Atmospheric lead flux

Atmospheric fluxes of lead in the United States rose steadily from the first decades of this century, reaching a maximum in the early 1970s (see Eisenrich et al., 1986 and references therein). Passage of the Clean Air Act of 1972 and its subsequent amendments resulted in dramatic reductions in atmospheric lead concentrations, although lead fluxes worldwide still remain 10-1000 times background levels (Settle et al, 1982 Settle and Patterson, 1982). 

Approximately 50% of the global flux of S to the atmosphere is derived from marine emissions of DMS. Oxidation of DMS in the atmosphere leads to production of S042-aerosols, which can influence global climate patterns (Charlson et al., 1987 Andreae and Crutzen, 1997). The key processes controlling DMS emissions from the euphotic zone... 

Patterson C. C. and Settle D. M. (1987) Magnitude of lead flux to the atmosphere from volcanoes. Geochim. Cosmochim. Acta 51(3), 675-681. 

The sedimentation of particles—that is, their downward motion due to gravitational settling—follows Stokes s law. Turbulent diffusion represents an opposing force, and sedimentation equilibrium is established when both forces cancel. Assuming a constant production rate of particles at the earth surface for each size group and a balance of upward and downward fluxes in the atmosphere leads to the following equation ... 

Following the decline of the western Roman Empire, Pb production continued, but at a much reduced pace, as witnessed by sediments and peat bogs [75]. However, the atmospheric Pb flux did not reach background values therefore, Pb continued to be mined and refined, especially in Asia [76]. Even at this time in Europe, Pb continued to be used for glass making and ceramic glazes [77]. Lead was needed for the cames of the stained glass windows of churches and cathedrals [53] the abundance of these windows in Europe today is a testimony to the usefulness of metallic Pb as a construction material. Lead was also used to... 

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. 

Lees and Whitehead" have shown that differences in boiler design lead to differences in furnace atmospheres, which are subsequently reflected in differences in scale morphology and corrosion performance. Hence they report that there is no unique scale morphology which is characteristic of furnace wall corrosion. They also warn that the scale that is examined during an investigation may not be an exact reflection of the scale on the tube surfaces during operation due to the possible hydrolysis of the scale on cooling (when hot flue gas is replaced by moist air) and the redistribution of phases in the scale due to the loss of the incident heat flux. 

Comparison of Figs 13-6a and 13-6b clearly demonstrates the degree to which human activity has modified the cycle of sulfur, largely via an atmospheric pathway. The influence of this perturbation can be inferred, and in some cases measured, in reservoirs that are very distant from industrial activity. Ivanov (1983) estimates that the flux of sulfur down the Earth s rivers to the ocean has roughly doubled due to human activity. Included in Table 13-2 and Fig. 13-6 are fluxes to the hydrosphere and lithosphere, which leads us to these other important parts of the sulfur cycle. 

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