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Sunday, November 6, 2022

Surrealism

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Surrealism

Surrealism
The Treachery of Images, by René Magritte (1929)
The Treachery of Images, by René Magritte (1929), featuring the declaration "Ceci n'est pas une pipe" ("This is not a pipe")
Years active1920s–1950s
CountryFrance, Belgium
Major figuresBreton, Dalí, Ernst, Magritte
Influences
Influenced

Surrealism is a cultural movement that developed in Europe in the aftermath of World War I in which artists depicted unnerving, illogical scenes and developed techniques to allow the unconscious mind to express itself. Its aim was, according to leader André Breton, to "resolve the previously contradictory conditions of dream and reality into an absolute reality, a super-reality", or surreality. It produced works of painting, writing, theatre, filmmaking, photography, and other media.

Works of Surrealism feature the element of surprise, unexpected juxtapositions and non sequitur. However, many Surrealist artists and writers regard their work as an expression of the philosophical movement first and foremost (for instance, of the "pure psychic automatism" Breton speaks of in the first Surrealist Manifesto), with the works themselves being secondary, i.e. artifacts of surrealist experimentation. Leader Breton was explicit in his assertion that Surrealism was, above all, a revolutionary movement. At the time, the movement was associated with political causes such as communism and anarchism. It was influenced by the Dada movement of the 1910s.

The term "Surrealism" originated with Guillaume Apollinaire in 1917. However, the Surrealist movement was not officially established until after October 1924, when the Surrealist Manifesto published by French poet and critic André Breton succeeded in claiming the term for his group over a rival faction led by Yvan Goll, who had published his own surrealist manifesto two weeks prior. The most important center of the movement was Paris, France. From the 1920s onward, the movement spread around the globe, impacting the visual arts, literature, film, and music of many countries and languages, as well as political thought and practice, philosophy, and social theory.

Founding of the movement

Max Ernst, The Elephant Celebes, 1921

The word 'surrealism' was first coined in March 1917 by Guillaume Apollinaire. He wrote in a letter to Paul Dermée: "All things considered, I think in fact it is better to adopt surrealism than supernaturalism, which I first used" [Tout bien examiné, je crois en effet qu'il vaut mieux adopter surréalisme que surnaturalisme que j'avais d'abord employé].

Apollinaire used the term in his program notes for Sergei Diaghilev's Ballets Russes, Parade, which premiered 18 May 1917. Parade had a one-act scenario by Jean Cocteau and was performed with music by Erik Satie. Cocteau described the ballet as "realistic". Apollinaire went further, describing Parade as "surrealistic":

This new alliance—I say new, because until now scenery and costumes were linked only by factitious bonds—has given rise, in Parade, to a kind of surrealism, which I consider to be the point of departure for a whole series of manifestations of the New Spirit that is making itself felt today and that will certainly appeal to our best minds. We may expect it to bring about profound changes in our arts and manners through universal joyfulness, for it is only natural, after all, that they keep pace with scientific and industrial progress. (Apollinaire, 1917)

The term was taken up again by Apollinaire, both as subtitle and in the preface to his play Les Mamelles de Tirésias: Drame surréaliste, which was written in 1903 and first performed in 1917.

World War I scattered the writers and artists who had been based in Paris, and in the interim many became involved with Dada, believing that excessive rational thought and bourgeois values had brought the conflict of the war upon the world. The Dadaists protested with anti-art gatherings, performances, writings and art works. After the war, when they returned to Paris, the Dada activities continued.

During the war, André Breton, who had trained in medicine and psychiatry, served in a neurological hospital where he used Sigmund Freud's psychoanalytic methods with soldiers suffering from shell-shock. Meeting the young writer Jacques Vaché, Breton felt that Vaché was the spiritual son of writer and pataphysics founder Alfred Jarry. He admired the young writer's anti-social attitude and disdain for established artistic tradition. Later Breton wrote, "In literature, I was successively taken with Rimbaud, with Jarry, with Apollinaire, with Nouveau, with Lautréamont, but it is Jacques Vaché to whom I owe the most."

Back in Paris, Breton joined in Dada activities and started the literary journal Littérature along with Louis Aragon and Philippe Soupault. They began experimenting with automatic writing—spontaneously writing without censoring their thoughts—and published the writings, as well as accounts of dreams, in the magazine. Breton and Soupault continued writing evolving their techniques of automatism and published The Magnetic Fields (1920).

By October 1924 two rival Surrealist groups had formed to publish a Surrealist Manifesto. Each claimed to be successors of a revolution launched by Appolinaire. One group, led by Yvan Goll consisted of Pierre Albert-Birot, Paul Dermée, Céline Arnauld, Francis Picabia, Tristan Tzara, Giuseppe Ungaretti, Pierre Reverdy, Marcel Arland, Joseph Delteil, Jean Painlevé and Robert Delaunay, among others. The group led by André Breton claimed that automatism was a better tactic for societal change than those of Dada, as led by Tzara, who was now among their rivals. Breton's group grew to include writers and artists from various media such as Paul Éluard, Benjamin Péret, René Crevel, Robert Desnos, Jacques Baron, Max Morise, Pierre Naville, Roger Vitrac, Gala Éluard, Max Ernst, Salvador Dalí, Luis Buñuel, Man Ray, Hans Arp, Georges Malkine, Michel Leiris, Georges Limbour, Antonin Artaud, Raymond Queneau, André Masson, Joan Miró, Marcel Duchamp, Jacques Prévert, and Yves Tanguy.

Cover of the first issue of La Révolution surréaliste, December 1924.

As they developed their philosophy, they believed that Surrealism would advocate the idea that ordinary and depictive expressions are vital and important, but that the sense of their arrangement must be open to the full range of imagination according to the Hegelian Dialectic. They also looked to the Marxist dialectic and the work of such theorists as Walter Benjamin and Herbert Marcuse.

Freud's work with free association, dream analysis, and the unconscious was of utmost importance to the Surrealists in developing methods to liberate imagination. They embraced idiosyncrasy, while rejecting the idea of an underlying madness. As Dalí later proclaimed, "There is only one difference between a madman and me. I am not mad."

Beside the use of dream analysis, they emphasized that "one could combine inside the same frame, elements not normally found together to produce illogical and startling effects." Breton included the idea of the startling juxtapositions in his 1924 manifesto, taking it in turn from a 1918 essay by poet Pierre Reverdy, which said: "a juxtaposition of two more or less distant realities. The more the relationship between the two juxtaposed realities is distant and true, the stronger the image will be−the greater its emotional power and poetic reality."

The group aimed to revolutionize human experience, in its personal, cultural, social, and political aspects. They wanted to free people from false rationality, and restrictive customs and structures. Breton proclaimed that the true aim of Surrealism was "long live the social revolution, and it alone!" To this goal, at various times Surrealists aligned with communism and anarchism.

In 1924 two Surrealist factions declared their philosophy in two separate Surrealist Manifestos. That same year the Bureau of Surrealist Research was established, and began publishing the journal La Révolution surréaliste.

Surrealist Manifestos

Yvan Goll, Surréalisme, Manifeste du surréalisme, Volume 1, Number 1, October 1, 1924, cover by Robert Delaunay
 

Leading up to 1924, two rival surrealist groups had formed. Each group claimed to be successors of a revolution launched by Apollinaire. One group, led by Yvan Goll, consisted of Pierre Albert-Birot, Paul Dermée, Céline Arnauld, Francis Picabia, Tristan Tzara, Giuseppe Ungaretti, Pierre Reverdy, Marcel Arland, Joseph Delteil, Jean Painlevé and Robert Delaunay, among others.

The other group, led by Breton, included Aragon, Desnos, Éluard, Baron, Crevel, Malkine, Jacques-André Boiffard and Jean Carrive, among others.

Yvan Goll published the Manifeste du surréalisme, 1 October 1924, in his first and only issue of Surréalisme two weeks prior to the release of Breton's Manifeste du surréalisme, published by Éditions du Sagittaire, 15 October 1924.

Goll and Breton clashed openly, at one point literally fighting, at the Comédie des Champs-Élysées, over the rights to the term Surrealism. In the end, Breton won the battle through tactical and numerical superiority. Though the quarrel over the anteriority of Surrealism concluded with the victory of Breton, the history of surrealism from that moment would remain marked by fractures, resignations, and resounding excommunications, with each surrealist having their own view of the issue and goals, and accepting more or less the definitions laid out by André Breton.

Breton's 1924 Surrealist Manifesto defines the purposes of Surrealism. He included citations of the influences on Surrealism, examples of Surrealist works, and discussion of Surrealist automatism. He provided the following definitions:

Dictionary: Surrealism, n. Pure psychic automatism, by which one proposes to express, either verbally, in writing, or by any other manner, the real functioning of thought. Dictation of thought in the absence of all control exercised by reason, outside of all aesthetic and moral preoccupation.

Encyclopedia: Surrealism. Philosophy. Surrealism is based on the belief in the superior reality of certain forms of previously neglected associations, in the omnipotence of dream, in the disinterested play of thought. It tends to ruin once and for all other psychic mechanisms and to substitute itself for them in solving all the principal problems of life.

Expansion

Giacometti's Woman with Her Throat Cut, 1932 (cast 1949), Museum of Modern Art, New York City

The movement in the mid-1920s was characterized by meetings in cafes where the Surrealists played collaborative drawing games, discussed the theories of Surrealism, and developed a variety of techniques such as automatic drawing. Breton initially doubted that visual arts could even be useful in the Surrealist movement since they appeared to be less malleable and open to chance and automatism. This caution was overcome by the discovery of such techniques as frottage, grattage and decalcomania.

Soon more visual artists became involved, including Giorgio de Chirico, Max Ernst, Joan Miró, Francis Picabia, Yves Tanguy, Salvador Dalí, Luis Buñuel, Alberto Giacometti, Valentine Hugo, Méret Oppenheim, Toyen, Kansuke Yamamoto and later after the second war: Enrico Donati. Though Breton admired Pablo Picasso and Marcel Duchamp and courted them to join the movement, they remained peripheral. More writers also joined, including former Dadaist Tristan Tzara, René Char, and Georges Sadoul.

André Masson. Automatic Drawing. 1924. Ink on paper, 23.5 × 20.6 cm. Museum of Modern Art, New York.

In 1925 an autonomous Surrealist group formed in Brussels. The group included the musician, poet, and artist E. L. T. Mesens, painter and writer René Magritte, Paul Nougé, Marcel Lecomte, and André Souris. In 1927 they were joined by the writer Louis Scutenaire. They corresponded regularly with the Paris group, and in 1927 both Goemans and Magritte moved to Paris and frequented Breton's circle. The artists, with their roots in Dada and Cubism, the abstraction of Wassily Kandinsky, Expressionism, and Post-Impressionism, also reached to older "bloodlines" or proto-surrealists such as Hieronymus Bosch, and the so-called primitive and naive arts.

André Masson's automatic drawings of 1923 are often used as the point of the acceptance of visual arts and the break from Dada, since they reflect the influence of the idea of the unconscious mind. Another example is Giacometti's 1925 Torso, which marked his movement to simplified forms and inspiration from preclassical sculpture.

However, a striking example of the line used to divide Dada and Surrealism among art experts is the pairing of 1925's Little Machine Constructed by Minimax Dadamax in Person (Von minimax dadamax selbst konstruiertes maschinchen) with The Kiss (Le Baiser) from 1927 by Max Ernst. The first is generally held to have a distance, and erotic subtext, whereas the second presents an erotic act openly and directly. In the second the influence of Miró and the drawing style of Picasso is visible with the use of fluid curving and intersecting lines and colour, whereas the first takes a directness that would later be influential in movements such as Pop art.

Giorgio de Chirico, The Red Tower (La Tour Rouge), 1913, Guggenheim Museum

Giorgio de Chirico, and his previous development of metaphysical art, was one of the important joining figures between the philosophical and visual aspects of Surrealism. Between 1911 and 1917, he adopted an unornamented depictional style whose surface would be adopted by others later. The Red Tower (La tour rouge) from 1913 shows the stark colour contrasts and illustrative style later adopted by Surrealist painters. His 1914 The Nostalgia of the Poet (La Nostalgie du poète) has the figure turned away from the viewer, and the juxtaposition of a bust with glasses and a fish as a relief defies conventional explanation. He was also a writer whose novel Hebdomeros presents a series of dreamscapes with an unusual use of punctuation, syntax, and grammar designed to create an atmosphere and frame its images. His images, including set designs for the Ballets Russes, would create a decorative form of Surrealism, and he would be an influence on the two artists who would be even more closely associated with Surrealism in the public mind: Dalí and Magritte. He would, however, leave the Surrealist group in 1928.

In 1924, Miró and Masson applied Surrealism to painting. The first Surrealist exhibition, La Peinture Surrealiste, was held at Galerie Pierre in Paris in 1925. It displayed works by Masson, Man Ray, Paul Klee, Miró, and others. The show confirmed that Surrealism had a component in the visual arts (though it had been initially debated whether this was possible), and techniques from Dada, such as photomontage, were used. The following year, on March 26, 1926 Galerie Surréaliste opened with an exhibition by Man Ray. Breton published Surrealism and Painting in 1928 which summarized the movement to that point, though he continued to update the work until the 1960s.

Surrealist literature

The first Surrealist work, according to leader Brêton, was Les Chants de Maldoror; and the first work written and published by his group of Surréalistes was Les Champs Magnétiques (May–June 1919). Littérature contained automatist works and accounts of dreams. The magazine and the portfolio both showed their disdain for literal meanings given to objects and focused rather on the undertones, the poetic undercurrents present. Not only did they give emphasis to the poetic undercurrents, but also to the connotations and the overtones which "exist in ambiguous relationships to the visual images."

Because Surrealist writers seldom, if ever, appear to organize their thoughts and the images they present, some people find much of their work difficult to parse. This notion however is a superficial comprehension, prompted no doubt by Breton's initial emphasis on automatic writing as the main route toward a higher reality. But—as in Breton's case—much of what is presented as purely automatic is actually edited and very "thought out". Breton himself later admitted that automatic writing's centrality had been overstated, and other elements were introduced, especially as the growing involvement of visual artists in the movement forced the issue, since automatic painting required a rather more strenuous set of approaches. Thus such elements as collage were introduced, arising partly from an ideal of startling juxtapositions as revealed in Pierre Reverdy's poetry. And—as in Magritte's case (where there is no obvious recourse to either automatic techniques or collage)—the very notion of convulsive joining became a tool for revelation in and of itself. Surrealism was meant to be always in flux—to be more modern than modern—and so it was natural there should be a rapid shuffling of the philosophy as new challenges arose. Artists such as Max Ernst and his surrealist collages demonstrate this shift to a more modern art form that also comments on society.

Surrealists revived interest in Isidore Ducasse, known by his pseudonym Comte de Lautréamont, and for the line "beautiful as the chance meeting on a dissecting table of a sewing machine and an umbrella", and Arthur Rimbaud, two late 19th-century writers believed to be the precursors of Surrealism.

Examples of Surrealist literature are Artaud's Le Pèse-Nerfs (1926), Aragon's Irene's Cunt (1927), Péret's Death to the Pigs (1929), Crevel's Mr. Knife Miss Fork (1931), Sadegh Hedayat's the Blind Owl (1937), and Breton's Sur la route de San Romano (1948).

La Révolution surréaliste continued publication into 1929 with most pages densely packed with columns of text, but which also included reproductions of art, among them works by de Chirico, Ernst, Masson, and Man Ray. Other works included books, poems, pamphlets, automatic texts and theoretical tracts.

Surrealist films

Early films by Surrealists include:

Surrealist photography

Famous Surrealist photographers are the American Man Ray, the French/Hungarian Brassaï, French Claude Cahun and the Dutch Emiel van Moerkerken.

Surrealist theatre

The word surrealist was first used by Apollinaire to describe his 1917 play Les Mamelles de Tirésias ("The Breasts of Tiresias"), which was later adapted into an opera by Francis Poulenc.

Roger Vitrac's The Mysteries of Love (1927) and Victor, or The Children Take Over (1928) are often considered the best examples of Surrealist theatre, despite his expulsion from the movement in 1926. The plays were staged at the Theatre Alfred Jarry, the theatre Vitrac co-founded with Antonin Artaud, another early Surrealist who was expelled from the movement.

Following his collaboration with Vitrac, Artaud would extend Surrealist thought through his theory of the Theatre of Cruelty. Artaud rejected the majority of Western theatre as a perversion of its original intent, which he felt should be a mystical, metaphysical experience. Instead, he envisioned a theatre that would be immediate and direct, linking the unconscious minds of performers and spectators in a sort of ritual event, Artaud created in which emotions, feelings, and the metaphysical were expressed not through language but physically, creating a mythological, archetypal, allegorical vision, closely related to the world of dreams.

The Spanish playwright and director Federico García Lorca, also experimented with surrealism, particularly in his plays The Public (1930), When Five Years Pass (1931), and Play Without a Title (1935). Other surrealist plays include Aragon's Backs to the Wall (1925). Gertrude Stein's opera Doctor Faustus Lights the Lights (1938) has also been described as "American Surrealism", though it is also related to a theatrical form of cubism.

Surrealist music

In the 1920s several composers were influenced by Surrealism, or by individuals in the Surrealist movement. Among them were Bohuslav Martinů, André Souris, Erik Satie, Francis Poulenc, and Edgard Varèse, who stated that his work Arcana was drawn from a dream sequence. Souris in particular was associated with the movement: he had a long relationship with Magritte, and worked on Paul Nougé's publication Adieu Marie. Music by composers from across the twentieth century have been associated with surrealist principles, including Thomas Adès, Pierre Boulez, György Ligeti, Mauricio Kagel, and Olivier Messiaen.

Germaine Tailleferre of the French group Les Six wrote several works which could be considered to be inspired by Surrealism, including the 1948 ballet Paris-Magie (scenario by Lise Deharme), the operas La Petite Sirène (book by Philippe Soupault) and Le Maître (book by Eugène Ionesco). Tailleferre also wrote popular songs to texts by Claude Marci, the wife of Henri Jeanson, whose portrait had been painted by Magritte in the 1930s.

Even though Breton by 1946 responded rather negatively to the subject of music with his essay Silence is Golden, later Surrealists, such as Paul Garon, have been interested in—and found parallels to—Surrealism in the improvisation of jazz and the blues. Jazz and blues musicians have occasionally reciprocated this interest. For example, the 1976 World Surrealist Exhibition included performances by David "Honeyboy" Edwards.

Surrealism and international politics

Surrealism as a political force developed unevenly around the world: in some places more emphasis was on artistic practices, in other places on political practices, and in other places still, Surrealist praxis looked to supersede both the arts and politics. During the 1930s, the Surrealist idea spread from Europe to North America, South America (founding of the Mandrágora group in Chile in 1938), Central America, the Caribbean, and throughout Asia, as both an artistic idea and as an ideology of political change.

Politically, Surrealism was Trotskyist, communist, or anarchist. The split from Dada has been characterised as a split between anarchists and communists, with the Surrealists as communist. Breton and his comrades supported Leon Trotsky and his International Left Opposition for a while, though there was an openness to anarchism that manifested more fully after World War II. Some Surrealists, such as Benjamin Péret, Mary Low, and Juan Breá, aligned with forms of left communism. When the Dutch surrealist photographer Emiel van Moerkerken came to Breton, he did not want to sign the manifesto because he was not a Trotskyist. For Breton being a communist was not enough. Breton denied Van Moerkerken's pictures for a publication afterwards. This caused a split in surrealism. Others fought for complete liberty from political ideologies, like Wolfgang Paalen, who, after Trotsky's assassination in Mexico, prepared a schism between art and politics through his counter-surrealist art-magazine DYN and so prepared the ground for the abstract expressionists. Dalí supported capitalism and the fascist dictatorship of Francisco Franco but cannot be said to represent a trend in Surrealism in this respect; in fact he was considered, by Breton and his associates, to have betrayed and left Surrealism. Benjamin Péret, Mary Low, Juan Breá, and Spanish-native Eugenio Fernández Granell joined the POUM during the Spanish Civil War.

Breton's followers, along with the Communist Party, were working for the "liberation of man". However, Breton's group refused to prioritize the proletarian struggle over radical creation such that their struggles with the Party made the late 1920s a turbulent time for both. Many individuals closely associated with Breton, notably Aragon, left his group to work more closely with the Communists.

Surrealists have often sought to link their efforts with political ideals and activities. In the Declaration of January 27, 1925, for example, members of the Paris-based Bureau of Surrealist Research (including Breton, Aragon and Artaud, as well as some two dozen others) declared their affinity for revolutionary politics. While this was initially a somewhat vague formulation, by the 1930s many Surrealists had strongly identified themselves with communism. The foremost document of this tendency within Surrealism is the Manifesto for a Free Revolutionary Art, published under the names of Breton and Diego Rivera, but actually co-authored by Breton and Leon Trotsky.

However, in 1933 the Surrealists’ assertion that a "proletarian literature" within a capitalist society was impossible led to their break with the Association des Ecrivains et Artistes Révolutionnaires, and the expulsion of Breton, Éluard and Crevel from the Communist Party.

In 1925, the Paris Surrealist group and the extreme left of the French Communist Party came together to support Abd-el-Krim, leader of the Rif uprising against French colonialism in Morocco. In an open letter to writer and French ambassador to Japan, Paul Claudel, the Paris group announced:

We Surrealists pronounced ourselves in favour of changing the imperialist war, in its chronic and colonial form, into a civil war. Thus we placed our energies at the disposal of the revolution, of the proletariat and its struggles, and defined our attitude towards the colonial problem, and hence towards the colour question.

The anticolonial revolutionary and proletarian politics of "Murderous Humanitarianism" (1932) which was drafted mainly by Crevel, signed by Breton, Éluard, Péret, Tanguy, and the Martiniquan Surrealists Pierre Yoyotte and J.M. Monnerot perhaps makes it the original document of what is later called "black Surrealism", although it is the contact between Aimé Césaire and Breton in the 1940s in Martinique that really lead to the communication of what is known as "black Surrealism".

Anticolonial revolutionary writers in the Négritude movement of Martinique, a French colony at the time, took up Surrealism as a revolutionary method – a critique of European culture and a radical subjective. This linked with other Surrealists and was very important for the subsequent development of Surrealism as a revolutionary praxis. The journal Tropiques, featuring the work of Césaire along with Suzanne Césaire, René Ménil, Lucie Thésée, Aristide Maugée and others, was first published in 1941.

In 1938 André Breton traveled with his wife, the painter Jacqueline Lamba, to Mexico to meet Trotsky (staying as the guest of Diego Rivera's former wife Guadalupe Marin), and there he met Frida Kahlo and saw her paintings for the first time. Breton declared Kahlo to be an "innate" Surrealist painter.

Internal politics

In 1929 the satellite group associated with the journal Le Grand Jeu, including Roger Gilbert-Lecomte, Maurice Henry and the Czech painter Josef Sima, was ostracized. Also in February, Breton asked Surrealists to assess their "degree of moral competence", and theoretical refinements included in the second manifeste du surréalisme excluded anyone reluctant to commit to collective action, a list which included Leiris, Limbour, Morise, Baron, Queneau, Prévert, Desnos, Masson and Boiffard. Excluded members launched a counterattack, sharply criticizing Breton in the pamphlet Un Cadavre, which featured a picture of Breton wearing a crown of thorns. The pamphlet drew upon an earlier act of subversion by likening Breton to Anatole France, whose unquestioned value Breton had challenged in 1924.

The disunion of 1929–30 and the effects of Un Cadavre had very little negative impact upon Surrealism as Breton saw it, since core figures such as Aragon, Crevel, Dalí and Buñuel remained true to the idea of group action, at least for the time being. The success (or the controversy) of Dalí and Buñuel's film L'Age d'Or in December 1930 had a regenerative effect, drawing a number of new recruits, and encouraging countless new artistic works the following year and throughout the 1930s.

Disgruntled surrealists moved to the periodical Documents, edited by Georges Bataille, whose anti-idealist materialism formed a hybrid Surrealism intending to expose the base instincts of humans. To the dismay of many, Documents fizzled out in 1931, just as Surrealism seemed to be gathering more steam.

There were a number of reconciliations after this period of disunion, such as between Breton and Bataille, while Aragon left the group after committing himself to the French Communist Party in 1932. More members were ousted over the years for a variety of infractions, both political and personal, while others left in pursuit of their own style.

By the end of World War II the surrealist group led by André Breton decided to explicitly embrace anarchism. In 1952 Breton wrote "It was in the black mirror of anarchism that surrealism first recognised itself." Breton was consistent in his support for the francophone Anarchist Federation and he continued to offer his solidarity after the Platformists supporting Fontenis transformed the FA into the Fédération Communiste Libertaire. He was one of the few intellectuals who continued to offer his support to the FCL during the Algerian war when the FCL suffered severe repression and was forced underground. He sheltered Fontenis whilst he was in hiding. He refused to take sides on the splits in the French anarchist movement and both he and Peret expressed solidarity as well with the new Fédération anarchiste set up by the synthesist anarchists and worked in the Antifascist Committees of the 60s alongside the FA.

Golden age

Throughout the 1930s, Surrealism continued to become more visible to the public at large. A Surrealist group developed in London and, according to Breton, their 1936 London International Surrealist Exhibition was a high-water mark of the period and became the model for international exhibitions. Another English Surrealist group developed in Birmingham, meanwhile, and was distinguished by its opposition to the London surrealists and preferences for surrealism's French heartland. The two groups would reconcile later in the decade.

Dalí and Magritte created the most widely recognized images of the movement. Dalí joined the group in 1929, and participated in the rapid establishment of the visual style between 1930 and 1935.

Surrealism as a visual movement had found a method: to expose psychological truth; stripping ordinary objects of their normal significance, to create a compelling image that was beyond ordinary formal organization, in order to evoke empathy from the viewer.

1931 was a year when several Surrealist painters produced works which marked turning points in their stylistic evolution: Magritte's Voice of Space (La Voix des airs) is an example of this process, where three large spheres representing bells hang above a landscape. Another Surrealist landscape from this same year is Yves Tanguy's Promontory Palace (Palais promontoire), with its molten forms and liquid shapes. Liquid shapes became the trademark of Dalí, particularly in his The Persistence of Memory, which features the image of watches that sag as if they were melting.

The characteristics of this style—a combination of the depictive, the abstract, and the psychological—came to stand for the alienation which many people felt in the modern period, combined with the sense of reaching more deeply into the psyche, to be "made whole with one's individuality".

Between 1930 and 1933, the Surrealist Group in Paris issued the periodical Le Surréalisme au service de la révolution as the successor of La Révolution surréaliste.

From 1936 through 1938 Wolfgang Paalen, Gordon Onslow Ford, and Roberto Matta joined the group. Paalen contributed Fumage and Onslow Ford Coulage as new pictorial automatic techniques.

Long after personal, political and professional tensions fragmented the Surrealist group, Magritte and Dalí continued to define a visual program in the arts. This program reached beyond painting, to encompass photography as well, as can be seen from a Man Ray self-portrait, whose use of assemblage influenced Robert Rauschenberg's collage boxes.

Max Ernst, L'Ange du Foyer ou le Triomphe du Surréalisme (1937), private collection

During the 1930s Peggy Guggenheim, an important American art collector, married Max Ernst and began promoting work by other Surrealists such as Yves Tanguy and the British artist John Tunnard.

Major exhibitions in the 1930s

  • 1936 – London International Surrealist Exhibition is organised in London by the art historian Herbert Read, with an introduction by André Breton.
  • 1936 – Museum of Modern Art in New York shows the exhibition Fantastic Art, Dada and Surrealism.
  • 1938 – A new Exposition Internationale du Surréalisme was held at the Beaux-arts Gallery, Paris, with more than 60 artists from different countries, and showed around 300 paintings, objects, collages, photographs and installations. The Surrealists wanted to create an exhibition which in itself would be a creative act and called on Marcel Duchamp, Wolfgang Paalen, Man Ray and others to do so. At the exhibition's entrance Salvador Dalí placed his Rainy Taxi (an old taxi rigged to produce a steady drizzle of water down the inside of the windows, and a shark-headed creature in the driver's seat and a blond mannequin crawling with live snails in the back) greeted the patrons who were in full evening dress. Surrealist Street filled one side of the lobby with mannequins dressed by various Surrealists. Paalen and Duchamp designed the main hall to seem like cave with 1,200 coal bags suspended from the ceiling over a coal brazier with a single light bulb which provided the only lighting, as well as the floor covered with humid leaves and mud. The patrons were given flashlights with which to view the art. On the floor Wolfgang Paalen created a small lake with grasses and the aroma of roasting coffee filled the air. Much to the Surrealists' satisfaction the exhibition scandalized the viewers.

World War II and the Post War period

Yves Tanguy Indefinite Divisibility, 1942, Albright Knox Art Gallery, Buffalo, New York

World War II created havoc not only for the general population of Europe but especially for the European artists and writers that opposed Fascism and Nazism. Many important artists fled to North America and relative safety in the United States. The art community in New York City in particular was already grappling with Surrealist ideas and several artists like Arshile Gorky, Jackson Pollock, and Robert Motherwell converged closely with the surrealist artists themselves, albeit with some suspicion and reservations. Ideas concerning the unconscious and dream imagery were quickly embraced. By the Second World War, the taste of the American avant-garde in New York swung decisively towards Abstract Expressionism with the support of key taste makers, including Peggy Guggenheim, Leo Steinberg and Clement Greenberg. However, it should not be easily forgotten that Abstract Expressionism itself grew directly out of the meeting of American (particularly New York) artists with European Surrealists self-exiled during World War II. In particular, Gorky and Paalen influenced the development of this American art form, which, as Surrealism did, celebrated the instantaneous human act as the well-spring of creativity. The early work of many Abstract Expressionists reveals a tight bond between the more superficial aspects of both movements, and the emergence (at a later date) of aspects of Dadaistic humor in such artists as Rauschenberg sheds an even starker light upon the connection. Up until the emergence of Pop Art, Surrealism can be seen to have been the single most important influence on the sudden growth in American arts, and even in Pop, some of the humor manifested in Surrealism can be found, often turned to a cultural criticism.

The Second World War overshadowed, for a time, almost all intellectual and artistic production. In 1939 Wolfgang Paalen was the first to leave Paris for the New World as exile. After a long trip through the forests of British Columbia, he settled in Mexico and founded his influential art-magazine Dyn. In 1940 Yves Tanguy married American Surrealist painter Kay Sage. In 1941, Breton went to the United States, where he co-founded the short-lived magazine VVV with Max Ernst, Marcel Duchamp, and the American artist David Hare. However, it was the American poet, Charles Henri Ford, and his magazine View which offered Breton a channel for promoting Surrealism in the United States. The View special issue on Duchamp was crucial for the public understanding of Surrealism in America. It stressed his connections to Surrealist methods, offered interpretations of his work by Breton, as well as Breton's view that Duchamp represented the bridge between early modern movements, such as Futurism and Cubism, to Surrealism. Wolfgang Paalen left the group in 1942 due to political/philosophical differences with Breton.

Though the war proved disruptive for Surrealism, the works continued. Many Surrealist artists continued to explore their vocabularies, including Magritte. Many members of the Surrealist movement continued to correspond and meet. While Dalí may have been excommunicated by Breton, he neither abandoned his themes from the 1930s, including references to the "persistence of time" in a later painting, nor did he become a depictive pompier. His classic period did not represent so sharp a break with the past as some descriptions of his work might portray, and some, such as André Thirion, argued that there were works of his after this period that continued to have some relevance for the movement.

During the 1940s Surrealism's influence was also felt in England, America and the Netherlands where Gertrude Pape and her husband Theo van Baaren helped to popularize it in their publication The Clean Handkerchief. Mark Rothko took an interest in biomorphic figures, and in England Henry Moore, Lucian Freud, Francis Bacon and Paul Nash used or experimented with Surrealist techniques. However, Conroy Maddox, one of the first British Surrealists whose work in this genre dated from 1935, remained within the movement, and organized an exhibition of current Surrealist work in 1978 in response to an earlier show which infuriated him because it did not properly represent Surrealism. Maddox's exhibition, titled Surrealism Unlimited, was held in Paris and attracted international attention. He held his last one-man show in 2002, and died three years later. Magritte's work became more realistic in its depiction of actual objects, while maintaining the element of juxtaposition, such as in 1951's Personal Values (Les Valeurs Personnelles) and 1954's Empire of Light (L’Empire des lumières). Magritte continued to produce works which have entered artistic vocabulary, such as Castle in the Pyrenees (Le Château des Pyrénées), which refers back to Voix from 1931, in its suspension over a landscape.

Other figures from the Surrealist movement were expelled. Several of these artists, like Roberto Matta (by his own description) "remained close to Surrealism".

After the crushing of the Hungarian Revolution of 1956, Endre Rozsda returned to Paris to continue creating his own word that had been transcended the surrealism. The preface to his first exhibition in the Furstenberg Gallery (1957) was written by Breton yet.

Many new artists explicitly took up the Surrealist banner. Dorothea Tanning and Louise Bourgeois continued to work, for example, with Tanning's Rainy Day Canape from 1970. Duchamp continued to produce sculpture in secret including an installation with the realistic depiction of a woman viewable only through a peephole.

Breton continued to write and espouse the importance of liberating the human mind, as with the publication The Tower of Light in 1952. Breton's return to France after the War, began a new phase of Surrealist activity in Paris, and his critiques of rationalism and dualism found a new audience. Breton insisted that Surrealism was an ongoing revolt against the reduction of humanity to market relationships, religious gestures and misery and to espouse the importance of liberating the human mind.

Major exhibitions of the 1940s, '50s and '60s

  • 1942 – First Papers of Surrealism – New York – The Surrealists again called on Duchamp to design an exhibition. This time he wove a 3-dimensional web of string throughout the rooms of the space, in some cases making it almost impossible to see the works. He made a secret arrangement with an associate's son to bring his friends to the opening of the show, so that when the finely dressed patrons arrived they found a dozen children in athletic clothes kicking and passing balls, and skipping rope. His design for the show's catalog included "found", rather than posed, photographs of the artists.
  • 1947 – International Surrealist Exhibition – Galerie Maeght, Paris
  • 1959 – International Surrealist Exhibition – Paris
  • 1960 – Surrealist Intrusion in the Enchanters' Domain – New York

Post-Breton Surrealism

In the 1960s, the artists and writers associated with the Situationist International were closely associated with Surrealism. While Guy Debord was critical of and distanced himself from Surrealism, others, such as Asger Jorn, were explicitly using Surrealist techniques and methods. The events of May 1968 in France included a number of Surrealist ideas, and among the slogans the students spray-painted on the walls of the Sorbonne were familiar Surrealist ones. Joan Miró would commemorate this in a painting titled May 1968. There were also groups who associated with both currents and were more attached to Surrealism, such as the Revolutionary Surrealist Group.

During the 1980s, behind the Iron Curtain, Surrealism again entered into politics with an underground artistic opposition movement known as the Orange Alternative. The Orange Alternative was created in 1981 by Waldemar Fydrych (alias 'Major'), a graduate of history and art history at the University of Wrocław. They used Surrealist symbolism and terminology in their large scale happenings organized in the major Polish cities during the Jaruzelski regime, and painted Surrealist graffiti on spots covering up anti-regime slogans. Major himself was the author of a "Manifesto of Socialist Surrealism". In this manifesto, he stated that the socialist (communist) system had become so Surrealistic that it could be seen as an expression of art itself.

Surrealistic art also remains popular with museum patrons. The Guggenheim Museum in New York City held an exhibit, Two Private Eyes, in 1999, and in 2001 Tate Modern held an exhibition of Surrealist art that attracted over 170,000 visitors. In 2002 the Met in New York City held a show, Desire Unbound, and the Centre Georges Pompidou in Paris a show called La Révolution surréaliste.

Surrealists groups and literary publications have continued to be active up to the present day, with groups such as the Chicago Surrealist Group, the Leeds Surrealist Group, and the Surrealist Group of Stockholm. Jan Švankmajer of the Czech-Slovak Surrealists continues to make films and experiment with objects.

Impact and influences

While Surrealism is typically associated with the arts, it has impacted many other fields. In this sense, Surrealism does not specifically refer only to self-identified "Surrealists", or those sanctioned by Breton, rather, it refers to a range of creative acts of revolt and efforts to liberate imagination. In addition to Surrealist theory being grounded in the ideas of Hegel, Marx and Freud, to its advocates its inherent dynamic is dialectical thought. Surrealist artists have also cited the alchemists, Dante, Hieronymus Bosch, the Marquis de Sade, Charles Fourier, Comte de Lautréamont and Arthur Rimbaud as influences.

May 68

Surrealists believe that non-Western cultures also provide a continued source of inspiration for Surrealist activity because some may induce a better balance between instrumental reason and imagination in flight than Western culture. Surrealism has had an identifiable impact on radical and revolutionary politics, both directly — as in some Surrealists joining or allying themselves with radical political groups, movements and parties — and indirectly — through the way in which Surrealists emphasize the intimate link between freeing imagination and the mind, and liberation from repressive and archaic social structures. This was especially visible in the New Left of the 1960s and 1970s and the French revolt of May 1968, whose slogan "All power to the imagination" quoted by The Situationists and Enragés from the originally Marxist “Rêvé-lutionary“ theory and praxis of Breton's French Surrealist group.

Postmodernism and popular culture

Many significant literary movements in the later half of the 20th century were directly or indirectly influenced by Surrealism. This period is known as the Postmodern era; though there is no widely agreed upon central definition of Postmodernism, many themes and techniques commonly identified as Postmodern are nearly identical to Surrealism.

First Papers of Surrealism presented the fathers of surrealism in an exhibition that represented the leading monumental step of the avant-gardes towards installation art. Many writers from and associated with the Beat Generation were influenced greatly by Surrealists. Philip Lamantia and Ted Joans are often categorized as both Beat and Surrealist writers. Many other Beat writers show significant evidence of Surrealist influence. A few examples include Bob Kaufman, Gregory Corso, Allen Ginsberg, and Lawrence Ferlinghetti. Artaud in particular was very influential to many of the Beats, but especially Ginsberg and Carl Solomon. Ginsberg cites Artaud's "Van Gogh – The Man Suicided by Society" as a direct influence on "Howl", along with Apollinaire's "Zone", García Lorca's "Ode to Walt Whitman", and Schwitters' "Priimiititiii". The structure of Breton's "Free Union" had a significant influence on Ginsberg's "Kaddish". In Paris, Ginsberg and Corso met their heroes Tristan Tzara, Marcel Duchamp, Man Ray, and Benjamin Péret, and to show their admiration Ginsberg kissed Duchamp's feet and Corso cut off Duchamp's tie.

William S. Burroughs, a core member of the Beat Generation and a postmodern novelist, developed the cut-up technique with former surrealist Brion Gysin—in which chance is used to dictate the composition of a text from words cut out of other sources—referring to it as the "Surrealist Lark" and recognizing its debt to the techniques of Tristan Tzara.

Postmodern novelist Thomas Pynchon, who was also influenced by Beat fiction, experimented since the 1960s with the surrealist idea of startling juxtapositions; commenting on the "necessity of managing this procedure with some degree of care and skill", he added that "any old combination of details will not do. Spike Jones Jr., whose father's orchestral recordings had a deep and indelible effect on me as a child, said once in an interview, 'One of the things that people don't realize about Dad's kind of music is, when you replace a C-sharp with a gunshot, it has to be a C-sharp gunshot or it sounds awful.'"

Many other postmodern fiction writers have been directly influenced by Surrealism. Paul Auster, for example, has translated Surrealist poetry and said the Surrealists were "a real discovery" for him. Salman Rushdie, when called a Magical Realist, said he saw his work instead "allied to surrealism". David Lynch regarded as a surrealist filmmaker being quoted, "David Lynch has once again risen to the spotlight as a champion of surrealism," in regard to his show Twin Peaks. For the work of other postmodernists, such as Donald Barthelme and Robert Coover, a broad comparison to Surrealism is common.

Magic realism, a popular technique among novelists of the latter half of the 20th century especially among Latin American writers, has some obvious similarities to Surrealism with its juxtaposition of the normal and the dream-like, as in the work of Gabriel García Márquez. Carlos Fuentes was inspired by the revolutionary voice in Surrealist poetry and points to inspiration Breton and Artaud found in Fuentes' homeland, Mexico. Though Surrealism was a direct influence on Magic Realism in its early stages, many Magic Realist writers and critics, such as Amaryll Chanady and S. P. Ganguly, while acknowledging the similarities, cite the many differences obscured by the direct comparison of Magic Realism and Surrealism such as an interest in psychology and the artefacts of European culture they claim is not present in Magic Realism. A prominent example of a Magic Realist writer who points to Surrealism as an early influence is Alejo Carpentier who also later criticized Surrealism's delineation between real and unreal as not representing the true South American experience.

Stand-up comedian Steven Wright became popular for his surreal humor. Delivered in a drowsy, deadpan monotone, Wright conjured up situations that were totally unreal. "There was a switch on my wall that didn't do anything. I flicked it on and off and nothing happened. A week later I got a telegram from a woman in Germany, saying, 'Cut it out!'"

Surrealist groups

Surrealist individuals and groups have carried on with Surrealism after the death of André Breton in 1966. The original Paris Surrealist Group was disbanded by member Jean Schuster in 1969, but another Parisian surrealist group was later formed. The current Surrealist Group of Paris has recently published the first issue of their new journal, Alcheringa. The Group of Czech-Slovak Surrealists never disbanded, and continue to publish their journal Analogon, which now spans 80 volumes.

Surrealism and the theatre

Surrealist theatre and Artaud's "Theatre of Cruelty" were inspirational to many within the group of playwrights that the critic Martin Esslin called the "Theatre of the Absurd" (in his 1963 book of the same name). Though not an organized movement, Esslin grouped these playwrights together based on some similarities of theme and technique; Esslin argues that these similarities may be traced to an influence from the Surrealists. Eugène Ionesco in particular was fond of Surrealism, claiming at one point that Breton was one of the most important thinkers in history. Samuel Beckett was also fond of Surrealists, even translating much of the poetry into English. Other notable playwrights whom Esslin groups under the term, for example Arthur Adamov and Fernando Arrabal, were at some point members of the Surrealist group.

Alice Farley is an American-born artist who became active during the 1970s in San Francisco after training in dance at the California Institute of the Arts. Farley uses vivid and elaborate costuming that she describes as "the vehicles of transformation capable of making a character's thoughts visible". Often collaborating with musicians such as Henry Threadgill, Farley explores the role of improvisation in dance, bringing in an automatic aspect to the productions. Farley has performed in a number of surrealist collaborations including the World Surrealist Exhibition in Chicago in 1976.

Alleged precursors in older art

Various much older artists are sometimes claimed as precursors of Surrealism. Foremost among these are Hieronymus Bosch, and Giuseppe Arcimboldo, who Dalí called the "father of Surrealism." Apart from their followers, other artists who may be mentioned in this context include Joos de Momper, for some anthropomorphic landscapes. Many critics feel these works belong to fantastic art rather than having a significant connection with Surrealism.

Mojave Desert

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Mojave_Desert

Mojave Desert
Hayyikwiir Mat'aar (Mohave)
Mesquite Sand Dunes in Death Valley.jpg
Sand dunes in Death Valley
 
Mojave Desert map.svg
Location within North America
 
Ecology
RealmNearctic
BiomeDeserts and xeric shrublands
Borders

List
Bird species230
Mammal species98
Geography
Area81,000 km2 (31,000 sq mi)
CountryUnited States
StatesArizona, California, Nevada and Utah
Coordinates35°N 116°WCoordinates: 35°N 116°W
RiversColorado River, Mojave River
Conservation
Conservation statusRelatively Stable/Intact

The Mojave Desert (/mˈhɑːvi, mə-/ moh-HAH-vee, mə-; Mohave: Hayikwiir Mat'aar; Spanish: Desierto de Mojave) is a xeric desert in the rain shadow of the Sierra Nevada mountains in the Southwestern United States. It is named for the indigenous Mojave people. It is located primarily in southeastern California and southwestern Nevada, with small portions extending into Arizona and Utah.

The Mojave Desert, together with the Sonoran, Chihuahuan, and Great Basin deserts, forms a larger North American Desert. Of these, the Mojave is the smallest and driest. The Mojave Desert displays typical basin and range topography, generally having a pattern of a series of parallel mountain ranges and valleys. It is also the site of Death Valley, which is the lowest elevation in North America. The Mojave Desert is often colloquially called the "high desert", as most of it lies between 2,000 and 4,000 feet (610 and 1,220 m). It supports a diversity of flora and fauna.

The 20 million acres (81,000 km2) desert supports a number of human activities, including recreation, ranching, and military training. The Mojave Desert also contains various silver, tungsten, iron and gold deposits.

The spelling Mojave originates from the Spanish language, while the spelling Mohave comes from modern English. Both are used today, although the Mojave Tribal Nation officially uses the spelling Mojave. Mojave is a shortened form of Hamakhaave, an endonym in their native language, which means "beside the water".

Geography

The Joshua tree (Yucca brevifolia) is endemic and exclusive to the Mojave Desert.

The Mojave Desert is bordered to the west by the Sierra Nevada mountain range and the California montane chaparral and woodlands, and to the south and east by the Sonoran Desert. The boundaries to the east of the Mojave Desert are less distinctive than the other boundaries because there is no presence of an indicator species, such as the Joshua tree (Yucca brevifolia), which is endemic to the Mojave Desert. The Mojave Desert is distinguished from the Sonoran Desert and other deserts adjacent to it by its warm temperate climate, as well as flora and fauna such as ironwood (Olneya tesota), blue Palo Verde (Parkinsonia florida), chuparosa (Justicia californica), spiny menodora (Menodora spinescens), desert senna (Cassia armata), California dalea (Psorothamnus arborescens), and goldenhead (Acamptopappus shockleyi). Along with these other factors, these plants differentiate the Mojave from the nearby Sonoran desert.

The Mojave Desert is bordered by the San Andreas fault to the Southwest and the Garlock fault to the North. The mountains elevated along the length of the San Andreas fault provide a clear border between the Mojave desert and the coastal regions to the West. The Garlock fault separates the Mojave Desert from the Sierra Nevada and Tehachapi mountains, which provide a natural border to the Mojave Desert. There are also abundant alluvial fans, which are called bajadas, that form around the mountains within the Mojave desert and extend down toward the low altitude basins, which contain dried lake beds called playas, where water generally collects and evaporates, leaving large volumes of salt. These playas include Rogers Dry Lake, and China Lake. Dry lakes are a noted feature of the Mojave landscape. The Mojave Desert is also home to the Devils Playground, about 40 miles (64 km) of dunes and salt flats going in a northwest-southeasterly direction. The Devil's Playground is a part of the Mojave National Preserve and is between the town of Baker, California and Providence Mountains. The Cronese Mountains are within the Devil's Playground.

There are very few surface rivers in the Mojave Desert, even given the low precipitation level: two major rivers generally flow underground. The intermittent Mojave River, which begins on the San Bernardino mountains and disappears underground in the Mojave Desert. The Amargosa River also flows partly underground through the Mojave Desert along a southward path. The Manix, Mojave, and the Little Mojave lakes are all large but shallow. Soda Lake is the principal saline basin of the Mojave desert. Natural springs are typically rare throughout the Mojave desert, however, there are two notable springs, Ash Meadows, and Oasis Valley. Ash Meadows is formed from several other springs, which all draw from deep underground. Oasis Valley draws from the nearby Amargosa River.

Climate

Extremes in temperatures throughout the seasons characterize the climate of the Mojave Desert. Freezing temperatures as well as strong winds are not uncommon in the winter, as well as precipitation such as rain and snow in the mountains. In contrast, temperatures above 100 °F (38 °C) are not uncommon during the summer months. There is an annual average precipitation of 2 to 6 inches (51 to 152 mm), although regions at high altitudes such as the portion of the Mojave desert in the San Gabriel mountains. Most of the precipitation in the Mojave comes from the Pacific Cyclonic storms that are generally present passing Eastward in November to April. Such storms generally bring rain and snow only in the mountainous regions, as a result of the effect of the Sierra Nevada mountains, which creates a drying effect on its leeward slopes.

During the late summer months, there is also the possibility of strong thunderstorms, which bring heavy showers or cloudbursts. These storms can result in flash flooding.

The Mojave Desert has not historically supported a fire regime because of low fuel loads and connectivity. However, in the last few decades, invasive annual plants such as some within the genera Bromus, Schismus and Brassica have facilitated fires by serving as a fuel bed for fires. This has significantly altered many areas of the desert. At higher elevations, fire regimes are regular but infrequent.

Cities and regions

Las Vegas is in the Mojave Desert

While the Mojave Desert is generally sparsely populated, it has increasingly become urbanized in recent years. The metropolitan areas include Las Vegas, the largest urban area in the Mojave and the largest urban area in Nevada with a population of about 2.3 million. St. George, Utah, is the northeasternmost metropolitan area in the Mojave, with a population of around 180,000 in 2020, and is located at the convergence of the Mojave, Great Basin, and Colorado Plateau. The Los Angeles exurban area of Lancaster-Palmdale has more than 400,000 residents, and the Victorville area to its east has more than 300,000 residents. Smaller cities or micropolitan areas in the Mojave Desert include Helendale, Lake Havasu City, Kingman, Laughlin, Bullhead City and Pahrump. All have experienced rapid population growth since 1990. The California portion of the desert also contains Edwards Air Force Base and Naval Air Weapons Station China Lake, noted for experimental aviation and weapons projects.

The Mojave Desert has several ghost towns. The most significant are the silver and copper-mining town of Calico, California, and the old railroad depot of Kelso, California. Some of the other ghost towns are more modern, created when U.S. Route 66 (and the lesser-known U.S. Route 91) were abandoned in favor of the construction of Interstates.

Geology

Rock formations in Joshua Tree National Park

The rock that forms the Mojave Desert was likely created under shallow water in the Precambrian. Under this shallow coat of water, a large volume of sedimentary processes were likely taking place, causing in large deposits of limestones, silicates, and dolomites. During the Paleozoic era, the area that is now the Mojave was again likely submerged under a greater sea. During the Mesozoic era, major tectonic activities such as thrust faulting and folding resulted in distinctive shaping as well as intrusion. During the Cenozoic, more tectonic deformation occurred whilst the Mojave was partly submerged. Major volcanic activity is thought to have occurred during the Oligocene. Large downpours during the Miocene likely significantly eroded the rock in the Mojave and accelerated deposition.

The Mojave Desert is a source of various minerals and metallic materials. Due to the climate, there is an accumulation of weathered bedrock, fine sand and silt, both sand and silt sediments becoming converted into colluvium. The deposits of gold, tungsten, and silver have been mined frequently prior to the Second World War. Additionally, there have been deposits of copper, tin, lead-zinc, manganese, iron, and various radioactive substances but they have not been mined for commercial use.

Ecology

Flora

The flora of the Mojave desert consists of various endemic plant species, notably the Joshua Tree, which is a notable endemic and indicator species of the desert. There is more endemic flora in the Mojave desert than almost anywhere in the world. Mojave Desert flora is not a vegetation type, although the plants in the area have evolved in isolation because of the physical barriers of the Sierra Nevadas and the Colorado Plateau. Predominant plants of the Mojave desert include all-scale (Atriplex polycarpa), creosote bush (Larrea tridentata), brittlebush (Encelia farinosa), desert holly (Atriplex hymenelytra), white burrobush (Hymenoclea salsola), and most notably, the Joshua tree (Yucca brevifolia). Additionally, the Mojave desert is also home to various species of cacti, such as silver cholla (Cylindropuntia echinocarpa), Mojave prickly pear (O. erinacea), beavertail cactus (O. basilaris), and many-headed barrel cactus (Echinocactus polycephalus). Less common but distinctive plants of the Mojave desert include ironwood (Olneya tesota), blue Palo Verde (Parkinsonia Florida), chuparosa (Justicia californica), spiny menodora (Menodora spinescens), desert senna (Cassia armata), California dalea (Psorothamnus arborescens), and goldenhead (Acamptopappus shockleyi). The Mojave desert is generally abundant in winter annuals. The plants of the Mojave desert each generally correspond to an individual geographic feature. As such, there are distinctive flora communities within the desert.

Fauna

A desert tortoise, which can be found in the Mojave Desert

Notable species of the Mojave desert include bighorn sheep (Ovis canadensis), mountain lions (Puma concolor), black-tailed jackrabbits (Lepus californicus), and desert tortoises (Gopherus agassizii). Various other species are particularly common in the Mojave Desert, such as the LeConte's thrasher (Toxostoma lecontei), banded gecko (Coleonyx variegatus), desert iguana (Dipsosaurus dorsalis), chuckwalla (Sauromalus obesus), and regal horned lizard (Phrynosoma solare). Species of snake include the rosy boa (Lichanura trivirgata), Western patch-nosed snake (Salvadora hexalepis), and Mojave rattlesnake (Crotalus scutulatus). These species can also occur in the neighboring Sonoran and Great Basin deserts.

The animal species of the Mojave Desert have generally fewer endemics than its flora. However, endemic fauna of the Mojave Desert include Kelso Dunes jerusalem cricket (Ammopelmatus kelsoensis), the Kelso Dunes shieldback katydid (Eremopedes kelsoensis), the Mohave ground squirrel (Spermophilus Mohavensis) and Amargosa vole (Microtus californicus scirpensis). The Mojave fringe-toed lizard (Uma Scoparia) is not endemic, but almost completely limited to the Mojave desert. There are also aquatic species that are found nowhere else, such as the Devils Hole pupfish, limited to one hot spring near Death Valley.

In society

History

Before the European exploration of North America, tribes of Native Americans, such as the Mohave, were hunter-gatherers living in the Mojave Desert.

European explorers started exploring the deserts beginning in the 18th century. Francisco Garcés, a Franciscan friar, was the first explorer of the Mojave desert in 1776. Garcés recorded information about the original inhabitants of the deserts.

Later, as American interests expanded into California, American explorers started probing the California deserts. Jedediah Smith travelled through the Mojave deserts in 1826, finally reaching the San Gabriel Mission.

Human development

In recent years, human development in the Mojave desert has become increasingly present. Human development at the major urban and suburban centers of Las Vegas and Los Angeles has had an increasingly damaging effect on the wildlife of the Mojave Desert. An added demand for landfill space as a result of the large metropolitan centers of Las Vegas and Los Angeles also has the real potential to drastically affect flora and fauna of the Mojave Desert. Agricultural development along the Colorado river, close to the Eastern boundary of the Mojave Desert, also causes habitat loss and degradation. Areas that are particularly affected by human development include Ward Valley and Riverside county. The United States military also maintains installations in the Mojave Desert, making the Mojave a critical training location for the United States Department of Defense. The Mojave Desert has long been a valuable resource for people, and as its human population grows, its importance will only grow. Miners, ranchers, and farmers rely on the desert for a living. The desert is also helping California meet its renewable energy objectives: the desert is an excellent place to site wind and solar energy systems, although they can cause their own environmental impact.

Tourism

Panorama of Zabriskie point

The Mojave Desert is one of the most popular spots for tourism in North America, primarily because of the international destination of Las Vegas. The Mojave is also known for its scenery, playing host to Death Valley National Park, Joshua Tree National Park, and the Mojave National Preserve. Lakes Mead, Mohave, and Havasu provide water sports recreation, and vast off-road areas entice off-road enthusiasts. The Mojave Desert also includes three California State Parks, the Antelope Valley California Poppy Reserve, in Lancaster, Saddleback Butte State Park, in Hi Vista and Red Rock Canyon State Park. Mojave Narrows Park, operated by San Bernardino County, is a former ranch along the Mojave River.

Several attractions and natural features are in the Calico Mountains. Calico Ghost Town, in Yermo, is administered by San Bernardino County. The ghost town has several shops and attractions and inspired Walter Knott to build Knott's Berry Farm. The Bureau of Land Management also administers Rainbow Basin and Owl Canyon. The Calico Early Man Site, in the Calico Hills east of Yermo, is believed by some archaeologists, including the late Louis Leakey, to show the earliest evidence with lithic stone tools found here of human activity in North America.

Conservation status

A field of California poppies in the California Poppy Reserve in Antelope Valley

The Mojave Desert has a relatively stable and intact conservation status. The Mojave Desert is one of the best protected distinct ecoregions in the United States, as a result of the California Desert Protection Act, which established the Death Valley, Joshua Tree National Parks and the Mojave National Preserve. However, the southwest and central east portions of the Mojave Desert are particularly threatened as a result of off-road vehicles, human development, and agricultural grazing. The World Wildlife Fund lists the Mojave Desert as relatively "stable/intact".

Various habitats and regions of the Mojave Desert have been protected by statute. Notably, Joshua Tree National Park, Death Valley National Park, and the Mojave National Preserve by the California Desert Protection Act of 1994. (Pub.L. 103–433). Various other national parks and state parks have regions within the Mojave Desert. These include Antelope Valley California Poppy Reserve, which protects the fields of California poppies, Desert Tortoise Natural Area, Arthur B. Ripley Desert Woodland State Park, Desert National Wildlife Refuge, Lake Mead National Recreation Area, Providence Mountains State Recreation Area, Red Cliffs National Conservation Area, Red Rock Canyon State Park, Saddleback Butte State Park, Snow Canyon State Park and Valley of Fire State Park.

2009 litigation

In 2009, U.S. District Judge Susan Illston ruled against the Bureau's proposed designation of additional off-road vehicle use allowance in the western Mojave Desert. According to the ruling, the Bureau of Land Management violated its own regulations when it designated approximately 5,000 miles (8,000 km) of off-roading routes in 2006. According to Judge Illston, the Bureau's designation was significantly "flawed because it does not contain a reasonable range of alternatives" to limit damage to sensitive habitats. Judge Illston found the bureau had inadequately analyzed the routes' impacts on air quality, soils, plant communities, riparian habitats, and sensitive species such as the endangered Mojave fringe-toed lizard, pointing out that the desert and its resources are "extremely fragile, easily scarred, and slowly healed".

Atomic absorption spectroscopy

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Atomic_absorption_spectroscopy

Flame atomic absorption spectroscopy instrument
 
A scientist preparing solutions for atomic absorption spectroscopy, reflected in the glass window of the AAS's flame atomizer cover door

Atomic absorption spectroscopy (AAS) and atomic emission spectroscopy (AES) is a spectroanalytical procedure for the quantitative determination of chemical elements using the absorption of optical radiation (light) by free atoms in the gaseous state. Atomic absorption spectroscopy is based on absorption of light by free metallic ions.

In analytical chemistry the technique is used for determining the concentration of a particular element (the analyte) in a sample to be analyzed. AAS can be used to determine over 70 different elements in solution, or directly in solid samples via electrothermal vaporization, and is used in pharmacology, biophysics, archaeology and toxicology research.

Atomic emission spectroscopy was first used as an analytical technique, and the underlying principles were established in the second half of the 19th century by Robert Wilhelm Bunsen and Gustav Robert Kirchhoff, both professors at the University of Heidelberg, Germany.

The modern form of AAS was largely developed during the 1950s by a team of Australian chemists. They were led by Sir Alan Walsh at the Commonwealth Scientific and Industrial Research Organisation (CSIRO), Division of Chemical Physics, in Melbourne, Australia.

Atomic absorption spectrometry has many uses in different areas of chemistry such as clinical analysis of metals in biological fluids and tissues such as whole blood, plasma, urine, saliva, brain tissue, liver, hair, muscle tissue. Atomic absorption spectrometry can be used in qualitative and quantitative analysis.

Principles

The technique makes use of the atomic absorption spectrum of a sample in order to assess the concentration of specific analytes within it. It requires standards with known analyte content to establish the relation between the measured absorbance and the analyte concentration and relies therefore on the Beer–Lambert law.

Instrumentation

Atomic absorption spectrometer block diagram

In order to analyze a sample for its atomic constituents, it has to be atomized. The atomizers most commonly used nowadays are flames and electrothermal (graphite tube) atomizers. The atoms should then be irradiated by optical radiation, and the radiation source could be an element-specific line radiation source or a continuum radiation source. The radiation then passes through a monochromator in order to separate the element-specific radiation from any other radiation emitted by the radiation source, which is finally measured by a detector.

Atomizers

The atomizers most commonly used nowadays are spectroscopic flames and electrothermal atomizers. Other atomizers, such as glow-discharge atomization, hydride atomization, or cold-vapor atomization, might be used for special purposes.

Flame atomizers

The oldest and most commonly used atomizers in AAS are flames, principally the air-acetylene flame with a temperature of about 2300 °C and the nitrous oxide system (N2O)-acetylene flame with a temperature of about 2700 °C. The latter flame, in addition, offers a more reducing environment, being ideally suited for analytes with high affinity to oxygen.

A laboratory flame photometer that uses a propane operated flame atomizer

Liquid or dissolved samples are typically used with flame atomizers. The sample solution is aspirated by a pneumatic analytical nebulizer, transformed into an aerosol, which is introduced into a spray chamber, where it is mixed with the flame gases and conditioned in a way that only the finest aerosol droplets (< 10 μm) enter the flame. This conditioning process reduces interference, but only about 5% of the aerosolized solution reaches the flame because of it.

On top of the spray chamber is a burner head that produces a flame that is laterally long (usually 5–10 cm) and only a few mm deep. The radiation beam passes through this flame at its longest axis, and the flame gas flow-rates may be adjusted to produce the highest concentration of free atoms. The burner height may also be adjusted, so that the radiation beam passes through the zone of highest atom cloud density in the flame, resulting in the highest sensitivity.

The processes in a flame include the stages of desolvation (drying) in which the solvent is evaporated and the dry sample nano-particles remain, vaporization (transfer to the gaseous phase) in which the solid particles are converted into gaseous molecule, atomization in which the molecules are dissociated into free atoms, and ionization where (depending on the ionization potential of the analyte atoms and the energy available in a particular flame) atoms may be in part converted to gaseous ions.

Each of these stages includes the risk of interference in case the degree of phase transfer is different for the analyte in the calibration standard and in the sample. Ionization is generally undesirable, as it reduces the number of atoms that are available for measurement, i.e., the sensitivity.

In flame AAS a steady-state signal is generated during the time period when the sample is aspirated. This technique is typically used for determinations in the mg L−1 range, and may be extended down to a few μg L−1 for some elements.

Electrothermal atomizers

GFAA method development
 
Graphite tube

Electrothermal AAS (ET AAS) using graphite tube atomizers was pioneered by Boris V. L’vov at the Saint Petersburg Polytechnical Institute, Russia, since the late 1950s, and investigated in parallel by Hans Massmann at the Institute of Spectrochemistry and Applied Spectroscopy (ISAS) in Dortmund, Germany.

Although a wide variety of graphite tube designs have been used over the years, the dimensions nowadays are typically 20–25 mm in length and 5–6 mm inner diameter. With this technique liquid/dissolved, solid and gaseous samples may be analyzed directly. A measured volume (typically 10–50 μL) or a weighed mass (typically around 1 mg) of a solid sample are introduced into the graphite tube and subject to a temperature program. This typically consists of stages, such as drying – the solvent is evaporated; pyrolysis – the majority of the matrix constituents are removed; atomization – the analyte element is released to the gaseous phase; and cleaning – eventual residues in the graphite tube are removed at high temperature.

The graphite tubes are heated via their ohmic resistance using a low-voltage high-current power supply; the temperature in the individual stages can be controlled very closely, and temperature ramps between the individual stages facilitate separation of sample components. Tubes may be heated transversely or longitudinally, where the former ones have the advantage of a more homogeneous temperature distribution over their length. The so-called stabilized temperature platform furnace (STPF) concept, proposed by Walter Slavin, based on research of Boris L’vov, makes ET AAS essentially free from interference. The major components of this concept are atomization of the sample from a graphite platform inserted into the graphite tube (L’vov platform) instead of from the tube wall in order to delay atomization until the gas phase in the atomizer has reached a stable temperature; use of a chemical modifier in order to stabilize the analyte to a pyrolysis temperature that is sufficient to remove the majority of the matrix components; and integration of the absorbance over the time of the transient absorption signal instead of using peak height absorbance for quantification.

In ET AAS a transient signal is generated, the area of which is directly proportional to the mass of analyte (not its concentration) introduced into the graphite tube. This technique has the advantage that any kind of sample, solid, liquid or gaseous, can be analyzed directly. Its sensitivity is 2–3 orders of magnitude higher than that of flame AAS, so that determinations in the low μg L−1 range (for a typical sample volume of 20 μL) and ng g−1 range (for a typical sample mass of 1 mg) can be carried out. It shows a very high degree of freedom from interferences, so that ET AAS might be considered the most robust technique available nowadays for the determination of trace elements in complex matrices.

Specialized atomization techniques

While flame and electrothermal vaporizers are the most common atomization techniques, several other atomization methods are utilized for specialized use.

Glow-discharge atomization

A glow-discharge device (GD) serves as a versatile source, as it can simultaneously introduce and atomize the sample. The glow discharge occurs in a low-pressure argon gas atmosphere between 1 and 10 torr. In this atmosphere lies a pair of electrodes applying a DC voltage of 250 to 1000 V to break down the argon gas into positively charged ions and electrons. These ions, under the influence of the electric field, are accelerated into the cathode surface containing the sample, bombarding the sample and causing neutral sample atom ejection through the process known as sputtering. The atomic vapor produced by this discharge is composed of ions, ground state atoms, and fraction of excited atoms. When the excited atoms relax back into their ground state, a low-intensity glow is emitted, giving the technique its name.

The requirement for samples of glow discharge atomizers is that they are electrical conductors. Consequently, atomizers are most commonly used in the analysis of metals and other conducting samples. However, with proper modifications, it can be utilized to analyze liquid samples as well as nonconducting materials by mixing them with a conductor (e.g. graphite).

Hydride atomization

Hydride generation techniques are specialized in solutions of specific elements. The technique provides a means of introducing samples containing arsenic, antimony, selenium, bismuth, and lead into an atomizer in the gas phase. With these elements, hydride atomization enhances detection limits by a factor of 10 to 100 compared to alternative methods. Hydride generation occurs by adding an acidified aqueous solution of the sample to a 1% aqueous solution of sodium borohydride, all of which is contained in a glass vessel. The volatile hydride generated by the reaction that occurs is swept into the atomization chamber by an inert gas, where it undergoes decomposition. This process forms an atomized form of the analyte, which can then be measured by absorption or emission spectrometry.

Cold-vapor atomization

The cold-vapor technique is an atomization method limited only for the determination of mercury, due to it being the only metallic element to have a large vapor pressure at ambient temperature. Because of this, it has an important use in determining organic mercury compounds in samples and their distribution in the environment. The method initiates by converting mercury into Hg2+ by oxidation from nitric and sulfuric acids, followed by a reduction of Hg2+ with tin(II) chloride. The mercury, is then swept into a long-pass absorption tube by bubbling a stream of inert gas through the reaction mixture. The concentration is determined by measuring the absorbance of this gas at 253.7 nm. Detection limits for this technique are in the parts-per-billion range making it an excellent mercury detection atomization method.

Radiation sources

We have to distinguish between line source AAS (LS AAS) and continuum source AAS (CS AAS). In classical LS AAS, as it has been proposed by Alan Walsh, the high spectral resolution required for AAS measurements is provided by the radiation source itself that emits the spectrum of the analyte in the form of lines that are narrower than the absorption lines. Continuum sources, such as deuterium lamps, are only used for background correction purposes. The advantage of this technique is that only a medium-resolution monochromator is necessary for measuring AAS; however, it has the disadvantage that usually a separate lamp is required for each element that has to be determined. In CS AAS, in contrast, a single lamp, emitting a continuum spectrum over the entire spectral range of interest is used for all elements. Obviously, a high-resolution monochromator is required for this technique, as will be discussed later.

Hollow cathode lamp (HCL)

Hollow cathode lamps

Hollow cathode lamps (HCL) are the most common radiation source in LS AAS. Inside the sealed lamp, filled with argon or neon gas at low pressure, is a cylindrical metal cathode containing the element of interest and an anode. A high voltage is applied across the anode and cathode, resulting in an ionization of the fill gas. The gas ions are accelerated towards the cathode and, upon impact on the cathode, sputter cathode material that is excited in the glow discharge to emit the radiation of the sputtered material, i.e., the element of interest. In the majority of cases single element lamps are used, where the cathode is pressed out of predominantly compounds of the target element. Multi-element lamps are available with combinations of compounds of the target elements pressed in the cathode. Multi element lamps produce slightly less sensitivity than single element lamps and the combinations of elements have to be selected carefully to avoid spectral interferences. Most multi-element lamps combine a handful of elements, e.g.: 2 - 8. Atomic Absorption Spectrometers can feature as few as 1-2 hollow cathode lamp positions or in automated multi-element spectrometers, a 8-12 lamp positions may be typically available.

Electrodeless discharge lamps

Electrodeless discharge lamps (EDL) contain a small quantity of the analyte as a metal or a salt in a quartz bulb together with an inert gas, typically argon gas, at low pressure. The bulb is inserted into a coil that is generating an electromagnetic radio frequency field, resulting in a low-pressure inductively coupled discharge in the lamp. The emission from an EDL is higher than that from an HCL, and the line width is generally narrower, but EDLs need a separate power supply and might need a longer time to stabilize.

Deuterium lamps

Deuterium HCL or even hydrogen HCL and deuterium discharge lamps are used in LS AAS for background correction purposes. The radiation intensity emitted by these lamps decreases significantly with increasing wavelength, so that they can be only used in the wavelength range between 190 and about 320 nm.

Xenon lamp as a continuous radiation source

Continuum sources

When a continuum radiation source is used for AAS, it is necessary to use a high-resolution monochromator, as will be discussed later. In addition, it is necessary that the lamp emits radiation of intensity at least an order of magnitude above that of a typical HCL over the entire wavelength range from 190 nm to 900 nm. A special high-pressure xenon short arc lamp, operating in a hot-spot mode has been developed to fulfill these requirements.

Spectrometer

As already pointed out above, there is a difference between medium-resolution spectrometers that are used for LS AAS and high-resolution spectrometers that are designed for CS AAS. The spectrometer includes the spectral sorting device (monochromator) and the detector.

Spectrometers for LS AAS

In LS AAS the high resolution that is required for the measurement of atomic absorption is provided by the narrow line emission of the radiation source, and the monochromator simply has to resolve the analytical line from other radiation emitted by the lamp. This can usually be accomplished with a band pass between 0.2 and 2 nm, i.e., a medium-resolution monochromator. Another feature to make LS AAS element-specific is modulation of the primary radiation and the use of a selective amplifier that is tuned to the same modulation frequency, as already postulated by Alan Walsh. This way any (unmodulated) radiation emitted for example by the atomizer can be excluded, which is imperative for LS AAS. Simple monochromators of the Littrow or (better) the Czerny-Turner design are typically used for LS AAS. Photomultiplier tubes are the most frequently used detectors in LS AAS, although solid state detectors might be preferred because of their better signal-to-noise ratio.

Spectrometers for CS AAS

When a continuum radiation source is used for AAS measurement it is indispensable to work with a high-resolution monochromator. The resolution has to be equal to or better than the half-width of an atomic absorption line (about 2 pm) in order to avoid losses of sensitivity and linearity of the calibration graph. The research with high-resolution (HR) CS AAS was pioneered by the groups of O’Haver and Harnly in the US, who also developed the (up until now) only simultaneous multi-element spectrometer for this technique. The breakthrough, however, came when the group of Becker-Ross in Berlin, Germany, built a spectrometer entirely designed for HR-CS AAS. The first commercial equipment for HR-CS AAS was introduced by Analytik Jena (Jena, Germany) at the beginning of the 21st century, based on the design proposed by Becker-Ross and Florek. These spectrometers use a compact double monochromator with a prism pre-monochromator and an echelle grating monochromator for high resolution. A linear charge-coupled device (CCD) array with 200 pixels is used as the detector. The second monochromator does not have an exit slit; hence the spectral environment at both sides of the analytical line becomes visible at high resolution. As typically only 3–5 pixels are used to measure the atomic absorption, the other pixels are available for correction purposes. One of these corrections is that for lamp flicker noise, which is independent of wavelength, resulting in measurements with very low noise level; other corrections are those for background absorption, as will be discussed later.

Background absorption and background correction

The relatively small number of atomic absorption lines (compared to atomic emission lines) and their narrow width (a few pm) make spectral overlap rare; there are only few examples known that an absorption line from one element will overlap with another. Molecular absorption, in contrast, is much broader, so that it is more likely that some molecular absorption band will overlap with an atomic line. This kind of absorption might be caused by un-dissociated molecules of concomitant elements of the sample or by flame gases. We have to distinguish between the spectra of di-atomic molecules, which exhibit a pronounced fine structure, and those of larger (usually tri-atomic) molecules that don't show such fine structure. Another source of background absorption, particularly in ET AAS, is scattering of the primary radiation at particles that are generated in the atomization stage, when the matrix could not be removed sufficiently in the pyrolysis stage.

All these phenomena, molecular absorption and radiation scattering, can result in artificially high absorption and an improperly high (erroneous) calculation for the concentration or mass of the analyte in the sample. There are several techniques available to correct for background absorption, and they are significantly different for LS AAS and HR-CS AAS.

Background correction techniques in LS AAS

In LS AAS background absorption can only be corrected using instrumental techniques, and all of them are based on two sequential measurements: firstly, total absorption (atomic plus background), secondly, background absorption only. The difference of the two measurements gives the net atomic absorption. Because of this, and because of the use of additional devices in the spectrometer, the signal-to-noise ratio of background-corrected signals is always significantly inferior compared to uncorrected signals. It should also be pointed out that in LS AAS there is no way to correct for (the rare case of) a direct overlap of two atomic lines. In essence there are three techniques used for background correction in LS AAS:

Deuterium background correction

This is the oldest and still most commonly used technique, particularly for flame AAS. In this case, a separate source (a deuterium lamp) with broad emission is used to measure the background absorption over the entire width of the exit slit of the spectrometer. The use of a separate lamp makes this technique the least accurate one, as it cannot correct for any structured background. It also cannot be used at wavelengths above about 320 nm, as the emission intensity of the deuterium lamp becomes very weak. The use of deuterium HCL is preferable compared to an arc lamp due to the better fit of the image of the former lamp with that of the analyte HCL.

Smith-Hieftje background correction

This technique (named after their inventors) is based on the line-broadening and self-reversal of emission lines from HCL when high current is applied. Total absorption is measured with normal lamp current, i.e., with a narrow emission line, and background absorption after application of a high-current pulse with the profile of the self-reversed line, which has little emission at the original wavelength, but strong emission on both sides of the analytical line. The advantage of this technique is that only one radiation source is used; among the disadvantages are that the high-current pulses reduce lamp lifetime, and that the technique can only be used for relatively volatile elements, as only those exhibit sufficient self-reversal to avoid dramatic loss of sensitivity. Another problem is that background is not measured at the same wavelength as total absorption, making the technique unsuitable for correcting structured background.

Zeeman-effect background correction

An alternating magnetic field is applied at the atomizer (graphite furnace) to split the absorption line into three components, the π component, which remains at the same position as the original absorption line, and two σ components, which are moved to higher and lower wavelengths, respectively. Total absorption is measured without magnetic field and background absorption with the magnetic field on. The π component has to be removed in this case, e.g. using a polarizer, and the σ components do not overlap with the emission profile of the lamp, so that only the background absorption is measured. The advantages of this technique are that total and background absorption are measured with the same emission profile of the same lamp, so that any kind of background, including background with fine structure can be corrected accurately, unless the molecule responsible for the background is also affected by the magnetic field and using a chopper as a polariser reduces the signal to noise ratio. While the disadvantages are the increased complexity of the spectrometer and power supply needed for running the powerful magnet needed to split the absorption line.

Background correction techniques in HR-CS AAS

In HR-CS AAS background correction is carried out mathematically in the software using information from detector pixels that are not used for measuring atomic absorption; hence, in contrast to LS AAS, no additional components are required for background correction.

Background correction using correction pixels

It has already been mentioned that in HR-CS AAS lamp flicker noise is eliminated using correction pixels. In fact, any increase or decrease in radiation intensity that is observed to the same extent at all pixels chosen for correction is eliminated by the correction algorithm. This obviously also includes a reduction of the measured intensity due to radiation scattering or molecular absorption, which is corrected in the same way. As measurement of total and background absorption, and correction for the latter, are strictly simultaneous (in contrast to LS AAS), even the fastest changes of background absorption, as they may be observed in ET AAS, do not cause any problem. In addition, as the same algorithm is used for background correction and elimination of lamp noise, the background corrected signals show a much better signal-to-noise ratio compared to the uncorrected signals, which is also in contrast to LS AAS.

Background correction using a least-squares algorithm

The above technique can obviously not correct for a background with fine structure, as in this case the absorbance will be different at each of the correction pixels. In this case HR-CS AAS is offering the possibility to measure correction spectra of the molecule(s) that is (are) responsible for the background and store them in the computer. These spectra are then multiplied with a factor to match the intensity of the sample spectrum and subtracted pixel by pixel and spectrum by spectrum from the sample spectrum using a least-squares algorithm. This might sound complex, but first of all the number of di-atomic molecules that can exist at the temperatures of the atomizers used in AAS is relatively small, and second, the correction is performed by the computer within a few seconds. The same algorithm can actually also be used to correct for direct line overlap of two atomic absorption lines, making HR-CS AAS the only AAS technique that can correct for this kind of spectral interference.

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