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1 2005

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Arsen w technice i środowisku

Kociołek-Balawejder E., Ociński D.

Wiadomości Chemiczne

2005

[Z] 59, 3-4

353--386

The arsenic is an element which comes in the twentieth place in respect of its dissemination in the earth's crust and fourteenth in seawater. Average concentrations of arsenic in the earth's crust are reported to be 1,5 - 6 mg/kg. In the geosphere arsenic occurs connected especially with sulfide minerals. As a chalcophylic element it is commonly present in sulfide ores of other metals, mainly pyrites, chalcopyrites, galenite and zincblende. Arsenic is a constituent of more than 200 minerals. Sources of arsenic in the environment are natural and anthropogenic in essence. More than several dozens tons of arsenic are released annually to the terrestrial and aquatic environment and to the atmosphere. Natural sources of arsenic include volcanic activity, weathering, soil erosion, forest and grass fires and biological activity. Anthropogenic sources are mainly smelting of non-ferrous metal ores and burning of fossil fuel in household and power plants. Anthropogenic sources also include the production and application of arsenic compounds. From ages they were used in medicine, metallurgy and dye-production. In the last few hundred years arsenic compounds were also used in agriculture, wood-preservation, warfare production and semiconductor industry. In XVIII and XIX centuries the essential usage of arsenic was medicine. Until the discovery of antibiotics arsenotherapy was applicable in the treatment of a majority of diseases . In the XX century the most important applications arsenic compounds have found in agriculture and wood-preservation. In the first half of that century about 90% of the arsenic produced was used to manufacture a variety of pesticides, herbicides and fungicides. The utilization of arsenic compounds was systematically limited along with increasing of the ecological consciousness. Nowadays the use of arsenic in medicine and agricultural is declining. The most of the produced arsenic is used to manufacture Chromated Copper Arsenate (CCA) a wood preservative which is going to be replaced by alternative preservatives in the near futur. Small amounts of arsenic are utilized in the semiconductor industry, metallurgy and in the manufacturing of glass. Most of the arsenic is produced in form of arsenic trioxide, which is a by-product during the smelter of nonferrous ores. Arsenic compounds are mobile in environment and occur in natural waters, soils and in the air. Arsenic is mainly transported by water among environmental media and it is undergoing chemical and physical transformations (oxidation/reduction, metylation/demetylation, adsorption/desorption). In natural environment arsenic occurs mainly as inorganic species: arsenate and arsenite. In these chemical compounds certain bacteria can replace hydroxyl groups by methyl groups forming methyl derivatives, mainly monomethyl arsonic acid (MMAA) and dimethyl arsenic acid (DMAA). Methylated arsenic species can be transformed by bacteria, fungi and yeasts under anaerobic conditions to volatile forms of arsenic: monomethylarsine (MMA), dimethylarsine (DMA), trimethylarsine (TMA) and arsine (AsH3). In the air arsenic exists mainly adsorbed on particle matter in the form of arsenic trioxide, arsenate and arsenite. Arsenic compounds are toxic for humans and animals. The toxicity depends mainly on the chemical forms and oxidation states of arsenic, the most toxic are inorganic arsenites. Ingestion of a large dose of inorganic arsenicals can lead to death. A long-term exposure to arsenic increases risks of cancer in skin, lungs, bladder and kidney. Inorganic arsenicals have been classified as Group I carcinogens. This review represents a comprehensive knowledge about the present and old applications of arsenic, the anthropogenic sources of this element, the circulation of arsenic in the environment and its impact on human health.