bacterially (bacterial sulfate reduction) or inorganically (thermochemical sulfate reduction). This pathway involves the reduction of sulfate by organic compounds to produce hydrogen sulfide, which occurs in both processes.

The main products and reactants of bacterial sulfate reduction (BSR) and thermochemical sulfate reduction (TSR) are very similar. For both, various organic compounds and dissolved sulfate are the reactants, and the products or by-products are as follows: H2S, CO2, carbonates, elemental sulfur and metal sulfides. However, the reactive organic compounds differ for BSR and TSR because of the mutually exclusive temperature regimes. Organic acids are the main organic reactants for BSR and branched/n-alkanes are the main organic reactants for TSR. The inorganic reaction products in BSR and TSR are H2S (HS−) and HCO−
3 (CO2).

These processes occur because there are two very different thermal regimes in which sulfate is reduced, particularly in low-temperature and high-temperature environments. BSR usually occurs at lower temperatures from 0−80 °C, while TSR happens at much higher temperatures around 100–140 °C. Temperatures for TSR are not as well defined; the lowest confirmed temperature is 127 °C and the highest temperatures occur in settings around 160−180 °C. These two different regimes appear because at higher temperatures most sulfate-reducing microbes can no longer metabolize due to the denaturation of proteins or deactivation of enzymes, so TSR takes over. However, in hot sediments around hydrothermal vents BSR can happen at temperatures up to 110 °C.

BSR and TSR occur at different depths. BSR takes place in low-temperature environments, which are shallower settings such as oil and gas fields. BSR can also take place in modern marine sedimentary environments such as stratified inland seas, continental shelves, organic-rich deltas, and hydrothermal sediments which have intense microbial sulfate reduction because of the high concentration of dissolved sulfate in the seawater. Additionally, the high amounts of hydrogen sulfide found in oil and gas fields is thought to arise from the oxidation of petroleum hydrocarbons by sulfate. Such reactions are known to occur by microbial processes but it is generally accepted that TSR is responsible for the bulk of these reactions, especially in deep or hot reservoirs. Thus, TSR occurs in deep reservoirs where the temperatures are much higher. BSR is geologically instantaneous in most geologic settings, while TSR occurs at rates in the order of hundreds of thousands of years. Although much slower than BSR, even TSR appears to be a geologically fairly fast process.

BSR in shallow environments and TSR in deep reservoirs are key processes in the oceanic sulfur cycle.  Approximately, 10% (of the total gas) of H2S is produced in BSR settings, whereas 90% of the H2S is produced in TSR settings. If there is more than a few percent of H2S in any deep reservoir, then it is assumed that TSR has taken over. This is due to the fact that thermal cracking of hydrocarbons doesn't provide more than a couple percent of H2S. The amount of H2S is affected by several factors such as, the availability of organic reactants and sulfate and the presence/availability of base and transition metals.

Sulfur-oxidizing bacteria in hydrothermal vents

Hydrothermal vents emit hydrogen sulfide that support the carbon fixation of chemolithotrophic bacteria that oxidize hydrogen sulfide with oxygen to produce elemental sulfur or sulfate. The chemical reactions are as follows:

CO2 + 4 H2S + O2 → CH2O + 4 S0 + 3 H2O
CO2 + H2S + O2 + H2O → CH2O + SO2–
4 + 2 H+

In modern oceans, Thiomicrospira, Halothiobacillus, and Beggiatoa are primary sulfur oxidizing bacteria, and form chemosynthetic symbioses with animal hosts. The host provides metabolic substrates (e.g., CO2, O2, H2O) to the symbiont while the symbiont generates organic carbon for sustaining the metabolic activities of the host. The produced sulfate usually combines with the leached calcium ions to form gypsum, which can form widespread deposits on near mid-ocean spreading centers.

δ34S

Although there are 25 known isotopes of sulfur, only four are stable and of geochemical importance. Of those four, two (32S, light and 34S, heavy) comprise (99.22%) of sulfur on Earth. The vast majority (95.02%) of sulfur occurs as 32S with only 4.21% in 34S. The ratio of these two isotopes is fixed in the Solar System and has been since its formation. The bulk Earth sulfur isotopic ratio is thought to be the same as the ratio of 22.22 measured from the Canyon Diablo troilite (CDT), a meteorite. That ratio is accepted as the international standard and is therefore set at δ = 0.00. Deviation from 0.00 is expressed as the δ34S which is a ratio in per mill (‰). Positive values correlate to increased levels of 34S, whereas negative values correlate with greater 32S in a sample.

Formation of sulfur minerals through non-biogenic processes does not substantially differentiate between the light and heavy isotopes, therefore sulfur isotope ratios in gypsum or barite should be the same as the overall isotope ratio in the water column at their time of precipitation. Sulfate reduction through biologic activity strongly differentiates between the two isotopes because of the more rapid enzymic reaction with 32S. Sulfate metabolism results in an isotopic depletion of −18‰, and repeated cycles of oxidation and reduction can result in values up to −50‰. Average present day seawater values of δ34S are on the order of +21‰.

Throughout geologic history the sulfur cycle and the isotopic ratios have coevolved with the biosphere becoming overall more negative with the increases in biologically driven sulfate reduction, but also show substantial positive excursion. In general positive excursions in the sulfur isotopes mean that there is an excess of pyrite deposition rather than oxidation of sulfide minerals exposed on land.

Marine sulfur cycle

The sulfur cycle in marine environments has been well-studied via the tool of sulfur isotope systematics expressed as δ34S. The modern global oceans have sulfur storage of 1.3×1018 kg, mainly occurring as sulfate with the δ34S value of +21‰. The overall input flux is 1.0×1011 kg/a with the sulfur isotope composition of ~3‰. Riverine sulfate derived from the terrestrial weathering of sulfide minerals (δ34S = +6‰) is the primary input of sulfur to the oceans. Other sources are metamorphic and volcanic degassing and hydrothermal activity (δ34S = 0‰), which release reduced sulfur species (such as H2S and S0). There are two major outputs of sulfur from the oceans. The first sink is the burial of sulfate either as marine evaporites (such as gypsum) or carbonate-associated sulfate (CAS), which accounts for 6×1010 kg/a (δ34S = +21‰). The second sulfur sink is pyrite burial in shelf sediments or deep seafloor sediments (4×1010 kg/a; δ34S = −20‰). The total marine sulfur output flux is 1.0×1011 kg/a which matches the input fluxes, implying the modern marine sulfur budget is at steady state. The residence time of sulfur in modern global oceans is 13,000,000 years.

Evolution of the sulfur cycle

The isotopic composition of sedimentary sulfides provides primary information on the evolution of the sulfur cycle.

The total inventory of sulfur compounds on the surface of the Earth (nearly 1019 kg of sulfur) represents the total outgassing of sulfur through geologic time. Rocks analyzed for sulfur content are generally organic-rich shales meaning they are likely controlled by biogenic sulfur reduction. Average seawater curves are generated from evaporites deposited throughout geologic time because again, since they do not discriminate between the heavy and light sulfur isotopes, they should mimic the ocean composition at the time of deposition.

4.6 billion years ago (Ga) the Earth formed and had a theoretical δ34S value of 0. Since there was no biologic activity on early Earth there would be no isotopic fractionation. All sulfur in the atmosphere would be released during volcanic eruptions. When the oceans condensed on Earth, the atmosphere was essentially swept clean of sulfur gases, owing to their high solubility in water. Throughout the majority of the Archean (4.6–2.5 Ga) most systems appeared to be sulfate-limited. Some small Archean evaporite deposits require that at least locally elevated concentrations (possibly due to local volcanic activity) of sulfate existed in order for them to be supersaturated and precipitate out of solution.

3.8–3.6 Ga marks the beginning of the exposed geologic record because this is the age of the oldest rocks on Earth. Metasedimentary rocks from this time still have an isotopic value of 0 because the biosphere was not developed enough (possibly at all) to fractionate sulfur.

3.5 Ga anoxyogenic photosynthesis is established and provides a weak source of sulfate to the global ocean with sulfate concentrations incredibly low the δ34S is still basically 0. Shortly after, at 3.4 Ga the first evidence for minimal fractionation in evaporitic sulfate in association with magmatically derived sulfides can be seen in the rock record. This fractionation shows possible evidence for anoxygenic phototrophic bacteria.

2.8 Ga marks the first evidence for oxygen production through photosynthesis. This is important because there cannot be sulfur oxidation without oxygen in the atmosphere. This exemplifies the coevolution of the oxygen and sulfur cycles as well as the biosphere.

2.7–2.5 Ga is the age of the oldest sedimentary rocks to have a depleted δ 34S which provide the first compelling evidence for sulfate reduction.

2.3 Ga sulfate increases to more than 1 mM; this increase in sulfate is coincident with the "Great Oxygenation Event", when redox conditions on Earth's surface are thought by most workers to have shifted fundamentally from reducing to oxidizing. This shift would have led to an incredible increase in sulfate weathering which would have led to an increase in sulfate in the oceans. The large isotopic fractionations that would likely be associated with bacteria reduction are produced for the first time. Although there was a distinct rise in seawater sulfate at this time it was likely still only less than 5–15% of present-day levels.

At 1.8 Ga, Banded iron formations (BIF) are common sedimentary rocks throughout the Archean and Paleoproterozoic; their disappearance marks a distinct shift in the chemistry of ocean water. BIFs have alternating layers of iron oxides and chert. BIFs only form if the water is allowed to supersaturate in dissolved iron (Fe2+) meaning there cannot be free oxygen or sulfur in the water column because it would form Fe3+ (rust) or pyrite and precipitate out of solution. Following this supersaturation, the water must become oxygenated in order for the ferric rich bands to precipitate it must still be sulfur poor otherwise pyrite would form instead of Fe3+. It has been hypothesized that BIFs formed during the initial evolution of photosynthetic organisms that had phases of population growth, causing over production of oxygen. Due to this over production they would poison themselves causing a mass die off, which would cut off the source of oxygen and produce a large amount of CO2 through the decomposition of their bodies, allowing for another bacterial bloom. After 1.8 Ga sulfate concentrations were sufficient to increase rates of sulfate reduction to greater than the delivery flux of iron to the oceans.

Along with the disappearance of BIF, the end of the Paleoproterozoic also marks the first large scale sedimentary exhalative deposits showing a link between mineralization and a likely increase in the amount of sulfate in sea water. In the Paleoproterozoic the sulfate in seawater had increased to an amount greater than in the Archean, but was still lower than present day values. The sulfate levels in the Proterozoic also act as proxies for atmospheric oxygen because sulfate is produced mostly through weathering of the continents in the presence of oxygen. The low levels in the Proterozoic simply imply that levels of atmospheric oxygen fell between the abundances of the Phanerozoic and the deficiencies of the Archean.

750 million years ago (Ma) there is a renewed deposition of BIF which marks a significant change in ocean chemistry. This was likely due to snowball Earth episodes where the entire globe including the oceans was covered in a layer of ice cutting off oxygenation. In the late Neoproterozoic high carbon burial rates increased the atmospheric oxygen level to >10% of its present-day value. In the Latest Neoproterozoic another major oxidizing event occurred on Earth's surface that resulted in an anoxic deep ocean and possibly allowed for the appearance of multicellular life.

During the last 600 million years, seawater SO4 has generally varied between +10‰ and +30‰ in δ34S, with an average value close to that of today. Notably changes in seawater δ34S occurred during extinction and climatic events during this time.

Over a shorter time scale (ten million years) changes in the sulfur cycle are easier to observe and can be even better constrained with oxygen isotopes. Oxygen is continually incorporated into the sulfur cycle through sulfate oxidation and then released when that sulfate is reduced once again. Since different sulfate sources within the ocean have distinct oxygen isotopic values it may be possible to use oxygen to trace the sulfur cycle. Biological sulfate reduction preferentially selects lighter oxygen isotopes for the same reason that lighter sulfur isotopes are preferred. By studying oxygen isotopes in ocean sediments over the last 10 million years were able to better constrain the sulfur concentrations in sea water through that same time. They found that the sea level changes due to Pliocene and Pleistocene glacial cycles changed the area of continental shelves which then disrupted the sulfur processing, lowering the concentration of sulfate in the sea water. This was a drastic change as compared to preglacial times before 2 million years ago.

The Great Oxidation Event and sulfur isotope mass-independent fractionation

The Great Oxygenation Event (GOE) is characterized by the disappearance of sulfur isotope mass-independent fractionation (MIF) in the sedimentary records at around 2.45 billion years ago (Ga). The MIF of sulfur isotope (Δ33S) is defined by the deviation of measured δ33S value from the δ33S value inferred from the measured δ34S value according to the mass dependent fractionation law. The Great Oxidation Event represented a massive transition of global sulfur cycles. Before the Great Oxidation Event, the sulfur cycle was heavily influenced by the ultraviolet (UV) radiation and the associated photochemical reactions, which induced the sulfur isotope mass-independent fractionation (Δ33S ≠ 0). The preservation of sulfur isotope mass-independent fractionation signals requires the atmospheric O2 lower than 10−5 of present atmospheric level (PAL). The disappearance of sulfur isotope mass-independent fractionation at ~2.45 Ga indicates that atmospheric pO2 exceeded 10−5 present atmospheric level after the Great Oxygenation Event. Oxygen played an essential role in the global sulfur cycles after the Great Oxygenation Event, such as oxidative weathering of sulfides. The burial of pyrite in sediments in turn contributes to the accumulation of free O2 in Earth's surface environment.

Economic importance

Sulfur is intimately involved in production of fossil fuels and a majority of metal deposits because of its ability to act as an oxidizing or reducing agent. The vast majority of the major mineral deposits on Earth contain a substantial amount of sulfur including, but not limited to: sedimentary exhalative deposits (SEDEX), Carbonate-hosted lead-zinc ore deposits (Mississippi Valley-Type MVT) and porphyry copper deposits. Iron sulfides, galena and sphalerite will form as by-products of hydrogen sulfide generation, as long as the respective transition or base metals are present or transported to a sulfate reduction site. If the system runs out of reactive hydrocarbons economically viable elemental sulfur deposits may form. Sulfur also acts as a reducing agent in many natural gas reservoirs and generally ore forming fluids have a close relationship with ancient hydrocarbon seeps or vents.

Important sources of sulfur in ore deposits are generally deep-seated, but they can also come from local country rocks, sea water, or marine evaporites. The presence or absence of sulfur is one of the limiting factors on both the concentration of precious metals and its precipitation from solution. pH, temperature and especially redox states determine whether sulfides will precipitate. Most sulfide brines will remain in concentration until they reach reducing conditions, a higher pH or lower temperatures.

Ore fluids are generally linked to metal rich waters that have been heated within a sedimentary basin under the elevated thermal conditions typically in extensional tectonic settings. The redox conditions of the basin lithologies exert an important control on the redox state of the metal-transporting fluids and deposits can form from both oxidizing and reducing fluids. Metal-rich ore fluids tend to be by necessity comparatively sulfide deficient, so a substantial portion of the sulfide must be supplied from another source at the site of mineralization. Bacterial reduction of seawater sulfate or a euxinic (anoxic and H2S-containing) water column is a necessary source of that sulfide. When present, the δ34S values of barite are generally consistent with a seawater sulfate source, suggesting baryte formation by reaction between hydrothermal barium and sulfate in ambient seawater.

Once fossil fuels or precious metals are discovered and either burned or milled, the sulfur become a waste product which must be dealt with properly or it can become a pollutant. There has been a great increase in the amount of sulfur in our present day atmosphere because of the burning of fossil fuels. Sulfur acts as a pollutant and an economic resource at the same time.

Human impact

Human activities have a major effect on the global sulfur cycle. The burning of coal, natural gas, and other fossil fuels has greatly increased the amount of sulfur in the atmosphere and ocean and depleted the sedimentary rock sink. Without human impact sulfur would stay tied up in rocks for millions of years until it was uplifted through tectonic events and then released through erosion and weathering processes. Instead it is being drilled, pumped and burned at a steadily increasing rate. Over the most polluted areas there has been a 30-fold increase in sulfate deposition.

Although the sulfur curve shows shifts between net sulfur oxidation and net sulfur reduction in the geologic past, the magnitude of the current human impact is probably unprecedented in the geologic record. Human activities greatly increase the flux of sulfur to the atmosphere, some of which is transported globally. Humans are mining coal and extracting petroleum from the Earth's crust at a rate that mobilizes 150 x 1012 gS/yr, which is more than double the rate of 100 years ago. The result of human impact on these processes is to increase the pool of oxidized sulfur (SO4) in the global cycle, at the expense of the storage of reduced sulfur in the Earth's crust. Therefore, human activities do not cause a major change in the global pools of sulfur, but they do produce massive changes in the annual flux of sulfur through the atmosphere.

When SO2 is emitted as an air pollutant, it forms sulfuric acid through reactions with water in the atmosphere. Once the acid is completely dissociated in water the pH can drop to 4.3 or lower causing damage to both man-made and natural systems. According to the EPA, acid rain is a broad term referring to a mixture of wet and dry deposition (deposited material) from the atmosphere containing higher than normal amounts of nitric and sulfuric acids. Distilled water (water without any dissolved constituents), which contains no carbon dioxide, has a neutral pH of 7. Rain naturally has a slightly acidic pH of 5.6, because carbon dioxide and water in the air react together to form carbonic acid, a very weak acid. Around Washington, D.C., however, the average rain pH is between 4.2 and 4.4. Since pH is on a log scale dropping by 1 (the difference between normal rain water and acid rain) has a dramatic effect on the strength of the acid. In the United States, roughly two thirds of all SO2 and one fourth of all NO3 come from electric power generation that relies on burning fossil fuels, like coal.

As it is an important nutrient for plants, sulfur is increasingly used as a component of fertilizers. Recently sulfur deficiency has become widespread in many countries in Europe. Because of actions taken to limit acid rains atmospheric inputs of sulfur continue to decrease, As a result, the deficit in the sulfur input is likely to increase unless sulfur fertilizers are used.

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