Arsenic chemical forms

Under unusual circumstances, toxicity may arise from ingestion of excess amounts of minerals. This is uncommon except in the cases of fluorine, molybdenum, selenium, copper, iron, vanadium, and arsenic. Toxicosis may also result from exposure to industrial compounds containing various chemical forms of some of the minerals. Aspects of toxicity of essential elements have been pubhshed (161). 

The principal constituents of the paniculate matter are lead/zinc and iron oxides, but oxides of metals such as arsenic, antimony, cadmium, copper, and mercury are also present, along with metallic sulfates. Dust from raw materials handling contains metals, mainly in sulfidic form, although chlorides, fluorides, and metals in other chemical forms may be present. Off-gases contain fine dust panicles and volatile impurities such as arsenic, fluorine, and mercury. 

T. Baker Chemicals were used. The arsenic metal powder was Imbedded in indium foil for examination. An arsenic mirror formed on a reaction flask was also examined. 

Arsenic geochemistry in Chesapeake Bay, Maryland, depends on anthropogenic inputs and phytoplankton species composition (Sanders 1985). Inputs of anthropogenic arsenic into Chesapeake Bay are estimated at 100 kg daily, or 39 tons/year — probably from sources such as unreported industrial discharges, use of arsenical herbicides, and from wood preservatives (Sanders 1985). The chemical form of the arsenic in solution varies seasonally and along the axis of the bay. Arsenic is present only as arsenate in winter, but substantial quantities of reduced and methylated forms are present in summer in different areas. The forms and distribution patterns of arsenic... 

The literature emphasizes that arsenic metabolism and toxicity vary greatly between species and that its effects are significantly altered by numerous physical, chemical, and biological modifiers. Adverse health effects, for example, may involve respiratory, gastrointestinal, cardiovascular, and hematopoietic systems, and may range from reversible effects to cancer and death, depending partly on the physical and chemical forms of arsenic tested, the route of administration, and the dose. 

Arsenic metabolism and effects are significantly influenced by the organism tested, the route of administration, the physical and chemical form of the arsenical, and the dose. 

Identification and quantification of mineral and chemical forms of arsenic in rocks, soils, and sediments that constitute the natural forms of arsenic entering water and the food chain... 

In addition, the following techniques should be developed and implemented (1) more sophisticated measurements of the chemical forms of arsenic in plant and animal tissues (2) correlation of biologically observable effects with particular chemical forms of arsenic and (3) management of arsenical wastes that accommodates recycling, reuse, and long-term storage. 

Saltwater biota tissue residues Depending on chemical form of arsenic, certain marine teleosts may be unaffected at muscle total arsenic residues of 40 mg/kg FW (NRCC 1978)... 

Developing standardized procedures to permit correlation of biologically observable effects with suitable chemical forms of arsenic... 

Kaise, T. and S. Fukui. 1992. The chemical form and acute toxicity of arsenic compounds in marine organisms. Appl. Organometall. Chem. 6 155-160. 

Phillips, DJ.H. and M.H. Depledge. 1986. Chemical forms of arsenic in marine organisms, with emphasis on Hemifusus species. Water Sci. Technol. 18 213-222. 

The chemical form of arsenic in marine environmental samples is of interest from several standpoints. Marine organisms show widely varying concentrations of arsenic [4-6] and knowledge of the chemical forms in which the element occurs in tissues is relevant to the interpretation of these variable degrees of bioaccumulation and to an understanding of the biochemical mechanisms involved. Different arsenic species have different levels of toxicity [7] and bioavailability [8] and this is important in food chain processes, while physicochemical behaviour in processes such as adsorption onto sediments also varies with the species involved [9]. It has... 

The distribution of the chemical forms of arsenic in the various marine compartments is summarized in Fig. 6. 

Uptake experiments have also been conducted with other forms of arsenic. M. edulis exposed separately to a number of organoarsenic compounds in seawater were found to be selective in their arsenic uptake (85). They did not accumulate arsenic when it was present as MMA, DMA, TMAO, or DMAE. When exposed to the three quaternary arsonium compounds (arsenobetaine, arsenocholine, and TeMA), however, the mussels accumulated substantial quantities of arsenic, with arsenobetaine being the most efficiently accumulated (Table VII). The chemical form of the accumulated arsenic was also examined. Mussels... 

Identifying the physical and chemical form of a trace element pollutant at the time of body penetration is probably the single most important prerequisite for meaningful biological testing. It is known, for example, that elemental arsenic (13) and beryllium (46) are nontoxic... 

Arsenic is a metalloid. Solid samples of elemental arsenic (As(0)) tend to be brittle, nonductile, and insoluble in water. These properties largely result from arsenic atoms forming strong covalent bonds with each other. Table 2.3 lists the common chemical and physical properties of arsenic, including its density, electronegativity, and first ionization potential. 

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