Residence times for atmospheric

Transport Patterns and Residence Times for Atmospheric Trace Constituents vs. Altitude... 

It has been suggested (Delwiche, 1981 Soderlund and Svensson, 1976) that in order to account for the estimated burden and residence time for atmospheric N2O, the global rate of nitrogen fixation, and consequently nitrification and denitrification, would have to be about an order of magnitude greater than current estimates. Numerous measurements have found that the ocean, at certain times and places, is supersaturated with respect to N2O (Hahn, 1981), suggesting a flux of nitrogen out of the ocean to balance the overall... 

Stedman and Shelter (1983) claim that the magnitude of the northern-southern hemispheric difference in N2O concentrations is consistent with a major terrestrial source and a large oceanic sink, as suggested by McElroy et al. (1976), since the largest land masses are in the northern hemisphere. The N2O model presented by Stedman and Shelter (1983) includes large soil source and sink terms, and gives an N2O residence time of about 20 years. Their model is consistent with much of the soil data (presented in the earlier sections of this paper) which suggest that soils are both a major source and sink for N2O (see also Keller et al., 1983). However, Stedman and Shelter s model is inconsistent with the data and calculations of Weiss (1981), the data of Hahn and Crutzen (1982), the residence time for atmospheric... 

Martell, E.A. (1970). Transport patterns and residence times for atmospheric trace constituents vs altitudes. In Radio-Nuclides in the Environment. In ACS Symposium Series, vol. 93. American Chemical Society, Washington, DC, pp. 138-157. 

Pollutants have various atmospheric residence times, with reactive gases and large aerosols being rapidly removed from air. In the London air pollution episode of December 1952, the residence time for sulfur dioxide was estimated to be five hours daily emissions of an estimated 2,000 tons of sulfur dioxide were balanced by scavenging by fog droplets, which were rapidly deposited. Most relatively inert gases remain in the atmosphere for extended periods. Sulfur hexafluoride, used extensively in the electric power industiy as an insulator in power breakers because of its inertness, has an estimated atmospheric lifetime of 3,200 years. 

The turnover time of water vapor in the atmosphere obviously is a function of latitude and altitude. In the equatorial regions, its turnover time in the atmosphere is a few days, while water in the stratosphere has a turnover time of one year or more. Table 7-1 Qunge, 1963) provides an estimate of the average residence time for water vapor for various latitude ranges in the troposphere. Given this simple picture of vertical structure, motion, transport, and diffusion, we can proceed to examine the behavior of... 

Figure 13-5 is the box model of the remote marine sulfur cycle that results from these assumptions. Many different data sets are displayed (and compared) as follows. Each box shows a measured concentration and an estimated residence time for a particular species. Fluxes adjoining a box are calculated from these two pieces of information using the simple formula, S-M/x. The flux of DMS out of the ocean surface and of nss-SOl back to the ocean surface are also quantities estimated from measurements. These are converted from surface to volume fluxes (i.e., from /ig S/(m h) to ng S/(m h)) by assuming the effective scale height of the atmosphere is 2.5 km (which corresponds to a reasonable thickness of the marine planetary boundary layer, within which most precipitation and sulfur cycling should take place). Finally, other data are used to estimate the factors for partitioning oxidized DMS between the MSA and SO2 boxes, for SO2 between dry deposition and oxidation to sulfate, and for nss-SO4 between wet and dry deposition. 

The average residence times for mercury in the atmosphere, terrestrial soils, oceans, and oceanic sediments are approximately 1 yr, 1000 yr, 3200 yr, and 2.5 x 10 yr, respectively. (See Bergan et al. (1999) for more details on atmospheric residence times.)... 

The results are shown in Figure 2-3, in which the solid line is the exact solution. This numerical approach shows no sign of instability even for a time step of 40 years, nearly five times larger than the residence time of atmospheric carbon dioxide (distime). In fact, the reverse Euler method is nearly always stable, and so I shall use it from now on. 

Eiceman et d. [23] determined that mixtures of product ions, M 02 and (M-H), can be observed when ion formation and determination are fast, as with an atmospheric pressure ionization (API) mass spectrometer. In contrast, usually (M—H) or M-02 (but not both) is observed with explosives in IMS drift mbes where residence times for ions are Sms or greater, enough time for proton abstraction to be complete [24]. Alternatively, the M-02 ion may undergo dissociation with charge retention by the analyte molecule as shown in Eq. (3) and Figure 6 ... 

The atmospheric concentration of natural and bomb-produced radionuclides has been measured at ground level for several years at three locations throughout the world. The manner in which the concentration decreased suggested a half-residence time for stratospheric aerosols of 11.8 months at 46°N latitude. The annual spring concentration maximum occurred one to four months earlier at 71°N than at 46°N. Cosmogenic 7Be attained a maximum concentration before the bomb-produced radionuclides at 71° N and later than the bomb-produced isotopes at 46°N. The rate of increase toward the annual peak concentration for most radionuclides could be approximated by an exponential in which the concentration doubled every 60 days likewise, the rate of decrease from the maximum concentration could be approximated by an exponential with a half-time of about 40 days for most radionuclides except 7Be at 46°N, which shows a half-time of about 60 days. 

Values of Wp for particle-associated chemicals are generally in the range 105 to 106 (Eisenriech et al., 1981 Bidleman, 1988). A value of W = 10s is calculated to result in a residence time for chemicals due to wet deposition in the well-mixed troposphere (with a scale height of 7 km) of 20 days for a constant precipitation rate of 1 m yr1 (the residence time = (height of atmosphere considered)/WJ, where J is the precipitation rate). 

No data were located on the residence time of radium in the atmosphere or its deposition rate. However, data for other elements adsorbed to particulate matter indicate that the residence time for fine particles is about 1 to 10 days (EPA 1982b Keitz 1980). Radium may, therefore, be subject to long-range transport in the atmosphere. 

The distribution of water vapor in the troposphere is controlled by general climatic conditions rather than by atmospheric photochemistry. On the basis of rainfall measurements, Junge (128) estimated a 10-day average residence time for water vapor. 

Makide Y. and Rowland F.S., Tropospheric concentrations of methylchloroform, CH CClj, in January 1978 and estimates of the atmospheric residence times for hydrohalocarbons. Proc. Nad. Acad. Sci. USA , 78, 5933-5937 (1981). 

Croot, P. L., Streu, P., and Baker, A. R. (2004b). Short residence time for iron in surface seawater impacted by atmospheric dry deposition from Saharan dust events. Geophys. Res. Lett. 31, L23-S08. 

Grasslands managed for animal production (e.g., cattle) are much more leaky with respect to loss of added Nr. The addition of fertilizer and/or grazing animals increases the amount of Nr available for loss, especially via the atmosphere (e.g., NH3 (Sommer and Hutchings, 1997) and N2O (Fowler et al., 1997)). Thus, the effective residence times for managed ecosystems are potentially less than those for unmanaged systems. 

Long-term studies of the nutrient balance at the Hubbard Brook Experimental Forest show that much of the S04 entering via atmospheric deposition passes through vegetation and microbial biomass before being released to the soil solution and stream water. Gaseous emission loss of sulfur is probably small. The residence time for S in the soil was determined to be 9 yr (Likens et ah, 2002). 

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