Atmosphere cycle

The agricultural emissions of NHj, NjO and NO must be considered in context the processes which lead to net loss from the soil and vegetation are natural and form a part of the land-atmosphere cycling of this vital nutrient. The current agricultural processes, however, create conditions in which the small natural background fluxes, in the range of a few ngNm s are dwarfed by losses from fertilized land. 

The present sources to the ocean are the weathering of old evaporites (75% of river flux) and CP carried by atmospherically cycled sea-salts (25% of river flux). Loss from the ocean occurs via aerosols (about 25%) and formation of new evaporites. This last process is sporadic and tectonically controlled by the closing of marginal seas where evaporation is greater than precipitation. The oceanic residence time is so long for CP ( 100Myr) that an imbalance between input and removal rates will have little influence on oceanic concentrations over periods of less than tens of millions of years. 

Ereyer, H.-D. (1979). Atmospheric cycles of trace gases containing carbon. In The Global Carbon Cycle" (B. Bolin, E. T. Degens, S. Kempe and P. Ketner, eds), pp. 101-128. Wiley, New York. 

Fig. 13-2 The chemical and physical transformations of sulfur in the atmospheric cycle. Circles are chemical species, the box represents cloud-liquid phase. DMS = CH3SCH3, DMDS = CH3SSCH3, Siv = (S02)aq + HSOi" + SO3 + CH20HS03, and MSA (methane sulfonic acid) = CH3SO3H. The chemical transformations are as... 

Chameides, W. L. and Stelson, A. W. (1992). Aqueous-phase chemical processes in deliquescent sea-salt aerosols a mechanism that couples the atmospheric cycles of S and sea salt. /. Geophys. Res. 97, 20565-20580. 

Jouzel, J., Russell, G. L., Koster, R. D. et al. (1987). Simulations of the HDO and H2 0 atmospheric cycles using the NASA GISS general circulation model the seasonal cycle for present-day conditions. /. Geophys. Res. 92(D12), 14739-14760. 

Fig. 3. Example of similarity between atmospheric C02 and groundwater C02 annual cycles. The groundwater cycle lags the atmosphere cycle by 6 months.

Ehhalt DH. 1976. The atmospheric cycle of methane. In Schlegel HG, Gottschalk G, Pfennig N, editors. Microbial prodution and utihzation of gases. Gottingen, Germany Goltze p 13-22. 

Chameides, W. L., and A. W. Stelson, Aqueous Phase Chemical Processes in Deliquescent Sea-Salt Aerosols A Mechanism That Couples the Atmospheric Cycles of S and Sea Salt, J. Geophys. Res., 97, 20565-20580 (1992b). 

Keitz EL. 1980. Atmospheric cycles of cadmium and lead Emissions, transport, transformation and removal. The Mitre Corporation. McLean, VA MTR-80W343 2-29-2-30. 

Let us now determine the functional and dynamic characteristics of the fluxes of phosphorus (Table 4.4) based on analysis of existing ideas about their nature. The atmospheric cycle is governed by rock weathering, volcanic eruptions, and by the leaching of phosphorus by precipitation. From available estimates, the content of phosphorus in the lithosphere constitutes 0.093%, and the processes of weathering deliver annually to the atmosphere from 0.67 mgPcm 3 yr 1 to 5.06mgPcm-3 yr-1. Every year, volcanic eruptions contribute to the atmosphere about 0.2 106 tP. Since these processes are complicated and stochastic in nature and their models are absent, as a first approximation fluxes H and //f9 can be considered constant. 

Current research on the atmospheric cycling of sulfur compounds involves the experimental determination of reaction rates and pathways (see Plane review, this volume) and the field measurement of ambient concentrations of oceanic emissions and their oxidation products. Photochemical models of tropospheric chemistry can predict the lifetime of DMS and H2S in marine air however there is considerable uncertainty in both the concentrations and perhaps in the identity of the oxidants involved. The ability of such models to simulate observed variations in ambient concentrations of sulfur gases is thus a valuable test of our assumptions regarding the rates and mechanisms of sulfur cycling through the marine atmosphere. 

The sixth, seventh, and eighth sections of this volume deal with the atmospheric cycling of biogenic sulfur compounds. This aspect of the sulfur cycle has received a great deal of attention in recent years because of its obvious relationship to the add rain problem and the discovery that natural marine sources constitute a major portion of the total global atmospheric sulfur burden. The chapters in these sections focus on three aspects of this cycle field measurements and techniques used to establish the distributions and fluxes, experimental studies of reaction mechanisms and rates, and numerical simulations of the atmospheric sulfur cycle. Two chapters address the chemical processes involving cloud... 

Unfortunately as Kellogg et al., Robinson and Robbins, Junge, and Eriksson have all pointed out, most of the atmospheric measurements have been made in polluted areas of the United States and Europe, so not much is known about normal background concentrations of sulfur compounds and their global distribution. Therefore the atmospheric cycle is somewhat speculative, as are also estimates of individual sinks, sources, and concentrations. 

The atmospheric cycle for the oxygen species is shown in Figure 3. At night there is no photolysis, and the only reaction that takes place is the oxidation of... 

Though microbial biotransformation is an important removal process, it is not complete in the sense that the biphenyl backbone is not broken. Moreover, recent studies [116-118] indicate PCBs that flow to terrestrial, fresh water, and ocean surfaces are returned to the atmosphere. So it is important to identify permanent PCB sinks that is, sinks that result in the complete removal of the PCB molecule from atmospheric cycling. Burial of PCBs in fresh water or marine sediments below the resuspension layer and transformation processes initiated by OH attack in the troposphere are identified as major permanent sinks. 

Because tropospheric OH is photochemically controlled, a complete understanding of OH requires an understanding of the processes which control the distributions of the species which influence the OH photochemical equilibrium. Of these species the most important are O3, H2O, CH4, CO, and NOx. The levels of atmospheric EhO are largely controlled by the processes of evaporation and condensation and are not discussed here brief discussions of the atmospheric cycles of the other species are presented below. 

The central role of hydroxyl radicals in atmospheric chemistry is well illustrated by examining the atmospheric cycles of methane and carbon monoxide. A quantitative assessment of both of these species was carried out in the 1920s in Belgium by Marcell Migeotte, who detected their absorption lines in the spectrum of infrared solar radiation reaching Earth s surface. 

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