Parts per thousand, ppt

Marecek and colleagues developed a new electrochemical method for the rapid quantitative analysis of the antibiotic monensin in the fermentation vats used during its production. The standard method for the analysis, which is based on a test for microbiological activity, is both difficult and time-consuming. As part of the study, samples taken at different times from a fermentation production vat were analyzed for the concentration of monensin using both the electrochemical and microbiological procedures. The results, in parts per thousand (ppt), are reported in the following table. 

Ketkar and co-workers developed a new analytical method for measuring trace levels of atmospheric gases.The analysis of a sample containing 40.0 parts per thousand (ppt) 2-chloroethylsulfide yielded the following results... 

For measurement of the oaks we used, per force, a mass spectrometer of somewhat low accuracy, and achieved the accuracy to demonstrate that trees are thermometers by making many measurements on each sample. On the tree sequences which we measured later, we used high precision spectrometers with accuracies of 0.1 parts per thousand (ppt) for 180/160 and 13C/12C, and 2 ppt for D/H. The measurements are expressed in terms of 8D and 6 g. 

All three of your titrations should agree to within at least 0.05 mL in order to be acceptable. This would mean a parts per thousand (ppt) relative standard deviation of less than approximately 2.5 ppt. If they do not agree in this manner, more titrations must be performed until you have three good answers to rely on or until you have a precision satisfactory to your instructor. 

The error thus obtained is invariably stated with regard to the actual size of the measured quantity i. e., either in percent (%) or in parts per thousand (ppt). Therefore, the relative error is given by ... 

Multiplying the RSD by 1000 gives the relative parts per thousand (ppt) standard deviation ... 

Numerous other options exist for specifying a concentration common ones are parts per thousand (ppt or %o), parts per million (ppm), or parts per billion (ppb). For the soil and air cases just mentioned, ppm on a mass basis is numerically equal to milligrams (mg) of chemical per kilogram (kg) of soil or air. Parts per million is also sometimes used on a volume basis. This may be inferred from context or made clear by the term ppm(v) 1 ppm(v) of helium in air would correspond to 1 ml of helium in 1000 liters (1 m3) of air. For water, the density of which is approximately 1 g/cm3, parts per million corresponds to milligrams of chemical per liter of water (mg/liter) in dilute solutions. 

Salinity is presently determined by measuring the conductance of seawater by using a salinometer. The modem definition of salinity uses the practical salinity scale, which replaces the chlorinity-salinity relationship with a definition based on a conductivity ratio (Millero, 1996). A seawater sample of salinity S= 35 has a conductivity equal to that of a KCl solution containing a mass of 32.435 6g KCl in 1 kg of solution at 15 °C and 1 atm pressure. No units are necessary on the practical salinity scale however, in practice, one often sees parts per thousand, ppt, or the abbreviation psu. New salinometers using this method are capable of extremely high precision so that the salinity ratio can be determined to 1 part in 40 000. At a typical salinity near 35 this procedure enables salinities to be determined to an accuracy of 35.000 0.001. This is much better than most chemical titrations, which, at best, achieve routine accuracy of 0.5 parts per thousand. 

Relative error is also expressed in parts per thousand (ppt). For example, the relative error for the mean of the data in Figure 5-1 is... 

In Table 20.4, the abbreviation psu, short for practical salinity unit, indicates salinity expressed in the Practical Salinity Scale of 1978 (PSS-78) as a dimensionless quantity. The term psu is not an official unit (Unesco, 1985 Siedler, 1998) but is in widespread use and is particularly helpful to distinguish, say, a given salinity value from absolute salinity in g/kg. Before 1978, salinity was computed from chlorinity, CL by the Cox scale, 5= 1,80655 xCZ (Mamayev et al, 1991), The recommended numerical conversion factor between the PSS-78 salinity and the Cox salinity is 1, Cox salinity is usually expressed in parts per thousand, ppt, %o, or g/kg. None the less, it is lower by about 0.5% than the absolute salinity of seawater in grams of dissolved substance per kilogram of seawater, which in turn is not exactly known but can be estimated sufficiently well (Millero et al., 2008), see Section 20.2.1. 

An ecotoxicological investigation of the Sk-agerrak area off the Swedish coast was undertaken in 1992 (Granbom, 1996). Analysis of sediment samples taken in the area where ships loaded with chemical agents and weapons were scuttled showed low levels of HD, up to 190 parts per thousand (ppt). 

Trace concentrations are usually given in smaller units, such as parts per thousand (ppt, %o), parts per million (ppm), or parts per billion (ppb). These are calculated in a maimer similar to parts per hundred (%) ... 

Chlorine is the most abnndant of the halogens having a concentration of 19.87 parts per thousand (ppt) by weight in seawater and an average of 0.17 ppt in Earth s crust. It is produced commercially by electrolysis of seawater and brines. Sodinm chloride (NaCl), or common table salt, can be obtained from seaside evaporation pools or mined from undergronnd deposits. 

Few investigations on arsenite oxidation in the marine environment have been published (15,16). Andreae (15) found lower concentrations of arsenite in surface water samples than in deep water samples from the Pacific Ocean. He found arsenite concentrations in surface waters in the range of 0.15-0.01 parts per billion (ppb), whereas below 400 m he found the average concentration to be 7.9 parts per thousand (ppt). He attributed this difference in concentration between surface and deep water to biological uptake and transport. Andreae s measurement of an observed ratio of As(V)/As(III) in deep water of 2.5 x 10 indicated to him a thermodynamic disequilibrium, because at equilibrium the expected ratio was 10 based on a pE of 8.0 and standard activity coefficients of the two arsenic species in seawater. The observed ratio would be expected at a pE of 2.0. Andreae... 

It should also be noted that cyanide toxicity to fish increases with any reduction in dissolved oxygen below 100%. The presence of zinc and ammonia results in a greater than additive increase in toxicity (Moran, 1998). Fish are about 1000 times more sensitive to cyanide than are humans. Even if the levels are less than lethal, there are still toxic effects, including physiological and pathological responses. For example, cyanide can reduce swimming ability, which will leave fish more vulnerable to predators, or interfere with reproductive capacity, which can lead to deformed offspring. It should be noted that cyanide toxicity in fish increases three- fold with a 12°C decrease in temperature. As well, 17 parts per thousand (ppt) of chloride ion or 8.8 ppt (Moran, 1998) is known to decrease the survival time (UNEP/ OCHA, 2000). 

The mass spectrum generated with an ICP-MS is extremely simple (see Figure 1.1). Each elemental isotope appears at a different mass e.g. Al would appear at 27 amu) with a peak intensity directly proportional to the initial concentration of that isotope in the sample solution. A large number of elements ranging from lithium at low mass to uranium at high mass are simultaneously analysed, typically within 1-3 minutes. With ICP-MS, a wide range of elements in concentration levels from parts per thousand (ppt) to ppm level can be measured in a single analysis. 

An ocean is a major body of saline water, and a principal component of our planet s remarkable hydrosphere. Approximately 71% of the Earth s surface (an area of 361 million km (139 million mi ) is covered by ocean, a continuous body of seawater that is customarily divided into several principal named oceans and smaller named seas. More than half of this area is deeper than 3,000 m (9,842 ft). Average oceanic salinity is around 35 parts per thousand (ppt) (3.5%), and nearly all seawater has a salinity in the range of 31-38 ppt. Interestingly, the place furthest from the world-ocean—that is, the official pole of inaccessibility is in Asia (46° 17 N 86° 40 E), according to Garcia-Castellanos and Lombardo (2007). The volume of Earth s ocean is approximately 1.3 billion km (0.312 billion mi ), and its average depth is 3,790 m (12,434 ft). The vast volume of the deep ocean (anything below 200 m, 656 ft) covers about 66% of our Earth s surface. 

Mass fraction (dimensionless) is commonly used and is suitable for either solvent or solute. Volume fraction (dimensionless) is commonly used for gaseous solutions. Percent, % (dimensionless), should actually be called parts per hundred (pph) and is widely used in everyday life. Parts per million, ppm (dimensionless), is usually used for solute, which is in a very small amount. Parts per thousand, ppt (dimensionless), is usually used to define salinity of sea water. 

Commonly, relative uncertainty is expressed in parts per thousand (ppt) a value given by multiplying the result of the above equation by 1000. In the example of the volume of 36.27 mL delivered by a buret as discussed above, the relative uncertainty in parts per thousand is... 

The mineral/salt content of the water is usually measured by the water quality parameter total dissolved solids (TDS), in milligrams per liter (mg/L) or parts per thousand (ppt). Natural water sources such as sea, bay, and ocean waters usually have TDS concentration higher than 15,000 mg/L. Seawater TDS and temperature are the two key source water quality parameters that have the most significant influence on the cost of seawater desalination. Table 3.2 presents typical TDS concentration and temperature for various seawater sources. 

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