Measurement, atmospheric gases

FTIR Fourier transform infrared spectroscopy has been used for many years to measure atmospheric gases. Because FTIR has become such a common analytical method, we do not describe the technique itself here but rather refer the reader to several excellent books and articles on the subject (e.g., see Griffiths and de Haseth, 1986 Wayne, 1987). For reviews of some atmospheric applications, see Tuazon etal. (1978,1980), Marshall et al. (1994), and Hanst and Hanst (1994). 

A device commonly used to measure atmospheric pressure is the mercury barometer (Figure 5.1), first constructed by Evangelista Torricelli in the seventeenth century. This consists of a closed gas tube filled with mercury inverted over a pool of mercury. The pressure exerted by the mercury column exactly equals that of the atmosphere. Hence the height of the column is a measure of the atmospheric pressure. At or near sea level, it typically varies from 740 to 760 mm, depending on weather conditions. 

In fluid reservoirs like fhe afmosphere or the ocean, the turnover time of a tracer is also related to the spatial and temporal variability of ifs concentration within the reservoir a long turnover time corresponds to a small variability and vice versa (Junge, 1974 Hamrud, 1983). Figure 4-2 shows a plot of measured trace gas variability in the atmosphere versus turnover time estimated by applying budget considerations as indicated by Equation (1). An inverse relation is obvious, but the scatter in the data... 

Battle, M., Bender, M., Dowers, T. et al. (1996). Atmospheric gas concentrations over the past century measured in air from fim at the South Pole. Nature 383,231-235. 

Flow-Type Ionization Chamber (PFC). The Flow -Type Ionization Chamber Method (PFC) has been developed for continuously measuring radon gas in the atmospheric air. The detail of the device has been described elsewhere (Shimo, 1985). Briefly, measurements are continuously carried out by drawing air through the detector at 1.0 2.0 /min. The ionization currentdue to alpha particles from radon and its daughters is detected with a vibrating reed electrometer (VRE) in the same manner as the DSC. The sensitivity... 

The elements whose isotopes are routinely measured with gas inlet mass spectrometers are carbon (12C and 13C, but not 14C), oxygen (160, 170, l80), hydrogen ( H, 2H, but not 3H), nitrogen (14N and 1SN) and sulphur (32S, 33S, 34). Stable isotopes of H, C, N, O, and S occur naturally throughout atmosphere, hydrosphere, lithosphere, and biosphere. They are atoms of the same elements with a different mass. Each element has a dominant light isotope with the nominal atomic weight (I2C, 160,14N, 32S, and H) and one or two heavy isotopes (l3C, nO, 180, 15N, 33S, 34S, and, 2H) with a natural abundance of a few percent or less Table 1). 

The estimation of the solubility at one atmosphere gas pressure was made by one of two procedures. If the solubility was measured at only one pressure at a given temperature, Henry s law was used, and the inverse of Henry s constant was calculated as X2(1 atm) = 1/H2 i = X2/P2. The procedure works well at moderate gas partial pressures, but at higher gas partial pressures of 25 atm or more the procedure often appears to give low solubility values. However, it is the only practical procedure when the solubility was measured at only one pressure. When solubility values were measured at several pressures at a given temperature, the data were fitted by a linear regression to an empirical function X2/P2 = a + bP2 to obtain the unit pressure solubility value. In some cases a quadratic rather than a linear function of pressure was used. 

The aim of dispersion models is the prediction of atmospheric dilution of pollutants in order to prevent or avoid nuisance. Established dispersion models, designed for the large scale of industrial air pollution have to be modified to the small scale of agricultural pollutions. An experimental setup is described to measure atmospheric dilution of tracer gas under agricultural conditions. The experimental results deliver the data base to identify the parameters of the models, For undisturbed airflow modified Gaussian models are applicable. For the consideration of obstacles more sophisticated models are necessary,... 

With emission source chemical signatures and corresponding aerosol or rainwater sample measurements PLS can be used Co calculate a chemical element mass balance (CEB). Exact emission profiles for the copper smelter and for a power plant located further upwind were not available for calculation of source contributions to Western Washington rainwater composition. This type of calculation Is more difficult for rainwater Chan for aerosol samples due Co atmospheric gas to particle conversion of sulfur and nitrogen species and due Co variations In scavenging efficiencies among species. Gatz (14) has applied Che CEB to rainwater samples and discussed Che effect of variable solubility on the evaluation of Che soil or road dust factor. 

The formation and fate of peroxyacyl nitrates, RC(0)00N02, were discussed in Chapter 6.1. These compounds are almost universally measured using gas chromatography with electron capture detection (GC-ECD), although a luminol chemiluminescence detector has also been used in which PAN is thermally decomposed to N02 at the end of the column and the N02 measured (Burkhardt et al., 1988 Blanchard et al., 1990 Gaffney et al., 1998). In polluted atmospheres where the concentrations are higher, FTIR has also been used (Table 11.2). For a summary of methods, see reviews by Gaffney et al. (1989) and Kleindienst (1994). 

Helium-3 is a decay product of radioactive tritium (3H, half-life = 12.44 years) that has been produced by nuclear bombs as well as naturally by cosmic rays in the upper atmosphere. Because virtually all 3He atoms escape from the surface ocean to the atmosphere, the 3He/tritium ratio in subsurface seawater samples indicates the time since the water s last exposure to the atmosphere. Both 3He and tritium are measured by gas mass spectrometry. Alternatively, tritium may be measured by gas counting with a detection limit of 0.05 to 0.08 tritium unit, where 1 tritium unit represents a 3H/H ratio of lxl0 18. A degassed water sample is sealed and stored for several months to allow the decay product 3He to accumulate in the container. The amount of 3He is then measured by mass spectrometry, yielding a detection limit of 0.001 to 0.003 tritium unit when 400-gram water samples are used. With this technique, the time since a water mass left the surface can be determined within a range from several months to 30 years. 

Gundel, L.A. and D.A. Lane. 1999. Sorbent-coated diffusion denuders for direct measurement of gas/particle partition by semivolatile organic compounds. In Lane, D.A., Ed., Gas and Particle Measurements of Atmospheric Organic Compounds. Gordon and Breach Science Publishers, Amsterdam, pp. 287-332. 

Hiyagon and Ozima (1986) employed a laboratory approach of measuring crystal-melt partition coefficients. They measured noble gas concentration in olivine crystals and basalt melts, which were synthesized at 1370-1300°C under an atmospheric pressure, and also at 1360-1050°C under high pressure (0.2-1.5 GPa), of noble gas mixture. From these experimental results, they obtained ranges for noble gas partition coefficients XHe = 0.07, XNe = 0.006-0.08, KM = 0.05-0.15, KXe = 0.3. These partition coefficients are much larger than the values obtained by Marty and Lussiez (1993) and also these of common incompatible elements such as U (-0.002) or K (0.0002 - 0.008) between olivine and basalt melt (e.g. Henderson, 1982). 

An important parameter used to quantify dry deposition processes is the velocity of deposition (Kg) (Chamberlain, 1953). Vg is defined as the downward flux of aerosol or gas to a vegetation or soil surface, normalised to the ambient atmospheric gas or aerosol concentration above that surface. In the case of radionuclide deposition processes flux and concentration are, respectively, measured in units of radioactivity per unit area and volume, hence... 

When the water level inside the tube is the same as the water level outside the tube, this is an indicator that the gas pressure inside the tube is equal to the air pressure outside the tube. Because in your lab there is no way to directly measure the gas pressure inside the tube, this allows you to determine the pressure by direct comparison to atmospheric pressure. Atmospheric pressure can therefore be substituted into the gas equation. 

The anesthetics are introduced from conventional vaporizers. For the determination of MAC, an initial concentration is used that permits movement of the rats in response to noxious stimulation. A tail clamp is applied for 1 minor until the animal moves, and the anesthetic partial pressure is measured by gas chromatography. If the animal moves, the partial pressure is increased by 0.2% or 0.3% atmospheres. After equilibration for 30 min, the tail clamp is applied again and the anesthetic partial pressure measured by gas chromatography. This procedure is repeated until the partial pressures bracketing movement-nonmovement are determined for each rat. 

Atmospheric plasma research was originally stimulated by the interest in radio wave propagation and therefore was focussed on the ionosphere. Thus, the early in situ ion composition measurements were made in the ionosphere at altitudes above about 100 km using rocket-borne spectrometers [15, 16, 17]. Below 100 km, the atmospheric gas pressure becomes so large that mass spectrometers have to be pumped which represents a major barrier for extending in situ ion composition measurements downwards into the mesosphere. Such measurements became technically feasible only with the advent of compact high speed cryopumps which could be used on rockets. 

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