Atmospheric measurements

Fig. 4-1. The same atmosphere measured by (a) a rapid-response irvstrument and by sampling and analytical procedures that integrate the concentration arriving at the receptor over a time period of (b) 15 min, (c) 1 hr, and (d) 6 hr.

Long Path Measurement an atmospheric measurement process that is made over distances in excess of a few hundred meters. 

Applications The differential optical absorption spectrometer has been used to monitor concentrations of gases or intermediate compounds such as SO, NO, O5, HCHO, HNO, CS, NO, and OH in the atmosphere.In atmospheric measurements with open paths of 100 to 1000 m, a detection limit of about 1 ppb can be achieved. In the emission measurements, the path length across the duct or the plume can range in meters. 

Corrosion rates in normal industrial atmospheres measured as loss of weight over a period are extremely uniform among the various alloys. Table 4.19, last column, gives the corrosion rates (in g m d" ) for a number of alloys determined at Clifton Junction in recent years. The highest value recorded (0-4 g m d ) is equivalent to a rate of penetration of 0-076 mm/y, which is appreciably less than that of mild steel. 

A detailed analysis of the atmospheric measurements over Antarctica by Anderson et al. (19) indicates that the cycle comprising reactions 17 -19 (the chlorine peroxide cycle) accounts for about 75% of the observed ozone depletion, and reactions 21 - 23 account for the rest. While a clear overall picture of polar ozone depletion is emerging, much remains to be learned. For example, the physical chemistry of the acid ices that constitute polar stratospheric clouds needs to be better understood before reliable predictions can be made of future ozone depletion, particularly at northern latitudes, where the chemical changes are more subtle and occur over a larger geographical area. 

Figure 1. Atmospheric methane increases over the last 300 years. Points are annual averages the concentrations before 1960 are from ice core analyses more recent data from atmospheric measurements. From Khalil and Rasmussen (40).

Fig. 11-3 Direct atmospheric measurements of the CO2 concentration (left-hand scale) at Mauna Loa (Hawaii) and the South Pole station (Keeling et al., 1995) together with the concurrently observed decrease in atmospheric oxygen content (right-hand scale) at La Jolla, CA after 1989. (Taken from Heimann (1997) with permission from the Royal Swedish Academy of Sciences.)...

The results for 14C are plotted in Figure 6-3. Again, the response of the atmosphere is quite pronounced. The response of the shallow ocean is less marked, and the deep ocean shows no response at all on this time scale. Radiocarbon ratios are lower in the ocean than in the atmosphere because radioactive decay reduces the 14C ratio. The difference between the steady-state atmosphere and the steady-state values in the oceanic reservoirs is an indication of how much time has elapsed since these masses of water last equilibrated with the atmosphere. Measurements of radiocarbon are an important source of information on the circulation of the deep ocean, and the differences between 13C ratios in the different reservoirs have quite different causes The deep ocean is lighter than the surface ocean because... 

There are a variety of ways to do the calculations. Most of these, however, involve the calculation of the number of moles (n) from the ideal gas equation n = PV/RT. The mass of the vapor sample is calculated from the difference between measurements 1 and 2. The temperature (measurement 3) is converted to kelvin. The pressure (measurement 4) is converted to atmospheres. Measurement 5 is converted to liters. Inserting the various numbers into the ideal gas equation allows you to calculate the number of moles. The molar mass is calculated by dividing the mass of the sample by the moles. 

Singh HB, Salas LJ, Smith A, et al. 1979a. Atmospheric measurements of selected toxic organic chemicals. Report to U.S. Environmental Protection Agency, Environmental Sciences Research Laboratory, Atmospheric Chemistry and Physics Department, Research Triangle Park, NC, by SRI International, Menlo Park, CA, 3-4, 28, 33, 35. 

Whether the prediction scheme is a simple chart, a formula, or a complex numerical procedure, there are three basic elements that must be considered meteorology, source emissions, and atmospheric chemical interactions. Despite the diversity of methodologies available for relating emissions to ambient air quality, there are two basic types of models. Those based on a fundamental description of the physics and chemistry occurring in the atmosphere are classified as a priori approaches. Such methods normally incorporate a mathematical treatment of the meteorological and chemical processes and, in addition, utilize information about the distribution of source emissions. Another class of methods involves the use of a posteriori models in which empirical relationships are deduced from laboratory or atmospheric measurements. These models are usually quite simple and typically bear a close relationship to the actual data upon which they are based. The latter feature is a basic weakness. Because the models do not explicitly quantify the causal phenomena, they cannot be reliably extrapolated beyond the bounds of the data from which they were derived. As a result, a posteriori models are not ideally suited to the task of predicting the impacts of substantial changes in emissions. 

Singh HB, Salas LJ, Shigeishi H. 1981. Atmospheric measurements of selected hazardous organic... 

ISO 11844-3.-Corrosion of metals and alloys. Classification of corrosivity of indoor atmospheres. Measurement of environmental parameters affecting indoor corrosivity. 

Anderson, J. G Free Radicals in the Earth s Atmosphere Measurement and Interpretation, in Ozone Depletion, Greenhouse Gases and Climate Change, National Academy Press, Washington, DC, pp. 56-65, 1989. 

The application of chemiluminescence to atmospheric measurements is reviewed by Navas et al. (1997). 

Mass spectrometry has the potential for being a very powerful analytical technique for atmospheric measurements, and indeed, it has been used for a number of decades in upper atmosphere measurements of ions and neutrals. Viggiano (1993) has reviewed ion chemistry and the application of mass spectrometry to tropospheric and stratospheric measurements through 1993. The first mass spectrometric measurements were made in the upper atmosphere from 64 to 112 km in 1963 (Narcisi and Bailey, 1965), followed by stratospheric measurements in 1977 (Arnold et al., 1977) and, finally, tropospheric measurements in 1983 (Eisele, 1983 Heit-mann and Arnold, 1983). They have also been extended... 

Holland, F., U. Aschmutat, M. HeBling, A. Hofzumahaus, and D. H. Ehhalt, Highly Time Resolved Measurements of OH during POPCORN Using Laser-Induced Fluorescence Spectroscopy, in Atmospheric Measurements during POPCORN—Characterization of the Photochemistry over a Rural Area, pp. 205-225, Kluwer Academic, Dordrecht/Norwell, MA, 1998. 

Schiff, H. I G. I. Mackay, C. Castledine, G. W. Harris, and Q. Tran, Atmospheric Measurements of Nitrogen Dioxide with a Sensitive Luminol Instrument, Water, Air Soil Pollution, 30, 105-114 (1986). 

Schiff, H. I G. I. Mackay, and J. Bechara, The Use of Tunable Diode Laser Absorption Spectroscopy for Atmospheric Measurements, Res. Chem. Intermed., 20, 525-556 (1994a). 

Atmospheric measurements of CIO, BrO, 03, and NzO confirm the importance of reactions (43a)-(45) in the destruction of 03. For example, Anderson et al. (1989) showed that this cycle is the largest contributor to ozone loss in the Antarctic vortex from 14-18 km. 

This understanding of the mechanism of formation of Type I PSCs is consistent with atmospheric measurements. For example, Massie et al. (1997) showed that gas-phase HN03 over Scandinavia in January 1992 decreased as the temperature fell while the volume of... 

Light scattering and absorption techniques have also been used, for example to obtain the index of refraction of the particles and then to compare these atmospheric measurements to laboratory measurements of NAT, NAD, etc. determined in laboratory studies. Adriani and co-workers (1995), for example, using light scattering in the visible, report four types of particles... 

The ratio Fx/FCFC n is the fraction of the compound X that has been dissociated in the stratosphere compared to that of CFC-11, determined from atmospheric measurements. This term is most important at short times, i.e., right after release of the compound, in terms... 

Although not fully fluorinated, HFC-23 (CHF3) also has a long lifetime ( 250 years WMO, 1995) because its reaction with OH is slow, k298 = 2.8 X 10 1(1 cm1 molecule-1 s-1 (DeMore et al., 1997). A major source is the production of HCFC-22 (CHC1F2), where HFC-23 is a byproduct. As the use of HCFC-22 and its atmospheric levels have increased (Fig. 13.6), the levels of HFC-23 would be expected to increase as well, and indeed, this is the case. Oram et al. (1998) reported the first atmospheric measurements of this compound at Cape Grim, Australia. HFC-23 increased from 2 ppt in 1978 to 11 ppt in 1995, with a growth rate of 5% per year in 1995. 

After the apparatus has again reached room temperature, bring the pressure in it to atmospheric. Measure the volume of the water displaced from the apparatus by the evolved hydrogen. Write the equation of the chemical reaction. Calculate the equivalent of the metal taken. Compare the value of the found equivalent of magnesium with its true value, and enter the results in your laboratory notebook, using Form 5. 

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