Sulfur anthropogenic emission

Consequently, an intensive uptake of sulfur occurs in hydrosphere, lithosphere, and biosphere. This is the main reason that the content of gaseous sulfur species in the atmosphere is rather small and even in polluted air does not exceed 2-3 ppmv. In unpolluted atmosphere the concentration of most S compounds is at ppbv levels, despite the intense sulfuroutgassing from the Earth s interior. The atmospheric content of the major gaseous S species, either SO2 or H2S, is highly variable and is influenced by both natural and anthropogenic factors. The role of anthropogenic sulfur emission in acid rain chemistry will be discussed in Chapter 10. The influence of natural parameters, microbiological activity in particular, is described in Box 7. 

This problem is a first-order attempt to quantify the possible anthropogenic perturbation of the northern hemisphere (NH) marine sulfur cycle. First, assume that present-day anthropogenic sulfur emissions result in 20 Tg S/year being transported from North America to the atmosphere over the NH Atlantic and 10 Tg S/year being transported from Asia to the atmosphere over the NH Pacific. Assume a uniform concentration in the N-S direction, average westerly wind speeds... 

An atmospheric sulfur inventory for the whole European continent has been recently constructed by E. Meszaros et al. (1978). These authors show on the basis of the comparison of anthropogenic sulfur emission (Semb, 1978) and sulfur advection from the Atlantic that the sulfur gained by advection is small. 70-85 % of the sulfur emitted and imported is removed over the continent equally by dry (mostly in form of S02) and wet deposition. Meszaros and his associates have estimated the dry deposition of S02 by using an average European S02—S concentration calculated from data in Table 13 (3.2 /tg m-3) and a dry deposition velocity of 1cm s (Garland, 1978). The value of wet deposition was based on precipitation chemistry measurements. It follows from this quantitative calculation that Europe contributes 15-30 % of its sulfur emission to the tropospheric sulfur cycle of other areas. 

Fig. 10-8. Flux diagram for the disposal of anthropogenic sulfur emissions in the continental troposphere of the northern hemisphere. Fluxes are given in units of Tg S/yr. Numbers on boxes indicate column densities in units of mg S/m2. They were derived from the adopted ground-level concentrations and scale heights below 5.5 km. Above this level, mixing ratios are assumed constant with m(S02) = 65 ng S/m3 and mfSOj-) = 70 ng S/m3. Chemical conversion of S02 to SC>4 occurs only in the lower troposphere. Dry deposition velocities are 8 mm/s for S02) 0.15 mm/s for SO2- on flat terrain, and 5 mm/s for SO2- interception by forests, which are assumed to occupy 50% of the continental area.

FIGURE 2.1 Estimated global anthropogenic sulfur emissions. The range of global natural sulfur emissions (excluding seasalt) is indicated. [Adapted from Lefohn et al. (1999).]... 

Hemisphere. Figure 2.1 shows estimates of global anthropogenic sulfur emissions since 1850, and Table 2.3 summarizes observed mixing ratios and atmospheric lifetimes of atmospheric sulfur gases. 

Figure 5.4.1 Global anthropogenic sulfur emissions (as SO2) from 1850 to 2000 [data from Stern (2005)].

Anthropogenic sulfur emissions have recently reached a plateau of about 80 Mt S/year. Worldwide conversion to cleaner fuels (above all to natural gas), desulfurization of more than half of the coal-based electricity generating capacity in the United States, and post-1990 declines of industrial production in the former Soviet empire were the main causes of the subsequent decrease in emissions in North America, Europe, and Russia. In contrast, China, now the world s largest consumer of coal, has been experiencing rapid increases in SO2 emissions and in the area affected by acid rain. 

---