Halogens volcanic

Jordan A (2003) Volcanic Formation of Halogenated Organic Compounds. In Gribble GW (ed) Natural Production of Organohalogen Compounds, The Handbook of Environmental Chemistry, vol 3, part P. Springer, Berlin, p 121... 

The reactions observed in the photochemical smog, especially those concerning decomposition and oxidation of volatile organic substances, are accelerated by atmospheric aerosols, eg oxidation of some halogenated hydrocarbons, isoprene, monoterpenes, and aromatic hydrocarbons is enhanced by the surfaces of metal oxides, desert sand, volcanic ash, and sea salt [8],... 

The more soluble volatile components of volcanic plumes (e.g., halogens) can be removed from eruption clouds rapidly by adsorption on to tephra, or deposition in hydrometeors. The estimates of atmospheric burdens of volcanic volatiles in eruption clouds, therefore, depend on the time after eruption that the measurements were made, and can, in general, be lower than the total volatile release. Surprisingly, little work has been undertaken to quantify the total volatile budgets of eruptions (see De Hoog et al., 2001, for an exception). 

Measurements of gas samples collected at Augustine Volcano, Alaska, indicate typical orders of magnitude concentrations of different halogen species in volcanic emissions (Table 11). With peak SO2 emission rates of nearly 280kgs during minor eruptive episodes at... 

Table 11 Volcanic halogens at Mt. Augustine, all figures as mole fractions.

The atmospheric, climatic, environmental, and health effects of volcanic volatile emissions depend on several factors but importantly on fluxes of sulfur and halogens. As discussed in Section 3.04.5.1, intermittent explosive emptions can pump >10 kg of sulfur into the stratosphere, against a background of continuous fiimarolic and open-vent emission into the troposphere. The episodic, large explosive eruptions are the principal perturbation to stratospheric aerosol levels (e.g., 30 Mt of sulfate due to the 1991 emption of... 

Symonds et al. (1988) used equihbrium thermodynamic considerations to conclude that the overwhelming fraction of gaseous halogens that is released by volcanic eruptions are in the form of the hydrogen haUdes— they examined HCl and... 

HF. They estimated the magnitude of the halogen source of different types of volcanic eruptions and found that up to several hundred terragrams of HCl could be emitted into the atmosphere in the largest eruptions. Only a small fraction (down to — 0.01% Tabazadeh and Turco, 1993) of this reaches the stratosphere, most HCl being removed by precipitation in the emption plume. More passively degassing volcanoes could produce —(0.4-4) X 10 g HCl per year which predominantly remains in the troposphere. From stratospheric observations there is no indication of any growth in chlorine or bromine after the eruptions of Pinatubo or El Chichon. 

Atmospheric halogen compounds (Penkett, 1982) are of both natural and industrial origin. Probably the most abundant halocarbon in the troposphere is methyl chloride, CH3CI, which is present at a level of 0.6-2 parts in 10 . It appears to be present in volcanic emissions, formed by microbial fermentation, by the combustion of vegetation (Lovelock, 1975), and by the SN2 reaction of methyl iodide (a constituent of marine algae) with the large excess of chloride ion in seawater (Zafiriou,... 

Airborne particulates typically contain increased concentrations of halogens near the ocean, in polluted areas, and in regions of volcanic activity. Fluoride concentrations are increased near aluminum and steel miUs and phosphate-fertilizer plants. Bromide concentrations were once increased near urban areas as aresult ofthe burning of gasoline additives (ethylene dibromlde, a lead scavenger), but environmental legislation has resulted in a decline of this chemical s utilization. The enrichment of iodine in marine air as compared to sea water has been attributed to concentration of the element in organic surface films. Iodine-enriched material then enters the atmosphere in the form of spray. 

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