Isotopes composition of common

Although the predominant source of arsenic and metals to most soils and sediments in New England is sulfide-rich rock, the extensive application of arsenical pesticides and herbicides (lead arsenate, calcium arsenate, and sodium arsenate, and others) on apple, blueberry, and potato fields may have been a possible anthropogenic source of arsenic and lead. The main objective of this study was to determine the lead isotopic compositions of commonly used pesticides, such as lead arsenate, sodium metarsenite, and calcium arsenate, in order to assist in future isotopic comparisons and to better characterize this anthropogenic source of Pb. The pesticides plot along a linear trend in isotope diagrams, for example, in values of... 

Ayuso, R., Foley, N., Robinson, G., Jr., Wandless, G., and Dillingham, J. (2004b). Lead isotopic compositions of common arsenical pesticides used in New England. United States Geological Survey. Open-file report 2004-1342, 14. [URL http //pubs.usgs.gov/of/2004/1342/]. 

Every lead contains a measurable quantity of lead-204 and can be represented by a three-dimensional diagram of the variables a, P, and y. There are large variations in the isotopic composition of common lead from different sources. Understanding this was initially difficult because earlier observations impHed that common lead had a constant average atomic mass. It soon became clear that this supposed constancy was fortuitous and reflected the fact that the increase in the [ ° Pb/ ° Pb] atomic ratio is often accompanied by a comparable rise in the [208pb/204pb] Efforts were made to construct quantitative models for the isotopic... 

The composition of the Earth was determined both by the chemical composition of the solar nebula, from which the sun and planets formed, and by the nature of the physical processes that concentrated materials to form planets. The bulk elemental and isotopic composition of the nebula is believed, or usually assumed to be identical to that of the sun. The few exceptions to this include elements and isotopes such as lithium and deuterium that are destroyed in the bulk of the sun s interior by nuclear reactions. The composition of the sun as determined by optical spectroscopy is similar to the majority of stars in our galaxy, and accordingly the relative abundances of the elements in the sun are referred to as "cosmic abundances." Although the cosmic abundance pattern is commonly seen in other stars there are dramatic exceptions, such as stars composed of iron or solid nuclear matter, as in the case with neutron stars. The... 

Water is a mixture of varying isotopic composition (Franks, 2000). In addition to the two most common isotopes, 160 and there are two stable oxygen isotopes (170, lsO), one stable hydrogen isotope (2H, deuterium), and one radioactive hydrogen isotope (3H, tritium, half-life = 12.6 years). Water also contains low concentrations of hydronium (H30+) and hydroxide ions (OH-) and their isotopic variants. In total, water consists of more than 33 chemical variants of HOH however, these variants occur in relatively minor amounts (Fennema, 1996). Table II gives the natural abundance isotopic composition of the four major water species. 

Similar equations can be written for Pb and Pb using their appropriate radioactive parents and decay constants. If t = 0 is taken to represent the time of the formation of the Earth s crust, then these three equations describe the trajectory of the isotopic composition of terrestrial lead from that time. If T is the time elapsed since the formation of the Earth, (i.e., the age of the Earth), and tm is the time before present at which the lead minerals were formed, then, using the assumptions of the Holmes Houtermans model given above, the isotopic composition of a common lead deposit formed tm years ago is given as follows ... 

Mansuy et al. [97] investigated the use of GC-C-IRMS as a complimentary correlation technique to GC and GC-MS, particularly for spilled crude oils and hydrocarbon samples that have undergone extensive weathering. In their study, a variety of oils and refined hydrocarbon products, weathered both artificially and naturally, were analyzed by GC, GC-MS, and GC-C-IRMS. The authors reported that in case of samples which have lost their more volatile n-alkanes as a result of weathering, the isotopic compositions of the individual compounds were not found to be extensively affected. Hence, GC-C-IRMS was shown to be useful for correlation of refined products dominated by n-alkanes in the C10-C20 region and containing none of the biomarkers more commonly used for source correlation purposes. For extensively weathered crude oils which have lost all of their n-alkanes,it has been demonstrated that isolation and pyrolysis of the asphaltenes followed by GC-C-IRMS of the individual pyrolysis products can be used for correlation purposes with their unaltered counterparts [97]. 

In addition to providing the means for calculating the isotopic compositions of ancient fluids based on analysis of minerals, mineral-fluid isotope fractionation factors provide an opportunity to combine fractionation factors when there is a common substance such as water. A fundamental strategy for compiling databases for isotopic fractionation factors is to reference such factors to a common substance (e.g., Friedman and O Neil 1977). For example, the quartz-water fractionation factor may be combined with the calcite-water fractionation factor to obtain the quartz-calcite fractionation factor at some temperature. It is now recognized, however, that the isotopic activity ratio of water in a number of experimental determinations of mineral-fluid fractionation factors has been variable, in part due to dissolution of... 

Figure 4. Efficiency of ionization as described by Saha s law as a function of the ionization potential for a representative electronic density of 10 m". The ionization potentials of some elements for which the isotopic composition is commonly analyzed are shown at the top.

Given the difference in Li concentration between MORE and sea floor altered MORE (which are commonly >12 ppm Stoffyn-Egli and Mackenzie 1984 Chan et al. 1992), small contributions of altered oceanic crust could have a substantial impact on the measured Li isotopic composition of sea floor lavas. Indeed, two basalts that were petrographically fresh were excluded from consideration as pristine MORE by Chan et al. (1992) by virtue of slightly higher KjO contents (>0.13 wt. % Fig. 5). Within the global MORE data set no correlation between KjO and 5Ei is observed, suggesting that the variations in Li isotopes in MORE are not controlled primarily by near-surface contamination. 

Isotopic abundances are listed either as their sum being 100 % or with the abundance of the most abundant isotope normalized to 100 %. The latter is used throughout this book because this is consistent with the custom of reporting mass spectra normalized to the base peak (Chap. 1). The isotopic classifications and isotopic compositions of some common elements are listed below (Table 3.1). A full table of the elements is included in the Appendix. 

Table 3.1. Isotopic classifications and isotopic compositions of some common elements lUPAC 2001 [4,5]...

Despite the close association of intnisions with many ore deposits, there is still debate about the extent to which magmas contribute water and metals to ore-forming fluids. Many early studies of the stable isotope composition of hydrothermal minerals indicated a dominance of meteoric water (Taylor 1974), more recent studies show that magmatic fluids are commonly present, but that their isotopic compositions may be masked or erased during later events such as the influx of meteoric waters (Rye 1993 Hedenquist and Lowenstem 1994). 

John SG, Park JG, Zhang Z, Boyle EA (2007b) The isotopic composition of some common forms of anthropogenic zinc. Chem Geol 245 61-69... 

There are two basic ways to apply the 87Rb-87Sr technique to natural samples. The original method is to simply measure the isotopic composition of strontium and the abundance of rubidium in a rock and then calculate a date. If the rock contains no common strontium, a date can be calculated from ... 

The common-lead method looks at the isotopic evolution of lead in systems with U/Pb and Th/Pb ratios similar to or less than the ratios in bulk solar system materials. The original formulation, by Holmes and Houtermans, is a single stage model that accounts for the isotopic composition of any sample of common lead in terms of primordial lead plus radiogenic lead produced in the source up to the time that lead was separated from uranium and thorium. Multistage models that more accurately describe the evolution of natural systems have been developed. The common-lead method is used in cosmochemistry primarily to study the time of differentiation and reservoir evolution in differentiated bodies... 

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