Abundance Of Zn Research Articles

Doping limits in ZnSe

We explore doping problems in p-type ZnSe using ab initio total-energy calculations. Our method determines the formation energies of native point defects and of acceptor dopants as a function of the relative abundance of Zn, Se and the dopant atoms, resulting in a map of the concentrations of defects and dopants over the entire thermodynamically allowed range of conditions. For native point defects, which were often assumed to compensate the doping of ZnSe, we show that their concentrations are negligibly small over most of the range of allowed stoichiometry. For a ZnSe acceptor-doped with Li Zn or Na Zn, we find that compensation by Li i and Na i donors is possible, but can be avoided in a sufficiently Se-rich environment. The most stringent limits on acceptor doping of ZnSe come from the solubility limits of the three dopants. Our calculations show that Na Zn has a very low solubility limit, with a much higher limit for Li Zn, and the highest for N Se.

Heavy metals and organic carbon in sediments from the Tuy River basin, Venezuela

The Tuy River basin, located in north-central Venezuela with an annual average temperature of 27°C and precipitation of 140 cm, was selected to conduct a geochemical study of bottom sediments, with the object of establishing the natural and human influences in the abundance and distribution of Fe, Mn, Cr, Co, Cu, Ni, Pb, Zn and organic carbon. The basin is lithologically divided into two sub-basins, north and south. The north sub-basin drains a iow-grade metasedimentary terrain with a population density of 800 persons km(-2) and approximateiy 600 industrial sites, while the south sub-basin in underlain by metavolcanic and ultramafic rocks, with a population density of less than 10 persons km(-2).Stream bottom sediment samples (150) were collected during the years of 1979-1986 in 16 unpolluted sites and 13 polluted sites. The sediments were air dried at room temperature and sieved through a 120 stainless steel mesh (125 μm). Samples of grain size smaller than 125 μm were analysed, the heavy metals being determined by atomic absorption spectrometry and the organic carbon (Corg) by dry combustion.The higher concentrations of heavy metals and organic carbon found in the pristine areas were in the south sub-basin, especially in those areas with higher annual precipitation and tropical forest. This indicated that the metavolcanic and ultramafic rocks yield higher concentrations of heavy metals than the metasedimentary rocks. It was also noted that the higher concentrations of Cr and Ni are associated with the ultramafic rocks. The results obtained from the sediment samples collected in the polluted sites showed that the elements Pb, Zn and Corg are enriched up to 4 times as a result of ail the human activities taking place in the basin. Organic carbon is an excellent indicator of domestic wastewater, Pb and Zn are good indicators of the automotive traffic and industrial effluents. The concentrations of each heavy metal did not show any significant correlation with grain size fractions; however, the concentration of organic carbon did show a negative correlation with grain size. The lithological, climatic and vegetation influence in the abundance of heavy metals and organic carbon in stream sediments clearly indicates the necessity of establishing background levels for the area under study when carrying out studies in environmental geochemistry.

Copper and zinc balance in soils, rice plants and aquatic systems in an area along the fuchu precipice line, Tokyo, Japan

The abundance and distribution of Cu and Zn in spring water, irrigation water and sediment from the Fuchu Irrigation Canals, ground water for irrigation, rice plants and paddy soil at Tokyo University of Agriculture and Technology's Hommachi Farm were studied. The balance of Cu and Zn in the paddy field at the Hommachi Farm was investigated. The discharge of Cu and Zn influenced by human activities was observed in sediment of the Fuchu Irrigation Canal, and rice plants and paddy soil at the Hommachi Farm where irrigation water from the Fuchu Irrigation Canal was used until 1970. From Cu and Zn balance calculated, several hundred years are needed to decrease by half the present level of these metals at the Hommachi Farm.

The abundance of zinc in Hg-Mn stars

view Abstract Citations (19) References (30) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Abundance of Zinc in Hg-Mn Stars Sadakane, Kozo ; Jugaku, Jun ; Takada-Hidai, Masahide Abstract The resonance line of singly ionized zinc (Zn II) at 2062.00 A is quantitatively analyzed, and the abundances of Zn in atmospheres of early-type stars have been determined for the first time. The line is analyzed in IUE spectra of six reference (normal) stars between spectral types B5 and A0 and of 23 Hg-Mn stars. The abundances of Zn in the reference stars coincide with the solar value within + or - 0.5 dex. Zn is overabundant in five Hg-Mn stars, while it is underabundant by at least 1.0 dex in 12 of them. The Hg-Mn stars Phi Her and Mu Lep show the strongest and the weakest Zn II lines, respectively, and the abundance of Zn in Phi Her is at least 100,000 times higher than that in Mu Lep. No clear dependence of the Zn abundance on the effective temperature is found. There also is no clear correlation between the degree of abundance anomaly of Zn and those of the two neighboring elements Cu and Ga. A definite nonsolar abundance pattern, excesses of both Cu and Ga over Zn, is found for six Hg-Mn stars. Publication: The Astrophysical Journal Pub Date: February 1988 DOI: 10.1086/166048 Bibcode: 1988ApJ...325..776S Keywords: Abundance; Manganese; Mercury (Metal); Metallic Stars; Stellar Spectra; Zinc; A Stars; Early Stars; Iue; Peculiar Stars; Resonance Lines; Stellar Atmospheres; Astrophysics; STARS: ABUNDANCES; STARS: PECULIAR A; ULTRAVIOLET: SPECTRA full text sources ADS | data products SIMBAD (29) MAST (1) INES (1)

The stable carbon isotopes in enstatite chondrites and Cumberland Falls

The carbon isotopic composition of the total carbon in the enstatite chondrites Indarch, Abee, St. Marks, Pillistfer, Hvittis and Daniel's Kuil and the enstatite achondrite Cumberland Falls has been measured. The empirical relationhip between carbon isotopic composition and total carbon content is distinct from that of carbonaceous and ordinary chondrites. Within the enstatite chondrite group the average 13C content increases with petrographic type: E4 < E5 < E6. Daniel's Kuil shows the largest 13C enrichment in the bulk carbon of any meteorite. The carbon isotopic composition is most clearly correlated with the abundance of the elements Zn, Cd and In. Insofar as these elements may hold the key to the understanding of enstatite chondrites, more detailed combined carbon isotope and trace element studies of these meteorites will play an important role in the deciphering of their history.

A mercury vapor survey in an area of thick transported overburden near Shanghai, China

Experimental surveys of Hg vapor in alluvium cover (up to 180 m thick) over a skarn copper deposit in the vicinity of Shanghai have shown encouraging results. Abundance and zoning of Cu, Pb, Zn, Ag, Mo, Mn, Sn, W, Ba, Bi, Co and Cl in soils and drill cores were studied for comparison. A distinct soil-gas Hg anomaly was discovered over the deposit. Repeated surveys carried out in different seasons during 1978 and 1979 show little variation in shape, dimension and intensity of the Hg anomalies. High soil-gas Hg values appear to be closely related to contacts, faults and fracture zones. Element zoning is well defined by the dispersion of Hg, Cu, Ag, etc. The zoning index of Hg and other elements shows that Hg is a typical front element. Thermo-release curves of Hg obtained by heating rock, ore and alluvium samples indicate that Hg has three forms of occurrence: easily volatilized Hg, chloride Hg, and sulphide Hg. Mercury chloride and volatile Hg represent the predominant phase in alluvium samples.

The abundance of cadmium and zinc in meteorites

A stable isotope dilution technique using solid source mass spectrometry has been used to accurately determine Cd and Zn in a wide range of materials. The abundance of Cd has been determined in 19 iron, 28 stone and 1 stony-iron meteorites, together with a number of other samples. The abundance of Zn has also been determined for most of these samples. This has enabled the relationship between Cd and Zn to be examined in iron and stone meteorites. The abundance pattern of Zn in iron meteorites supports the existence of chemical groups.

Fractionation of chlorine, germanium, and zinc in chondritic meteorites

Thirty-nine ordinary chondrites, five enstatite chondrites, and four carbonaceous chondrites have been analyzed for Cl, Ge, and Zn. These elements are shown to be fractionated among the carbonaceous, enstatite, and ordinary chondrites in a pattern similar to that of Pb, Bi, Tl, I, Te, and Hg as reported previously. The patterns of fractionation of Cl, Zn, and Ge however, differ among themselves and from the heavy chalcophile elements. Of the carbonaceous chondrites, only Orgueil is enriched in Zn and Ge, whereas all are enriched in Cl; in the enstatite chondrites only Indarch is enriched in Cl and Zn, and all are uniformly enriched in Ge. The most notable finding is the fractionation of Zn and Ge within the carbonaceous chondrite group. Of these meteorites, only Orgueil has the solar abundance of Zn and Ge. These data suggest that the fractionated elements cannot be explained by simple mechanisms; they further indicate that the group 1 carbonaceous chondrites most closery resemble the primitive material from which all meteorites evolved.

Untersuchungen zur Geochemie des Zinks

A spectrochemical method for the determination down to 10 −4% Zn in numerous rocks and minerals has been developed. By means of fractionated distillation the separation of Zn occurring in silicates and spinells from Zn in ZnS-bearing rocks has been made possible. The result of 130 analyses confirms the figures given by Clarke-Washington (1924) (0.004%Zn) and the unpublished results by V.M. Goldschmidt (1938) (≤ 0,004% Zn) for the abundance of Zn in the lithosphere.