Arsenic abundance

Pichler, T., R. Brinkmann, and G.I. Scarzella. 1998. Arsenic abundance and variation in golf course lakes. Sci. Total Environ. 394 313-320. 

Figure 13. Histograms and descriptive statistics of arsenic abundance in U.S. coals, a) Coals from the Powder River basin of Montana and Wyoming, b) Coals of the midcontinental U.S. including Illinois, Indiana, and western Kentuclq/. c) Coals of the Black Warrior basin, Alabama. Also shown for each histogram are the number of samples (n), the mean (x) and median (x,s)...

Uranium, not as rare as once thought, is now considered to be more plentiful than mercury, antimony, silver, or cadmium, and is about as abundant as molybdenum or arsenic. It occurs in numerous minerals such as pitchblende, uraninite, carnotite, autunite, uranophane, and tobernite. It is also found in phosphate rock, lignite, monazite sands, and can be recovered commercially from these sources. 

Antimony [7440-36-0J, Sb, belongs to Group 15 (VA) of the periodic table which also includes the elements arsenic and bismuth. It is in the second long period of the table between tin and tellurium. Antimony, which may exhibit a valence of +5, +3, 0, or —3 (see Antimony compounds), is classified as a nonmetal or metalloid, although it has metallic characteristics in the trivalent state. There are two stable antimony isotopes that ate both abundant and have masses of 121 (57.25%) and 123 (42.75%). 

Arsenic [7440-38-2J, although often referred to as a metal, is classified chemically as a nonmetal or metalloid and belongs to Group 15 (VA) of the periodic table (as does antimony). The principal valences of arsenic are +3, +5, and —3. Only one stable isotope of arsenic having mass 75 (100% natural abundance) has been observed. 

Arsenic is widely distributed about the earth and has a terrestrial abundance of approximately 5 g/t (4). Over 150 arsenic-bearing minerals are known (1). Table 2 fists the most common minerals. The most important commercial source of arsenic, however, is as a by-product from the treatment of copper, lead, cobalt, and gold ores. The quantity of arsenic usually associated with lead and copper ores may range from a trace to 2 —3%, whereas the gold ores found in Sweden contain 7—11% arsenic. Small quantities of elemental arsenic have been found in a number of localities. 

Detection limits in ICPMS depend on several factors. Dilution of the sample has a lai e effect. The amount of sample that may be in solution is governed by suppression effects and tolerable levels of dissolved solids. The response curve of the mass spectrometer has a large effect. A typical response curve for an ICPMS instrument shows much greater sensitivity for elements in the middle of the mass range (around 120 amu). Isotopic distribution is an important factor. Elements with more abundant isotopes at useful masses for analysis show lower detection limits. Other factors that affect detection limits include interference (i.e., ambiguity in identification that arises because an elemental isotope has the same mass as a compound molecules that may be present in the system) and ionization potentials. Elements that are not efficiently ionized, such as arsenic, suffer from poorer detection limits. 

None of the three elements is particularly abundant in the earth s crust though several minerals contain them as major constituents. As can be seen from Table 13.1, arsenic occurs about halfway down the elements in order of abundance, grouped with several others near 2 ppm. Antimony has only one-tenth of this abundance and Bi, down by a further factor of 20 or more, is about as unabundant as several of the commoner platinum metals and gold. In common with all the post-transition-element metals. As, Sb and Bi are chalcophiles, i.e. they occur in association with the chalcogens S, Se and Te rather than as oxides and silicates. 

Arsenic and Bi (like P) each have only 1 stable isotope and this occurs with 100% abundance in... 

Six elements are metalloids B, Si, Ge, As, Sb, and Te. Of these, silicon is by far the most abundant, making up over 27% of the Earth s crust, more than any other element except oxygen, hi fact, S1O2 and silicate minerals account for 80% of the atoms near the Earth s surface. Despite its great abundance, silicon was not discovered until 1824, probably because the strong bonds it forms with oxygen makes silicon difficult to isolate. Two much rarer metalloids, antimony (known to the ancients) and arsenic (discovered ca. 1250 ad) were isolated and identified long before silicon. 

Uranium is not a very rare element. It is widely disseminated in nature with estimates of its average abundance in the Earth s crust varying from 2 to 4 ppm, close to that of molybdenum, tungsten, arsenic, and beryllium, but richer than such metals as bismuth, cadmium, mercury, and silver its crustal abundance is 2.7 ppm. The economically usable tenor of uranium ore deposits is about 0.2%, and hence the concentration factor needed to form economic ore deposits is about 750. In contrast, the enrichment factors needed to form usable ore deposits of common metals such as lead and chromium are as high as 3125 and 1750, respectively. 

The principal controls on the microbial reaction rate in our example, then, are biomass and thermodynamic drive (Fig. 33.2). Initially, in the presence of abundant lactate and arsenate, the rate is controlled by the size of the microbial population available to catalyze lactate oxidation. As the population increases, so does reaction rate. Later, as reactants are consumed and products accumulate, the reaction approaches the point at which the energy liberated by its progress is balanced by that needed in the cell to synthesize ATR Reaction rate is governed now by the energy available to drive forward the cellular metabolism, this energy represented by the thermodynamic potential factor Ft over the course of the experiment, the kinetic factors Fd and Fa play minor roles. 

Dissolved arsenic is correlated with ammonia (Fig. 4), consistent with a release mechanism associated with the oxidation of organic carbon. Other chemical data not shown here provide clear evidence of iron, manganese and sulfate reduction and abundant methane in some samples indicates that methanogenesis is also occurring. It is not clear however if arsenic is released primarily by a desorption process associated with reduction of sorbed arsenic or by release after the reductive dissolution of the iron oxide sorbent. Phreeqc analysis shows PC02 between 10"12 and 10"° bars and that high arsenic waters are supersaturated with both siderite and vivianite. 

Generally, inorganic arsenic can occur in the environment in several forms but in natural waters and thus in drinking water, it is mostly found as trivalent arsenite or pentavalent arsenate. Organic arsenic species, abundant in seafood, are very much less harmful to health and are readily eliminated by the body5. 

Cells made from GaAs are more costly than silicon cells, because the production process is not as well developed, and gallium and arsenic are not abundant materials. GaAs cells have been used when very high efficiency is needed regardless of cost such as required in space applications. They were also used in the Sunraycer, a photovoltaic-powered electric car, which won the Pentax World Solar Challenge race for solar-powered vehicles in 1987. It ran the 3000-km from Darwin to Adelaide, Australia at an average day time speed of 66-km per hour. The 1990 race was won by a... 

In theory, the notion had much to recommend it and when the Wolff Committee submitted its report in 1955, a research road map seemed clearly marked. Army Chemical Corps scientists were soon venturing into unexplored territory. Since Edgewood Arsenal had facilities for animal testing, an abundance of chemical expertise and a volunteer program that was nascent but capable of expansion, it was a natural choice as a location for LSD investigative work,... 

Cobalt is the 32nd most abundant element on Earth even though it makes up only 0.003% of the Earth s crust. It is not found in the free metallic state, despite being widely distributed in igneous rocks as minerals. Its two most common mineral ores are cobaltite (CoAsS) and erythrite [Co lAsO l ]. These ores are placed in blast furnaces to produce cobalt arsenide (COjAs), which is then treated with sulfuric acid to remove the arsenic. Finally, the product cobalt tetraoxide (Co O ) is reduced by heat with carbon (Co O + C — 3Co + 2COf resulting in cobalt metal. 

Arsenic is the 53rd most abundant element and is widely distributed in the Earths crust. It occurs naturally in several minerals, but high-grade deposits are rare. Most of the minerals and ores that contain arsenic also contain other metals. Some major sources of arsenic are the minerals orpiment, scherbenkobalt, arsenopyrite, niccohte, realgar, gersdorffite, and smaltite. In addition, most sulfide ores of other metals also contain some arsenic. The three major minerals that produce arsenic are realgar (arsenic monosulfide, AsS), orpiment (arsenic trisidfide, ASjSj), and arsenopyrite (iron arsenosulfide, FeAsS). 

Nickel and vanadium are the most abundant metals found in crude oil. Other metals, metalloids, and nonmetals including aluminum, arsenic, barium, calcium,... 

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