Oxygen volcanic gases

It is important to see that symbols can designate either an atom or a molecule of an element. Consider hydrogen and oxygen. Hydrogen gas is present in volcanic gases and can be prepared by many chemical reactions. Regardless of their source, all samples of free hydrogen gas consist of diatomic molecules. 

Sulfur forms several oxides that in atmospheric chemistry are referred to collectively as SOx (read sox ). The most important oxides and oxoacids of sulfur are the dioxide and trioxide and the corresponding sulfurous and sulfuric acids. Sulfur burns in air to form sulfur dioxide, S02 (11), a colorless, choking, poisonous gas (recall Fig. C.1). About 7 X 1010 kg of sulfur dioxide is produced annually from the decomposition of vegetation and from volcanic emissions. In addition, approximately 1 X 1011 kg of naturally occurring hydrogen sulfide is oxidized each year to the dioxide by atmospheric oxygen ... 

Acid rain is caused primarily by sulfur dioxide emissions from burning fossil fuels such as coal, oil, and natural gas. Sulfur is an impurity in these fuels for example, coal typically contains 2-3% by weight sulfur.1M Other sources of sulfur include the industrial smelting of metal sulfide ores to produce the elemental metal and, in some parts of the world, volcanic eruptions. When fossils fuels are burned, sulfur is oxidized to sulfur dioxide (SO2) and trace amounts of sulfur trioxide (SC>3)J21 The release of sulfur dioxide and sulfur trioxide emissions to the atmosphere is the major source of acid rain. These gases combine with oxygen and water vapor to form a fine mist of sulfuric acid that settles on land, on vegetation, and in the ocean. 

Sulfur isotopes also show mass-independent effects that are probably produced by the same photochemical mechanism as oxygen effects in the Earth s upper atmosphere. Mass independent variations in sulfur from Martian meteorites have been interpreted to result from volcanic injections of SO2 and H2S into the Martian atmosphere followed by photolysis, which fractionates the sulfur isotopes. There is also evidence from ancient terrestrial sediments that the same photo lytic process was operating on sulfur in the Earth s atmosphere prior to 2.4 Ga, before oxygen began to accumulate in the atmosphere (see review by Thiemens, 2006). 

Cameroon, in 1986. The gas, although not toxic in itself, is heavier than air. Released suddenly from solution, possibly as a result of volcanic activity, it blanketed the shores and overflowed into lower-lying surrounding regions, displacing oxygen and suffocating some 1700 people. 

Volcanic eruptions can influence the total amount of ozone in the atmosphere (total ozone). The mechanisms of this influence can be very different. For instance, in non-volcanic periods the accumulation of ozone may take place, due to the presence of sulphur dioxide (SO2, the sulphmous gas) in the atmosphere and its photooxidation by air oxygen (Ivlev et. al, 1990). We shall examine some mechanisms of the accumulation and exhaustions of die... 

Archaean (3.8 Ga) the oxygen activity of the depleted mantle was broadly the same as it is today. Hence models for the evolution of the Earth s atmosphere, which require a changed proportion of oxidizing to reducing gases from volcanic sources over geological time, cannot be sustained. 

What is not clear, however, is the precise cause of the rise in oxygen at between 2.3 and 2.4 Ga. It was not simply an increase in cyanobacterial oxygen production, because cyanobacteria had already been in existence for several hundred million years. Another, inorganic trigger is required - related perhaps to a change in the proportion of reducing volcanic gases produced, or to the way in which... 

Wiechert UH, Halliday AN, Lee DC, Snyder GA, Taylor LA, Rumble D (2000) Oxygen- and tungsten-isotopic constraints on the early development of the moon. Meteoritics Planetary Sci 35 A169 Woodhead JD, Greenwood P, Harmon RS, Staffers P (1993) Oxygen isotope evidence for recycled crust in the source of EM-type ocean island basalts. Nature 362 809-813 Woodhead JD, Harmon RS, Fraser DG (1987) O, S, Sr, and Pb isotope variations in volcanic rocks from the northern Mariana islands implications for crastal recycling in intra-oceanic ares. Earth Planet Sci Letters 83 39-52... 

Volcanoes are a major source of sulfur dioxide (SO2) gas in the atmosphere. This gas is poisonous and is an irritant to the mucous membranes found in your throat, eyes, and nose. Sulfur dioxide also reacts with oxygen, sunlight, dust, and water to create S04 droplets and sulfuric acid (H2SO4), which leads to a type of smog referred to as volcanic smog, or vog. Vog can cause asthma attacks and damage the upper respiratory tract. The sulfuric acid produced can also cause acid rain. 

Conclusions about the atmospheric composition of the early earth have been drawn from the gas exhalations of the so-called Hawaiian volcanoes type (Table 2.6). Oxygen is almost entirely missing from volcanic exhalations. Where O2 is... 

---