Standard mean ocean water-

SMOW. standard mean ocean water (a standard for oxygen and hydrogen isotopes)... 

Eig. 4. The bulk oxygen isotopic composition of different meteorite classes where (—) is the terrestial fractionation line. The 5 notation refers to the normalized difference between or ratios to those in standard mean ocean water (SMOW) in relative units of parts per thousand. The... 

The amounts of the standard isotopic species and the tracer isotopic species are represented by X and X for the sample and the reference material. The reference substance is chosen arbitrarily, but is a substance that is homogeneous, available in reasonably large amounts, and measurable using standard analytical techniques for measuring isotopes (generally mass spectrometry). For instance, a sample of ocean water known as Standard Mean Ocean Water (SMOW) is used as a reference for and 0. Calcium carbonate from the Peedee sedimentary formation in North Carolina, USA (PDB) is used for C. More information about using carbon isotopes is presented in Chapter 11. 

For water, the standard ratios are approximately the average ratios for modern seawater (these standards are called SMOW, or Standard Mean Ocean Water), so and <5D both equal zero for modern seawater (if a standard other than SMOW is used, this will not be true). S values are typically very small numbers and so are usually multiplied by 1000, in which case the units are "per mil."... 

V-SMOW, Vienna Standard Mean Ocean Water. V-CDT, Vienna Canyon Diablo Troilite. 

SMOW Acronym for Standard Mean Ocean Water, used as a chemical and isotopic reference standard, for example, when studying oxygen isotope ratios. soap A cleaning agent made by the reaction of an oil or fat with an alkali such as soda. 

The 8180 of a sample is the relative deviation in permit of its 180/160 ratio relative to that ratio in a reference material, usually the standard mean ocean water (SMOW)... 

Oxygen isotopes were analyzed using the technique of Clayton and Mayeda (69). Data are presented using the standard 6 notation relative to Standard Mean Ocean Water (SMOW). 

SMOW = Standard Mean Ocean Water IAEA(AgS) = International Atomic Energy Agency (silver sulfide) SMOC = Standard Mean Ocean Chloride... 

Baertschi P (1976) Absolute content of standard mean ocean water. Earth Planet Sci Lett 31 341-344... 

That is, the 0/ 0 ratio in a sample is compared with a standard, and the difference is expressed as per mil (per thousand). The standard for oxygen isotopes is standard mean ocean water (SMOW). The exchange reaction of 0 and O between two minerals is a heterogeneous reaction and may be written as, e.g.. 

These delta values (read delta C-13 , or delta carbon-13 ) are typically given in parts per thousand ( permil , %o). For historical reasons, carbon stable isotopes are reported relative to the PDB (Pee Dee Belemnite, a fossil) or the equivalent VPDB (Vienna PDB) standard. Oxygen and hydrogen stable isotopes are reported relative to SMOW (Standard Mean Ocean Water) or the equivalent VSMOW (Vienna SMOW). The VPDB and VSMOW standards are preferred, not only because the original standards, PDB and SMOW, are no longer available, but also because they imply that the measurements have been calibrated according to international conventions. 

Table 4.2 and similar tables should not be used as the source of isotopic compositions of terrestrial standards for high-precision isotopic measurements. While Table 4.2 gives a good overview of the abundances of the isotopes, the values in the table do not always represent state-of-the-art isotopic measurements. Nor do they attempt to take into account the isotopic fractionations that occur in terrestrial materials. Typically, an isotope system that has been measured for many years has a convention about how isotopic ratios are reported. For example, oxygen isotopic compositions are typically reported relative to the Vienna determination of Standard Mean Ocean Water... 

Oxygen isotopic compositions for bulk chondrites, after Clayton (2004). By convention, 170/160 and 180/160 ratios are plotted as deviations from the composition of standard mean ocean water (SMOW) in units of parts per thousand (permil). The 8 values are calculated as follows S170 = [((170/160)sampie/(170/160)SMOw)-1] x 1000, and similarly for S180. 

Oxygen isotopic compositions (relative to standard mean ocean water, SMOW) of several mineral grains in three Stardust particles, each grain denoted by a separate symbol. Open circles are from a CAI comet particle. After McKeegan et al. (2006). 

Various isotope standards are used for reporting isotopic compositions the composition of each of the standards has been defined as 0 per mil. Oxygen and hydrogen isotopic compositions are commonly reported relative to standard mean ocean water (SMOW or V-SMOW) (17). 

For hydrogen Standard mean ocean water (SMOW) D/H = 0.0001557... 

Oxygen isotopes have been the most thoroughly studied isotopes in carbonate mineral systems. There are three stable isotopes of oxygen 160 = 99.763%, 170 = 0.0375% and 180 = 0.1995% (Garlick, 1969). The fractionation of 180 relative to 160 is commonly measured and reported as the value of 8180 relative to a standard. Two standards have been widely used in reporting 8180 values. The most common one in general usage now is "SMOW," which stands for standard mean ocean water. 

---