Arsenic contamination with

Reisinger, H.J., Burris, D.R. and Hering, J.G. (2005) Remediating subsurface arsenic contamination with monitored natural attenuation. Environmental Science and Technology, 39(22), 458A-464A. 

Before this treatment, the cassiterite content of the ore is increased by removing impurities such as clay, by washing and by roasting which drives off oxides of arsenic and sulphur. The crude tin obtained is often contaminated with iron and other metals. It is, therefore, remelted on an inclined hearth the easily fusible tin melts away, leaving behind the less fusible impurities. The molten tin is finally stirred to bring it into intimate contact with air. Any remaining metal impurities are thereby oxidised to form a scum tin dross ) on the surface and this can be skimmed off Very pure tin can be obtained by zone refining. 

Fig. 9.3 Schematic diagram of purification of underground water contaminated with arsenic...

Boron (finely divided forms) reacts violently with cone, acid and may attain incandescence. The vapour of phosphorus, heated in nitric acid in presence of air, may ignite. Boron phosphide ignites with the cone, acid [1], Silicon crystallised from its eutectic with aluminium reacts violently with cone, acid [2], arsenic may react violently with the fuming acid, and finely divided carbon similarly with cone, acid [3], Use of cone, acid to clean a stainless steel hose contaminated with phosphorus led to an explosion [4],... 

Woolson et al. (1971) used a modified soil P procedure to study distribution of As in U.S. soils. The mass of the residual As in both uncontaminated and soils contaminated with arsenic pesticides from Washington and Oregon is found as the Fe oxide bound As (0.1 N NaOH extractable), followed by the Al oxide and the Ca bound As (extracted by NH4F and H2S04, respectively). 

Figure 9.1. Measured and fitted global annual industrial age As production, (a) by mining (b) released by coal burning (c) released by petroleum burning and (d) gross annual release into the environment (See explanations in the text) (after Han et al., 2003b. Reprinted from Naturwissenschaften, 90, Han F.X., Su Y., Monts D.L., Plodinec M.J., Banin A., Triplett G.B., Assessment of global industrial-age anthropogenic arsenic contamination, pp 396-397, Copyright (2003), with kind permission of Springer Science and Business Media)...

Fig. 8. Arsenic extraction from a reddish brown tropical soil deliberately contaminated with arsenate as a function of reaction time by 0.005M chloride, sulphate, carbonate and phosphate. Redrawn from Goh and Lym (2005).

Martin et al. (2007a) investigated the accumulation and potential release of arsenic in a paddy field in Bangladesh irrigated with arsenic contaminated groundwater. The oxalate-extractable fraction related to amorphous hydrous oxide-bound arsenic represented the dominant arsenic form in the surface layer (47%). A high percentage of arsenic was removed by phosphate (22%). 

Martin M, Violante A, Barberis E (2007a) Fate of arsenite and arsenate in flooded and not flooded soils of South West Bangladesh irrigated with arsenic contaminated water. J Environ Sci Health, Part A 42 1775-1783 Martin M, Violante A, Barberis E (2007b) Comparing surface interaction of arsenite and arsenate on soil colloids I Adsorption. Soil Sci Soc Am J (submitted)... 

Structural firefighters protective clothing is recommended for fire situations only it is not effective in spill situations or release events and should never be used as the primary chemical protective garment to enter an area contaminated with arsenic vesicants. 

All foodstuffs in the area of release should be considered contaminated with residual arsenic. Unopened items packaged in glass, metal, or heavy duty plastic and exposed only to agent vapors maybe used after decontamination of the container. Opened or unpackaged items, or those packaged only in paper or cardboard, should be destroyed. 

Arsine is highly volatile and there is little risk of direct residual contamination. However, potential persistent decomposition products include arsenic and arsenic oxides. Wash the remains with soap and water. Pay particular attention to areas where agent may get trapped, such as hair, scalp, pubic areas, fingernails, folds of skin, and wounds. If remains are heavily contaminated with residue, then wash and rinse waste should be contained for proper disposal. Once the remains have been thoroughly decontaminated, no further protective action is necessary. Body fluids removed during the embalming process do not pose any additional risks and should be contained and handled according to established procedures. Use standard burial procedures. 

According to the Illinois Environmental Protection Agency (IEPA), a series of gas blowouts has occurred at two waste injection wells in the state (Brower el al., 1989). In each case, well operators were injecting concentrated hydrochloric acid into a dolomite bed. At its plant near Tuscola, the Cabot Corporation injects acid waste from the production of fumed silica into the Cambrian Eminence and Potosi Formations below 5 000 ft (1 500 m) depth. Allied Chemical Corporation injects acid into the Potosi formation below about 3 600 ft (1 100 m). The acid, which is contaminated with arsenic, is a byproduct of the manufacture of refrigerant gas. Since some of the blowouts have caused damage such as fish kills, there is environmental interest as well as operational concern in preventing such accidents. 

Soils amended with arsenic-contaminated plant tissues were not measurably affected in C02 evolution and nitrification, suggesting that the effects of adding arsenic to soils does not influence the decomposition rate of plant tissues by soil microorganisms (Wang et al. 1984). The half-life of cacodylic acid is about 20 days in untreated soils and 31 days in arsenic-amended soils (Hood 1985). Estimates of the half-time of inorganic arsenicals in soils are much longer, ranging from 6.5 years for arsenic trioxide to 16 years for lead arsenate (NRCC 1978). 

Porter 1989). It is speculated that these deer licked trees injected with Silvisar 550, which contains monosodium methanearsonate, probably because of its salty taste (Mathews and Porter 1989). Snowshoe hares (Lepus sp.) appear to be especially sensitive to methylated arsenicals hares died after consuming plants heavily contaminated with monosodium methanearsonate as a result of careless silviculture practices (Hood 1985). 

Japanese infants poisoned (128 deaths) from consumption of dry milk contaminated with arsenic average exposure of 3.5 mg As daily for 1 month. Severe hearing loss, brain wave abnormalities, and other CNS disturbances noted 15 years after exposure... 

Wang, D.S., R.W. Weaver, and J.R. Melton. 1984. Microbial decomposition of plant tissue contaminated with arsenic and mercury. Environ. Pollut. 34A 275-282. 

In ultra pure crystalline silicon, there are no extra electrons in the lattice that can conduct an electric current. If however, the silicon becomes contaminated with arsenic atoms, then there will be one additional electron added to the silicon crystal lattice for each arsenic atom that is introduced. Upon heating, some of those "extra electrons will be promoted into the conduction band of the solid. The electrons that end up in the conduction band are able to move freely through the structure. In other words, the arsenic atoms increase the conductivity of the solid by providing additional electrons that can carry a current when they are promoted into the conduction band by thermal excitation. Thus, by virtue of having extra electrons in the lattice, silicon contaminated with arsenic will exhibit greater electrical conductance than pure silicon at elevated temperatures. 

This research is an outgrowth of an earlier project which sought to characterize the mechanism of arsenic metabolism in a population currently drinking arsenic-contaminated water in Taiwan. There were three parts to the study, a cohort study, a case control study for skin cancer, and a study of intra-individual variability associated with chronic arsenic exposure. The latter three research projects are complete and being submitted for publication. The results of this research are highly relevant since they indicate that alterations in methylation capacity may affect arsenic carcinogenesis. 

In Ganges Delta, groundwater contaminated with arsenic causes health risk of 40 million people.1 Since arsenic exists as both arsenite (As(III)) and arsenate (As(V)), removal methods for both arsenic species are desired to resolve the arsenic calamity in Ganges Delta.2 Granular adsorbents specific... 

The process can be used to immobilize heavy metals such as Cd, Zn, Cu, Pb, Ni and Co. Cr(VI) can be reduced by some metal-reducing bacteria to the less toxic and less soluble form Cr(III). Arsenate [As(V)] can be reduced to the more mobile arsenite [As(III)] which precipitates as AS2S3, and is insoluble at low pH. Several laboratory-scale tests (batch and column) are currently available to study the feasibility of this process. However, only a few field tests have been performed to date. Two such tests have been conducted in Belgium, one at a non-ferrous industrial site, where the groundwater was contaminated with Cd, Zn, Ni and Co, and the other which was treated by injection of molasses in order to reduce chromium (VI) to chromium (III). A third demonstration in The Netherlands has been performed at a metal surface treatment site contaminated by Zn. The outcomes of a batch test of a groundwater heavily contaminated by Zn, Cd, Co and Ni are presented in Table 5. The initial sulphate concentration was 506mg/l. With the addition of acetate, a nearly... 

Silicon s tetravalent pyramid crystalline structure, similar to tetravalent carbon, results in a great variety of compounds with many practical uses. Crystals of sihcon that have been contaminated with impurities (arsenic or boron) are used as semiconductors in the computer and electronics industries. Silicon semiconductors made possible the invention of transistors at the Bell Labs in 1947. Transistors use layers of crystals that regulate the flow of electric current. Over the past half-century, transistors have replaced the vacuum tubes in radios, TVs, and other electronic equipment that reduces both the devices size and the heat produced by the electronic devices. 

To obtain MSMA, the DSMA solution is partially acidified with sulfuric acid and the resulting solution concentrated by evaporation. As the aqueous solution is being concentrated, a mixture of sodium sulfate and sodium chloride precipitates out (about 0.5 kg per 100 kg of active ingredient). These salts are a troublesome disposal problem because they are contaminated with arsenic. The salts are removed by centrifugation, washed in a multistage, countercurrent washing cycle, and then disposed of in an approved landfill. 

In other areas of the world, such as Bangladesh, elevated arsenic levels in the drinking water are more acutely life threatening. People were encouraged to establish local wells to reduce exposure to drinking water contaminated with bacteria. 

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